BMW Forum - BimmerFest BMW Forums banner

Cooling system - What gives??

1.3K views 1 reply 2 participants last post by  aleks001  
#1 ·
Hi all.. E90 325i 2006:

My car has been over heating lately... I'll be driving along, and suddenly the yellow coolant light pops up. Pull over quickly and I let it cool down... This happened two days ago. This morning, same issue.

A few days back, a petrol jockey opened the coolant cap to check, while the motor was hot. I thought that air had gotten into the system, so I bled it (ran the water pump)

I've been watching my temp (hidden menu) and it heats up fine, no issues, however, when the temp reaches around 70 deg Celsius, the fan starts blowing, on, then off, then on... constantly powering up then powering down.... Then when the car reaches 100 deg Celsius, it slows to a slow spin... When I'm doing city driving, the coolant doesn't go over 110... on the freeway, it goes up to 120...that's when I pull over and shut it down... I'm not losing coolant.

Any help here, please guys. When I bleed the system, you can see the coolant being pushed into the reservoir, but its not a very strong stream. I'm not sure what its meant to sound like (the water pump, while it bleeds).
 
#2 · (Edited)
This seems tricky, I would try and get the car scanned for error codes first you might get lucky and find something has already been reported, especially if a warning light has already come on.

I think it could be three things.
1. Water pump, although working, isn't working properly and is in the dying stages and can not push the water through at the right pressure. Also you say you can see the coolant being pushed around, I assume this because you had the lid off the expansion tank. I could be wrong here, but I think if the pump is working properly, it would blow the coolant out of the expansion tank if you had the lid off. I think it is quite a high pressure system.

2. The thermostat is acting up somehow.

3. Some sort of weird electrical gremlin (Unlickely though)

Get the codes red, will save you a lot of time hopefully.