[Ghibli]

Hey all, I own a 2007 bmw 335i coupe with 92,000 miles on it. My car over heated and then my mechanic replaced the water pump AND thermostat a couple weeks ago. Was driving it the other day and it started over heating again. Filled it with coolant, didn’t give me a light, and now it’s over heating again. I opened the hood and saw some coolant underneath the coolant reservoir although I’m not sure if it was leakage from when I filled it earlier today. Any ideas on why it would be over heating even if I just replaced the pump and thermostat? Thanks in advance.
-Greg

[theslowe90]

I think your coolant reservoir is leaking if you see coolant underneath it... Try to replace that as well and see what happens.

[Ghibli]

Originally Posted by tonyttot

I think your coolant reservoir is leaking if you see coolant underneath it... Try to replace that as well and see what happens.

Alright thank you I appreciate it

[clegg]

You may need to bleed the cooling system if you have no leaks.

There is an easy procedure. Google E90 coolant bleed or search on here.

[C4maro]

Wouldn't you get a low coolant light before a overheat if it was a leaking resovoir?

Also what about faulty resovoir cap?

[mainbearing]

I would think if it leaked enough then a low coolant light should come on. However, a cracked reservoir also means the system will not hold pressure, and this can cause a boilover.

[Ghibli]

Originally Posted by clegg

You may need to bleed the cooling system if you have no leaks.

There is an easy procedure. Google E90 coolant bleed or search on here.

Okay I'll try that, thank you.

[Ghibli]

Originally Posted by mainbearing

I would think if it leaked enough then a low coolant light should come on. However, a cracked reservoir also means the system will not hold pressure, and this can cause a boilover.

Yeah i think I've gotten a low coolant light before (my rear turbo leaks) and I didn't get that light. I only got the yellow temperature light followed but the red temperature light and then limp mode after that. So maybe it is cracked and won't hold pressure?

[Ghibli]

Originally Posted by C4maro

Wouldn't you get a low coolant light before a overheat if it was a leaking resovoir?

Also what about faulty resovoir cap?

I'm not sure if it's the cap or not. The cap would cause the car to overheat?

[Tambohamilton]

Cap has a pressure relief valve built in - if that doesn't hold pressure, the water in the system will boil at a much lower temp than it needs to...and result in overheating.

[nsjames]

Originally Posted by Tambohamilton

Cap has a pressure relief valve built in - if that doesn't hold pressure, the water in the system will boil at a much lower temp than it needs to...and result in overheating.

this.

a cap is worth a shot, but someone needs to pressure test the cooling system.

if it passes a pressure test with no leaks, then replace cap.

your previous overheat may have led to an increase in the pressure the system had to contain, and damaged something.

[Ghibli]

Originally Posted by nsjames

this.

a cap is worth a shot, but someone needs to pressure test the cooling system.

if it passes a pressure test with no leaks, then replace cap.

your previous overheat may have led to an increase in the pressure the system had to contain, and damaged something.

Alright that makes sense. Thanks a lot. However, I turned the car on and opened the reservoir before doing so to check for leaks and there was some smoke coming from that area as the car warmed up. Definitely leaking then?