overheating question

green_machine

green_machine

Gay_machine
Driver
my car is acting really strange.

after my car warms up my temperature gauge goes from about 200*-210*(the normal temp) to about 240* and then goes back to normal temperatures. However, It jumps up to 240* and stays for like 10 seconds and then goes back down quickly. Then it never overheats again and i can keep it driving for hours. But as soon as it cools down and I go to drive it again, it does the same thing.

I changed the headgasket a few hundred miles ago and i put in a new thermostat (my first guess) but nothing changed. I am STUMPED!! please help. Also, there are no leaks...
 
dose it actually overheat? or could the coolant temprature sensor have a bad connection making the gauge climb? Could your gauge in the cluster be bad? Do you have all the air out of the coolant system and you have the radiator filled correct right.
 
240SicknessX said:
dose it actually overheat? or could the coolant temprature sensor have a bad connection making the gauge climb? Could your gauge in the cluster be bad? Do you have all the air out of the coolant system and you have the radiator filled correct right.
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^ what he said...

I vote for either air in the system or a bad coolant temp sensor (the one for the guage not the one for the ECU)
 
there is a write up on www.240sx.org on how to get all air out of the cooling system. Maybe give that a try?

OH OH OH OH when you put the thermostat in, did you put it in upside down? there is a little hole thingy majig that is supposed to be placed in the up position, no where else. that the only thing i was able to read on my nismo thermostat instructions.
 
I have a separate mechanical gauge. and yeah, i put it in the corect way. I didn't fill it the corect way but i'm gonna try something else. Thanks guys.
 
i took the themostat out and it runs at 180* which is good (i thought it's be cooler than that) but I dont like to run without a thermostat. However, it's better than 210-220* running temperature and that odd spike of 240*. Perhaps my intercooler is blocking too much air? OH well, 180 degrees is not going to hurt my engine so that's my short term fix. Thanks for the help guys
 
I think you should try another thermostat. It's easy to overheat with no thermostat in place unless you're constantly moving at some substantial speed.
 
^ the water is moving faster through your cooling system with no thermo because there is no restriction so the water doesnt have time to absorb as much heat so either put it back in or take the center out of the thermo and put the ring in to slow the water down so that it grabs the heat.

Demolition derby trick
 
Piner said:
^ the water is moving faster through your cooling system with no thermo because there is no restriction so the water doesnt have time to absorb as much heat so either put it back in or take the center out of the thermo and put the ring in to slow the water down so that it grabs the heat.

Demolition derby trick
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Exactly and the water never has enough time to cool in the radiator. It keeps getting hotter and hotter without sufficient cooling time. That's why thermostats exist.
 
I guess there's some truth to that. but there's something in thermodynamics that's called convection, it's how radiators work in the first place. the faster the coolant (air, water, fluid, gas, etc) moves over the medium, the cooler the medium gets. therefore, the faster the coolant moves through the engine, it cools the engine faster. Denying that is like saying if you go really fast, the air moving over the fins of a radiator is going too fast to cool the coolant in your radiator.

But... the air temp outside (a cool reservior) is not changed due to your radiator (global warming is an extreme case) it always stays cool. The coolant doesn't act as a cool reservior, as it changes temperature due to your engine so.... whatever, my car works now. If i wasn't overheating in the first place i wouldn't have done it.
I did think about that durby trick with bending the thermo but i thought i'd try this first
 
green_machine said:
I guess there's some truth to that. but there's something in thermodynamics that's called convection, it's how radiators work in the first place. the faster the coolant (air, water, fluid, gas, etc) moves over the medium, the cooler the medium gets. therefore, the faster the coolant moves through the engine, it cools the engine faster. Denying that is like saying if you go really fast, the air moving over the fins of a radiator is going too fast to cool the coolant in your radiator.
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GOOD! And since licking a 9-volt won't hurt you, humans are immune to electrical shock right? Lol, you guys crack me up sometimes. If you've gotten lucky enough driving around in traffic (especially in sofla) without a thermostat and not overheating, congrats. Keep on believing that the added convection from the increase in water/coolant velocity does the trick! Just don't go taking any trips down the strip any time soon.
 
I've been running without a thermo for a while now. Only a problem at long idle periods like Taco Bell/Pizza Hut drive through at 1am. At mid/high RPM it does not matter if you have a thermo or not. It's better to have one though so you don't over cool your engine and waste gas. Plus, takes a lot longer to warm up your car with no thermo :-D.
 
I didn't want to sound like a smart *** on that last post. I agree the engineers put them in for a reason. However, My car was running 200 to 230 degrees and that's almost overheating right there... I really have no idea whats up with that... but i dont drive the car very much anyway so it's all i can do for now.
 
my car was over heating just like urs one time.... found out the belt on the water pump was loose lol tighten it up and it got rid of the problem... i ran around 4 yrs without a thrermostat.. i drive from west palm beach to miami daily in the last 3 years... not one single over heating problem.
 
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