1992 240SX: installed Koyo, now overheating?

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SIeeper
Posts: 95
Joined: Sat Jan 29, 2005 7:33 am

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I drive a 92 240, everything stock. Recently my car had an overheating problem. It sounded a lot like a thermostat so I replaced my old one with a part from NAPA. That didn't solve the problem, but people told me it was probably because I didn't use a Nissan thermostat. I replaced it again, this time using an OEM Nissan thermostat. My car ran fine for a week until my radiator (had old plastic end tanks) blew a hole in itself.

I didn't want to replace it with another plastic end tank design, so I decided to upgrade to a Koyo aluminum. After installation I took it for a test drive and my car got really hot in about 1/8 of a mile. I realized that I forgot to use the bleeder screw when I filled my system back up with coolant, so I drained the system and tried it again, this time using the bleeder screw (like I was supposed to) when I bled the system.

This time when I took a test drive, it didn't overheat until about 5 minutes of driving on residential streets. I pulled over, let it cool off, and then drove back home. I also noticed as I was revving the engine during bleeding that white smoke was coming out of my tailpipe.

I didn't have the overheating problem when I had the stock radiator (there was still a small amount of white smoke but not nearly as much) and I'm pretty damn sure I bled the cooling system correctly the second time around. Anyone know what could be up? I have about 70% water and 30% coolant mix. Thanks.

Edit: When I got back home from the test drive with the Koyo, the coolant overflow reservoir had a fair amount of coolant in it (it was empty when I started the drive). My radiator felt very hot and you could feel a pulsing sensation in my upper radiator after the engine was turned off.
Modified by SIeeper at 7:34 AM 7/26/2006


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teddy
Posts: 2013
Joined: Tue Dec 07, 2004 11:16 am
Car: Saab Turbo and MR2

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Plain white smoke usually means that you're burning coolant. White smoke with a bluish tint is oil burning.

When you replaced the radiator, was the coolant you drained out fairly clean looking? Or did it look like something may have mixed in with it?

SIeeper
Posts: 95
Joined: Sat Jan 29, 2005 7:33 am

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Since my car had overheated a few times when my thermostat (and then radiator) was going out, I was worried that I could have blown a head gasket. But when I drained my radiator and flushed my cooling system, all the coolant was green, not a chocolate milk color.

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rogoman
Posts: 848
Joined: Fri Feb 17, 2006 5:44 pm
Car: 1991 240SX FB
2012 Altima 2.5 S

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There's a possibility that the head gasket is blown. Perform a compression test on all cylinders.

SIeeper
Posts: 95
Joined: Sat Jan 29, 2005 7:33 am

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Would a blown head gasket cause the overheating?

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rogoman
Posts: 848
Joined: Fri Feb 17, 2006 5:44 pm
Car: 1991 240SX FB
2012 Altima 2.5 S

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Yes, it could cause overheating if combustion gases enter the coolant system.

SIeeper
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Joined: Sat Jan 29, 2005 7:33 am

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rogoman wrote:Yes, it could cause overheating if combustion gases enter the coolant system.
Good call. I'll see what I can do about that compression check.

navysnail
Posts: 3335
Joined: Wed Feb 11, 2004 1:33 pm
Car: 1990 Nissan 240SX fastback

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when you replaced the thermostat was the small hole in it facing up?

SIeeper
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Joined: Sat Jan 29, 2005 7:33 am

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navysnail wrote:when you replaced the thermostat was the small hole in it facing up?
Yes, I made sure the hole was facing up. I also boiled the thermostat to make sure that it opened.


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