Hey guys, i have a question, i have been having a issue with my engine since i had the car, and I'm really trying to tackle it because i don't like driving the car like this. The engine is a 305 TPI and Here's the deal, the car overheats while Im accelerating, but when i slow down or stop accelerating the temperature hand USUALLY goes back down but when it does go up sometimes it gets really close to the redzone...... One thing I do notice about the car is that when its overheating and I turn the heat on in the car it usually will go back down(Cant keep doing that its getting warm down here in St. Louis MO)

Here are the things that i know is not the problem:

I replaced the water pump

I replaced the radiator

I replaced the thermostat

I don't think its the head gaskets because there is no white smoke coming from tailpipes

There is no antifreeze in the oil.....

So my next question is what else to check.... I know i need to get a new air dam because mine is missing, and i read that on the board that the air dam could cause overheating but besides that what else is there could possibly cause the car to overheat while driving and go back down when i slow down and/or when the heat is on, i want to check every possible thing that could possibly be causing this.......

 

Definitely air dam - cars will run hot and overheat on highway without one.

Do the fans come on? If not, look into that. Do you have single or dual fans?

Is it boiling over, or is the gauge just reading hot? These gauges are far from accurate. If it's not boiling over, then it's not overheating.

 

Rad fans only provide air flow across the rad at slow speeds. Usually below 30 mph. Faster than that and the vehicle is moving fast enough that there's enough air flow to keep it cool. If you don't have the proper ducting to force air across the rad, it will likely run too hot.

If you have electric fans, wire them up so you can turn them on at any time then go for a drive again. If they're on while driving and the engine doesn't overheat, you can assume it's a frontal air flow problem.

 

Maybe your radiator is air locked? Let it get a little hot and shut it off and run your hand across the radiator to feel for cold patches.

 

yea i keep hearing about the air dam i just need to find one but alot of my friends have f-bodies with out air dams and there cars dont run hot thats why i think it might be something else

Yes the fans come on right when it gets to halfway on the temp gauge, im not sure if there single or dual, i know its one big fan right in front of the radiator, but it does come on, i believe at 220, not sure tho, but its not just the gauge because when i pop the hood when is overheating and grab the radiator hose its really tight and you cant squeeze it like you can when the temp is normal, and what exactly do you mean by boiling over, are you referring to the coolant in the overflow tank because no that is not boiling over


Well i know i dont have electric fans on the car, but how do i tell if i dont have the proper ducting??? Im not sure of anything about the radiator because i dont know where it came from, my stepfather is a mechanic and he bought it from some warehouse where he gets all his parts and also could you suggest a good radiator, what kind do you have on your f-body???



ok ill do that, soon as i get off work today, so what is air locked?? and if it is air locked what do I do to fix it???


also guys can anybody explain why it seems to go down when I turn the heat on in the car, that has to be some connection to that some kind of way......

 

It can get an air pocket in the radiator that causes it to "hiccup". I've never known the proper way to fix it but what works for me is when its hot (this is going to sound very dumb of me) I crack the radiator cap about 1/3 of a turn and let it all bubble back through the reservoir.

 

Sounds to me like everything is working normally then. 220 is not too hot, neither is 230. These cars were designed to run warm, part of GM's attempt at better emissions numbers. I'd find an air dam and install ... "friends don't let friends drive hot".

1 big fan is a single fan, 2 smaller fans are dual fans.

If you would like it cooler, swap for a lower temp fan switch. Fan switch is in pass side head, between #6 & #8 spark plug. Has a single wire connector that looks like a mushroom shape. Careful, there is another sensor (knock sensor) just below in the block that looks the same - make sure you take out the switch in the head not in the block. If you do a search for "fan switch alternatives" you'll see a thread listing all the available fan switch part numbers and their temp ratings.

 

It depends what rad is currently in your car. Maybe you have a V6 rad and need a V8 rad.

I use a tiny rad from a Pontiac Firefly and I rarely turn on the fan. Running alcohol as a fuel doesn't create a lot of heat and my car isn't street legal so it doesn't get driven enough to need a huge cooling system.

 

I've been having the same issue as you and here is what I have discovered. INSTALL AN AIR DAM lol. Also you can put a 180* thermostat in to replace the stock 195*, and like they are saying before install a switch for the fan to make it turn on earlier. Stock fans kick on around 238* so if you turn your AC switch to one without turning the AC fan on. The radiator fan will kick on and stay on, it will cool your car down as you drive it until you can get an air dam.

Also, the temp gauge in my car is about 20*-25* off reading to high. I also thought my car was over heating, one thing you can do to test your temp gauge is to run the car until it reaches 220* on the temp. Then use a non contact/infrared thermometer and take the temp of your thermostat housing. That will give you an accurate reading on how hot the car is running VS what your temp gauge is telling you.

I'm not sure if this one will work or not on your car, but maybe they have the right one you need on the site somewhere:

http://thirdgenranch.com/-strse-958/...air/Detail.bok

Good luck!

 

220 is just when the fan usually comes on, but the temp usually goes way beyond that, like i said it usually gets really close to the red until, i slow down, or turn the heat on or both, but im going to find a air dam and see if that helps since everybody on the boards suggest it

 

I really appreciate all the help guys, Im really trying to get this problem resolved because its holding me back, I have a freshly built 355 and i have the HSR that I bought off a fellow TGO member, and i wanted to drop it in my T/A by April, but I feel that what ever is causing the overheating is unrelated to my current engine(headgaskets etc) so I dont want to put my 355 HSR in and burn it up...... I am definitely going to find a air dam and put that on asap hopefully in the next couple of days, but besides that, is there any other suggestions that you guys can give me, because Im really exhausted trying to solve this mystery, ive even took it to a couple of shops(Firestone, Midas) and they couldn't figure it out...... Please Help!!!!

 

My plow truck has the same issue lately. Under normal driving conditions it runs hot, it can idle all day though. Just changed thermostat, waterpump, and radiator. All I can think of now is the belt is slipping on the mechanical fan when its under load.

 

The very first thing to check when everything that normally goes wrong isn't........... check to see if your electric cooling fan has been wired to run the wrong direction!!!!

 

I don't see why you still seem to fight the idea that all of your problems are the result of not having an air dam. You said it all yourself, the car overheats until you slow down or let it idle. The air dam is a VERY important part of your cars cooling system when your above 30mph. Now you said you will be looking for one, so once you find one and install it I bet your issues go away. I would be focusing on that, I know it seems silly that the idea of a piece of plastic hanging from the bottom of your bumper is going to cool your car off. But it is! I feel this is 100% your issue is not having that. Because I have gone through the exact same process you have. I have replaced EVERYTHING in my car that has to do with cooling. And I'm still over heating going down the road because I don't have an air dam. So I have one on it's way right now, and I know for a fact it will fix my issues. So just find yours, install it and I bet you will find it was the main issue this whole time. Good luck!

 

1991 Camaro RS v6 cooling fan (single fan model) won’t come on and car overheats

My perception of what should take place:

1. Start car
2. Engine runs in ‘open loop’ based on pre-programmed ECU prom chip values until reaching operating temperature of 195 degrees at which point thermostat mechanically opens.
3. After thermostat opens the coolant temperature sensor in manifold triggers ECU to switch to ‘closed loop’ at which point sensor values are read and ECU makes necessary adjustments.
4. At 220 degrees (max operating temp) coolant temperature sensor mounted in manifold triggers ECU to switch on electric fan via fan relay and fan switch to cool engine down.

Problem:

1. Car starts, car stationary.
2. Engine runs in ‘open loop’ based on pre-programmed ECU values until reaching operating temperature of 195 degree thermostat.
3. At 195 degrees mechanical thermostat opens (assumed) and coolant temperature sensor in manifold triggers ECU to switch to ‘closed loop’ at which point sensor values are read and ECU makes necessary adjustments (you can hear the idle adjustment at this point).
4. Car continues past 220 degree limit to full gauge and overheats due to fan not turning on (single fan model).
5. Connecting an obd reader (no codes) with car stationary and not running cause’s fan to run showing that fan circuitry is functional. Assuming that the only thing potentially bad would be the coolant temperature sensor mounted in the manifold it was replaced but that didn’t fix it. Am I looking at a bad sensor from the parts store or is there something I’m missing?

Related parts replaced:

Radiator
Water pump
Coolant temperature sensor
Thermostat (some time ago)
unibelt

Since the fan runs when the obd reader is connected that must be activating the fan relay mounted on the firewall showing it’s functional. It is also testing the circuitry to the fan as well as the fan switch and motor showing those are functional. The gauge in the car is functioning and a thermostat problem shouldn’t be an issue as the car isn’t running when the fan works with the obd reader connected. The only thing I can think of is the coolant temperature sensor is still malfunctioning by not telling the ecu the correct temperature when the car is running hence the fan is not being activated. Does anyone know if I can connect the OBD reader when the engines running to see if the fan comes on? If not I will run a wire from the motor to a switch in the car for now to activate it manually until I figure it out (turning on the ac does not activate the fan either but I’m not sure if the ac is functional. Any info is greatly appreciated. Thanks in advance.

note- oxygen sensor was replaced prior to this problem by another party, could that be an issue?

 

I agree. Wether it winds up being the problem or not, you know you dont have one and you know these cars are supposed to have one. In my opinion, there is no reason to try anything else before you get the air dam on.

 

Ok guys I went ahead and ordered a air dam off ebay for 70 bucks, I really hope this resolves my issue!!, ill post back once I get it on

 

I didn't see this in this thread, and I could have missed it, but you can ground the green wire that comes from your fan switch on the block to your relay. Connect the ground wire to a toggle switch, and place it under the steering wheel. I have done this to both of my camaros, and it works great. I keep the fan on when in traffic, or when I am idling so it doesn't go over 180 degrees. A cool engine is a happy engine.

 

Ok so I put the air dam on today,I only put the middle piece on because I didn't know how to put the small pieces on the sides and I must say PROBLEM SOLVED!!! I did approx. 60 to 80mph up the freeway and 80mph back home and the temp hand stayed between 100 and 220 nearly the whole time... I Never thought a piece of plastic would cool the car off that much.... THANKS GUYS!!!

 

The small pieces on the sides???? The air dam I am familiar with is one piece.

 

From my understanding some of the3rd gen firebirds and Trans Am's had a 3 piece air dam one long piece the one you are probably referring too and two smaller pieces that go on the sides of the long piece..... I honestly have no idea how to put thrse side pieces on

 

Right; the Birds in some years and/or models came with the 3-pc deal.

The end pieces aren't real big and probably don't make a whole lot of difference though. The middle one is the main thing.

I doubt it matters which type you use on any given car.

 

Ohh. I am here to learn. Is the one middle piece the same as the one air dam on my camaros? Cause if it is, It should yield the same effect.

 

No, not quite the same; but fairly similar.