It overheated again...

I have had a problem since I have owned the 94 Ex. The temp gauge always stays low, but when I turn the A/C on, it heats up. The gauge will read between the A and the L in normal. This only happens after about 10 or 15 minutes with the air on. It never happens with the A/C off. Otherwise, it runs fine. If I am on the freeway, I can have the A/C running and it will NOT overheat at all, no matter how long it has been.

Well, today it was about 90 degrees in Chicago (bear in mind that I was doing in-city, heavy stop and go traffic as usual), and I felt the need to run the A/C. As usual, I ran it for a while and the gauge went almost all the way up. So I turned off the A/C, and let it cool down. Then I turned on the A/C 10 minutes later again, and the gauge went back up. I get home, park the Ex, and hear a bubbling noise. I pop the hood and the overflow tank is rising its level quickly and the fluid is boiling! It was a fierce boil too! I give it a few hours to cool off, get back in it without the A/C, and the temp gauge is normal throughout the drive.

Here are the facts:

-It isn't the T-stat (I replaced it 2 months ago and it still didn't fix the problem).

There are no visible leaks, and I don't seem to be losing any fluid.

I have to drive it 400 miles this weekend and I don't want to have any problems. Any suggestions? Could I possibly have a bad antifreeze/ water mix?

Thanks!

I've been fighting my '92 all summer trying to keep the engine cool. Turns out my fan clutch was bad. An easy check is to remove the fan clutch assembly, disconnect the spring on the front and turn it 1/4 turn counterclockwise, and reinstall. This will make the fan operate like a traditional fan. If that cures your overheating problem then you need a new fan clutch. Also be sure the radiator/condensor/transmission cooler(s) are clean so air can get through.

Ok, this morning I went outside and checked the fan clutch. The engine was cold. There is no side to side movement of the fan, and it does sipin freely. I did notice that THE FAN BLADE HAS LOTS OF CRACKS AT THE BASE OF THE BLADES. Could this be the problem?

I also noticed that the antifreeze was very green. It didn't seem like there was a good water/ antifreeze mix. Could thi sbe the problem?

In my opinion, an incorrect mixture doesn't necessarily effect how effectively the coolant mixture cools. The mixture is about getting adequate freeze-up protection and raising the boiling point of the mixture. I thought I used to see at the parts stores a little gadget that could measure the antifreeze mixture. If you think your mixture is off, look into that, or just replace the antifreeze in your system.
Cracks in the fan blade are a concern in that the fan could fly apart while your going sending fan shrapnel everywhere.
The fan clutch is supposed to freewheel while the engine is cold. As fan clutches age, however, they lose top speed RPM's which effects how much air it can suck through the radiator. When a fan clutch gets too old, it can't pull enough air through the radiator and it will overheat.

After much experience dealing with 2 Ex's with very similiar problems, your problem is most likely is not enough circulation in your radiator/cooling system. The problem relates to having the fluid traveling through your radiator and using the outside air flow to cool it down. When your system is clogged the coolant doesn't get as much air exposure. Hence, why when you are traveling on the freeway, everything is fine, because the higher speed is allowing more air flow. However, when you are driving in traffic, not as much air passes over the coolant, and it starts to heat up. My advice to you would be to go a place like Jiffy Lube and have them give you a full high pressure coolant system flush. Don't use the little home kits, those really don't do jack (although they say they do). That may be enough to blow out the debris that is causing the circulation problem. You would be surprised how much debris gets in there. It that doesn't work, the clog may be severe enough that a new radiator is in order. I doubt this though since your overheating problem isn't that severe. Give the flush a try and see how it runs then. Good luck.

Your water pump could be shot also. I just replaced one on my friends 93 X for the same issue. His fins were about gone on the pump. He was basically just chopping the coolant instead of pumping it. If you don't flush and refill with new coolant every 2 years, the old coolant additives get depleated. Then the old coolant starts to munch away at the innards.

Originally posted by SWLathrop
Your water pump could be shot also. I just replaced one on my friends 93 X for the same issue. His fins were about gone on the pump. He was basically just chopping the coolant instead of pumping it. If you don't flush and refill with new coolant every 2 years, the old coolant additives get depleated. Then the old coolant starts to munch away at the innards.

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Good point. irtySanchez, how many miles are on your Ex? It may be due to change that out and while your ate it, the radiator hoses.

My advice to you would be to go a place like Jiffy Lube and have them give you a full high pressure coolant system flush. Don't use the little home kits, those really don't do jack (although they say they do). That may be enough to blow out the debris that is causing the circulation problem. You would be surprised how much debris gets in there.

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Good point! I did the intake manifold gaskets a few months ago, and I am sure I spread alot of debris around. But I have had this problem for 2 years now, so 1 may not have anything to do eith the other. This was the first time I heard it boil over though.

Good point. irtySanchez, how many miles are on your Ex? It may be due to change that out and while your ate it, the radiator hoses

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149,000 miles and still running! Well, I was going to throw a new water pump on when I did the manifold gaskets, but I was a bit lazy. My fault for not doing so. The Ex has the original water pump as far as I know. No leaking around it or any of the hoses.



Thanks for the replies! Keep them coming...

What about the radiator cap?

Similar symptoms occurred recently on my dad's 88 F150. Turned out to be a bad radiator cap. Be sure to fill the radiator itself back up, and then the overflow tank to the cold fill line. I did this, and it's been running nice and cool since then. Cheap fix, too!