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From digest.v6.n49 Sun Jan 12 01:33:24 1997
From: Don Eilenberger <>
Date: Sat, 11 Jan 1997 22:39:34 -0500 (EST)
Subject: RE: E28 coolant change..

In the midst of some great advice, I saw:

>4. inside car, set temperature control knob to max position. This fully opens
>the heater control valve and will allow you to drain the heater core.

Nope. Not on any recent BMW. The heater coolant valve is electronically controlled - and not mechanically connected at all to the knob.

IF you are REALLY REALLY anal - and insist on getting ALL the coolant out'a the system, there are two ways to do it.

  1. Take every hose off everything and have antifreeze all over the place (I don't do this)


2. Drain system. Refill with clear water. Repeat several times running engine and heater system up to temp between changes. Let cool before repeating. (I used to do this)

Or you can be a bit less anal and with 2 year changes as mentioned, you can really get by without worrying yourself to death about some residual pockets of coolant left in the heater and block.

IF you remove the bottom radiator hose and open the air bleed on top of the thermostat (on earlier engines - the M50 uses a bleed in the top of the radiator itself), and let it drain, you'll easily have 80-90% of the old antifreeze out. The etheylene-glycol in antifreeze (propylene-glycol in the new 'safe' stuff) itself doesn't degrade with time - it is pretty much inert. What you are replacing is the additive anticorrosion packages and any sludge buildup - which is more common in systems with dissimular metals (wonder why aluminum radiator cores are more common now - think of the amount of aluminum in an engine - aluminum and copper REALLY don't get along at all..).

Anyway - drain, premix 50/50 and refill. If you do it every two years - you're not gonna have problems.


Don Eilenberger
Spring Lk Hts, NJ, USA
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