Help me diagnose this cooling problem.

I have open tracked this Cobra for four years.

Last week I was at Mont Tremblant. I logged 251 track miles without incident. I packed up my tire trailer, and pulled it 320 miles home after the event without incident. I then commuted to and from work for the next three days...again, without incident.

Last Saturday, I was leaving a bridal shower with the mother in law in the car, just putting home... The car started, I ran for less than 10 minutes and the temp gage went steadily straight up into the hot range. I noticed it because when I tried to use the throttle, even a little bit, the car went into what I thought was limp mode. I pulled off the highway immediately to let the car cool off. There was some spray from the over flow tank, and it made some steam, but it subsided quickly. After about five minutes parked, I turned the key to "on" to see where the gage was sitting, and it was in the middle.

I waited a little longer and started the car again, this time putting on the AC to force the fans to run (just in case they wouldn't run normally). The gage stayed in the middle for a little while then slowly climbed. I shut the car off.

As it turns out the shop that does my work was only the next exit up ont he highway. So I waited a bit to see if it would cool off enough to make the ride over there.

With my wife following in her car, I drove about half way to the exit and the gage started to spike again. I immediately pulled off onto the shoulder. At this point I called AAA and got t he car towed the rest of the way. There are no leaks of any kind.

Based on the symptoms I think the items up for bids in order of expense are:

Stuck T-stat (original t-stat in car.)
Bad water pump (also original)
Cooling fan controller failure (which I doubt)
Head gasket

Educated guesses will be appreciated.

The electric fan may be dead is my first impression... seems to be happening a lot this summer.

The reservoir cap can also go bad. I have heard of this many times.

I seriously doubt it is a head gasket, but, anything is possible.

At our shop, we saw both bad fans and bad expansion tank caps this summer on the Cobras.

MaximumVelocity said:

At our shop, we saw both bad fans and bad expansion tank caps this summer on the Cobras.

Click to expand...

Ditto: Both very common, and once hot, air ingestion is not out of the question, especially if the rad resv cap seal has been compromised.

If it spewed even a little past the cap the top suface of the resv. can easily warp and continue to leak.

This makes air purging nearly impossible.

jmproductions said:

The electric fan may be dead is my first impression... seems to be happening a lot this summer.

Click to expand...

My car overheated once because the fan didn't come on. A code came up and i checked it all out but nothing was wrong. That was about 8 months ago and it hasn't happened since.:shrug:

Have any of you seen the fluid solvent test? Two chambers with blue fluid pressed over the rad cap hole, you revv the car and then suck air from the expansion tank through the fluid. The test says if the fluid turns green there is exhaust gas in the expansion tank.

Guess what? Green.

I still want the results of the leak down/compression tests, but it isn't looking good.

This happened to me. Basically had the coolant flushed made sure there's no air bubbles. Had to do this twice to get it right. Also changed the coolant cap when this happened. They tend to go bad.

Do yourself a favor and ignore the temp gauge on the dash. That thing is completely worthless. What you need to do is access the diagnostic mode on the gauge cluster you will get the precise tempature in celcius that your car is running at. DEGC is were you want to be. 87 C to 90 C is the normal range when your just cruising down the road. Once your over 100 C watch out. That's typically when your going to start spewing coolant. This will also vary based on your coolant to water ratio.

http://www.mustangworld.com/ourpics/fcar/dtcodes.htm

Once you spew coolant out of the cap you will have to add coolant to the cross over tube. Without doing this it's just going to overheat again. Even if the fan is bad you should still be able to drive at highway speeds without it overheating. As long as you maintain 60+ it typically won't overheat without a fan.

true dat. with a dead fan, you'll overheat at stoplights but temps will come down once the airflow starts moving through the radiator.

the evans thermostats tend to stick shut on me at the track, and that will cause overheating...its easy enough to remove that i remove it for open track activities.

but your exhaust gas in the coolant suggests a warped head and/or lifted head gasket.

shifting a 5,000rpm instead of 6,000rpm on the road course will help keep temps under control too.

good luck.

Problem is once you overheat the first time, whatever reason that might be even if you fix the original cause, you now have air in the system and will continue to overheat, even faster and more often than before, until you fully burp and refill through the tube.

Cooling system is a closed system. If it overheats and expands and forces coolant out somewhere, air has to enter through the same place to displace the lost coolant when it cools down and creates vacuum (usually through the cap or the location of the leak that caused the first loss).

Ok.. I thought long and hard about it, and I've come to a very definite conclusion. I, am a serious D I P S H I T....

It still doesn't all add up yet, but here's what is going on so far. All the shop did was that res headspace solvent test, no leak down or compression test have been performed as yet. The shop tech is convinced there is exhaust gasses in the coolant, but they didn't want the job to replace the gasket, so they didn't bother to continue with the dianosis.

I pre-priced a head gasket job with another shop, but I didn't want to bring the car to them until I had some time to run my own investigation. I finally got to start that investigation today. The car started fine, ran fine, idled fine.....I drove the car into the trailer, then I pulled all the plugs, and they look perfect......every one of them. I dropped a scope down each chamber and there were no signs of any debris or damage of any kind. The pistons looked very clean.

As I was working I looked over the res, the level of which was a little on the low side. I filled that with less than a quart of 50/50 mix coolant/water.....but I still noticed the hoses offered very little resistance to squeezing.

This is when I cracked open the cross over tube plug......it was BONE DRY in there. I pulled a funnel out and filled with coolant. All said and done, the car took 1.75 gallons of 50/50.

Ok...so here is where I am an asshat. I have never added coolant in the years I have had this car. I have always looked at the line on the res. The cap has puked coolant since day one at events, but I never really thought it amounted to much. I guess it adds up.

It makes perfect sense in retrospect that once coolant starts to leave that it would leave quicker and quicker as more boils in the air pockets and turns to steam.

I am still going to do a leak down, and compression tests on saturday before I do any serious driving. There is still the test result of the solvent test that has me wondering if I still have a head gasket leak. Better to be safe than sorry. I have all the tools to do the tests.

I'm very hopeful that I may have dodged a bullet....I'll post the test results and see what you guys think.

Thanks so much for the replies.

Do a compression test and a leakdown test. I work at a Ford dealership and I can tell you from personal experience that the fluid solvent test is pretty accurate.

yeah , sounds like a air bubble.......or some kind of a pressure problem...i would change the fluid and flush it really good

While your doing all this go ahead and change the coolant, thermostat, and cap. Can't hurt it. I would have to think that the head gasket (if a problem) would be a result of the overheating which was caused by another item.

It's probably not a head gasket so much as a warped head if you overheated it that often for that long and it turns out to be the problem.

Agreed on all of that. I'll be doing the compression and leak down tomorrow. I would have done it yesterday, but ran out of time.

Take the cross over tube cap off again. Place a funnel in it and use electrical tape and tape it down good. Then with just enough coolant to see in the very bottom of the funnel start the car. One this will get rid of most of the air in the system but if you rev it then you will see the exhaust getting into the coolant system. Sounds to me like you have a blown head gasket. I am going through this rite now as well. Here is what it would look like. Good luck and hope I'm wrong! Hope this helps-Shane

Thanks for the vid. I hope you're wrong too. With the solvent test results, it is still very likely it is a head gasket. I may buy a solvent tester if I can find one and do the test again myself with the system full of new coolant.

Sounds bad man...