We have a 1983 280ZX coupe, nonturbo, automatic that has an overheating problem when we use the A/C. We have replaced the fan clutch, radiator cap, thermostat, and added 2 10" electric cooling fans with a thermostat and still overheats when the A/C is used. Does anyone have any idea on what the problem might be?

 

how old are the radiator and waterpump?

 

I don't know how old the radiator and water pump is. But my son, the mechanic, doesn't seem to think those are the problems. The water pump isn't leaking any water and he thinks the radiator is okay.

 

Well since you have changed everything else. It would have to be either the water pump or the radiator. H2o pump is about $30 and the radiator is a couple of hundread. If you go ahead and do the job...new hoses would be a good idea.

 

Could also be a blown headgasket. I know ya don't want to hear that, but even a small leak in the coolant chanels of the head can cause overheating. No matter how hard you try to keep it cool, it will still overheat. Check your oil to see if it has any water or foam in it. Check the color of your exhaust... any white smoke will give it away. Also use a mirror & look under the exhaust manifold to see if there are any mineral streaks down the block starting at the headgasket... also on the oil filter side of the block.

 

Sounds like you might have a restriction in the radiator. Check it to make sure there isn't alot of debris blocking the front of it or the condensor and that the fins of either aren't all smashed up. You may not be having a problem when the AC is off because what air is getting through isn't warmed by the condensor. I doubt it's the water pump though. Water pumps generally don't cause cooling problems unless they're leaking or the impeller shears off(not likely). And the head gasket would most likely cause the problem full time rather than just when the AC is on. Have you tried actually taking the car on a long drive without the AC on to see if it still overheats?

 

I Had The Same Problem, I Have 3 Core Dense Rad, Elec. Fan, New Block, Everything. So I Asked Rad Shop, He Said Put A 195 Deg. Thermostat In It. Stock Is 180ish. The Reason Being Is, Coolant Isnt Staying In The Rad Long Enough To Cool, Also Make Sure The Little Rubber Thing At The Front Of The Hood And Under The Hood Are There, That Makes A Big Diff. And Also That Your Elec. Fan Is Tight Against The Rad. Thry That.

 

any of the following or a combination of them: low compression, running extra lean, to much dragging of a/c compressor(not in good working order but pumping) may cause overheating

 

Sounds "Rad" to me... In light of what you say about the cooling system, I'm gonna have to lean toward the radiator. If that's not it, I might suspect the compressor clutch, but if it were bad you should hear the belt squealing.


Rod.

 

If it was the radiator...wouldn't it be overheating all the time? I'm thinking its your condenser fan, if it's working against your e-fans, then the air isn't moving...check that both are pulling.

 

Uh, the short answer to your question is NO, It would not overheat all the time. If the Radiator is going south, it's gonna have a harder time cooling depending on the load it's under. I drove around with a radiator like that for a year. Worked good until it was under a load (almost like a head gasket problem). Put in new 3 row radiator and no mas problemos senor.

Rod.