View Full Version : 97 528i thermostat trouble


schneider4
03-18-2006, 01:36 AM
Hello all –
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I’m writing about my 1997 528i (automatic transmission), which has 70,000 miles on it. About 5 months ago, I began experiencing a problem where the temperature gauge would climb into the red zone. This problem was happening regardless of speed or outside temperature. Switching the heat onto full blast at 90 degrees usually brought the needle down to the halfway (normal) mark. I took it to my longtime mechanic, who replaced the thermostat and water pump.
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On the way home from the shop, the same problem briefly reappeared. Then, for about 2 months, nothing – everything was normal. My mechanic told me that he thought there might have been some air trapped in the cooling system, which might “fool” the thermostat. Since the problem seemed to correct itself, I gave it no more thought. Then, one chilly night on the way home from the airport (where the car had been parked for 3 days) it started again, within 5 minutes of picking the car up.
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To make a long story short, I got stuck in some traffic a few days later, and boiled over: the normal trick of turning the heater on full blast didn’t help. I had the car towed into the same mechanic, who replaced the thermostat (again), as well as the radiator, which had been cracked when it overheated. Luckily that was the only damage we discovered. His theory at the time was that perhaps the radiator had a small crack in it all along, which caused air leakage and the thermostat strange behavior that I had been experiencing.
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So here I am: $800 poorer and the “proud” owner of two new thermostats, a radiator, and a water pump. Tonight, the same damn problem happened again. It’s about 45 degrees outside, and once again, the needle started climbing towards the red zone after about 10 minutes of stop-and-go driving. Turning the heat on did the trick, but I’m tired of driving with one eye on the temperature gauge. I feel like I can’t trust this car – heaven help me if I get stuck in traffic once again.
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Does anyone out there have any clues as to what could be going on with this car? Thanks in advance for any insight.

thejlevie
03-18-2006, 10:51 AM
What you are describing could be the result of air bing pumped into the cooling system from a small head gasket leak. That is frequently accompanied by loss of coolant when there are no apparent leaks.

bimmerm3e36
03-19-2006, 11:25 PM
I would double check the operation of the front aux fan. It should come on when your temp gauge is climbing up. If it comes on when overheating, then it is possible that there is going to be a leaky headgasket. There is an easy way to check. First, make sure your coolant level is topped off and pull out the fuel pump fuse. Have another person crank the engine inside the vehicle and you are going to open the radiator cap to check if there are any air bubbles coming up from the coolant. If you see air bubbles, that means you have a leaky headgasket.

jakeprague
03-28-2006, 02:20 PM
I've been having exactly the same problem with my 97 528i with almost identicle miles. Thanks for the advice will be chaecking it out asap - so far its been a really frustrating problem.