Only for the wise.

[nunezfrancisco30]

OK thinking hats on! I just finished a swap from m42 to m20b25, I couldn't bleed the system myself due to open headers in a quiet neighborhood -_- so I took my car to a shop the other day so that they could install the exhaust and bleed it for me. Once the exhaust was on they found it impossible to bleed the system! A apparently it would only spit stem out of the thermostat housing bleeder, and huge amounts of bubbles would spill out of the m42 radiator reservoir. They believed it to be a bad water pump and thermostat. So I started working on it right away, checked the thermostat and water pump and bam perfectly fine, the next thing they suggested was a bad head gasket! ( mind you that I had already replaced the prior one and had the head resurfaced) So i took it apart ones again and no signs of any air leak or blown gasket, took the head to a machine shop and they found it perfect! the gasket was "beautiful" according to the guy of the machine shop. All of the hoses where checked and everything is perfect. CAN SOMEONE PLEASE HELP!!!

[MoreMayhem]

There are probably a gross of tutorials within this forum about coolant bleeding.
It can take what seems to be an extraordinarily long time to get all the air out of the system, as I recall from a complete drain/flush/refill I did earlier this year.
Stick with it, you'll get it.

Edit: my advice probably isn't worth much. I'm often called a dumbs**t, so that's why the "only for the wise" didn't scare me off.

[dude8383]

The m42 radiator can be a pain in the ass to bleed. My best guess is that it simply wasn't fully bled and they gave up.

You need to jack up the front to help aid in the bleeding process. In the past I simply opened the bleeder screw and drove the car around for like 30-60min. That would generally bleed the system.

[nunezfrancisco30]

MoreMayham that was too funny hahaha, as for the drive around with bleeder open, My temperature gauge would reach the hot zone in only 4 min, sounds like a good idea. Would I do the drive around after I try the stationary bleed procedure? thanks guys everyone else seems to have been scared off by the wise only tittle lol

[MPLFoster]

I too recently bled the coolant system on my 325i. It takes quite a bit of time to completly bleed the air out. Like others have said, stick with it till there is a steady stream of coolant from the bleeder, then top off the res and drive around for a bit. Check the level, it should have gone down a bit. Check the bleeder one more time. If there are no more bubbles/steam, you're aces.

[dnguyen1963]

Try this if you continue to have problem...

http://www.sjdiscounttools.com/uv550500.html

[MattAvino]

On an M30, I found it quite helpful to put some vacuum (I used my mouth) on the coolant reservoir at different times (hot/cold/running/not running)

[bmw325csi]

I used to suffer too but one day, after an cooling overhaul I:
-jacked up the driver side
-open radiator cap and bleed screw
-slowly filled the water in the reservoir
-wait for water to come out of the bleeder

All done. No more air in my system

[nunezfrancisco30]

Thanks for all of your inputs! I just finished putting everything back together, where should I fill the coolant thru to avoid the most air, I was told to fill it thru the thermostat housing by the machine shop?

[Earendil]

I used to suffer too but one day, after an cooling overhaul I:
-jacked up the driver side
-open radiator cap and bleed screw
-slowly filled the water in the reservoir
-wait for water to come out of the bleeder

All done. No more air in my system

This!

I use this method, and usually am able to tighten everything after this and go drive for 15 minutes with completely normal operation. I still bring it home hot and "bleed" it some more, but it rarely seems to need it. I also check my coolant reservoir a couple times over the next week as air will filter up into it and drop the reserve level a little.