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-   -   Z3 Complete Engine Block Coolant Drain (

Fred Parmenter 08-15-2012 11:41 AM

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?

ALM168 08-15-2012 12:48 PM

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.


flossy21 08-16-2012 05:06 AM

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.

pjdumpert 11-11-2012 06:31 PM

Filling the coolant
Is the only way to add all new coolant through the expansion tank cap?

ALM168 11-12-2012 04:52 AM

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.

Blacklane 11-12-2012 06:13 AM

Maybe this link will help.

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