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Old 11-29-2012, 04:53 PM   #18
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Join Date: Sep 2012
Location: Old Greg's Cavern
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My Ride: '13 128i STX
Originally Posted by aikmanson View Post
EDIT - the car should not be running.

Yes, keep adding coolant to tank while you bleed. Once coolant comes out, drain ET to normal level using a turkey Baster or equivalent.
Put your key in the 2nd position ("RUN"). Do not start the engine. Turn your AC fan on minimum and then turn the temperature to maximum. Undo your ET cap and bleed screw. Pour water in while watching bubbles come out of the screw. End when just coolant comes out.

Nevermind. Do this:

Originally Posted by BMW-North View Post
Hi Doug

I've done two complete coolant overhauls in the past 4 weeks on a 330 and 325 using pretty much the same method my dad taught me on old cars.

With car off pour coolant slowly into completely dry coolant system via the ET cap hole until full. In both cases the system only took about 3L of it's 8.4L capacity at this point.

Set ignition to position 2 and adjust heater so the max heat is on and the fan is on lowest setting. Leave ET cap OFF. Start car. The minute you start the car the water pump basically scoops all the coolant and starts to push it through the system. With only half the coolant in the system it will get hot fast and thermostat will open. The waterpump doesn't push air so you have to start adding the rest of the coolant.

Continue to add coolant slowly - at this point you need to rev the engine about 4 times up to about 4000 RPMs so that the waterpump is spinning hard enough to push the water through the coolant system. As the system fills it will push water easier and you will see the coolant starting to cycle as it will begin spitting back into the ET tank at the bottle neck. At this point you'll have about 90% full. Since the coolant is now getting hot put the cap on the ET tank.

Rev the car once or twice more and then open up the bleeder screw at the ET tank - don't remove it just turn it back a couple of turns to let the remaining air escape. This takes about 2 mins.

Turn car off - let it cool then adjust the ET tank level to the recommended bobbing position for a cold tank. Might take another 1/2 liter at most.


The TIS I have says basically the same thing except they forgot the engine reving. I think what many folk on here might not do is leave the cap off long enough and rev the engine - for me both of these things are essential for a proper bleeding of air.

BMW TIS: RA Venting cooling system and checking for leaks (M54 / M56)

Adding coolant:
To ensure the cooling system is properly vented, it is absolutely
essential to follow the steps below:
1. Open cap (1) on coolant expansion tank.
2. Open vent screw (2).
3. Switch on ignition.
4. Set heater control to maximum temperature.
5. Set fan to lower speed (so that heater valves open).
6. Fill with coolant slowly.
7. Close vent screw (2) when bubble-free coolant emerges.
8. Pour coolant into coolant expansion tank up to max. cold fill
level. Marking (2) is then on a level with upper edge of
coolant expansion tank.
9. Close coolant expansion tank
10. Allow engine to warm up until thermostat opens

Last edited by WDE46; 11-29-2012 at 04:57 PM.
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