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Overheating


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Sis-n-law is down from N. Ga, her 92 LE is overheating. Idles at normal temp, but after driving 20 or so minutes the temp starts to rise, putting it in neutral and reving drops it back to normal, so does turning on the heater. Her boyfriend diagnosed it from 400 miles away as a bad thermostat, which she bought, and I installed to no avail. I could stop the fan so I thought it needed a clutch, still to no avail. No coolant in oil, or oil in coolant, no visible leaks, no steam from exhaust, radiator looks nice and clean, swithed caps with my Q. Trying to burp the system, the metal tube was stopped up with crud, I cleared it. Ive been jacking up the front and clamped on a clear hose and routed it into a jug with water. While running (w/heater on), I rev it and get air bubbles when I let off, and it takes water from the jug. Radiator and purge tank maintain correct levels. I've done this 3 times. Am I missing something, or am I about to be forced to change the water valve (rear thermostat)? I'd really, really hate to do that if I can help it.

 

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Do the bubbles ever stop or only when you let off the throttle? That is a sign of exhaust gas or compression in the coolant. I would do a block test (parts stores rent these) before buying any more parts. Just to be sure.

 

The radiators are also known to get full of scale on these. My dads would get hot driving at speed or with a load (or the air con). The shop replaced half the cooling system before the radiator, but that was it.

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The radiator looks clean. Bubbles come up when decelerating. She drove it today and it did seem to take longer before temp rose. I'll burp it again in the morning, and I guess go get a tester and see if it will hold pressure.

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I got the water valve replaced, fuel injection back on, some rain and the day running out I quit for today, I'll finish putting intake back on in the morning. If that doesn't do it the only thing left is a radiator or waterpump.

Sucks to have to do all this when I could be working on mine.

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I got the water valve replaced, fuel injection back on, some rain and the day running out I quit for today, I'll finish putting intake back on in the morning. If that doesn't do it the only thing left is a radiator or waterpump.

Sucks to have to do all this when I could be working on mine. So while we waited on a radiator to arive I went ahead and flushed the coolant system. Didn't remedy the problem, but the new radiator did!

Thanks for the help!

The way I see it, everything else was prevented maintenance, to include power valve screws, pcv, and cleaned the maf & TB.

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