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How to diagnose overheat cause/damage

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_Madman_

15+ Year Contributor
327
1
Oct 14, 2004
Riga, Europe
It seems I overheated my car today.

I was driving actively in a city traffic, went to a highway, started to climb on a right handed on-ramp at around 50 mph (80 kph), 2nd gear. And at the end of the ramp CEL came on. I quickly checked the gauges and the oil temp gauge was at 250F (120C) and the stock coolant temperature gauge was at the max. I quickly pulled over and stopped the car.

The ambient air temperature was around 80F (25C)

The engine was obviously hotter than usual, but that's it, no unusual signs.

After letting the car to cool down a little 230F (110C), I managed to start and stop it again (very short moment) and the sound seemed normal.

Then, after a while, I checked the overflow bottle, and upper cap of the hose, and both bottle and the hose contained no coolant. There seemed to be no leaks on the ground after standing there for a while.

The blower in the car was blowing barely warm air when I cranked it to max power/heat. Most likely because coolant wasn't there.

It's hard to say now if the car had normal coolant level during the driving, as I checked it 3 days ago, and it was around min. The coolant was also some kind of red Toyota stuff that was leaving traces near upper hose fill cap, but I have been driving with it for like 5k miles already, without topping it, so even if there were leaks, they very very small.

Now the question is, what should I do. The car has been towed over to a garage, and now I need to understand what has happened.

Right now I'm thinking to check if there is coolant at the bottom of the radiator, then, probably, to take out all spark plugs, check for coolant traces, crank few times over without plugs to see if there is no water coming out of the slots. Check the oil for bubbles or unusual residues (visually through oil cap). Read the CEL code (probably something overheat related).

If that comes out fine, then probably flush the red coolant with some other one and try to start the car.

Is this approach ok, should I check anything else? What kind of damage could have been done?

The mods of the car are listed in the profile.

Are 250F (120C) temperatures very dangerous for DSMs or is it most likely ok?
 
Check for coolant in the oil first off, just to make sure that the head/headgasket didn't go. If it wasn't hot for to long, you SHOULD be ok, I know it pulls the timing pretty bad when coolant starts getting above 206 I believe. Just check for coolant in oil, fill it up with water, and start the car, if the water starts moving/flowing then the pump is good. Wait til it gets to operating temps and see if teh thermo opens and pulls it in.
 
It was the stupid thermostat :mad:

The warnings could have been made better, like an idiot light, or something, when coolant climbs past middle. Why does the ECU has to wait till the point where engine is about to crack to throw a stupid "Engine coolant temperature sensor" code? At 250F, the heat level at which the engine head can crack and warp?

It takes around 2-3 minutes for coolant to climb from mid mark to closer to max mark! Who on earth checks their gouges THAT often?!

I added almost 3 liters of distilled water today into the system, that's almost half of the total capacity! I guess it got blown through all the hoses and caps. There are coolant signs around refill cap.

So far car seems to work ok, the oil is clean, the spark plugs are all equal, all were showing overheat condition (white electrode, white clean insulator and black sides (NGK BPR7ES)).

I took it out to a test drive and from oil temp 125F (50C) to 180F (80C) it was running all right an pulling just fine through all rev range. There were no huge clouds of white smoke as well. Then the coolant gauge started to climb above middle, and I stopped 3 times before I got back to the parking lot. The radiator was cold, the upper heat pipe hot, the lower heat pipe cold.

I will try to find an OEM thermostat tomorrow and replace it, if not, I'll just throw the thing out for now.

Are OEM thermostats ok? I know there is no point in switching the heat range on them, but what about quality?

Oh, there was a little white smoke coming out of the exhaust during the idling, but it seemed to be normal compared to another DSM and it seemed to be from condensation after the rain.
 
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