Hey PPPL, How hard is it to change a water pump on a 94 corolla. Well first of all.. Why would a good running corolla over heatonly at freeway speeds? Sitting in the driveway with the AC on its perfect.... But when i take it out on the freeway it overheats? I changed the thermostat yesterday and i thought that would do it but nopoe! Any advise would be appreciated. dean..
Are you certain that you installed the thermostat correctly? If it's in backwards it won't work as designed.
Probably need a new radiator if the stat is ok. I wouldn't let it overheat any more. It is possible maybe the pump impeller is corroded away, but I'd be leaning radiator if it's ok at idle for extended periods of time. I don't know if the timing belt is with the pump on that engine, but if you do have to go into a timing case to get to the pump, you might as well change the timing belt also, unless it's fairly new. You don't want to have to do all that mess twice. There is an oil seal too probably.. But.. I almost bet your radiator is clogged up and toast.. MK
Your problem is with coolant flow rate. Something is restricting the flow, could be a plugged up radiator, a bad hose that's collapsing when the pump is running fast or you installed the thermostat backwards/upside down. Most likely it isn't the thermostat installation, you already had the problem when you changed that.
If the problem happened all at once, change out your hoses and see if that fixes it. If it developed gradually, look to your radiator. Take it to a good radiator shop and have them check it out. Don't try those do-it-yourself radiator flushes.
Jack
Also check base ignition timing to make sure it is not too advanced.
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