Dumb Question About Bleeding Coolant in 3.0i
 

FWIW: I have done numerous cooling system overhauls on BMWs. Probably around 20, including the 3.0 M54 in my wife's E85 Z4.

What has me stumped is the electric water pump in the E53 3.0. This is my usual procedure for bleeding coolant:

1. Engine off
2. Set heat controls to max heat
3. Loosen bleed screw
4. Remove expansion tank cap
5. Slowly pour in coolant until it comes out of the bleeder
6. Start the engine with the heater still on full heat
7. Watch the bleeder until a steady stream of coolant comes out with no air bubbles while keeping the expansion tank topped off
8. This usually takes 10-15 minutes, then shut off engine, tighten bleeder and install expansion tank cap
9. Let the car sit overnight, then loosen the bleeder to "burp" the system
10. Remove expansion tank cap and top off if necessary
11. Then I usually check the level after a couple of days - just to make sure it's good.

What's got me confused is that as soon as I turn on the key, the electric pump starts and sprays coolant out of the expansion tank and the bleeder. So it's impossible to keep it topped off or even tell if air is coming out.

Is there a trick to doing this? Can I unplug the electric pump while I'm bleeding the system? Or, is there a way to run the engine without the electric pump being activated?

When I did mine I had someone rev the engine while I had the tank cap on and bleeder screw opened until I saw a steady stream

Your procedure is mostly correct BUT you don't start the engine (#6 on your list), you simply switch the ignition to on, so that the electric pump for the heater will function.

When you have achieved condition in #7, THEN you start the car and warm it up and (continue to run the heater). #8 may not be fully needed, a short drive with a cool down would be enough.

Good tip. I will try that!

by chance, can you tell me what this is?

melted plastic :p

whats the underside of it look like?

Pretty nails, but oh she's taken. ;)

Where did you find it? It looks like some kind of a patch or plug, but isn't immediately obvious what it is.

here's the other side. long story short, it "fell" from inside the bottom of the dirt cover as i removed it from the undercarriage. @upallnight, not "taken," just a slave to ideals.

Pretty interesting the things we all find when we remove things like lower shields... which engine do you have? Might help us figure out where this may have come from. :dunno: