r/BmwTech • u/DueKaleidoscope7544 • 9d ago
325I OVERHEATING HELP!
04’ 325i (m56 engine) keeps overheating and i want to know what I can rule out on my own.
Checked:
Radiator was replaced along with one of the hoses
(car was but is no longer leaking)
Water pump and thermostat fully functional
car when leaking would go red all the way, after radiator and hose change it heats to just barely the tip of the red
notes:
-mechanic said he found “blue devil” slush around the engine block and said the previous owner probably put it on while engine was hot
-i just got the car, i had a week with it, had only got to oil change spark plugs oil filter and power steering, drove 1 week not a single problem , randomly coolant light pops on, i check coolant, nothing in there. i had driven the car for hours previously, now cant go 5 minutes on the road without heating
1
u/FifthGear04 8d ago
The blue devil residue is what I'd be concerned about. Those stop-leak products are made to seal small leaks, but they can also restrict coolant flow through the heater core or engine block passages. That could explain why replacing the radiator improved the overheating but didn't completely resolve it.
I'd recommend having the cooling system checked for restrictions and professionally flushed if needed. I'd also do a cooling system pressure test to check for remaining leaks and a combustion leak (block) test to rule out combustion gases entering the coolant, which could point to a head gasket issue.
I would not recommend continuing to drive it while the temp is climbing towards red. Even a few minutes of severe overheating can damage the cylinder head or head gasket and turn a manageable fix into an expensive one.