overheating when car is off??

[Armstec_S13]

Ok, I have a 1989 240sx coupe, (SOHC) two weeks ago I was driving to my bros house, I had a problem with my alternator light, I tightend my belt and the light was off and charging fine, one day I forgot my parking lights on, bro jumped me and the light was on again, I disconnected the battery and it ran fine so ALT is good, anyways, I got to my bros house and popped the hood to check the alt ground to see if that was it, I left the car running as I was checking, I looked at the light was still on, fine, I also noticed my gas needle and coolant temp needle, all was good, so I turned the car off to check the tension of the ALT belt, when I turned my car off I heard a loud hissing and smoke coming from the front of the car, I ran to the front of the car and saw coolant spraying out from what seemed to be the radiator cap area so I figured the radiator broke at the filler where the radiator cap connects, I went into the car and turned the key to the acc and noticed the coolant temp needle was to the top. No I didn't turn the car back on.Anyways, I went and looked at the cap and filler and nothing, no crack on the radiator or anything radiator cap looks fine. I let the car cool down I open the cap and refill my coolant but it barely took any coolant to fill up the radiator at all. That was like 2 weeks ago, after that I drove the car a crap load oof times and tonight it did it again, after dropping off my gf, I drove home and sat in front of my house for like 10 to 15 minutes talking to my gf on the phone as the car was still running, I was looking at my temp needle and it was fine (because of lastime), I turned the car off and I hear hissing and see steam, I didn't open the hood cause I knew it was the coolant again and it would burn the crap outta me, I turned the key to the acc and noticed my coolant temp needle is going up and the car isn't even on, WTF???? anyone have any ideas of what it could be? I was told it could be the thermostat, radiator cap, coolant temp sensor, who knows, I know its running fineand the needle reads normal when the car is on, no overheating or anything, as soon as I turn the car off that's when it starts acting up and when I turn the car on to the acc to make the lights on the cluster come on, that's when the needle was moving up to hot. Need any advice or help please.
Modified by Armstec_S13 at 1:44 AM 9/24/2009

[RCA]

Cliff notes?

[nothing]

I think there might be more than one problem.1) The signal from temp. sensor to temp. gauge. 2) There seems to be too much pressure in your cooling system. I'd try bleeding the system first, then thermostat or radiator cap.

I don't think there is any way your car is over heating while its off. If anything its overheating while its on idle. In this case I would suspect fan clutch, fan or any of the previously mentioned.

Good luck. Let us know what you find.

[nando]

i would sugest changing the thermostat and rad cap then burping the radiator

there may be an air pocket in your coolent system and because its a pressureized system its throwing things out of wack

hope this helps and good luck

[moso]

i would change both waterpump and termostat. one is baaad. you probably have a good air bubble in the block as well. both are fairly cheap and easy to replace and any overheating problem in a ka is putting your headgasket at risk. attend to this soon.

[sj240sx]

The same thing happened to my s13 ka24de and the problem is a leaky core (freeze) plug. i had a bunch of mechanics from work look at it and no one could find out what was wrong it and one time when i was giving my car a underbody inspection and i found the core plug under the exhaust manifold. once i changed it and it finally stopped acting up. hope that this helps

[kuraticus]

my s13 does something similar but i have noticed that it only overheats when I am at low rpm. and when i idle i get little bubbles out of the bleeder.

..New pump..new thermostat..electric fans..did proper bleed technique..multipe flushes..no oil in coolant,or coolant in oil..no white or watery exhaust.

when I drive it takes about 20-30 min then overheats unless i am at 2500rpm or higher. please help.....

[Klits562]

at low rpms I'd say its either water pump or fan clutch(unless you have electric)Those 2 are belt driven and higher rpms means the belts are spinning faster at least thats how it seems to me.

[kuraticus]

ya that makes sense to me too, but i do have electric fans that work good and also have a new water pump and im sure it works....??????????