so i`ve decided to replace my thermostat (bmw) to a colder one (non-oem) and now the cooling system doesnt want to bleed completely!

i`ve done this once or twice about a year ago.
here are the things i did..

1. drained coolant from engine.
2. drained coolant from rad.
3. opened up the thermostat housing and replaced the existing thermostat.
(in the previous one, the arrow was pointing opposite of the bleeder screw, i read somewhere that its supposed to be pointing TO the bleeder screw. so i did just that)
4. put everything back together, filled up with JUST WATER.
5. did the blow in the rad. exp. tank, open tstat bleeder .open rad bleeder.
6. turned on the car.. still overheats..
7. turned it off after it passed the 3/4 line.. opened the tstat bleeder screw and steam kept on comming out (no water) until theres no longer any steam then it just stops.
8. turned it back on.. still overheats and heater is cold. :mad

this is @#$$ frustrating me:mad:mad

tomorrow im going to

1. drain everything out again and test the new tstat.
2. buy some bmw coolant.
3. do the open rad cap while car is on bleeding method. ( i`ve read from old posts.. can someone explain this to me fully? )
4. pray.

also, i noticed that after i turn off the car when it passes the 3/4 line.. there seems to be a bit of leaking? in the expansion tank. could this be the problem? nothing leaks as long as the temp doesnt go over the 1/2 line which is my old "line".

:help:help:help

when blowing on the exp tank, do the termo housing screw first while the rad screw tight, then vice versa. from my understanding you did them both at the same time. dunno if this will make a difference. always work for me.

where exactly is the leak from exp tank coming from?

also, doesn't hurt to replace the rad cap.

the arrow was pointing opposite of the bleeder screw

umm did the car overheat with your old thermostat installed "incorrectly"? :confused Clearly that might be an issue. Also, you should definitely get bmw (or saab... it's the same blue stuff but cheaper) coolant..

Let me know how it turns out, best of luck!

^^the leak. i still have to confirm this to be absolutely positive. but it seems like water is seeping out of the where the exp. tank and the radiator overlaps. (black part) arcoss the side. i might pick up a new exp tank tomorrow if anything.

if there is a leak this could be the main prob right? or should i still be able to bleed the cooling system?



^^ the tstat was working absolutely fine when eventhough it was "upsidedown" i dont think it really matters though as long as its not installed sideways. can somone find me a diagram on how to put the tstat correctly. im going to double check tomorrow.

Thermostat:
http://www.realoem.com/bmw/showparts.do?model=HC13&mospid=47402&btnr=11_0790&hg=11&fg=35

Here is a failsafe method that i do when bleeding m20s (i'm an e30 guy.. done many)
1. Park the car with it's nose on a slight incline
2. Drain coolant
3. Open bleed screw, refill coolant until you see it seep out of the bleed screw
4. Close screw, start car with heater on full
5. Once thermostat opens ( reopen bleed screw to let rest of air out) keeping at 2k rpm helps
6. Profit.


If the expansion tank is leaking it means the system is overly pressurized, and stuck closed thermostat can cause this situation.

HTH
Julien

in step number 3-4.. do i close the rad cap? what about the tstat bleeder screw?

here's a method that a mechanic friend showed me that ive used for years on all my bmw's including my 525 m20, just take the upper rad hose off from the radiator only, put a garden hose in the exp. tank and run the engine for about 15 min with the water on flushing the system, gets all the air out, iv'e used it many times including last month when i did the head change on my 735, always works.

in step number 3-4.. do i close the rad cap? what about the tstat bleeder screw?

don't need to. having the car facing slightly uphill gets most of the airbubbles out quickly/easily

Thermostat:
http://www.realoem.com/bmw/showparts.do?model=HC13&mospid=47402&btnr=11_0790&hg=11&fg=35

Here is a failsafe method that i do when bleeding m20s (i'm an e30 guy.. done many)
1. Park the car with it's nose on a slight incline
2. Drain coolant
3. Open bleed screw, refill coolant until you see it seep out of the bleed screw
4. Close screw, start car with heater on full
5. Once thermostat opens ( reopen bleed screw to let rest of air out) keeping at 2k rpm helps
6. Profit.


If the expansion tank is leaking it means the system is overly pressurized, and stuck closed thermostat can cause this situation.

HTH
Julien
Thats exactly what the Bentley says to! Always do what the Bentley says :worship::worship:

in step number 3-4.. do i close the rad cap? what about the tstat bleeder screw?

Rad cap is irrelevant until the system is hot enough to need pressure to keep the coolant from boiling. Most bleeding problems come from not opening the bleed screw when filling the system. This leaves a huge pocket of air in the engine. The reason you're getting steam is because the system isn't full (and the coolant that's in the system is boiling) or there is no flow (you'd still have some coolant at the bleed screw). Depending on what's left in the system, it should take upwards of three gallons to fill it.


here's a method that a mechanic friend showed me that ive used for years on all my bmw's including my 525 m20, just take the upper rad hose off from the radiator only, put a garden hose in the exp. tank and run the engine for about 15 min with the water on flushing the system, gets all the air out, iv'e used it many times including last month when i did the head change on my 735, always works.

Only problem with this is that you end up with a bunch of tap water in the system, when it should have a 50/50 distilled water/coolant mix. There's a lot of junk in tap water that I wouldn't want collecting in the tiny passages of BMW cooling systems. Oxidized aluminum particulate is bad enough from using the wrong coolant or not changing it frequently enough.