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

[Kalevera]

Lennart - people are confusing the M30 and the M20. The M30 has the bleeder screw on top of the tstat housing, while the M20 has it on the radiator, IIRC.

Also, I've got a pic of a tstat with the tiny hole in it - will upload it when I get home. I think I did 1/16", which worked out fine once I had the sucker in there correctly. If you got a Vernet Calorstat (from BMA), it won't have the arrow on it.

best, whit

[Lennyz525i]

Hmmm, I also have a bleeding screw on top of the tstat housing and one on the radiator, confusing. I suppose the one on top of the tstat housing is not to be used then (in my case). I actually did use to have a Vernet tstat in there, but it started to act up so I decided to replace it with an OEM bmw one. I'm going to take the tstat out tonight, see if that gasket is on the right side and follow the instructions you guys have given me to refill and bleed. Thanks a lot for the great help!

[Kalevera]

I think you want to use the one that's the highest point in the system (hence where the air will congregate). You may also have a heater hose with a bleeder in line (I know that there's a hose you can buy with one in it) to help purge the heater core of air.

Here's that pic:

http://img.photobucket.com/albums/v736/suzpectx/tstat.jpg

IIRC, the gasket is on the wrong side in that picture.

Best, whit

[Lennyz525i]

"IIRC, the gasket is on the wrong side in that picture." That's not where the o-ring is supposed to be? That's the part that sticks into the housing cover right?

[Kalevera]

Hi Lenny. I'm trying to remember...

The SPRINGloaded side goes into the tstat housing, the part in the picture is on the tstat cover side (at least, on the M30). Actually, now that I think about it, I guess the gasket is on the correct side in the picture. When I took it, I was about to stick it into the car the WRONG way (the gasket was on the wrong side) and it caused the car to overheat (up to the 3/4 mark) for a few days until I took it apart and put the gasket on the tstat COVER side of it -- so I guess it's right in the picture.

Interestingly, I replaced the thing exactly as the old one was in there (tstat, gasket, housing). The old one worked that way...the new one didn't. Go figure.

best, whit

[emw525E34]

Hi Lenny,

Of all the replies here. I DID NOT see how people *fill* in the coolant into the M20 engine!. You *must* remove the TOP hose from Radiator into the engine. Just square on the topmost part of the engine!. Fill in coolant there until it just about overflowed!. This ensures your system has more than 70% coolant in the system. Put back this host and fill into the radiator until it overflows. Then use tsat to bleed, you will get solid flow of coolant from Tstat screw. If not, your system is still VERY low on coolant. Wait for engine to cool , take off the Top host and fill there again until overflow!. I can guarantee you than after 2 fills in this way, you can bleed once or twice and your engine will NOT overheat!. I have this this many times and I believe, I perfected the method for the M20 engine only.

After doing that, next day, your radiator will be almost at half of 2/3 level. Full up some more and bleed one more time, now with Radiator bleed screw. Plastic screw. You are done!.

[Lennyz525i]

It's bled!!

Thanks a lot for all the tips and help guys. Here's what I ended up doing: yesterday during lunch break I drained the radiator again, took out the tstat to see if it was installed correctly. Put it back with the arrow pointing up. Then last night I put the front on jackstands, filled the reservoir up and opened the bleeder screw on the tstat housing. I then put a funnel (with some paper towel wrapped over the narrow end to make a better seal with the reservoir) into the reservoir, stuck a tube in there and started blowing really hard into the reservoir. You could here the cooling system starting to belch. Close the tstat bleeding screw, take a deep breath and start blowing really hard again into the reservoir, repeat and eventually a stream of coolant will gush out of the tstat cover. Then I filled up the reservoir and started the engine, waited untill it warmed up and started bleeding from the screw on the radiator. Just letting the little bubbles flow out. At this time the temp already wouldn't go past the 3/4th mark. I shut it off and let it cool down. Did this same thing two more times and during the last bleed I noticed the temp being steady at one needle width past 1/2. I tapped the accelerator a few times and the needle actually dropped a tick below 1/2, as I was playing with the heating I turned it back on and got hot air. Time for a little dance!

[632 Regal]

Congratulations!!!!!

[emw525E34]

Good, finally. I could do all of that in under 40 mins flat!.

[uscharalph]

Thanks for this post guys. I'm hoping all these good tips will help me out.

[E34-520iSE]

It's bled!!

Thanks a lot for all the tips and help guys. Here's what I ended up doing: yesterday during lunch break I drained the radiator again, took out the tstat to see if it was installed correctly. Put it back with the arrow pointing up. Then last night I put the front on jackstands, filled the reservoir up and opened the bleeder screw on the tstat housing. I then put a funnel (with some paper towel wrapped over the narrow end to make a better seal with the reservoir) into the reservoir, stuck a tube in there and started blowing really hard into the reservoir. You could here the cooling system starting to belch. Close the tstat bleeding screw, take a deep breath and start blowing really hard again into the reservoir, repeat and eventually a stream of coolant will gush out of the tstat cover. Then I filled up the reservoir and started the engine, waited untill it warmed up and started bleeding from the screw on the radiator. Just letting the little bubbles flow out. At this time the temp already wouldn't go past the 3/4th mark. I shut it off and let it cool down. Did this same thing two more times and during the last bleed I noticed the temp being steady at one needle width past 1/2. I tapped the accelerator a few times and the needle actually dropped a tick below 1/2, as I was playing with the heating I turned it back on and got hot air. Time for a little dance!
That's EXACTLY how I bled my M20 system. It's a skill that once mastered, gets easy to do. I could drain my car, refill and bleed in about half an hour. Anyone in N E England, UK want their M20 bled, give me a shout, I'll do it F O C!

Cheers,

Shaun

[winfred]

i guess it'd make you sick that i do it in under 5 :D


Good, finally. I could do all of that in under 40 mins flat!.

[vic525se]

Open the stat bleed screw take out the bleed screw next to the rad cap put the ign on [without the engine running] turn the right hand side heater control to the override setting and keep pouring water in the rad till it comes out of both bleed holes