One bleeding nightmare

[Lennyz525i]

Problems bleeding the M20... I know this topic pops op all the time, I've searched the boards, have tried a few tricks but nothing so far seems to work. (I've tried the one mentioned on Bruno's site). I've tried bleeding 9 times now, have probably wasted more then half a gallon of coolant/water mix and I still have air bubbles coming out of the Tstat housing any time I open the bleed screw. No heating yet either. I open the bleed the screw once the tstat opens, let some coolant with air bubbles out, close the screw, open it again, close it again etc.. until the engine reaches the 3/4th mark, which is when I shut it off.
Any advice or suggestions are very welcome.

[Kalevera]

Hey Lenny. Perhaps you've got some cavitation going on. One of the things you might do is drain it (at least partially -- ie, the radiator) and then refill with the front end up in the air and the heat/blower on "high" (ignition in the "run" position, but engine off). This will get the aux water pump moving the coolant as you pour it in and help remove air from the heater core. These systems are self bleeding...anything more than a few bleeds and there's got to be some other physical problem with it.

Good luck!

best, whit

[winfred]

m20 e34s can be a miserable bitch to bleed, i've seen more then one person roast a motor trying, remove the thermostat and drill a hole about 1/8" where the arrow is and reinstall with the hole in the 12:00 position, this will let the cooling system burp and allow the block and head to fill with water, open bleed screw and fill tank till it flows water then close, squeeze the hoses and open the bleeder and see if any more air comes out, then try running it

[Gene in NC]

RU sure you searched. Search on "525 bleed" and check out the "bleed--- mystery". Some odd sounding tips but applying to my recent purchase '89 525 seems to be helping. Engine did not oheat, even on 300 mi 75-80 mph trip, but coolant level did strange things.
Have had bleeding struggles with our long term '89 525a but nothing like this one. Can't tell for sure whether prob is simple bleeding bitch or a , warped, cracked or head gasket leak despite very, very recent head gasket replacement. On hte other hand, head gasket replacement doesn't mean that head was checked for warp or crack. There's a lot of half assed shop work done just like there are a lot of half baked owners. And then there ae alot of halfbaked owners doing really halfassed work. Didn't notice that you stated wht started your prob.

BUT most important is that M20 on the 525 is bled at the radiator bleed screw!!!!!!!!!!!!

[Alan_525i]

After having my head replaced, my shop complained about what a PITA these are too bleed. Since I had it done (about 700) miles I've had to add two expansion tanks worth of coolant from "burping". The first time I did it i forgot to open the rad bleed screw so I have a feeling I didn't really help things any that time. But it seems to have stabilized pretty well now. Finally. I'm sick of spending 14 bucks a gallon on BMW juice.

[Rory535i]

I know it might sound stupid but is the thermostat in the right way? I did a head job on my M30 and was so tired i put the thing in the wrong way round and couldn't bleed it. took me ages to figure it out.

[callen]

Lenny:

My 535 does that to me....I end up taking one of heater hoses off of the auxiliary waterpump attached to the firewall. Once I do that the heater core fills up and I'm done. It's a bit$h to get to the hose and unscrew but give it a try

Callen

[Lennyz525i]

Alright, tonight I'm going to drain the radiator again, check to make sure if I installed the tstat correctly. Winfred, "drill a hole about 1/8" where the arrow is and reinstall with the hole in the 12:00 position" Do you mean there's an actual arrow on the tstat or are you referring to one end of the tstat that sorta looks like an arrow?
"BUT most important is that M20 on the 525 is bled at the radiator bleed screw!!!!!!!!!!!!" While reading other posts, it seemed like radiator bleed screw and tstat bleed screw are used interchangeably. So I really shouldn't be touching the tstat housing screw then? The radiator bleed screw only lets out tiny little bubbles though, wouldn't it take years to bleed like that? Also, doesn't air gather at highest point in the cooling system? (I mean at the tstat). Alright, I'll go search some more posts on this. I'll let everyone know what eventually worked for me. Thanks for the help.

[callen]

telling you pull the feakin hose of heater core...

[winfred]

theres a arrow on most thermostats in the outer ring just to the inside of where the rubber o-ring goes, drill a 1/16 to 1/8" sized hole there and put the hole at the top when you install the thermostat, that keeps the thermostat from getting air locked, which meens theres a bubble of air insulating the thermostat from the heat of the coolent so it will not open