# Nissan 240sx heat issues



## KaosLuciano (Nov 6, 2011)

I changed the thermostat because it was acting up before, it was cold while stopped or slow driving and then hot while driving fast, so I assumed the thermostat and radiator cap I bought both new and let air out of the system, the heat works fine while the cars idling or driving normal it has no problems and heats up the car perfectly as in making you sweat inside your car perfect, I took it to the track yesterday and ran it a few times the heat stopped working and blew out cold, the bottom hose out of the heater core felt cold, after a while of driving it back home at slow speeds it start to kick in slowly, I am assuming its an over cooling problem, I bled the system for air, also used the bleeder screw, changed the coolant and its topped off, so i dont know what else to do...


----------



## rogoman (Dec 16, 2004)

Did you buy a Nissan OEM thermostat or an aftermarket unit? Many aftermarket thermostats don't work properly.


----------



## KaosLuciano (Nov 6, 2011)

I used an aftermarket one, from what i hear one of those crappy stant ones, the heat was working perfectly though after I changed the thermostat and bled the system, it was hot to the point if you kept it on high long enough you would sweat or have to open the windows which is good, so I dont know what changed in a two day period, now its working but barely, and I touch the bottom hose out of the heater core and its barely warm not hot after long period of driving...


:givebeer:


----------



## smj999smj (Jan 1, 2006)

Stant thermostats are ok (their "superstats" are better than their cheaper line), but I still prefer genuine Nissans. Seems that the aftermarket stats make the gauge run a bit in the 'cool' range rather than dead center like the Nissan part. I guess it's possible that there's air in the system, but I kinda doubt it. The air usually works its way out after a couple of heat cycles. I'd be suspect of a failed head gasket pushing some combustion gases into the coolant jacket and making it's way through the heater core. Definately try rebleeding first and jack the front of the vehicle up a little to help work any air up through the system. If you still have problems and the heater system itself is in good order, I would perform a cylinder leakdown test (make sure the rad cap is removed) to check for a bad head gasket.


----------



## trmn8r (Apr 16, 2005)

KaosLuciano said:


> I used an aftermarket one, from what i hear one of those crappy stant ones, the heat was working perfectly though after I changed the thermostat and bled the system, it was hot to the point if you kept it on high long enough you would sweat or have to open the windows which is good, so I dont know what changed in a two day period, now its working but barely, and I touch the bottom hose out of the heater core and its barely warm not hot after long period of driving...
> 
> 
> :givebeer:


beleive it when i say i use to run a nizmo thermostat on my sr and i would always have this issue. then i went to a stant one and never had a problem since. you have to avoid reving your motor when the engine is cold. the thermostats alsways mess up. air pocket would cause your temperature to fluctuate. what kind of radiator are you using?


----------



## 180SX-X (Sep 21, 2003)

you may have a clog in the line from corrosion. When driving slow/normal the pressure in the system isn't as high, and therefore this 'clog' probably remains dormaint. But when you start revving, it could flare up this clog and block flow to the heater core. I suggest removing the heater core and see if anythign comes out.

Jose


----------

