if you haven't done it, next time you have your tstat out, drill 2 1/16" holes in the disk near the outer edge. this goes for all fiero tstats. it will act as an air bypass and greatly simplifies bleeding air out of a system with a tstat high point.
with no tstat in, tho you should be able to force all the air out with the pump, unless you airbind the pump.
I forget now, but if you don;t have the heater core systemin place, do you have a bypass around the tstat? you must have some flow around the tstat in order to get the mechanism ot work, I think we discussed this a while back tho, just too lazy to re-read the whole thread. with no tstat installed, when you run it and it gets hot, and you open the system after it cools a bit, any air would be indicated in the tstat housing as it is the high point, if there is no air, I think you could be barking up the wrong tree.
also rarely, but does happen, a car with no tstat will run too hot, better to run with a restrictor in place, an old tstat with the center removed is usually sufficient, at least as a test.

Wiccantoy lent me his vacuum system and I just tried it. I guess my 3-gallon Craftsman compressor is not going to cut it.

bmwguru, I looked up the specs on the one you sent me the link for and it says 90psi and 6 bar minimum. Is "6 bar" the same as SCFM?

I'll have to run over to a friend's place to use a better compressor. It's raining all day today, so no driving. Rain is possible tomorrow, too, so I'll report back in.

Thanks for mailing the kit, Wiccantoy! If this doesn't work, I'm going to have to tow this car up to NY and visit bmwguru!

quote Originally posted by Saxman: If this doesn't work, I'm going to have to tow this car up to NY and visit bmwguru! Btw, when you refill using this tool, do you have to do anything to keep the air in the top of the hose from going back into the system after the vacuum is established?

Sax, I'm in NJ. My shop is just off exit 88 on the GSP in zip 08701.
As for the other tool. It looks identical. Once the cooling system is filled, the vacuum will be gone and the coolant will stay in the cooling system. It's a clever little tool.
Dave

Sorry I wasn't clear. I meant the hose that connects to the tool that pulls the coolant out of the container. How do you get that air out of the hose before refilling?

NJ it is. I may be Googling your town if this doesn't work.

Was I right about the small compressor not being enough?

quote Originally posted by Saxman: Sorry I wasn't clear. I meant the hose that connects to the tool that pulls the coolant out of the container. How do you get that air out of the hose before refilling? NJ it is. I may be Googling your town if this doesn't work. Was I right about the small compressor not being enough?

The air in the hose has never posed a problem for me. I've never thought about it until now. I was very skeptical about the tool until I started using it. Like I said, after replacing the water pumps on the 96-newer Audi's, it would take about 15minutes of running the engine at 3000rpms just to get heat. Then I would have to shut it off and let it cool for a while to top off the coolant. Now I use the tool and take it for a drive.
As for the compressor. I think it is too small for the Fiero. Most cars can get to 25" of vacuum in under 15 seconds. My Fiero took about a minute or so, but I didn't have a drop of coolant in the system. It also took about five pre mxed gallons if I remember.
Dave

Aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaargh!

I got a big compressor from Doc- today and fired it up. The vacuum quickly rose to 10lbs -then went right back down to 2lbs. Ahhhhh!

I went around the car and tightened all the coolant hose clamps I could reach (the from ones are out of reach with a screwdriver, but I could hear no suction from them at all). I also put a different cap on the radiator. All for naught. No vacuum - but the coolant reservoir was filling up each time I turned on the electric water pump with both caps on.

I took her out for a test run anyway because she is fun to run in and the temp went up to 215 after about 15 minutes. If I took her into a side neighborhood and drove slow, the temp went down a few degrees. I hit 55-60mph again and the temp started rising. I also took off both side covers and the air filter during the last few minutes, but nothing changed. The air filter was HOT. I couldn't hang on to it. So - back in the garage.

In the garage I can see that the coolant reservoir is completely full. I listened to the water pump before I pulled out and I could hear coolant swishing, which means air. I also heard the coolant overflow burp each time the water pump stopped. After the ride, I couldn't hear the swishing, so perhaps it had all mixed with the coolant into a nice foam.

I watched for a few minutes and could see that there are no leaks. No drips or anything. I guess the radiator cap could be letting air get by too easily. I just don't know. While the pump was going in the back, I put my ear to the from cap and heard no air noises, so I don't know. All I do know is that I can't get a friggin vacuum! Aaaaaaaaaaargh!

So, now that the rant has ended, whaddya'll think? I'm tempted to pull that "Nova" radiator to see if it is the problem.

OK, I use this type of vacuum system and something ain't right. You should be able to hold a vacuum. Try it again but take a pair of pliers and close the hose going to the overflow tank, might be sucking air in that way.
Are the hoses all collapsing flat?? Even the heater hoses?? They should be.

If none of this works after you're done and you're still overheating, we have to absolutely eliminate some things.
1. Get new caps, the right ones. They're cheap.
2. Make SURE you've got good flow through the radiator. Personally, I would take off the hoses at the engine or back of the underbody pipes (save all the coolant you can) and take a garden hose and backflush the radiator. An old waterpump could have shed some blades in the distant past and slowed down the flow. Lots of bends in the pipes.
3. I've seen hoses get soft and collapse on the suction side of the system at speed too. (Right side) Check for that.

Keep us posted and let us know what you find!!

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

quote Originally posted by cropduster: OK, I use this type of vacuum system and something ain't right. You should be able to hold a vacuum. Try it again but take a pair of pliers and close the hose going to the overflow tank, might be sucking air in that way. Are the hoses all collapsing flat?? Even the heater hoses?? They should be. If none of this works after you're done and you're still overheating, we have to absolutely eliminate some things. 1. Get new caps, the right ones. They're cheap. 2. Make SURE you've got good flow through the radiator. Personally, I would take off the hoses at the engine or back of the underbody pipes (save all the coolant you can) and take a garden hose and backflush the radiator. An old waterpump could have shed some blades in the distant past and slowed down the flow. Lots of bends in the pipes. 3. I've seen hoses get soft and collapse on the suction side of the system at speed too. (Right side) Check for that. Keep us posted and let us know what you find!!

Thanks, Cropduster. I don't have any rubber lines so there is nothing to collapse except the heater hoses. I need to get under there to see what is going on at the front end of the heater hoses. I don't know if they are connected or just blocked off.

New cap is coming soon. I should probably pull the radiator and take it to a rad shop for testing if the new caps doesn't work.

Anyone wanna buy this one for $5k? I won't shed a tear...

I'm leaning toward the head gasket thing again.
When my head gasket blew, the car would sit and idle fine. If you took it for a drive and hit the gas, the compression would leak into the water jackets, forcing coolant out of the radiator into the overflow bottle. Did I understand that yours is doing something similar?
That would also explain why you can't pull a vacuum.

A bad head gasket would be revealed in a chemical test by those symptoms. The system must hold vacuum. This must be corrected, or you will continue overheating. The good news is that it won't hold vacuum, so now we have a direction to go in to properly diagnose this problem. You could be sucking in air at a connection causing the system to get airbound. The next step would be to get a cheap cooling system pressure tester and see if you can get the system to hold 15psi. If it won't hold, you'll see coolant come out. You can also do a leakdown test in the cylinders to see about the head gasket or cracked head. With all the overheating, I wouldn't be surprised if the head gaskets pooped. The original problem may have been your water pump, but it may have damaged the head gaskets.
If the first two tests pass, it will be time to do a chemical test on the cooling system while the engine is running. This should show if the gaskets are bad.
To check the radiator for clogging. Get the engine up to operating temperature. Then feel the radiator with the palm of your hand. It should be hotter near the top, but no cool spots. Cool spots are clogs. This is very common on BMW and Mercedes, so I do this test a lot.
Dave

quote Originally posted by Raydar: ...That would also explain why you can't pull a vacuum.

Just thought about something. With the stock style Fiero radiator cap, you might not be able to pull much of a vacuum.
The radiator cap has a one-way valve to allow coolant to be sucked back in to the system out of the overflow bottle.
You'll have to pinch that hose.

quote Originally posted by Raydar: Just thought about something. With the stock style Fiero radiator cap, you might not be able to pull much of a vacuum. The radiator cap has a one-way valve to allow coolant to be sucked back in to the system out of the overflow bottle. You'll have to pinch that hose.

I had no problem pulling 25" of vacuum with the radiator cap up front. I believe I run a 22lb cap up front and a 15lb cap in the rear. I did it like this so I sealed off the front. My reservoir is in the rear.
Dave

If you think it is the radiator cap I would seal that one (hand, tape, or something) and run the test again. It shold hold the vacuum. Then you have it nailed. The need for a sealed system is to hold preasure (those 15lbs) that will rise the water boiling point from 220° to near 250°. Otherwise the coling system is compromised.

Thanks! I'll block off the front overflow hose and see what happens.

The two caps I have been using are new (one has no pressure relief valve on top), but a deeper (or higher pressure cap) cap may be first on my list!

I can also try a rubber plug to seal the front long enough to pull a vacuum and get the air out..

Sax, thinking about it...I took my Fiero out for a good ride today. I haven't driven it in a few weeks because I had to jet and sync the carbs, change out some body parts and other good stuff. Anyway, it was 90* here today and driving home after whupping a Corvette ZR1 my temp stayed at 215* and wouldn't drop. It didn't help I hit traffic and couldn't get to 5th gear at all.
With the system under proper pressure 215* may not be that bad. My wife's 2.8 runs around there and doesn't overheat...though I wish it would just blow up already. It has 210,000 on the clicker and she won't let me swap in the 3800 until "something major breaks on the Fiero requiring me to pull the engine or trans". I just can't get that clutch to let go dammit.
Anyway, I got a little nervous because my Fiero always runs at 180, but this is the hottest day I've taken her out, so being a high compression engine, 215* may just be fine and you are trying to fix something that isn't broke.
Dave

A little bit of good news! I put a carb vacuum plug on the radiator overfill fitting at the mouth of the radiator and pulled 20lbs of vacuum. Since my garage was closed, I didn't turn on the compressor because it would be too loud (and my pizza was getting cold!)

Anyway, not much of anything liquid came out while the vacuum was being pulled - it must have been all air.

I assume I still need to get that last 5lbs of vacuum to make it a success, but at least I know why there was no vacuum.

I think I still need to run a pressure check to make sure I am getting at least 15lbs of pressure when she is hot. Once I know that, I can feel better about letting the temp go above 220.

Dave, my wife's Trailblazer XT has run at 210 since the day we bought it new, so I'm interested in letting the temp go up a little like you said. I have also been wondering why people don't move the overflow to the rear since that is the highest point. It's time for an overflow tank transplant!

Holding 20" of vacuum for that time is great. Normally, I like to get to 23-25, but 20 will do.

I'm wondering about my Fiero. It has never gone over 200 before and it was a little scary. The only things that have changed are: new decklid that is more restrictive of ambient air, rejetting of carbs to make run more rich at part throttle, higher outside temperature, more aggressive on the throttle during test drive (I can do that now with the bigger tires), more traffic.
I conclude that the higher temp is expected, but not welcome. I'm going to look into a better cooling fan for the front and ride it out.
Dave
ps. I still need to rejet the main jets in my carbs...but it looks so cool blowing flames out of the tailpipes at night!

It certainly keeps the tailgaiters away!

OK - I forced water into the water pump via a water hose in the passenger side return hose (coming from the radiator) and that pushed the air out of the water pump - and boy did it start pumping water back out of the radiator inlet! That must have been why the old water pump died - too much air and the motor burned up. Anyway, when I got the radiator back on (I removed it to have it tested before I decided to try pushing the air out -stupid me!), I think I put a leak in it.

Tomorrow is the test drive, but just running the electric water pump has bubbles coming out of the radiator filler neck and I can hear water being sucked in through the bottom of the radiator. It sounds like sucking a straw when there is no liquid left in the bottom of the cup - something my kids do CONSTANTLY!

Anyway - I will report back in after the ride tomorrow. I now know the air by the pump was a flow problem, but this possible air leak in the radiator will now be the new problem. If I lose coolant while driving it tomorrow - at least I will know. I just hope the temp holds longer than 20 minutes. Getting the radiator repaired (or replaced) should be the easy part!

More to come!

I wish you good luck!

[This message has been edited by Hudini (edited 06-18-2007).]

quote Originally posted by Hudini: I wish you good luck!

I knew you would, Hudini. Thanks again for all your help!

Looks like no ride for me tonight. The wife just took off for a meeting. I just hope she gets back in time for me to go get that new compressor!!

It's almost 100 degrees out anyway, so I'm probably better off driving it out tomorrow if it doesn't rain (which, of course, is predicted )

All the while, this old beast is waiting patiently beside the purple bastard...

Saxman,


I've been following your thread with interest for some time now. My car is having the same issues as yours. Temps will rise to 220+. I'm getting my cooling system professionally purged of air this afternoon by the mechanics shop next door. I have high hopes that there is some rogue air pocket somewhere in my cooling system that is causing me all of the grief. I'm almost certain that I got it all out, though, through a combination of jacking opposing corners of the car, installation of bleeder valves, etc. Anyhow, for $80 it will eliminate air in the system as the cause for my overheating.

I'll let you know how it turns out.

Good call, Bullrider. I bet it makes all the difference. Post your results!

I just got a nice compressor tonight, so I hope to do the same once I get the system filled again.

normally when the system is airbound, you will lose heat from the dash vents while driving. The temp gauge sometimes will also fluctuate. At what temp does the car boil over?
When I get my Fiero back together next week, I'm going to run her hard then let her idle in my shop and see if she actually goes over 220. On my wife's 86SE the middle of the temp gauge is 220 and it runs there normally. She also has over 200k on her car and it may be getting a little whupped.
like I said before, my car normally ran at 190 until it started getting really hot outside. Going down the highway it will run at 180. In traffic, it will go to 200 with the fan on, but I don't lose heat and it never went higher than 220...I also didn't stick around to find out...I turned off the road to get out of traffic and it came down pretty fast.
Dave

quote Originally posted by bmwguru: normally when the system is airbound, you will lose heat from the dash vents while driving. The temp gauge sometimes will also fluctuate. At what temp does the car boil over? Dave

I know with my system, I get tons of heat from the heater, part of the reason that I'm thinking that air is not my issue here. Along with the purge, I'm going to actually remove my rad shroud in an effort to get more air flow during cruising speed (which is where my issues are arising). My homemade shroud is actually drooping from the heat coming off the rad, so I know there's a ton of heat coming off of there. The shroud is made from 1/4" thick Sintra board (plastic sheeting). Must be getting pretty damned hot under there.

If air is not the issue, I may look at removing my A/C rad, which is mounted in front of my engine rad. A/C is not plumbed in yet anyway, so I'm not losing out. If that doesn't help, I'll look at a bigger rad. Shop tells me that I'm running a two core rad right now, but that it should be sufficient for my needs. We'll see how things go. I'll let you know. Picking up the car tonight (hopefully), so I may have more info to share tomorrow.

Hey, Sax!

Got my car back from the shop yesterday (axle issues kept it through the weekend at the shop).

The cooling system was professionally purged, the proper high-grade orange coolant mixed and filled. System took about 22L to fill completely. The shop told me that there was quite a bit of crud in the lines. Everything was flushed out and cleaned prior to refill. I also removed the A/C condenser from in front of the rad.

The result....

.... she's still overheating on me.

I'm breaking down and getting the biggest rad that I can find. I also picked up some header wrap that I hope to install this week sometime. That should help the engine compartment heat quite a bit, I'd think.

I'm assuming that everyone here uses the stock Fiero coolant tubes with their conversions? No need for larger diameter tubes with the swap, is there? I wouldn't think so, as the inlet for the water pump is only something like 1" in diameter, but I thought I'd ask anyway.

I'll let you guys know what I pick up, when its installed, and how it works out.

Update on my overheating issue:

Turns out my old four core rad had some slight flow issues:


Rad guy says it was between 50% and 60% blocked off. I'm picking up the car this afternoon (driving home in the rain, too, by the looks of it :-[ ) and I'll see then what the heat is like. I might not have the opportunity for a longer drive until tomorrow morning, but I'll let you know if the problem is finally licked or not.

Stay tuned!

an easy way to tell if the radiator is partially clogged is to feel it when it is hot. You can feel cool spots around the core. I haven't checked this on mine yet, but I probably overlooked due to the radiator has less than 250 miles on it. I put it in and totaled the car a month later. Then it sat for four years while I built my current beast.
Dave

Argh!!!

New 5 core aluminum high-flow radiator is in and I'm still getting hot.

I'm going to check the plugs and see how the engine is running. Perhaps its not tuned in and I'm running way lean? Could that account for a high temp in the engine? I've got header wrap that I'm going to try to install this week. That should help the ambient air temperature around the engine, but I was really hoping that the darned thing would be at least cool enough to drive without needing to resort to the wrap. I'm also going to look at installing a larger radiator fan with integrated shroud, but that shouldn't be affecting things at highway speed, should it? At highway speed, she'll get hot fast enough that I can watch the gauge climb.

Things that have been addressed thus far:

1.) Electric water pump is flowing properly
2.) Brand new high-performance radiator installed
3.) Air dam installed under radiator
4.) System completely purged of air
5.) NOS rad additive added to system

Strangely enough, my car was running lean (sneezing from the carbs) and it wasn't running over 180 degrees. Then I rejetted the carbs idle jet and they were running rich-backfiring from the tailpipes and a few flames at the exhaust tips...and that's when I started running hot. The car is almost back together after my mishap and I should be able to provide more info to Saxman's thread later this week. I am rejetting the carbs down one step (I originally jetted up two steps) today and should have it ready for the 4th.
Andrew, How's it coming at your end. By the end of this we should be able to write a book titled "How to keep your cool with your V8 Fiero" Archie can give them out for free with his conversions. lol.
Dave

------------------

1999 Mercedes ML430, 450hp 1987 Fiero GT, 1986 Fiero SE-soon to be 3800, certified master technician
www.njautobahn.com

[This message has been edited by bmwguru (edited 07-02-2007).]

quote Originally posted by BullRider: Argh!!! New 5 core aluminum high-flow radiator is in and I'm still getting hot. I'm going to check the plugs and see how the engine is running. Perhaps its not tuned in and I'm running way lean? Could that account for a high temp in the engine? I've got header wrap that I'm going to try to install this week. That should help the ambient air temperature around the engine, but I was really hoping that the darned thing would be at least cool enough to drive without needing to resort to the wrap. I'm also going to look at installing a larger radiator fan with integrated shroud, but that shouldn't be affecting things at highway speed, should it? At highway speed, she'll get hot fast enough that I can watch the gauge climb. Things that have been addressed thus far: 1.) Electric water pump is flowing properly 2.) Brand new high-performance radiator installed 3.) Air dam installed under radiator 4.) System completely purged of air 5.) NOS rad additive added to system

I assume you checked all the return lines under the rockers to be sure nothing is crushed?

It may still be air in the pump. I really thought all the air was out of my system, but the electric pump just held air until I fFORCED it out with a water hose. I even used one of the vacuum systems to pull the air out, but it didn't do enough.

I will be back out playing with mine after the holiday (if wiccantoy doesn't buy it before then ). More to come!

any updates?
and yes, strangely enough there is at least one Fiero at my shop at all times...strange! The VAG diagnosis system is reserved for pretty women...er..I mean VW and Audi's. I'm going down to the shop today to finish up my Fiero to see if she still runs hot...I think I got it fixed.
Dave