Mechanics

RADIATOR BOILING

1999 Isuzu Bighorn

Engine Cooling problem
1999 Isuzu Bighorn 6 cyl Four Wheel Drive Automatic 85000 miles

Today I was driving my Bighorn up a snowy hillside in low range 4x4, it was very slippery and I got to the point where the wheels were spinning and I was no longer moving forward, I persisted for about 10 mins and then stopped to have a walk around. When I got out I noticed a boiling noise coming from under the bonnet and when I checked the coolant was boiling and spitting out of the overflow tank and spilling onto the ground. I then reconfirmed by putting the key back into the ignition and sure enough the temp gauge was in the red. I left the hood up for around 20 mins and the engine cooled down (I am living in Mongolia where it is - 25deg C outside) and the gauge went back to the half way point so I drove home. The engine temp remained at the half way point for the whole trip home and showed no additional signs of problems. While I was waiting for the engine to cool down I noticed one particular moment when there appeared to be a masive amount of pressure coming through and all of the hoses shook, something passed and then is settled down. Any suggestions, ideas would be greatly appreciated.
Pete Young
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Peteryoung
January 23, 2010.



Pete: I don't think you have anything to worry about. The reason it overheated is because you were not moving and there was no air circulation through the radiator.

As far as the noise you heard, the radiator cap has a pressure release built into it. When you hit the max pressure, rather than blowing a hose or damaging other items, the cap will release the pressure. Most are around 15 PSI. That is most likely what you heard and it would have seemed to affect all of the hoses because of the release.

Make sure the coolant level is still full. Also, you may want to make sure the fan clutch is working properly, After the underhood temp reaches a certain temp, the clutch on the fan should lock up causing the fan to spin faster. That way it helps draw air through the radiator to help cool the engine.

If you have other questions, let me know. Thanks for using 2carpros. Com

Joe

On that fan clutch. At what temp should it start to lock up? I can hardly spin mine more than 1/3rd turn when cold but with engine stopped at running temp, (82C) with new thermostat in it, fan spins nearly 1 turn or so.

Tiny
Cliffrt
Feb 26, 2010.