[Blaine325xi]

Hey guys please help me out. I finally pulled the trigger and bought my first BMW the other day and its got an overheating problem. The top radiator hose gets hot but the lower one stays cold to the touch. The water pump has been replaced along with the thermostat. It leaked out of the old coolant res but thats been since replaced as well. Im at a complete loss. A buddy of mine is thinking its the thermostat put in backwards?

Thanks,
Blaine

[EyeGuy]

Do you see where it is leaking from? Maybe at a hose connection or a crack in the radiator?

[Brian86]

Thermostat is integrated into a big plastic bagpipe looking manifold down by the pump. It's not really possible to install it incorrectly.

Thermostat housing could be defective, or not changed at all.

Assuming the car has been filled and the purge cycle is successful? Hear the quiet washing machine gurgling when running the bleed procedure? ECU giving you any water pump errors?

[Blaine325xi]

Figured it out today we think. It got too pressurized somewhere and blew the o ring out of the coolant reservoir. Replaced it with a new one and now its holding pressure and not overheating anymore. Thanks for the help guys!

[Suvorovo]

Originally Posted by Blaine325xi

Figured it out today we think. It got too pressurized somewhere and blew the o ring out of the coolant reservoir. Replaced it with a new one and now its holding pressure and not overheating anymore. Thanks for the help guys!

Which o-ring? The one for this expansion tank hose? I recently replaced mine as well. The old one started leaking when lightly touched.

https://www.fcpeuro.com/products/bmw...se-17127618510