Howdy PFF! It's been a while since I posted but I just got my Fiero running again after being down for about 2 years. I've had a bunch of work done to get her back in shape, but I'm still having a problem with overheating, only on the freeway though. I had the radiator and heater replaced since they were both leaking and I've had the radiator fan replaced since it was really old.

Now, the question I have is this: Is a Fiero supposed to have an air dam to help direct air onto the radiator? Mine does not and a mechanic friend suggested that it was overheating on the freeway because the air is all going under the car without a dam. It does ok at alower speeds because the fan can pull the air through. Does this sound correct? As far as I know it has never had an air dam since I've owned it. It makes sense that that could be the problem since the radiator is angled in such a way as to direct the air under the car.

Anyway, any assistance on this would be appreciated as my roommate is currently driving it to get to work and a non working car makes his half of the rent hard to come by

-Randy

Well.... given that it's just on the freeway, I'd guess insufficient coolant flow. Maybe a dented pipe or failing water pump.

Aero noses (Formula, GT, Indy, SE) have vertical black air dam, but it's in front of the radiator intake so it wouldn't help much. Some air comes in from the front of the nose, but I believe the rads are angled so as to function mostly as a bottom breather. A hood vent helps enormously with downforce and can help vent more air through the radiator as well. However, the stock Fiero cooling system is well more than adequate for the stock engine... if everything is working right.

Is your thermostat seated and working properly? I assume your rad fan works since you replaced it. Test by turning on the AC on max if you have it... it should kick the fan on. Is the rad temperature switch functioning? It's separate from the ECM's temp sensor and the dash's temperature sender. Check coolant pipes for any dents? I hope it's not a failing water pump that's not keeping up with the demand.

How is it overheating? Gauge reads high, dummy light comes on? The gauge gets a signal from one sensor, but IIRC the dummy light reads from the ECM's temp sensor?

If it's just the gauge, they're notorious for being inaccurate due to pegging when you start the engine. There is a wiring fix for this. Once that is done, you can calibrate and test your temp guage using the correct resistors on the temp sender.

[This message has been edited by FieroGT42 (edited 06-13-2007).]

If it has an aero nose I believe you must have the air dam. There have been post from others that have had the same problem occur at high speeds if the dam is missing.

I believe at high speeds it causes a air bubble to build on the front edge of the dam forcing air thru the rad. Without it the air starts to slip under the car actually pulling the air away from the rad. causing a neg. pressure.

[This message has been edited by Dodgerunner (edited 06-13-2007).]

I'm sorry, I should have included more information. Yes, I have an aero nose but I'm pretty sure I don't have the air dam as I can see the radiator through the hole in the nose. I'm pretty sure it wouldn't be visible if the dam was there but I can't check right now as I'm not near the car.

The thermostat is in and is brand new and tested (I made sure it opened properly at the right temp by heating it in a pot of water). Radiator fan is working ok when the car is sitting there so I assume it's ok on the freeway as well, although I haven't driven around with the hood removed to check When it overheats it is the temp gauge that reads high. It usually reads just below 220 when idling or puttering around town. On the freeway it will be ok for a few minutes but then slowly start to creep towards 260. I haven't seen the temp light come on, but that is because I pull over once it gets close to 260 and then it starts cooling down. I thought it might be the water pump but since it cools down pretty quickly when not moving I'm pretty sure it's not that. I guess it's possible though so I'll have to check on it. The coolant pipes are in pretty good shape although they are slightly dented on both sides due to a numbskull at Firestone using the wrong lift, even after I told him to be careful of the pipes. They aren't dented very badly though, at least not so badly that I would think it would cause that much of a problem. I could be wrong though as I don't know how badly they would have to be dented before causing issues.

BTW, when I say freeway speeds I mean around 75mph or so. It seems to be fine so long as I go 60 or less. It's only over that where the temp starts to creep up.

-Randy

Yes you can see the rad. looking thru the nose. The air dam is a chin dam that hangs right under the rear edge of the rad. going across the width of the car. Should be about three inches wide.
There should also be fillers on each side of the rad. running from the rad to the nose to close up the sides.
From the rad. face to the ground should be wide open.

Yes, you need an air dam. Without it, there's nothing to force the air through the radiator. At lower speeds, the fan performs this function, but at highway speeds, the air dam is needed to do it.

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1986 Fiero GT
1997 Camaro SS #2703
2005 Honda 600RR
2001 GMC 2500HD
2004 Cavalier

Ok, so the dam actually is connected to the radiator, not the nose. I'll have to check on it after my roommate gets home with the car, but I'm pretty sure it's not there anymore. I'm almost certain that the fillers aren't there anymore. Looks like I may be making a junkyard run this weekend

-Randy

[This message has been edited by debug (edited 06-13-2007).]

This is one of the same problems I was having. I have the 2.8 with aero nose. I would do fine around town but the temp would climb on the highway. My aero nose has been hit three times at least and it is kinda droopy. I thought it may be blocking some of the air. I got under the front and used zip-ties to pull the openings wider and to angle the air dam towards the front so it would perform more like a scoop.

All that work didn't do a single thing to help cool the car. In my efforts to correct this problem, I replaced the thermostat several times, replaced the radiator, replaced the water pump, and came up with a pretty good coolant burping procedure. I don't know which of these things finally did the trick but my temps are back under control.

I hate to say it but I think that air in the system was my biggest problem. I spent all that time and money to fix a problem that should have been fixed for free. I can post my burping procedure or e-mail it to you if you want it.

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Boostdreamer
Admin for Fiero Pilots group on Flickr.com
1987 SE Daily Driver
1986 SE parts car

quote Originally posted by Dodgerunner: If it has an aero nose I believe you must have the air dam.

I agree because I'm one of those people that had the overheating problem with no stock Fiero air dam.

Lengthwise (from one side of the car to the other), the stock Fiero air dam has essentially the same shape and curved ends as the REARMOST section of the aero nose's bottommost surface.

After it's reinstalled, the stock air dam is adjacent to and hangs below that rearmost section of the aero nose's bottommost surface by about 1-1/4," at least at the sides, where I just measured it. (I didn't measure the air dam's installed depth at its center, just at its sides.)

OK picture worth a 1000 w's
Went out and took a couple pics of my latest restorer.

your radiator is clogged, dirty/coated, green/corroded, or, just plain old shot.
the motor creates ALOT more heat at sustained freeway driving.

He has a new radiator. the pic is of DR's latest project.
you should have an air dam there to help the flow, but that symptom is also the same if you have a bad water pump. they cannot handle the sustained higher flow, expecially if it is one of those pieces of junk pumps with the plastic impeller. I have the air dam and it would overheat on the highway (pre rebuild). around town it was managable with the fan and the lower load, but it would still occasionally overheat, and it got worse as time went on.

I had to enhance these photo's alot to show the air dam, here's a couple more pics, from front and side. You should be able to fab one up fairly easily. most home centers sell a semi soft flexible moulding for commercial edges, comes in 6' lengths, differrent colors , it has a curved out edge at the bottom, about 5inches high, you see it used in most offices where the floor meets the wall. you can trim it down and attach it with some small brackets, and should suffice and last a while...

quote Originally posted by tjm4fun: He has a new radiator. the pic is of DR's latest project.

ah - went and re-read.....yup
maybe a clog/kink in the coolant pipes.
I have had a radiator get clogged by them white fuzzies that float around - could just need a hosing off.
or perhaps thermostat not opening fully.
I doubt its the plastic water pump impeller or the air damn.

If my "1st generation nosed" 1986 Fiero has half of the air dam missing (busted off by previous owner?) Should that be replaced? I have a clean coolant system and new 195 degree stat, on my guage the needle goes up to 220 then back down to 1/4 guage, and repeats, so it seems to run a little warmer than it should but not bad. The air dam on this car is much bigger than the Aero nose dam in your pics.

quote Originally posted by 2.5: If my "1st generation nosed" 1986 Fiero has half of the air dam missing (busted off by previous owner?) Should that be replaced? I have a clean coolant system and new 195 degree stat, on my guage the needle goes up to 220 then back down to 1/4 guage, and repeats, so it seems to run a little warmer than it should but not bad. The air dam on this car is much bigger than the Aero nose dam in your pics.

I would guess your fan is a bit slow about kicking on. maybe, take the switch out, and clean it off - might have a nice crusty build-up. or, just replace.

This would be on a 55 mph rd where I should need no fan. The fan shoudl only be for sitting still right? Wouldn't the fan kick on at about 220 anyway? Thanks for replying

quote Originally posted by 2.5: This would be on a 55 mph rd where I should need no fan. The fan shoudl only be for sitting still right? Wouldn't the fan kick on at about 220 anyway? Thanks for replying

yup - you are correct. I was assuming stop & go traffic. you be slightly low on coolant, and the heat surge is when the air bubble is in the T-stat housing, and then it cools, when the air bubble is pushed by.

Thanks, I changed it recently. So I should run it until (what temp would the bubble get there but stat not open at?) and then let it cool and open the cap, pop out stat, add some and put back in?

Just normal running should cause air to collect under the stat cap due to the distance from the out pipe to the cap.
You might try parking with the nose down to see if you can get more to collect at the stat.
Have you checked the stat cap often to see if there is air there often?

Well, long story I haven't driven it in 2 weeks because I'm waiting on a clutch master from monsterparts. I will though, thanks again.