weird overheating

[roger75]

hey everyone i have a nissan 240sx which i recently changed the water pump and the thermostat...the weird thing is that when i accelerate the needle goes down to cold but the more i stop the more the needle goes to hot and it gets to the point to where it starts throwing steam out the overflow tank...anyone know what it can be?

[dm-ka]

Most likely it is your thermostat. I had once that I went through 3 thermostats before got one that worked.

[n240sxfnatic]

U dont have a radiator fan, do you? Thats why when u speed up it goes down.

[YF19Alpha]

I have a similar problem, after dropping my son off at school, about 15 min drive, i noticed steam coming from the hood, overflow bottle has been cracked for a while, so i recently replaced it. drove for last 2 days no issue, but noticed again the overflow bottle was boiling and spewing steam, i let a friend borrow the car, bad move i know, still kicking myself for it, but on the way to return the car to me, said "friend" says the car is overheating when they go past 60 or 65 mph. that doesn't make any sense to me. any ideas. I was thinking about changing the thermostat, but seems like worst case scenerio i'm hearing is head gasket... please help. car is a 93 240sx SE coupe.

[wantz87]

i had that problem too, for me i only needed to refill all the fluid. dunno how it got low, but thee wasn't enough fluid to adequately pull the heat out.

[t34stud]

could be stuck thermo....accelerating can increase pressure througout the system....check for proper releasing of thermostate spring.

[helluvasinger]

I just dealt with the same problem.. On the thermostat, there is a little brass nipple. You MUST make sure that the nipple is straight up top!!! It's a breather. Like trying to pour gas out of a gas can without opening the vent. When you open the vent, the gas flows freely. This works the same way... After I realized this, I tried a few different ways just to see what happened. Depending where the brass breather is, it will either overheat under acceleration, or overheat at idle.

Hope this helps!!!

[YF19Alpha]

i'm going to check the thermostat today. thanks. will let you know if that's it.

[YF19Alpha]

OK, i changed the thermostat yesterday, and still overheating within a few mins after starting the car. I did notice that there was a belt that was off the pulley. not sure what it is though. it is just behind and a little lower than the fan belt.

[zer0c123]

Did you bleed the coolant system properly?

[YF19Alpha]

update: i feel pretty silly now. my problem has since been fixed, but to let you know. I had a friend help me with the issue and we figured that there was a loose belt. tensioner (sp?) was missing and so the water pump was not running. hmm... i had a DuH!! moment. thanks for all the help.

[edwards30]

so, my 95 240sx is overheating strangely. It's heat goes up past H and will go back down without any changes in driving. It doesn't blow out heat at all. Sometimes it will run normal heat all day and then out of no where go up to hot then not go up again. It has had a CX Racing radiator put in, new thermostat, and water pump. Possible heater core?

[turbos4me]

Sounds like you are in the right place but I don't think a bad heater core is going to make you overheat. 240's have heat issues, my 98' does so I am there with you. Run a waterpump test at idle with the radiator cap off and thermostat open make sure you can see strong circulation. Change out the engine coolant temperature sensor in the front of the block if the gauges are not showing extreme heat before you see steam. Consider a radiator flush and refill and do the antifreeze purge where you open the breather valve by the throttle body to purge all the coolant. Follow the refill procedure carefully to avoid any air pockets and never be to proud to go back over your work, it may be as simple as a bad 'new' thermostat! One more thing make sure your clutch fan is working properly...http://www.offroaders.com/tech/fan-clutch.htm....Happy troubleshooting Bro'

[edwards30]

ok, so i burped my 240 once before work. It was running good for awhile till the heat rose on my way home. very soon after that a light turned yellow so i stomped it and my heat went down(I'm guessing i accelerated the air bubble past the sensor?) when i had my cap off while burping i didn't see any movement..

[Azrial]

so, my 95 240sx is overheating strangely. It's heat goes up past H and will go back down without any changes in driving. It doesn't blow out heat at all. Sometimes it will run normal heat all day and then out of no where go up to hot then not go up again. It has had a CX Racing radiator put in, new thermostat, and water pump. Possible heater core?

That sounds like an air bubble to me. Make sure you take the radiator cap off and run the car until the thermostat opens then fill it with fluid.

[edwards30]

should i have heat after i get the air bubble out? when i first got the car i smelt antifreeze.