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Old 11-29-2012, 11:39 AM   #10
tonyguns
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Join Date: Aug 2012
Location: Nashville
Posts: 53
My Ride: 2001 330i
Quote:
Originally Posted by WDE46 View Post
I don't know how an open thermostat would cause this problem. I can see it if the problem was the reverse: heat while idling, no heat while driving. For this situation an open thermostat doesn't fit.
I completely agree with this, and it sounds more like you have air in the system, or a system leak which would create low coolant flow to the peripheral systems, like heat. When you are spinning the motor at higher RPMs, you are generating more coolant pressure in the system, which will then flow coolant through your heater core. I'd check for leaks in the ET and radiator first before replacing random parts, then if no leaks are detected, properly bleed the system, and add coolant as necessary.
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