WHY is my Cobra overheating????

Ok long story short here....
Flushed the system twice, replaced stat, refilled and burped properly. Ran car for thirty minutes at IDLE with the heat and A/C on. Left vent cap slightly open the whole time and the car never went above half on the temp gauge. Got it the car and drove it for about two minutes and temp starting climbing again all the way to almost limp mode.

However, I did notice that between half and "H" on my gauge I was noticeably losing power, as if my boost wasn't even adding any power to the engine. Another note is that I only filled the system with approximately 8 or 9 quarts of coolant/water, and correct me if I'm wrong but don't our cars take at least 15 quarts? I stopped filling because it was overflowing from the overflow. I was filling from the vent cap on the drivers side coolant tube to the head. ANY ideas would be appreciated. I also had code P1506 Idle Air Overspeed but I don't think that is causing my current debacle. This crap is enough to piss off the Good Humor man and it's really pissing me off so please help guys!!! Thanks in advance!

I had them vacume mine and then it just sucked the coolant back in, I have not had a single problem other than a bit of run off from them putting a bit to much in the coolant overflow tank.

You mean the dealer? And by vacuum you mean creating a vacuum on the system to draw the coolant in?

How bad has it over heated in the past?? Did the temp guage ever run up into the red?

Mine was overheating... mostly I would notice it would leak out the fill cap a bit at a time... and it was worse when I got into the boost, and when it was cold.

I ended up having a warped head and I was told it was because it had overheated really badly one time. I pulled the engine, milled the heads, rebuilt them too.... $3000 later it runs like a scalded dog!

whiteboyz yeah the dealership or other service shop with an expensive vacuum fluid exchanger does it completely through the resevoir cap and it is thorough. but you can do it yourself

it sounds like you did it right by filling at the crossover tube

yes the system takes 16.1 quarts (4 gallons)

but unless you do ALOT of work you are only gonna get about half that to drain

so it sounds right that it would only take 8 quarts when you refilled it

the key is to full at the resevior to the add coolant line or slightly above, then cap that and continue to add at the crossover tube until all the way full.

cap the crossover tube and you should be fine barring any damage such as stuck t-stat or head/head gasket.

I had this issue too. I had a froze thermostat. Replaced it and problem fixed. Then that one froze up about 3 months later and the car ran VERY hot. Warped a head, blew a gasket and $5k ( got new heads) later it runs great and haven't had a problem since. But by the way you are discribing it, it sounds like what happend to my car the 2nd time. Air is entering the coolant from one of the cylinders. Sp? But I hope that its just the t-stat or a clogged radiator.

black_on_black said:

I had this issue too. I had a froze thermostat. Replaced it and problem fixed. Then that one froze up about 3 months later and the car ran VERY hot. Warped a head, blew a gasket and $5k ( got new heads) later it runs great and haven't had a problem since. But by the way you are discribing it, it sounds like what happend to my car the 2nd time. Air is entering the coolant from one of the cylinders. Sp? But I hope that its just the t-stat or a clogged radiator.

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Ditto. Had the same thing. Replaced T-Stat and no problems since.

It doesn't sound that the car was properly burped. There are constantly guys on here posting lately about overheating after refilling the system and then you come to find out that after filling they did 1-2 heat cycles and called her burped. Then went out and took her for a drive and were shocked it started to overheat. And thats simply because there is definitely air in the system. Its very rare to burp her in one day and you can easily find yourself doing it up to 3 days. You should be allowing 4 hrs in between heat cycling sessions unless you are burping the car with a funnel in the crossover tube. It would have to be rare to have a new t-stat going in that wasn't working properly. But it could happen. Without the vacuum system that Ford uses, its just very hard to properly burp her after 1-2 heat cycles. Especially if you have an air bubble in your heater core or even the block. You just never know. Go back to burping her.

What stat does did you put in? does it have holes in it or one of the emergency bypass holes? If so you didn't burp it enough or correcty.

remove both crossover plug, and rad cap.

Fill coolant tank to fill line and put on the cap.

Continue filling from crossover tube until full.

Put in crossover plug gently and start the car so you dont get a gyser.

Remove crossover plug and top it off. Let it get warm and when coolant rises, replace the plug so there is NO AIR.

I put a Motorcraft 180 degree stat in. Filled the system from the crossover tube until the overflow tank got full. I'll try capping the system and filling the rest from the crossover tube like you all suggested. I'll also call the dealerships around here and see if they have a vacuum system just in case. I'm really hoping it's as simple as air still in the system and not a warped head. So was I correct in driving the car moderately with the vent cap not tightened all the way to allow more air to escape, but tight enough not to allow coolant to get out? I appreciate all the help guys!

Your radiator is not flowing properly. If the car idles without overheating and it does when driving, thats the problem. The motor in my car had to be replace due the same problem back at 14K miles. The Ford dealer didn't figure it out and tried all the stuff you have and it didn't fix the problem. Replace the Radiator and your problem will be solved.

I replaced my radiator at the same time as my t-stat cause I thought the same thing. When it wouldn't stop I had a test done on the degass tank and there was exhaust in my coolant. He gasket was gone and when I got into the motor the head was warped.

I sure hope this isn't your problem though

black_on_black said:

I replaced my radiator at the same time as my t-stat cause I thought the same thing. When it wouldn't stop I had a test done on the degass tank and there was exhaust in my coolant. He gasket was gone and when I got into the motor the head was warped.

I sure hope this isn't your problem though

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Not trying to hijack the thread, but was your Cobra modded when you developed the HG issue? You do any high speed runs above 120mph?

no big mods. CAI, and exhaust. And I had done 140 before. ONCE. But I was kinda scared at that point. I had heard about a lot of death stories about high speed runs so I stayed away from anything over 140.

It's air...

It usually takes several heat cycles to get it filled and all the air out. Unless you use the vacuum fill tool.

Repeat your fill -- heat--- cool--- fill--- repeat on an angled driveway if possible nose up .... several times. Don't check or try to refill at the burp plug unless the motor is cool. Coolant expands when it is hot... you want to top it when it's cool so there is room.

It is possible to do catastophic damage it's also but pretty rare...

Syracuse Native here..... now happily relocated to the land of all year long open track events!!!

Though I do miss the Ice Racing!!:rockon:


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not that it really matters but im an hvac tech and odds are its not the t-stat, I am 99% sure it has to be purged more as stated above

Jimmysidecarr said:

It's air...

It usually takes several heat cycles to get it filled and all the air out. Unless you use the vacuum fill tool.

Repeat your fill -- heat--- cool--- fill--- repeat on an angled driveway if possible nose up .... several times. Don't check or try to refill at the burp plug unless the motor is cool. Coolant expands when it is hot... you want to top it when it's cool so there is room.

It is possible to do catastophic damage it's also but pretty rare...

Syracuse Native here..... now happily relocated to the land of all year long open track events!!!

Though I do miss the Ice Racing!!:rockon:


..

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Nice to see another 'Cuse native bud!! Update on the problem. I did in fact park the car on an incline for a few days, filled more water/coolant in to it and then let her warm up again and took it for a spin. Never went above half on the temp gauge. Now here is the part that gets me......I let it sit for about a half hour when I went inside, came back out and drove it again and it immediately got to half and then started going above normal AGAIN. By my calculations I only have 15 quarts of coolant mix in the system, however with my overflow cap on tight coolant is still leaking out after the car has warmed up and been driven, and my radiator hoses are scalding hot. Now what? Still air? Burp it some more and give it more time? Drain and refill again?

don't rely on the gauge, it is not nearly accurate

use the odometer readout to keep an eye on the temp while you are having this problem

shut down if it starts going above 108

if you really filled it correctly and this problem persists you must start looking at why - ie damage to head gasket, stuck t-stat, inoperative cooling fan, etc

Hmmm. Warped head may be my problem as well. I too have the over heating problem. I am also now burning a lot more oil and I also smell radiator fluid out of the exhaust (with lots of bluish/grey smoke) upon startup after the car has sat for a little while. I'm also getting some smoke coming out of what appears to be between the head and engine block on each side of the engine.

Question, can these heads be removed while in the car? I seem to remember reading that it's very difficult if near impossible. I don't want to pull the damn motor again.

DanTheCobraMan said:

Hmmm. Warped head may be my problem as well. I too have the over heating problem. I am also now burning a lot more oil and I also smell radiator fluid out of the exhaust (with lots of bluish/grey smoke) upon startup after the car has sat for a little while. I'm also getting some smoke coming out of what appears to be between the head and engine block on each side of the engine.

Question, can these heads be removed while in the car? I seem to remember reading that it's very difficult if near impossible. I don't want to pull the damn motor again.

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I've read a few posts in the past where guys were able to get the driver side head out after removing the brake boost. But even then, the heads are pretty damn heavy to take out at that angle. But the posters indicated that they were able to get the head out. The passenger head appeared to be a lot easier because there really isn't much obstructing it.

Sorry to hear about your motor. It sure sounds like it has every imaginable thing that could go wrong, going wrong at the same time.