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View Full Version : m30 overheating problem resolved . . .



gale
07-05-2006, 07:32 PM
I've been cruising along for years with the temp gauge dead-nuts at 12:00 o'clock & out of the blue it took a hike into the red zone last week for unknown reasons, so I took a "shotgun" approach & replaced the waterpump, thermostat, fan clutch, & aux. fan switch along with a few hoses & a new coolant reservoir that had been sitting on a shelf in the garage for a few years. Fixed the problem but can't blame any single component for the overheating. I put the old & new thermostats in a pot of boiling water & they both opened simultaneously at the 80C mark. No obvious defects with the waterpump other than a little play in the shaft. Fan clutch was definitely due -- coulda been the culprit. The new one really takes off with a roar after sitting at a light with the a/c on. Good to have fresh blue coolant in it. No residue in the old coolant and no indications it was a headgasket issue.

I flushed it numerous times without a thermostat, definitely more difficult to bleed with the thermostat in, even with an 1/8" vent hole drilled thru the top of the main flange. Next time I'll drill a 1/16" hole as well in the smaller disk that seats in the back of the head side of the t-stat housing.

She's rock steady at 12:00 o'clock now, so whatever the problem was, I consider it cured. Who knows, maybe it was the old coolant tripple point as Ryan suggested.

I'll put the old aux. switch in a pot of water & measure what temps it kicks in at for low/hi, should be 91/95C. It's never kicked in the whole time I've owned the car, makes me a little suspicious.

Cheers!