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Discussion Starter #1
I had never had an overheating problem until this past 4th of July weekend. I was in stop and go traffic on the highway on a very hot day. Engine temp gauge was all the way on hot. Pulled off immediately and let the engine cool for a while. No leaks or anything, no steaming, etc. The radiator ended up taking a fairly good amount of coolant. Maybe a couple pints. Got back on the road and all was well.

A few days ago the same thing happened. Again, the radiator took some coolant. This time not quite as much as before. Hit the road and all was well.

I have never seen my car leak coolant. I brought it to a shop and a pressure check and engine block check did not reveal a problem. They simply could not get the car to exhibit symptoms, but of course it wasn't a hot day and the car was in a garage as opposed to a highway surrounded by other hot cars.

No matter how I look at it, this seems like a puzzle because of conflicting symptoms, etc. Here are some thoughts:

- When I start the car and idle, the fan comes on. So that suggests proper fan operation. Or could it be that in really hot situations it doesn't come on? Under what circumstances would a fan work in hot conditions but not really hot conditions?

- Thermostat - if it got stuck then surely that would send the temp way up, but why would a thermostat work fine in every situation except stop and go traffic in hot weather?

- Water pump - I know inefficient pumping could cause problems but why would the problems just occur in the stop and go hot weather scenario?

Regrdless of any of the above, it doesn't explain why my car is leaking coolant. I was hoping maybe it was a bad radiator cap, but the shop said it is fine. That would have explained coolant loss without seeing evidence.

Also, would a loss of a pint or two really cause the temp gauge to redline?

I also wonder about bad sensors. Maybe a temp gauge that is just giving an incorrect reading? Or a bad coolant temp sensor? Where are these located?But regardless of those options, why would the topping off of coolant had resulted in the gauge going back to the middle and the overheat problem going away? And still doesn't exaplain why coolant is leaking...

So then I have to think that the shop's tests were flawed due to the fact that they did not have the engine running as hot as it was during my overheat moments.

What do you guys think? I am about to drive cross country, coast to coast. Would really like to figure this out...

thanks,

brian
 

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What year is your car? Does it have distributor cap & rotor? Is the timing adjustable? If yes, check the timing. It might be too advance, which lead to overheating. And try to change the thermostat, i think it's the best way to start diagnosing your car. Because you said " no leaks found when they pressure test your cooling system". The same as block test, came out negative.
Your thinking also bad sensor. Further diagnosis using better scanner so we can see Datastream for Engine coolant Temperature(ECT) sensor. But try to change the thermostat. It's not that expensive :)
 

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Discussion Starter #4
Turns out there is a leaking head gasket... The car wouldn't start last week and so I brought it to a place and they confirmed there is leak into 4th cylinder. What replacement part should I get? I see these Ishino Head Gasket sets that claim to be OEM but I am skeptical.

thanks,

brian
 
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