Coolant System bleeding... [Archive] - Bimmerfest - BMW Forums

: Coolant System bleeding...

06-13-2012, 11:53 AM
Just replaced the standard issue exploding coolant expansion tank last week. Before that, I got the low coolant code and "P112B - Coolant below minimum value" code. I cleared the codes but today the P112B code came back. The only way that can happen is if there is air in the system. So I'd like to bleed the system but I don't see any bleeder screws. I'm sure they're there but where?

2006 550.

06-13-2012, 12:45 PM
IIRC you leave the cap open and run the engine for a minute or two. Maybe someone else can chime in here - that is what I did when I changed out my expansion tank. No air bubbles...

How low is the coolant after replacement?? Did you fill it all the way? Is it just a top off that you require now? And I am assuming you plugged the sensor in under tha tank but maybe check it to make sure its snug.

06-13-2012, 12:51 PM
It should be the highest point in the system which the reservoir is not... Not sure why that code is reoccurring though. It would have to be air in the system or a poorly timed sensor failure.

06-14-2012, 06:15 PM
There are no bleeding screws. the bleeding procedure is completely computer controlled on these cars. The procedure from the bentley manual is below. I too replaced my own expansion tank and did the below procedure. worked like a charm. I hope this fixes your coolant low level warning but I will say that you could have a leak somewhere else that you can't see. I have had a valley coolant leak for 6 months now and have never seen a drop. I get a low level warning once a month or so and top it off. My indy said it's fine until the leak becomes worse and the low level light comes on more frequently. then it's time for the $3k fix :cry: good luck!

Before filling radiator:
Switch ignition ON, but don't start engine
Set heater controls to full hot
Set heater fan control to low
Set seat heat controls to low

Slowly fill cooling system and expansion tank to MAX using 50:50 mix of BMW coolant and distilled water

Leave expansion tank cap off
Start engine, let it idle for one minute
Install cap
Run engine until it reaches operating temperature
Let engine cool
check coolant level, add coolant to MAX level