OK, I have a '96 SE with auto climate control. It spits out hot air and then all of the sudden it switches to colad air (eveni if put the heater up to 85 it still shoots cold).

i'm thinking it's a thermostat or the water pump. anyone out there experience somehting like this? i have 132k miles, water pump last repalced at 60k.

thanks,

seth

 

you may need a heater core..

 

If the heat goes away at higher speeds it is probably your thermostat. A thermostat is only about $15 and less then 1/2 hour to change so it doesn't hurt to try changing it. You will lose a lot of antifreeze when you take off the old thermostat.

 

it does go away at high speeds and then comes back irregularaly. also, when i'm driving on the highway, the engine temp. fluctuates as well. driving on the thruway at 80mph, the temp goes from middle of guage to 7/8 of the way up and back in the span of 1/2 mile! i can't image the engine is actually changing temp that fast. the needle seems to go up when i'm going downhill more then uphill (could be related to modified exhaust with heavy backpressure?)

i have a water pump in my trunk and nissan says to replace it every 60k, maybe this is why. i like the idea of repalcing the thermo alos for $15.

seth

 

Replace Water pump every 60K miles?? No. Replace it when it starts leaking. I have 120K on my pump. No leaks.

Your problem sounds like the thermostat.

DW

 

what you are describing was the precursor to my car overheating. If I couldnt get hot air from the heater, the car was low on water and about to overheat. If your car doesnt overheat, it, in my opinion and educated guess, isnt the water pump. But I dont know about the thremostat. I dont know why that would affect the hot/cold air coming out from the heater. Doesnt the heater just blow air over the water in the radiator? could be wrong on that. If it is the water pump, shop around, prices were anywhere from 290-600 dollars. And make sure its a decent place, they have to take of the head to do that job. I had oil leaking afterwards because a seal didnt seat properly. They fixed it with no problem afterwards, but that could have been a big problem.

 

Check your radiator fluid level. It sounds like the fluid is low and when you go up hill or down hill the fluid moves away from the temperature sending unit. This will give you erratic readings.

You shouldn't just trust the temperature guage for diagnosing problems; you could have a problem with the guage itself. Use a thermometer in the radiator fill neck.

 

It was the damn radiator fluid!!

Easy fix, but I feel like a mOron.

Anyway, a flush and refill eliminated all problems.

Just to let you guys know, I performed the renowned starter re-lube and my screeeech noice on startup is gone, also cleaned the throttle body intake while i had the car apart and my idle is smooth at 800 rpm.

it's amazing what 2 hours on a saturday can do for your car!

seth

 

any tips or advice, that is a project i have been meaning to take up.

 

it's very straight forward.

there's a great online tutorial but i don't remember where!

basically take off the air intake stuff back to the throttle body and the take the starter off by undoing 2 bolts. once you have it off and wires disconnected, take 2 bolts off started to loosen stuff inside. take apart, clean and regrease with litium grease or somehting that likes heat. then reassemle.

seth