S14 A/C Thermostat Problem

[base9se]

For the past week my '95 240sx has been having thermostat problems. Once the car is started and the A/C is on, the thermostat starts climbing to H in the gauge. The A/C is not blowing cold air at all when the thermostat is rising. It usually takes about 2-3 minutes for the thermostat to go back to normal. I took it to a shop and they couldn't figure out what was wrong with my car after keeping it for 2 days.

The first time this happened was when I changed my belts and hoses about 6 months ago. The coolant was flushed and changed with Prestone Antifreeze/Coolant 5/150 Extended Life 5 years or 150,000 miles. After re-installing everything back it and drove it around the block, it did the same thing as its doing now, heating up (for about 2-3 minutes) and then going straight back down to normal (after about 2-3 minutes in the high thermostat range). It only did it that one time and now it's doing it all over again. Anyways, could the coolant be the problem? If so, What coolant are you guys using or would recommend?

Also, a friend suggested that it might be a bad thermostat? How can I find out if it is? Is there a simple test to find out if its the thermostat or not?

Need help, any other ideas of what else it could be?

[KaDrifter]

The same thing happened on my S-14 and my friends S-14 put a water pump in both and fixed the problem. What was wrong with the was the weep hole on the bottom where the bearings are was leaking.

[NISTECH]

You may have an air pocket in the system. try bleeding it with the front of the car elevated as high as possible. get one of those bleeder funnels from the parts store and let it run with the funnel filled about half way. let it run for 20 mins or so and during that time bring the rpm up to 2500 rpms a few times to help the circulation of coolant. if its not an airpocket you could have a partially restricted radiator not allowing good coolant flow. way to check for that is to feel the radiator when it starts getting hot[car shut off of course,wouldnt want to loose a hand or something] see if there is a substantial temp difference from top to bottom of the radiator. if this seems ok a couple other things could be the cause. The A/C condensor electric fan could be bad and not turning on, or the mechanical clutch fan is not locking up.

[base9se]

I actually had air pockets in the system and got rid of it. Hopefully this solves my problem. Thanks.

[KaDrifter]

you wouldn't need it on the 240 it has a bleeder at the highest point of the cooling system

[NISTECH]

I have had several 240s that still got air trapped in the heater core and would not purge out through the bleeder port. Had to lift up the front and run the car to get the air out.

[KaDrifter]

Wouldn't he hear a sloshing sound like on the new Maxima's and also he did a flush not drain the system dry,so I wouldn't think there would be air in the heater core

[NISTECH]

not nessesarily I have had a problem with the flush machine on the newer pathfinders getting air in them and trapping air in the cyl heads Did not hear any sloshing but it got pretty hot on the R/T.