91 Nissan 240sx overheating

[Liquidus]

my 91 nissan 240sx is overheating. Can you guys give me some tips on how to figure out what is exactly causing it. The one thing i did figure out is that it seems like sometimes changing things w/ the heater makes it better. What can i do to figure out what is causing it and how to fix it.

Thanks,Rob

[driftingmy240sx]

have you looked for any leaks? it there anything blocking the radiator from getting frsh air like a plastic bag? how much of a difference does turning on the heat make?

[vancouverbc]

make sure you enough coolant. most people start changing parts. there are some articles on google. i dont think there are any simple tricks. some people say watch the water flow in radiator but i never noticed anything moving and mine was fine. my first quess would be clogged radiator.

[Liquidus]

Here is an update from today. I tried turning the heater on again to see if it would still help, but the heat was not working. Only cool air was coming through. Could this be related?

The weirder part is that at after driving for like 20 minutes the heat all of a sudden started working. Like from cold to hot instantly.

Could the heater and the overheating of the car be related?

Also, i have not noticed any leaks, and there is nothing blocking the radiator.

[vancouverbc]

the heater doesnt work until the coolant gets a certain temp. not sure what controls the flow of coolant to heater core. the heater is like a second radiator so use it. dont drive when your car is overheating of course. your rad fins may be blocked by rust picked up by the coolant. one guy said to open up the outlet hose of the rad and see how much flows out.

if you have done any recent work on cooling system your problem may be air in system

[Liquidus]

Okay, final update. Today i had the heater on and it was working. The car did not overheat AT ALL. Does this change the diagnosis at all or is it still just clogged radiator/air in system.

I plan on getting a flush/fill this weekend on the coolant. Is this the best way to solve the problem?

Thanks a lot for all your help!

*also no i have not done any work on the coolant system. So its probably rust picked up by the coolant like you said

[vancouverbc]

the thermostat opens up once the coolant reaches a certain temperature and allows flow of coolant to heater. if your car was overheating and at the same time you had no heat, that would suggest your thermostat is not opening up when it should. did your overheating problems totally disappear when the heater starts working?