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E36/7 Z3 (1996-2002)
E36/7 Z3 Roadster, Z3 coupe, Z3 M Roadster and Z3 M Coupe talk with our gurus here.

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Old 08-15-2012, 12:41 PM
Fred Parmenter Fred Parmenter is offline
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Location: Medfield, MA
Join Date: Feb 2011
Posts: 34
Mein Auto: Z3 Black 2.8 2000 Roadstr
Complete Engine Block Coolant Drain

This question has to be about the silliest ever asked in a Z3 forum, so I apologize ahead of time, but I can't figure it out.

I am wondering how you can get a complete engine coolant flush by removing the engine coolant drain plug. The reason I ask is that the engine coolant drain plug is fairly high up on the engine, much higher than the water pump which is almost at the bottom of the block. How can removing the engine coolant drain plug possibly allow the coolant below it to drain?

I guess a second question would be, if you are going to replace water pump, why do you even need to remove the engine coolant drain plug? Wouldn't all the coolant come pouring our the water pump hole as you start to remove the water pump? And wouldn't this be a much better way to drain the engine block completely?

Last edited by Fred Parmenter; 08-15-2012 at 12:45 PM.
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Old 08-15-2012, 01:48 PM
ALM168 ALM168 is offline
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Location: NJ
Join Date: May 2012
Posts: 99
Mein Auto: Z3, e46, Ford Explorer
There are two drain plugs on the Z3, one on the side of the block and the second on the radiator. You need to remove both plugs for a complete coolant drain. You normally open the radiator drain first, then the block....and this will still make a mess on the ground. The radiator plug must be opened before removing the water pump.

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Old 08-16-2012, 06:06 AM
flossy21 flossy21 is offline
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Location: Williamsburg, VA
Join Date: Jul 2008
Posts: 32
Mein Auto: Ford Explorer
air in the system

If you think about it your coolant system is a bunch of channels and tunnels that go through the block. The more turbulent the flow the better the heat transfers so the coolant has to go through little turns and twists quite a bit. If you don't drain the block and the rad seperately then you would have coolant and air pockets in one or both.

If you are just changing the WP then you can get away without draining the block completely but why not flush it all out since you in there anyway. I actually ran a garden hose wide open where the WP and thermostat meet the block to make sure and move all the old coolant out when I changed my WP.
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Old 11-11-2012, 07:31 PM
pjdumpert pjdumpert is offline
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Location: USA
Join Date: Nov 2012
Posts: 3
Mein Auto: 1998 BMW Z3
Filling the coolant

Is the only way to add all new coolant through the expansion tank cap?
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Old 11-12-2012, 05:52 AM
ALM168 ALM168 is offline
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Location: NJ
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Mein Auto: Z3, e46, Ford Explorer
Yes, filling the coolant system is done via the expansion tank. Make sure you follow the directions per Bentley manual or you will have air pockets in your system.
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Old 11-12-2012, 07:13 AM
Blacklane Blacklane is offline
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Location: Springfield, Ohio, USA
Join Date: Jun 2011
Posts: 1,123
Mein Auto: 1998 Z3 Roadster
Maybe this link will help.

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coolant, drain plug, flush, water pump

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