5-Series (E12,E28, E34, E39, E60)Chat relating to the BMW 5-Series of all generations. Specific models include: BMW 518, BMW 520, BMW 520i, BMW 530i, BMW 528i, BMW 530i, BMW 518i, BMW 524d, BMW 525i, BMW 525e, BMW 528e, BMW 540i, BMW 535i, BMW 520d, BMW 525td, BMW 525d, BMW 530d, BMW 525i/xi, BMW 530i/xi. (BMW 5-Series Forum)
My automatic '91 525i had a peculiar problem today. I noticed halfway through my 8.5 mile trip to college, my coolant temp was in the high blue mark. It had raised at a normal pace up until then and then stuck there, or so I thought. I turned off the heat, and it didn't do much of anything for the indicator.
On the way home, I had the same problem. I took it extra easy on the engine in case it wasn't just a thermostat error or something like that.
So I pop the hood once I'm back here at the house, touch the motor, and it's cool to the touch. Same for the radiator's tank; I carefully opened it and there was a low hiss, but the coolant was already cool. The bleeder valve seemed fine, I had enough coolant... It's certainly strange. It was just around freezing today, not any colder than the car's already seen so far this season.
What might the culprit be? I would really hate to damage the motor. For what it's worth, the car drove perfectly normal for it being a colder day, it took a while to shift (bad trans) from the cold start and a few minutes of warmup, but after that acceleration and shifting were normal.
My 528i temp gauge would stay in the blue while driving and would go to 12 o'clock position when just idling. I changed the thermostat and now it stays at the 12 o'clock position steady after running for a few minutes. Try the thermostat. Remember to bleed the air out of your cooling system after changing the thermostat.
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