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OVERHEATED!!!

Joined
31 January 2002
Messages
919
Location
Raleigh, NC
i was parked on a semi steep incline with the engine idling. about 5-7min later i heard a strange noise (sort of like a humming?) at which time i noticed the temp gauge pointing full red. i shut down immediately and opened the engine hatch. after a few minutes i released the pressure in the overflow tank (steamed like hell and overun- not too much fluid though) i waited for the car to cool a bit and refilled the resevoir. after about 20 minutes, i started it back up, put it on level ground and drove it home. it seemed perfectly fine. no more overheating episodes and the car operated the same as always. the fan was going nonstop during the idle on the incline. is it possible that the fluid couldn't circulate to the block from the radiator? (air in the system? not purged?) (i was on an incline facing nose down) . any ideas what could be wrong? is there chance that damage could have occured from the overheat?

thanks for any insight.
 
We've heard in these forums from the best advice-giver there is that ANY form of overheating can cause damage and should be checked out professionaly. Because you're having trouble with your heater too (seperate thread) I would have the car towed to a dealer and checked. Don't drive it at all.
 
Having it towed is over reacting a bit. If damage was done, it's done, and if you can drive it now and the temp is normal, then don't risk some tow truck screwing up your car.

You didn't mention if it was a hot day and/or if you had the AC running, which makes a big difference.

There are four major possible causes:

~ 1 One or both radiator fans not working. This is the simplest to test. Let the car idle while you monitor both fans and the temp gauge. Turning on the AC will also start them, but that does not prove they will turn on thermostatically.

~ 2 Coolant was low for whatever reason, which could be for any number of reasons including a leaky hose, water tank, radiator core/tank, water pump, blown head gasket, cracked water jacket, etc., etc. The really bad ones are also least likely.

~ 3 Stuck or weak thermostat. This is my bet if you have not recently replaced the coolant or otherwise messed with the cooling system in some way. It is not uncommon for an old thermostat to start opening at exactly at the correct temperature, but then never open all the way. That of course restricts flow and can cause your problem. When you replace it out (which you should anyway after a bad overheat) suspend it and a new one side by side in a pot of water on the stove. As the water temp rises, watch them both closely and see if the old one ever opens all the way.

~ 4 There is an air bubble in the coolant system. This is my bet if you have recently replaced the coolant. The NSX cooling system is tough to bleed properly because the radiator is in front and the engine in back. What the book does not tell you is that when bleeding the system from any given point, you should jack the nearest corner of the car up a few inches to encourage the air bubbles to come toward the bleeder. If this is the real problem, then you could have started to drive and instantly seen the temp fall back towards normal. Not because of increased air flow, but because the air bubble was pushed through the system and your temp gauge sees the real water temp. I have seen this more than once.

There are other possibilities, but I would start with these.

Good luck.


[This message has been edited by sjs (edited 29 March 2002).]
 
thanks sjs.
it is a very mild day (high 40s) so external temp was definitely not a factor. i purchased the car a few months ago, so i'm not sure when the coolant was changed. i will change the thermostat and perform the test that you suggested. good idea. the car seems to run fine now and even at idle on flat ground it doesn't overheat. i think i'll flush the system and get my mechanic to purge it properly for safety measures. by the way, the fans do work. the one in the front cooling the raditator was running the entire time. not sure about the one in the rear.

thanks again.
 
thanks sjs.
it is a very mild day (high 40s) so external temp was definitely not a factor. i purchased the car a few months ago, so i'm not sure when the coolant was changed. i will change the thermostat and perform the test that you suggested. good idea. the car seems to run fine now and even at idle on flat ground it doesn't overheat. i think i'll flush the system and get my mechanic to purge it properly for safety measures. by the way, the fans do work. the one in the front cooling the raditator was running the entire time. not sure about the one in the rear.

thanks again.
 
I have to agree with all possiblilities. I do beleive that #4 is the most likely, based on the symptom, including the other thread about the heat issue.

I think you really have to ask the question, if the system needs bleeding and filling to correct it, why am I loosing coolant?

HTH,
LarryB
 
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