In Reply to: Ugh... Coolant Overheat posted by DaveR on January 25, 2000 at 22:20:47:
The car is a 95 525iT, M50 engine, radiator with attached overflow. I let the engine cool and checked coolant level; it was at the lower mark so I added enough to bring it up to the top mark. I started the engine and opened the bleed valve; fluid came out.
I drove the car around for a few miles and all seemed fine, then the heater started blowing cold and the temp gauge went up (bing!). After about one minute, maybe less, the heater started blowing hot air again and the temp gauge dropped to normal. Grrrrrrr. I checked everything again when I got home; bleeder bled fluid, and the top hose was hot and pressurized.
This AM, I took a screwdriver with me on the way to work, the idea being that if it started overheating, I could pull off a side-street and bleed the system. Well, all was fine until the final 1/2 mile where there was no way to get off the road. Less than a minute later, the temp dropped to normal and stayed there. After parking, I popped the hood and checked the bleeder... it bled fluid. GRrrrrrR!
So, any idea what the deal is? I can't imagine a water pump being intermittant. The way that the heater vents change temp (inversely) with the temp gauge seems to indicate that hot water is NOT flowing when the car starts overheating. Is my thermostat playing mind games with me? Or do I have some transient bubble of air in my system that's making the rounds?