99 Civic--Overheat when idle w/AC on

My 99 Civic seems to overheat when I am at a light or parked, idling, with the AC on, it only does this in the summer months. Thermostat is new. Any ideas on
what else to check?
TIA
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snipped-for-privacy@gmail.com wrote:

Is the radiator fan working?
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On Monday, July 16, 2012 3:35:39 PM UTC-5, (unknown) wrote:

AC on, it only does this in the summer months. Thermostat is new. Any ideas on what else to check?

Radiator fan works fine, coolant levels are fine, no obstructions in radiator (new one installed about two years ago.) and no head gasket leaks. This only happens when it is hot outside 90+ and the a/c is on and i am idle.
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snipped-for-privacy@gmail.com wrote in

Just a possibility - check engine rpm when you're idling with ac on....as opposed to ac off...Could be that the engine isn't turning the water pump fast enough to circulate a sufficient volume of coolant to keep the temp down...DaveD
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On 07/17/2012 11:47 PM, Dave Dodson wrote:

that would only happen if the timing belt was broken. and then of course, the engine wouldn't run at all.
--
fact check required

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jim beam wrote:

I have a similar problem with a Subaru 2.5L. Only after the engine has run for more than half an hour and then left to idle for a short while. Temp drops once on the road again. Replaced thermostat, no real change. Radiator is full, no signs of leakage though maybe I am not looking in the right place.
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speed fan, but with AC on there should be a fan running constantly, while with AC off the fan should cycle with temperature. On the run you get enough air speed to cool without the fan on all but the hottest days so it generally doesn't overheat until you slow down.
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Double checked again, I have two fans, one not on the radiator, running the whole time, one on the radiator comes on after getting to normal operating temp. I don't know what it could be, inline cooling sensor? Since it only happens when ac is on that has to limit it to only a few things right?
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I have a 2000 Forester 2.5 that is doing that. It's been diagnosed as a problem with the A/C fan. It is sporadic, one time runs as it should then doesn't run at all and runs hot. I have to use the heater to drive normally. I have a new fan on order and hopefully that will solve it.
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snipped-for-privacy@snyder.on.ca wrote:

Both fans run and push a lot of air. It was cool last night, yet the overheat problem still present if the engine is allowed to idle long enough.
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Cyrus wrote:

Not sure about the OP who had the Civic, but the temperature of the upper and lower tanks of the radiator on my Subaru differed dramatically while the car was idling. Near 200 Fahrenheit at the top of the radiator and 95 degrees at the bottom. Measured with an IR thermometer with the engine and fans off. Yet the dash gauge showed overheating.
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{{
Water pump impeller slipping/cavitating?
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