Question about BMW 735i
Water flows in the bottom, and out the top of your engine. If bottom is cold, not just cooler than the top, could be a plugged radiator or failed water pump.
thermostat typically stays closed til about 170 deg F to 185, to warm the engine. When it opens, top hose gets hot quick. Thermostat sounds fine to me.
Posted on Apr 25, 2015
it sound like the thermostat is playing up, replace the thermostat and your BMW will be OK.
Posted on Apr 25, 2015
This sounds like a coolant flow problem. possible rad plugged or water pump problem.
Posted on Apr 24, 2015
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Posted on Jan 02, 2017
Your thermostat is stuck closed. It needs to be changed right away. By the way the operating temp on that motor is 160 degrees so you are running hot you have just been lucky so far. Good Luck
Posted on Dec 01, 2008
When the car is completely cool,check the electric fan(s) for smooth rotation.
Clean/check/change the thermo sensor,contact and wire.
Excavate air pocket in coolant system / check for head gasket leak
This test will kill two birds with one stone.
MAKE SURE THE COOLANT SYSTEM and ENGINE IS COLD!
RAN THIS TEST IN A WELL VENTILATED AREA ONLY!
You will spill some coolant during this air pocket purge test.......BE KIND TO THE ENVIRONMENT and ANIMAL please clean up after the test!
Put the front end on a pair of ramp or park your car on a VERY STEEP HILL (radiator facing top of the hill) .
Top of the coolant reserve tank
Let it ran for 10-15 minutes.
Monitor for air pockets escaping from coolant reserve tank.
Small amount of bubbles is OK at 1-5 minute mark
After the thermostat open up (after 195 F warm up) at
5-12 minute mark or after high idle you should see less bubbles.
If you do not see any in rush of bubbles then your thermostat may be partially stuck or rusted badly inside the thermostat hosing.
Give the thermostat host few gentle taps.
If you see larger bubbles surfacing after 15 minutes then should do a hydrocarbon (HC) dye test to test for potential head gasket leak.
Let engine cold down and top off coolant reserve tank.
Start monitor for coolant lost
A coolant flush is require every 2 years or 24,000 miles.
I recommend the thermostat that has a relief pop-let to reduce the change of burst radiator and coolant hoses.
Make sure you get a new thermostat gasket,black RTV and fresh coolant for the job.
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Posted on Dec 05, 2009
Either the water pump has failed, the radiator core is plugged, or the lower hose has collapsed and blocking the flow of coolant. Hope this helps!
Posted on Oct 15, 2010
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