Norm. then HOT

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  #1  
Old 06-07-03, 04:36 AM
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Question Norm. then HOT

I have an 88 Nisson Max. front wheel drive with about 195000.00 miles. The problem is that when I drive down the road in hot weather the temp. is norm. When I turn on the A/C and drive for a few more miles the temp. starts to get real HOT. If I turn off the A/C and drive futher the temp. starts to come down.
Any ideas????????

Don
 
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Old 06-07-03, 04:56 AM
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Lots of things come to mind, all in the cooling system: cooling fan(s), water pump, thermostat, radiator, water passages in block. Any or all could be the culprit. You're gettting sufficient flow and cooling for normal operation, but when you turn on the ac the extra strain on the engine is overtaking the cooling ability.

Order of things I would do: Flush cooling system; check cooling fan(s) for operation and/or install additional aux fan; replace thermostat; replace water pump; replace radiator.

Also possible the ac compressor could be a problem. Any sign of bearing noises when it's turned on?

All this assumes the engine is in otherwise good condition, i.e. doesn't have head gaskets that leak or other factors that would contribute to overheating. Check Joe Cool's signature file for "The Basics".
 
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Old 06-07-03, 06:22 AM
Joe_F
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I agree.
 
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Old 07-01-03, 05:09 AM
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Exclamation Here is what I did

I have had a new Rad. cap, water pump and thermastat installed and still the car heats up to max. when the A/C is turned on. The only the only thing I have not done is flush the rad.

Still confused
Don
 
  #5  
Old 07-01-03, 05:52 AM
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Check for debris blocking airflow through the radiator and condensor.Look between them also,clean as needed but do it carefully.
 
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Old 07-01-03, 06:51 AM
Joe_F
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Agree with Davo.
 
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Old 07-03-03, 03:38 AM
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I looked

I could not see any debris. I did notice that when the car is turned on only one fan comes on. Should both come on or will the second one come on when the engian get hotter? The water level stays fine, Still in the dark.

Don
 
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Old 07-03-03, 03:41 AM
Joe_F
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Remove the stat. Run it. If you don't have the problem, new stat is defective. Replace with an OEM dealer one.
 
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Old 07-03-03, 04:45 PM
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Might want to check repair manual or the autolibrary link for info on the fan operation. The fan operation varies by manufacturer. My wife's Camry has two fans and they are two-speed. With ac off and engine cool the fans are off. If you turn on ac they come on low speed and when the engine gets hot it kicks up to high speed. A Nissan may use a different operation such as one fan comes on for most operation and the second when a certain temp is reached.

When changing t-stat, make sure it is installed in the proper direction.
 
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Old 07-03-03, 06:37 PM
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When the temp of the engine is at normal operating range, turning on the A/C should cause the second fan to come on.. 1 fan is labled radiator fan, the other is condenser fan..Each should have their own relay to turn them on and off, as needed..
If you supply a ground and battery power directly to the fan that doesn't come on, you'll be able to see if the fan motor is good or whether you have an electrical problem elsewhere..I assume that the A/C blows cold until the temp starts to rise?
 
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