92 240sx KA24de Overheating

[Portal-S13]

ok, so now im stumped, My 240 has been overheating lately, i dont see any leaks from anywhere. i just replaced the thermostat, coolant temp sensor and water pump gasket yesterday and then i dropped a gallon of prestone 50/50 in it. it wont reach the top heat line but it will ht the second to last one. did i use the wrong coolant? do i need to run it with he radiator cap off for a little? or is there something else i need to do?

[CJH]

1st- You could have an air bubble. Squeeze your radiator hoses a couple times and try and pop any possible air bubbles.
2nd- Turn on your heater. The heater core can act like a second radiator and help cool your car down. Whenever you over heat you should always turn it on. See if this helps. It might also pop any possible bubbles.
3nd- Take your radiator cap off with the car on. Watch to make sure that your coolant is flowing. Your water pump might be dead. I have checked this before and it appeared to be flowing, I replaced my water pump and it solved my problem.
4th- Check your coolant level a couple times at different times of the day and different days. See if it goes down. If you are missing some, logic says you are leaking it or burning it. Check your exhaust for a blueish tint to it. This can be a sign of burning coolant. Smell it also (don't stick your nose in your exhaust pipe). Check your oil and coolant for any mixing. You can blow your headgasket in a couple different ways. You can blow it a little between a coolant port and a cylinder. This would allow you to burn coolant and your car would still function somewhat normally. Or you can blow it out where coolant or oil leak from your head out. Or the typical blown headgaskt where it all went to s***, but your car probably wouldn't run right at this point.

Hope this helps.

[Portal-S13]

thanks

[mechanicalmoron]

1st- You could have an air bubble. Squeeze your radiator hoses a couple times and try and pop any possible air bubbles.
2nd- Turn on your heater. The heater core can act like a second radiator and help cool your car down. Whenever you over heat you should always turn it on. See if this helps. It might also pop any possible bubbles.
3nd- Take your radiator cap off with the car on. Watch to make sure that your coolant is flowing. Your water pump might be dead. I have checked this before and it appeared to be flowing, I replaced my water pump and it solved my problem.
4th- Check your coolant level a couple times at different times of the day and different days. See if it goes down. If you are missing some, logic says you are leaking it or burning it. Check your exhaust for a blueish tint to it. This can be a sign of burning coolant. Smell it also (don't stick your nose in your exhaust pipe). Check your oil and coolant for any mixing. You can blow your headgasket in a couple different ways. You can blow it a little between a coolant port and a cylinder. This would allow you to burn coolant and your car would still function somewhat normally. Or you can blow it out where coolant or oil leak from your head out. Or the typical blown headgaskt where it all went to s***, but your car probably wouldn't run right at this point.

Hope this helps.

Yes, but:

Bear in mind that taking off a hot radiator cap will blast you with hot coolant. If you run with it off, either take it off while the car is cold and THEN start it, or use a thick junk rag over it, and be ready to have coolant all over everything.

Also, bear in mind that there will be less coolant when it cools than when hot, because it expands when hot, filling the overflow tank. So compare cold levels.

Did you have the problems BEFORE replacing those things, and do them to try to fix it? Or did it just start happening? I had a thermostat stuck open, and replaced it, and it ran fine at normal temp in a parking lot, but a half mile down the road, started overheating-I pulled over but didn't kill the engine, it got to the bottom of the safety flag, last I saw-got out to check for coolant leaks, and by the time I was back in the car it had come back down, and I drove off, it never happened again. I think either a chunk of RTV got somewhere it shouldn't have been, or the new thermostat caught and took an initial heat spike to get working right.

Make sure you used the right thermostat-You could try running without one, just to make sure that's not it. But first, take off the radiator cap (I suggest hot, with a rag, if a mess is okay) and play with the throttle body. If revving to like 3k makes the rad bubble, keep doing it. Add more coolant as it runs, until it not only doesn't bubble, but overflows. Then cap it, and make sure the overflow tank has plenty for it to suck back as it cools. (in your case, might wanna have someone watch the temp gauge to make sure you don't seriously overheat while doing this)

[PapaSmurf2k3]

+1 for not taking the cap off while hot.
+1 for your water pump may be dead... you should have replaced it while you did the gasket anyway. They are cheap.

KAs are notoriously difficult to bleed the cooling system. There is a bleeder screw on top of the upper hose gooseneck (like on the intake manifold). Loosen that up (again, do it while it's cold). Start the car up and massage your hoses to try and work out any air bubbles. Tighten it back up and see if everything is back to normal. You might have to do this multiple times.

[Portal-S13]

i didnt have any coolant problems before i accindently took off my water pump, then it all started happening, i think that air probably got in the system, just bought a brand new water pump today and installed it, new gaskets and new coolant, just flushed the whole system, havent poured the coolant in yet, what do you reccomend would be the best way to add the coolant and not retain air in the system

[mechanicalmoron]

i didnt have any coolant problems before i accindently took off my water pump, then it all started happening, i think that air probably got in the system, just bought a brand new water pump today and installed it, new gaskets and new coolant, just flushed the whole system, havent poured the coolant in yet, what do you reccomend would be the best way to add the coolant and not retain air in the system

With bleeder open (forgot about that) and cap off, fill with the motor cold (unless you want a block in multiple pieces), start the car, and follow the procedure that I described, adding more coolant as you can. Some people say things about rocking the car or parking on an incline, but from personal experience, I'm inclined to think that using the throttle to move things along will do the trick. And to check, you can also take the cap off on a cold morning, and fill it up the last bit, if it's down.

And if it only happened since you played with everything, it IS something you broke, like a bubble, seal, or bad thermostat/improper installation..... Not a head gasket.