Cooling System Diagnostics.

All fieros have two discrete cooling cycles, Closed Loop and Open Loop.

The closed loop cycle is from the engine to the heater core than back
to the engine. This is the starting cycle.

The open loop is the running cycle. Once the internal temp in the engine
is reached the tstat opens and cycles fluid through the radiator and
heater core than back to the engine.

Simple right.

There is one problem we have all fought with and that is poor coolant flow.
We have tried burping, at nausiem. The engine starts out alright in the
closed loop then starts to over heat during the open loop.

The inherit problem with fieros is not air blockage but the plastic
impellers on the water pump. In time they deteriate and the capacity
of the water pump is reduced.

So here is a super simple diagnostic, it takes less than an hour and
cost around $ 20.00. Plus once complete in some cases the car is
functional, without a heater though. Plus you dont have to crawl around
the car!

Isolate the cycles.

Closed Loop

With the tstat in the closed loop is isolated. Top off coolant and start
the car cold. Turn the heater on high, vent setting, feel the vent. It should
start off cold then warm up in minutes. Continue to feel the vent and watch
the engine temp. At around 160 or 180, depending on your tsat. You will
feel a sudden drop in temp. In most cases the engine temp will drop
then heat up. After it hits 220, stop the engine.

If this happens the closed loop is operating, next the open loop.

Open Loop

Parts Required: Preston flush system $ 12.50,2 - Brass plugs $ 5.00,
hose clamps $ 2.00.

Tools Required: hand clamps, utility knife, socket set.

To isolate this loop the parts are required. Open hood. Clamp off supply
and return lines at heater core with hand clamps. Cut hoses and install
plugs at other end of cut, fasten tight with hose clamps. Unplug electric
fan at radiator, remove tstat and top off with fluid front and back.

This successfully removes the closed loop from the cooling cycle.

Start the engine and let idle. While the engine heats up you have to keep
checking 3 things, 1 - The plugs at the service connection, 2 - THe engine
temp, 3 - The radiators hosing and temp.

When checking the radiator squeese the supply line, top left and the
external temp of radiator with your hand. You should feel the hose
charging and the temp slowly rise from top to bottom of radiator.

During this process the engine temp will run up to around 120. If the
engine stays at that temp your open loop is fine.

Therefore the problem is with your water pump. It cannot keep up with
both cycles running.

So you have a choice. If you need heat in the car you must replace
water pump and install connections at splices in heater core. Use the
tconnection from the coolant flush system at the top hose and a 3/4 x
3/4 brass splice in the bottom.

If you dont need heat right away dont do anything. Just make sure your
plugs are clamped in tightly. Always use a socket set and not a screw
driver to tighten.

Best of luck guys.

Matt

Why are you doing this?

I'm speechless.

Edit - I lied. I'm not speechless. I can't let this go.

The terms open loop and closed loop have nothing to do with how the cooling system is configured.
Open loop refers to the engine running off of pre-programmed parameters, with no input from the O2 sensor.
Closed loop refers to engine operation that is responding to input from the O2 sensor, and making adjustments accordingly.

If there is a cooling system problem there is absolutely nothing to be gained by closing off the heater core or lines. It could potentially cause problems because it's designed as a pressure bypass until the thermostat opens. (And if the impeller is slipping, it'll slip even worse.)
If there is air in the system jack up the back of the car, take off the thermostat cap and remove the thermostat. Top off the coolant. Put the cap back on and start the engine. Let it run for about half a minute.
Stop the engine. Take off the cap. Top off the coolant.
Repeat until it doesn't take any more coolant.
Put the thermostat back in, and the cap back on. Done.

The slipping water pump impeller is uncommon enough that it baffles the kwrap out of everybody when it happens. It's pretty much what you check for when all of the easy stuff has been checked.

Sorry. Not trying to bust your nads, but there is some patently incorrect info in your post.

[This message has been edited by Raydar (edited 01-17-2007).]

well if we are gonna nitpick:

the heater circuit is not a pressure bypass. first of all understand that the presure in the cooling system comes from the expansion of the fluids due to heat, not the pump. the purpose of the heater core bypass is to flow coolant past the tstat. if there is no flow, the element in the tstat that expands to open it will not be heated up fast enough before the engine is technically over heating. the bypass also serves to move coolant thru the heads where it would be possible to boil the coolant from heat in just a few minutes cold if there was no fluid motion. many older cars that used a valve to valve off the heater core had a small bypass hose from the water pump to the manifold. this would allow flow past the tstat and flow thru the motor. (you will find that on many SBC's in older cars, not sur if they still use it or it is implemented differrently now, I haven;t really looked)

the reason coolant systems are now pressurized is to raise the boiling point of the coolant over ambient air pressure to a controlled setpoint. this allows them to use smaller components in the radiator, as they now use the radiator cap as a regulator valve and the overflow tank to handle the excess coolant. overall a more efficient system that is lower cost.

Burping the system.... now with some strange flow motors that get swapped in, you might need to raise the car, but in stock form, there is absolutely no need to raise the car. air will accumulate in the highest point, the tstat housing, and to some extent the manifold/heads. statically , you would have to stand the car on it's nose practically to make the under car tubes for the radiator or heater core high enough to move the air to the tstat. (remember all the routing goes down under the car. for air to move to the highest point, it will not first travel down to get to the tubes, then back up to the motor, so you would need to get the car high enough that the tubes are higher than the top of the radiator to move any air back to the motor.)
the pump will move all the air out quite nicely without all that work. once you fill the system statically, ie fill from the tstat to the radiator til the radiator overflows, cap the radiator, then top the motor, you have most of the coolant in the system. removing the tstat and running for a very short time, (30 seconds) will move enough water thru to push the air to the motor, where as laws of gravity and fluids will have it, the air will tend to trap. 2 sessions of "top n run" will have 99% of the air out of the system. the rest will work it;s way out in normal cycling. the first run with the tstat in will force any air trapped in the heater core out. the design of the system will not allow a core to get air locked unless there is a restriction in it that will not allow flow.

as for the terms used, open loop/closed loop that;s just a nit, as cooling systems are also discussed in terms of loops. but in automotive terms, under operating temp and at operating temp would be a better description, or for those that hate typing, cold and hot will suffice.

the simplist test for the whole system is to run without a tstat with the car sitting. watch the temp guage, or use winaldl to monitor the temps more accurately. at idlem it should take a while, but you should see the temp climb up to around 220 degrees, where if you have a working fan switch, the radiator fan will kick in and the temp should drop very rapidly to around 160,
then climb back up and repeat. this is a no load condition, and only tests that there is some flow, and the fan circuit works.
raising the idle to 2-3k will add some load (tho not much) and will acclerate the fan on cycling, but is not sufficient to really test flow, but if the pump is really bad, this cycle would end up with the average low temp with the fan on climbing higher and higher until the point where it never shuts off and an overheat is starting.
with the tstat in, you will get to that point much faster. a stock car should be able to sit there all day and never overheat while idling or even with racing the motor.
diagnosing a flow problem is not really easy, as it is possible that there are restrictions, ie clogs from corrosion or additives in the radiator that will also cause this reduced/insufficient flow problem. without some type of flowmeter in one of the lops, you can really only best guess it. an original radiator is always suspect since previous maintenance makes it suspect. if properly maintained, and not leaking there should be minimal corrosion, and it should handel any of the stock motors just fine.
so the reall issue is what to do? try pulling the waterpump and check that the impeller is not slipping on the shaft? alot of work, but unless it is known for sure that the pump has metal impellers always a haunting question, or replace the radiator, which tho alot easier than a waterpump, is not the cheapest way out. if you have a competent radiator shop tho, you can have them test it, and that would tell the tale there.
in short, there is no easy way to defintively say "this is bad" without knowing the complete history of the car, from cooling system fluid changes to parts replacement, to any additives used.
That said, if you want a dependable driver, and especially if you live in a warm climate, unless you know for a fact the radiator is only a few years old, and the water pump is good and has metal impellers, those are the 2 things to replace first. for a total cost of about 150$ (new aftermarket radiator 100$, new waterpump 50$) plus a short days work, how much time do you want to spend jerking around guessing which part is bad? or what was done previously?
if you dirve your car, especially daily, and you have an overheat problem,it's a no brainer what you need to do.

The heater circuit *is* a bypass.
If the thermostat was closed, and the heater circuit was blocked off, the pump would be pushing against water that could not go anywhere. Which was the main point of my previous post. I can't see how "deadheading" a pump is ever a good idea.

And sure, you don't have to jack up the back of the car to burp it, but it only takes a minute, and it does help.
Other people have had trouble, and it worked for them, where other methods didn't.
Truthfully, you're the first person I've ever seen post that said it was anything other than helpful.

[This message has been edited by Raydar (edited 01-17-2007).]

Proper latin would suggest it is "ad nauseum". Sorry, I got bored....

------------------
carpe diem

This procedure will work with out starting the engine every time. After I started at the Caddy dealer 3 years ago I started installing a lot of pistons. I new that the factory could fill the cooling system from a dry state and get it right. I purchased an Air lift/evac tool. It is a tool that pulls a vacuum on the cooling system and then draws in the coolant. It can also check for a leak. The only problem is that if coolant gets on the Venturi it does not work very well. About 3 weeks after I purchased it GM sent out one that had a vacuum storage tank. The thing is I can pull a vacuum, fill pull a vacuum get a lot more air out, and refill. This could not be done with out the tank. The tank can be made simply. The cheap Air lift that I purchased only had an expandable bottom that fit in the radiator. Some nice radiator pressure testers have interchangeable ends that come off with disconnects. This is better for tight areas around the radiator cap. GM is the only one that I have found with the tank and you don't won't to know the price.


The advantage of the GE-47716 Vac-N-Fill tool is that is provides a complete cooling system fill while simultaneously purging air from the system. This can save time by eliminating the need to bleed the coolant system or thermocycle the engine when performing a coolant fill. The tool can be used on a full system, partially empty system, or a completely empty system. The tool can also be used to drain or partially drain coolant from some cooling system components using the extraction hose.

Tank

Radiator adaptor

Venturi

Vacuum guage

Continue to draw vacuum until the needle stops rising. This should be 610 mm to 660 mm Hg (24 to 26 in Hg).

I know everybody can not do this, but I have built 2 for other people.

Pardon my lack of proper nomenclature. All I know is that I tried
every purping proceedure known to man. Jacking front, back and sideways
(just kidding about the sideways thing). In addition I have pressure
flushed the system and refilled last weekend.

The cooling issues remained. It would start off cold, slow rise to
180 +/-, tstat kicks in, temp drops (just once) then assends. Heater
core warming then immediate cools. Felt radiator during normal operations
and stayed cold, ie no flow.

I have removed and pressure tested my radiator. Clear of obstructions
flows freely. Physically felt supply and return piping for kinks, nothing.

When I installed the plugs at heater core to bypass, system ran like a
dream. Maintained 120 indefinately.

Whereas I dont want to run it juryrigged, I purchased a new water pump for
this weekends project.

I know what I did was not common but please explain to this neophite why
it worked. Because to this simplton engineer it makes sense.

Thank you in advance.

Matt

I`m trying to follow along with the coolant issues posts--and getting confused---so this may out in left field--everything works bad ---until you bypass the heater core ? Then when the heater core is bypassed it works fine? Wouldn`t that say by process of elemination of every cooling system part on the car, that the heater core is the problem?

quote Originally posted by 3800superfast: I`m trying to follow along with the coolant issues posts--and getting confused---so this may out in left field--everything works bad ---until you bypass the heater core ? Then when the heater core is bypassed it works fine? Wouldn`t that say by process of elemination of every cooling system part on the car, that the heater core is the problem?

Thanks Superfast, the heater core is also fine. I removed and pressure tested it, tight. With the Tstat in the core heats up nicely. THen when the Tstat opens temp drops.

Thanks

Matt

Raydar, you seem to have missed my point. it is a FLOW bypass, not a pressure. in some form or another water must flow around the tstat or it will not open till the steam of the over heat forces it too, then its too late. all motors have that bypass in some form or another. A centrifical pump like the water pump in most cars doesn't create enough pressure to care about dead heading, it will only cavitate the coolant, and possibly damage the impeller, but not likely as the rpms are not high enough.

on filling the system, people should picture what is happening, so,
I found a nice sideview of the chassis in the service guide, used for checking frame measurements. I put in the various cooling components, tho I may be a tad off on the hieghts, it is close enough. also to show the under car tubes , only the blue one is a good ref for the height, all the tubes are really in parallel, and would be invisible, I just stuck them in for ref.



there are 3 highspots in the system. the radiator, A, heater core B, tstat C. Now if you picture the car filling, remember water seeks it;s own level, as you fill from the tstat, there are a few things that happen, if you pour straight down into the block, the block fills. eventually it reaches the height of the water pump passages and starts to fill the blue line, this is the side from the radiator cap (normally the return line).
eventually with the cap off, the radiator will also fill, and start back filling the tube on the drivers side from the top of the radiator, allowing the air to come out the passage in the tstat housing. at the point where the fluid fills the tube to the back and starts going up to the motor, it will reach the same height as the radiator cap and start to overflow there. if you then put on the radiator cap and continue to fill straight down into the block, it will continue to force the fluid up till it is even in the opening in the tstat housing and the block is filled. That leaves the heater core. this will act differently on pre 88's than 88';s.
in the pre 88, the return is on the top of the waterpump, on the 88 is on the undercar coolant tube as it comes up behind the passenger seat.
so in pre 88, as the water reaches the level of the waterpump, it will also flow down the core line, and force the air out thru the tstat housing. since it is filling backwards of normal flow, it will go in the topand flow out the bottom, and will trap air in there.
in the 88, it will fill sooner but will still trap the air.
now if you look at the relative heights, the biggest air bubble will bein the core, with a small bubble in the radiator tub, and a few bubbles in the block. tilting the car would only get and small pockets in the tubes out, it will do nothing for the core or any air trapped in the radiator.
Now if you top of the tstat, close the cover and run it with no tstat, there is no flow restriction, water will flow out thru the radiator and back up thru the block, collecting any air trapped and pocketing it in the top of the tstat housing. great that clears the majority of the system, but not the core, so you put in the tstat to force the flow thru the core. that forces the air out and traps it in the upper block if you don;t run it too long.
I also read thru the fsm method, which in short says top it off, start it with the cap off and tstat out, do not race, check flow, shut off, top off, tstat back in, run til warm, open and top off.
the real key is to fill it slowly so the air has time to move out of the system. then run/check/run check a few times.
tilting the car isn't going to help on a stock system, but if it helped anyone, it is probably because they now followed all the other directions.
the real key is filling slowly straight into the block, not dumping it in and filling both tubes, as you can trap the air in the system. even at that ,the short runs with no tstat in will clear the air out, but it may take a couple of passes.

now for MMesko's problem, maintining 120 indefinately says you have no tstat in,or it;s whacked.
your symptom:

quote It would start off cold, slow rise to 180 +/-, tstat kicks in, temp drops (just once) then assends. Heater core warming then immediate cools. Felt radiator during normal operations and stayed cold, ie no flow. When I installed the plugs at heater core to bypass, system ran like a dream. Maintained 120 indefinately.

the first time you reached operating temp, the plastic impeller started to slip as it softened, once it starts slipping, you lose flow, and it;s all down hill from there.
with no stat, there is almost no flow restriciton, so the pump won;t slip as much.

Before the rebuild, mine did exactly that. I could run with no tstat, and not over heat unless I got stuck in traffic. if I turned on the a/c to force on the fan and kept the temp under 160, it wouldn;t overheat. let it get over 180, and was dead in the water til the whole assembley cooled off. when I pulled the pump, I could spin the impeller on the knurled shaft with my pinky. once they start to slip tho, it is all downhill, and fast as each overheat worsens the impeller fit on the shaft.
your weekend project shoult fix your problem, and increase your ability to string 4 letter words in non repeating sequences.
have fun!

I hope you already know to make sure the new pump has the metal impellor. If it is plastic, take it back! If you already knew that, sorry to repeat, but it is very important.

Thanks tjm4fun for the diagram and explanation. That's the best description I have ever seen, and undoubtedly took you a while to make. I appreciate the effort.

------------------
1988 Fiero GT
Cleveland Fiero Club

I hope this post is helping others as it is me. New WP in from da fiero store ready for some warm weather to install. Last nigh I removed plugs at heater core, restored loop through core. Removed tstat and topped off both front, core and back. Good level no loss only needed to add alittle, less than a pint to top off.

Installed tstat. Started car, temp rose slowly initally as it heated up. Once over 140 it continued to rise, 160 tstat, to over 220. No heat from core, radiator warm. Powered off and let sit over night.

There is nothing else I can isolate. It appears there is no trapped air, nor leaks.

There is one thing to note, When driving the other day I did hear some belt squeakage.

So if my assumption is correct it appears that my WP cannot keep up. Ready to invest 10hr in installing new one. Unless there are any tricks to install a 87 GT easier. I am going to replace and test with new belt first.

Again thanks guys for all of your help.

A 12 pack...Ok just kidding--from Ed http://www.thefierofactory.com/qawaterpump.php
http://www.calgaryfieros.co...docs/water-pump.html

Best advice I got from on here was to use a piece of cardboard with an outline of the waterpump drawn on it. As you remove bolts, push them through the cardboard in the general location where they belong. Then you will know which goes where. Be thorough when removing the sealant, but careful not to damage the thin metal edges of the timing cover and block. Put new sealant on the edges and don't forget to put some on the bolts. I forgot which bolts went into the water jacket, so I just put sealant on all of them. Then, while you have it all apart, take a wire brush to the pulleys to clean any residue from the slipping belts off of them.

I just put the old bolts in the correct location on the new waterpump, then transfered them to the old waterpump before installing the new one.

I also use Permatex Hylomar HPF. Works great and does not dry. Makes the next change easier.

http://www.neverseezproducts.com/gasketseal.htm

The above link is just for info, not recommending them for buying......

quote Originally posted by tjm4fun: Raydar, you seem to have missed my point...

Big time!
Thanks for the clarification. Good info.

Based on my research all of the bolts from the WP to the engine have different torque ratings correct.

Matt

no, they are all 7 ft/lb.
I use a paper thin coat of rtv ultra blue on the metal surface, put the gasket on, then another paper thin coat on the other metal surface.

be very careful cleaning the old sealant off, after 20 years the gasket likes to become one with the surface. I use a razor blade held almost parallel to the surface to clear the bulk off, very light pressure. then rub it down with a fine scotchbrite pad.
Take your time, look at what is where and think out how to get what wrench on that bolt and keep the skin on your hands.

quote Originally posted by mmesko: Installed tstat. Started car, temp rose slowly initally as it heated up. Once over 140 it continued to rise, 160 tstat, to over 220. No heat from core, radiator warm. Powered off and let sit over night. There is nothing else I can isolate. It appears there is no trapped air, nor leaks. So if my assumption is correct it appears that my WP cannot keep up.

If you're heater core is blowing cold and the tempature is high, you dont have coolant flow plain and simple. 99% of the time its from not burping the system properly. So many people have a cooling issue and start tearing things apart and hacking up the hoses only to end up with the same problem in the end.

I've never seen a plastic water pump impeller in my life. Im sure the exist, but I wonder how many people assume that is the problem only to get it off and find a metal one. Im sure a lot of these "fixes" are from people draining the system when the change the pump, and then when they refill it the air pocket comes out.

I would take off the thermostat cap, make sure the system is full, pull the thermostat and watch for movement. You really wanna be sure, rev the engine a little. You'll get coolant gushing out the thermostat housing. If not, change the WP, if so, (actualy even if not) its probably just an air bubble.

[This message has been edited by 86GT3.4DOHC (edited 01-19-2007).]

ummm, the one I got from the fiero store had a plastic impeller (acdelco). the one I removed from the car had a plastic impeller (also marked as an acdelco unit)

let's see, that;s 2 out of 2 waterpumps I had off fiero's. don;t know what was on my 86 cause in 100k of driving, it never overheated once. So, I would have to say with the number of people I;ve seen on this forum who found plastic impellers, it is a major suspect.

[This message has been edited by tjm4fun (edited 01-19-2007).]

I posted this query in the other thread and nobody had any comments, so I'll try again.
If the heater core is plumbed backwards ie trying to draw back to the engine from the top of the heater core, is it possible that a steam bubble might keep the heater core from flowing properly? A steam bubble could dissapear when the system is cold, but while running, a bubble might be light enough to stay at the top of the heater core and more or less stop any flow through the heater core. If there is no flow through the heater core the T-stat won't get an accurate reading till you realy start to get steam produced at the T-stat, along with the steam production you would get a dramatic rise in preasure and expansion of the total fluid volume.
mmesko, have you tried drilling small holes in your T-Stat? Other PFF members swear buy them

------------------
Ol' Paint, 88 Base coupe auto.
Turning white on top, like owner.
Leaks a little, like owner.
Doesn't smoke, unlike owner

Not really possible, unless you have no flow. the coolant is under pump pressure to flow thru the core. with the tstat closed, the only path for water being moved by the pump is thru the core and back to the engine.at best you could get a bubble in the core(which will eventuelaly get blown out by the coolant), but not steam unless your motor is steaming, which says you either have no flow or low coolant.
the core has differrent sized tubes, makes getting it wrong kinda hard., and I think I may have my diagram backwards, I did it from memory, usually the large tube is the return, and that might have been the top one. either way, would not be an issue, as there is more flow than needed to blow out that small volume in the core.

The tstat holes are the best way to assure flow, and should be done on any system prone to an air bubble forming under the tstat.

Curiousty---Matt didnt you post something a couple of days or so ago about making and alteration or solder to the new heater core you installed ? What did you do exactly ?

OK, don't also forget the heater core could be plugged or semi-plugged. I've had several (other vehicles) that had no or little heat because of this. Water would barely flow through enough to warm the hoses thinking all was good but not enough to do any good. Unhook the hoses and get your garden hose and try to blow water BOTH ways through the core. If water won't flow keep trying. I was able to finaly blow the plug of crap out of all of them by alternating hoses. After all, a heater core is a miniature radiator with those same small passages. If it won't unplug, replace it. The Fiero is THE EASIEST heater core I have replaced in my life - 10 minutes.
Think about it, this would almost stop flow till the thermostat opened and cause all kinds of weird cooling (and burping) problems. Do the flow test and eliminate the core as a possible problem.

------------------
Mick
1986 GT

quote Originally posted by 86GT3.4DOHC: I've never seen a plastic water pump impeller in my life. Im sure the exist, but I wonder how many people assume that is the problem only to get it off and find a metal one. Im sure a lot of these "fixes" are from people draining the system when the change the pump, and then when they refill it the air pocket comes out.

The reason so many of us are adamant about this is that we have personal experience with it. I tried everything and finally gave up; then I removed my waterpump and I could turn my plastic impellor on the shaft with very little effort. Example: if I swung the pump while holding the shaft, the impellor would twirl in the wind. I think the girl at Autozone thought I was nuts because I demanded to see the impellor of the waterpump before I bought it. Surprisingly, the cheap one had the metal impellor! For those of us who have experienced it, it *is* a VERY REAL problem. It should probably still be a last resort item to replace simply because everything else is cheaper and easier. Still, DO NOT overlook the plastic impellor.

[This message has been edited by TG oreiF 8891 (edited 01-20-2007).]

quote Originally posted by tjm4fun: ummm, the one I got from the fiero store had a plastic impeller (acdelco). the one I removed from the car had a plastic impeller (also marked as an acdelco unit) let's see, that;s 2 out of 2 waterpumps I had off fiero's. don;t know what was on my 86 cause in 100k of driving, it never overheated once. So, I would have to say with the number of people I;ve seen on this forum who found plastic impellers, it is a major suspect.

I've handled over a dozen Fiero water pumps, and probably near if not more than 100 other water pumps, not counting the year I worked in a parts store, who knows how many there. Pretty much every one I sold the guy would take out of the box and look at. Never saw anything but metal. Im not denying they exist, but people talk like its a common thing. People start assuming this before they've even done any real diagnostics. There were over 250,000 Fieros, and we've heard of maybe 40 plastic impellers, thats not a signifigant amount, of the thousands that we've changed here, no one mentions finding a metal impeller, and its not something you would find signifigant or remember if you heard about it. Now someone finds a plastic impeller and he starts a whole thread about it and thats the kind of thing you rememeber. Some guy says "Ive got a cooling problem, I think its a plastic impeller." He takes it apart and finds a metal, he either doesnt say anything, or people dont care, he finds plastic and he tells everyone, and everyone makes a big deal about it.

They DO exist, but its by no means a common thing, and not one of the first things you should be checking. Having seen hundreds of water pumps, I would not be suprised, or even amused to see a metal impellor, I would be blown away to be able to find a plastic one.

Take off the T-stat cap and give the engine a little gas and see what happens, nothing comes out, go for it, but if it spews coolant everywhere, its safe to assume there is flow.

I don;t doubt that the majority are metal, and people change them out needlessly. But the remove the tstat gieser test is useless tho. the one I had in my car would geiser. no load on it. removed, as I said it spun with little to no effort.

quote Originally posted by 86GT3.4DOHC: I've handled over a dozen Fiero water pumps, and probably near if not more than 100 other water pumps, not counting the year I worked in a parts store, who knows how many there. Pretty much every one I sold the guy would take out of the box and look at. Never saw anything but metal. Im not denying they exist, but people talk like its a common thing. People start assuming this before they've even done any real diagnostics. There were over 250,000 Fieros, and we've heard of maybe 40 plastic impellers, thats not a signifigant amount, of the thousands that we've changed here, no one mentions finding a metal impeller, and its not something you would find signifigant or remember if you heard about it. Now someone finds a plastic impeller and he starts a whole thread about it and thats the kind of thing you rememeber. Some guy says "Ive got a cooling problem, I think its a plastic impeller." He takes it apart and finds a metal, he either doesnt say anything, or people dont care, he finds plastic and he tells everyone, and everyone makes a big deal about it. They DO exist, but its by no means a common thing, and not one of the first things you should be checking. Having seen hundreds of water pumps, I would not be suprised, or even amused to see a metal impellor, I would be blown away to be able to find a plastic one. Take off the T-stat cap and give the engine a little gas and see what happens, nothing comes out, go for it, but if it spews coolant everywhere, its safe to assume there is flow.

Let's all settle down; there's no need to get after each other we're all trying to help. I agree, look elsewhere first because its time consuming and more expensive of a fix than checking the other items. However, there are many reports (myself included) that some new / remanufactured waterpumps come with a plastic impellor. If there are flow problems, and the pipes are not constricted, radiator isn't plugged, etc - take a look at the waterpump impellor.

I think it is a case that can be pretty easily deduced by process of elimination. However, it is often overlooked because the problem is wierd. Because it is so odd, I always try to mention it to people. Usually, by the time someone mentions a cooling problem on here, they've covered most of the standard items: fan operation, coolant fill procedure, etc. and they still have a wierd problem. Well, the plastic impellor is a wierd solution; so it fits.

Now for some conjecture: I do not think that any Fiero's came from the factory with a plastic water-pump impellor. Mine, for instance, had the engine replaced by the previous owner. I *think* that the waterpump was replaced at that time. Some 40,000 miles later I *think* he sold the car to me because he had wierd cooling problems and he wasn't a member of this forum to get help from all you guys. My guess is that one of the remanufacturing companies is using plastic impellors on the pumps. If you go down to Autozone they list 3 (as I recall) pumps for the Fiero. Only one of them has the plastic impellor. Other parts stores may not even carry the plastic impellor.

I didn't see anything on when the overheating first started. Did you just buy the car? Did you just install a new engine? I've heard that some major overbores can cause overheating due to the thinner cylinder walls. I just replaced my orig 214K V6 in my 88 GT with a rebuilt 2.8 long block and don't have any overheating (yet). I'm sure that the block must have been bored and honed at the rebuilders because I don't think that they use new blocks. It DID have a plastic impeller on the WP that was removed and not re-installed. It probably had 60-80K miles on it. The ONLY time that I've had overheating was when I had weeds etc clogging the rad between it and the condenser and when I had an air dam installed (which reduced the air flow some) and the A/C on. Have you checked the eng timing? Also, I've gotten bad thermostats before and had to replace them. You may want to try the old boiling-water-on-the-stove trick to see if it's opening all the way. It's too bad that there are so many causes to check-out in a problem cooling system.

I am a moron! This weekend I reconnected all lines to original routing. I installed my 180 tstat, topped off fluid. And sprayed my belts with belt restore. And small wonder the unit runs like a dream now. Top temp 120, good heat.

So the issue wasnt my WP or trapped air, just a bad belt.

Now I feel like a complete idiot! Thanks for your help guys.

Matt

Was the belt squeeling or making any noise?

Mine isnt but now I wonder if that is the root of my problem?

It didnt squeek that often when I was fighting the cooling problem, for a couple of weeks. Now that I reconditioned my belt it squeeks more often due to the fact that the belt is not conditioned all the way around.

So when reconditioning belt do the following. Apply spray to exposed section. Turn car over a tad, reapply spray. Continue for a couple of cycles. Let set for 30 mins and run car.

I was surprised at how well and quick it worked. Make sure you have no air in the system. When running turn up the heater and feel the vent. The unit should heat up and stay there for a while. If it does that may have been your problem

Best of luck

Matt

quote Originally posted by Raydar: Truthfully, you're the first person I've ever seen post that said it was anything other than helpful.

I have tried it once (raising the rear) and have not found it to be helpful. I have had no real problems 'burping' the car on a level floor.

quote Originally posted by 86GT3.4DOHC: Take off the T-stat cap and give the engine a little gas and see what happens, nothing comes out, go for it, but if it spews coolant everywhere, its safe to assume there is flow.

Tried this once (and so have a couple of others in the club) and found you don't even have to rev the motor, as soon as it starts, it's spits coolant all over the place. There is no way you can run the motor with the thermostat cap off without losing a wack of coolant.

...just my 0.02

[This message has been edited by Mickey_Moose (edited 01-22-2007).]

I removed the thermostat cap and the stat. Put the cap back on half way to just the first bump. Start her up. When the idle has setteled down and lowered remove the cap. I made up a tube from a one gallon milk jug and some duct tape about 8 " long. I jammed it down into the thermostat housing . I can now let it run for a short time wit the lid off, trying to purge any trapped air. I was also able to add coolant this way down into the exit hose headed towards the radiator. Once the coolant starts to expand , pretty quick, it will leak past the tube sides. Add the cap and the thermostat while it is expanding, so as it cools you will, if your system doesn't leak, have a vacume and draw water from the overflow tank. Worked for me.

I think everybody methods might be a little different from the other guys, but sharing your methods is an attempt to help anyone and everyone else out of a tight spot. Lets keep up the sharing of information, thats what makes up a FORUM. I have repaired many things Fiero from reading other folks experiences, and their unselfish offerings of thought. I thank you all
Joe Crawford
Texas