Curious M50 bleeding issues - help -

[Tom Bombadil]

I replaced the thermostat, housing, gaskets, water pump, and hoses.
I filled the resivoir with 50/50 BMW coolant and distilled water (pre-mixed) to full cold.
I put about 8 quarts of the mix in, with the top hose detached to let air out.
I then reconnected the hose, loosened the bleed screw, and started the car.
When it heated up to just over 1/2 it started spewing coolant and blowing steam from the bleed valve.
I am not used to this scenario. I have bled my M20 engines many times and dealt with only bubbled coolant escaping from the bleed valve. Never pure steam.
It appears I have *lots* of air in the system, which of course I must bleed, but the temp gets too high (3/4) if I let id go.
I have stopped for the evening and will re-bleed inthe AM.

Any ideas???

BTW, it had no cooling issues previously. I was doing preventative maint.

[DaveVoorhis]

Try pressure bleeding it. Fill the reservoir, and poise a wrench on the bleed screw. Stick your mouth in the reservoir filler neck and blow hard to pressurize the system. While maintaining pressure, crack open the bleed screw, then close it before you run out of pressure. Repeat until coolant comes out the bleed screw. Marvel at the efficiency of this technique, and the level of newfound intimacy you'll feel for your car.

[Kalevera]

Not enough coolant was put into the circuit; a questionable bleeding procedure was used.

There's absolutely no need to remove hoses to bleed air on an M50. In fact, I'd argue that it's a detriment. Close the system after repairs are made, open the bleed screw, fill the tank until the bleed screw starts weeping coolant. Then close the bleed screw and continue filling the tank until it hits the cold mark (or, to make it much simpler, just fill the expansion tank all the way to the top and close the cap). Turn on the heat. Start the car, crack the bleed screw open momentarily and see what comes out -- no air, close it and drive it. If it starts to overheat, crack the bleed screw to remove any air. If using the method of overfilling the tank, bleed off some of the excess once things are working correctly (on an M50 or other non-drain tube systems -- M30/M20 and the like will bleed off any excess on their own), then fill to the correct level once the car is cold.

You got steam and boiling coolant because there was little or no flow in the system, because there wasn't enough coolant in it.

best, whit

[Tom Bombadil]

Thanks.

I'll fill it all the way up again and then re-commence bleeding.
Is there any other way to ensure I have the maximum amount of coolant in the system? Or is the expansion tank the only way? Obviously I am about 3-4 qts. low.

[Bill R.]

10 quarts total. Before bleeding always turn the heater control to full hot and the blower to high. This opens the heater valve and turns on the auxillary pump if needed to circulate water through the heater core and the remaining hoses to help push the air out. Bmw also states that after doing this you leave the radiator cap on loosely and rev the motor to aprox. 4500 rpm 3 times or so and then shut the engine off not letting it run more than 30 seconds initially. Then after shutting it down you fill the cooling system again , then start and use the bleeder screw to get the remaining air out. The procedure for the 525 m50 is in the Tis under the e36 m50 procedure.

Thanks.

I'll fill it all the way up again and then re-commence bleeding.
Is there any other way to ensure I have the maximum amount of coolant in the system? Or is the expansion tank the only way? Obviously I am about 3-4 qts. low.

[Kalevera]

Yes, leave the bleed screw open while initially filling the system. Close it and continue filling after you've got coolant at the screw. The expansion tank/bleed screw on M50 E36/E34 cars are at the highest point in the system. So a careful fill will usually eliminate air pockets completely. It should only take a few minutes to bleed, most of which is waiting for the system to come up to temperature.

best, whit

[Tom Bombadil]

Thank a lot everyone, especially the TIS mention, as the Bentley is lacking in some areas.