Not heating up


Old 01-30-08, 09:23 PM
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Not heating up

6 years ago I used to own a 86 Honda Prelude. The car is long gone now, but there was an issue I could never resolve that I was just reminded of today.

During idle, the temperature gauge would reach the middle(normal). Adequate heat was produced. As soon as I began to drive, the temp gauge would automatically drop back down to cold and little to no heat was produced. The most common cause for this is the thermostat. I remember replacing it numerous times which did not resolve the issue. All I remember was shoving cardboard in front of the rad and dreading each highway trip I had to make in the cold. What else would have caused it to not heat up? Would a bad heater core cause that?
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Old 01-30-08, 11:21 PM
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lack of circulation from the water pump. or if you live in a very cold climate it just might not be able to get all the way up yo temp. if the guage shows normal range but no heat, suspect the heater core,heater hoses, gate valve, or even the blend door
Old 01-31-08, 08:38 AM
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Yeah, I think it may have been water pump in that car. It's probably busy RIPing in a junkyard somewhere.
Old 01-31-08, 05:49 PM
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Will this still happen even if you try not using your heater/blower?

If the radiator was being chilled TOO much, the thermostat should simply stay closed and allow the engine temp. to continue to climb, until it reaches the open-temp of the thermostat.

I can only think of things below that could even cause this from a theory standpoint:

1. That you have some massive heater core and blower that can cool down the car more than what one would normally expect (doubt this though).

2. Your coolant system is full of junk and the thermostat is not able to close as junk gets caught up in it.

2. The temp gauge reading is not right, perhaps. The temp is actually not registering right because there is an air pocket and the sending unit is not picking up the temp correctly as it is not submersed in water. Check actual temp by testing temp of the thermostat housing at idle (when your engine shows gauge in middle); and then after you think it cools down while driving, hurry and stop the vehicle and test again, with infrared contactless thermometer.

3. Extreme cold air is getting in and thru your engine compartment more than what most cars do, and is cooling down the engine.

Note that a defective water pump would make the engine overheat, not overcool.

Note that too cold of engine coolant due to sub-zero temps outside is superchilling the radiator, but THIS does not cause engine overcooling either, as all that causes is for the thermostat to stay closed longer. Take it from me. MY car's temperature actually climbs HIGHER in sub-zero, if anything, even during below zero actual temp/minus 35 windchills outside!

The only thing that caused MY car to run at normal operating temp while idling or driving in town, but then dropped way down to cool, is when I drove on the highway with no thermostat in the car.

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