Quote:
Originally Posted by F82///M
Majority of vehicles if not all, have heat exchanger (cabin radiator) in closed loop with the "hot side" of engine coolant or before thermostat. That way cabin heat is always available as long as coolant around cylinders is hot.
Some older vehicles are just poorly designed, usually with one coolant pump for the whole system, long coolant hoses with small diameter to the heater core with bunch of heat loss everywhere in seriously cold conditions. More often it's an old diesel engine which cools itself idling hence high idle invention for them.
When engine struggles getting to operating temperature it means thermostat is stuck open (fully or slightly or simply coolant flow pushes it open) and coolant flows trough radiator up front cooling it down further instead of just circulating trough the engine itself and heat exchanger. On cold engine thermostat is always closed and while it warms up, it opens to bring cooled coolant from the radiator and maintain safe operating temperature.
On older vehicles thermostat is often mechanical which gets weak after few years and should be replaced more often. Bmw has had ECU controlled thermostat for a long time now. It makes engine run hot (example 105-110C) while driving slow for better efficiency or if driving high speeds or high revs for a while it lowers the engine temperature down (example 78-90C). This would be opposite with mechanical thermostat.
BTW that efficiency thing of running hot is what's been killing plastic cooling components and baking rubber gaskets into the plastic on Bmw's since late 80's. If it never run above 90C everything would last much longer.
Engine coolant pump is belt driven, there is electric one for heat exchanger. I'd suspect that one is dead or weak and with rpms raised belt driven pump pushes more coolant and heat comes in.
Electric one is helpful when the engine is off and cabin heat is needed, it'll blow warm until coolant gets cold. That's a way to test it if it works and if you can find it underneath the hood. Should be on the drivers side of the engine, behind/bellow coolant expansion tank, closer to the cabin. Number 9 in the picture.
I drove mine in -36C and haven't experience lack of cabin heat while idling even for longer periods.
|
im also having squeky belt issue at cold start maybe they are related,gonna find out at dealer soon