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825i overheats

3.8K views 12 replies 4 participants last post by  Ohsarg  
#1 ·
Temp sensor was broken off and replaced with new. Still overheating. Changed oil/filter still overheating. Flushed coolant and ran with new coolant in barn, when I came back the engine was off and coolant was everywhere, seemingly from the radiator or front end area. I removed the radiator and it looks pretty gnarly. ( Bent fins, debri in fins, "wet" spots on fins)Any suggestions on what to do next besides ordering a radiator. (395 used!) I
 

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#2 ·
Did you check to see if the thermostat was opening? Just because the radiator is wet doesn't mean it leaked from there... These have flow from the front to the back and also require being bleed when changing coolant... When I do a Gator I generally use a Vacuum Fill apparatus that puts a vacuum on the cooling system and then releases the vacuum and sucks the coolant from a bucket back into the system... They also have screws you can remove that bleed off the air as you fill it with coolant...
 
#3 ·
Here's how I would diagnose it knowing I over heated it... First I would go down and buy a block check kit with the dye from the auto parts store... Follow the instructions and verify you don't have a blown head gasket cracked head, or cracked block... The kit comes with dye and when the dye changes color it means you have exhaust gases getting into the system and that right there causes an engine to vapor lock, pressurize the system and blow coolant all over the radiator... Next I'd verify my thermostat was working correctly... There are plenty of tests to show how to test a thermostat in boiling water... I have a kettle on my bench just for this... But before any of this if you think the radiator is partially plugged you can by an infrared thermometer and as the unit is running you can temp the radiator all over and look for cool spots on it... Cool spots indicate it being no flow and blocked in those areas.
 
#4 ·
I’d agree with Seth on the radiator. If you have a shop nearby to pressurize it I would be wise to get it checked before buying new or reinstalling.

Make sure your water pump/alternator belt is on and working. If you have a leak on the passenger side of the engine your water pump is likely bad.

If these units are not bled from the coolant bleed screw by the intake manifold on the drivers side (a black T in the coolant line a 4mm Allen or a 13mm wrench on a 6 point hex head bolt, depending on your serial number) the unit will always overheat coolant will never make it thru the thermostat, thus never turning on your radiator fan.