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      07-06-2015, 04:25 PM   #129
mi_bimmer
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Drives: 2006 325i E90 N52
Join Date: Dec 2012
Location: SE Michigan

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Quote:
Originally Posted by neoexodus View Post
I purchased a (Fluid Transfer Pump) from ECS and was hoping that someone could explain what I've seen said in a few places. I can't recall if I saw something like this in here, but would appreciate information all the same.

Basically, I've seen it said that you can put the new Diff Oil into the Fluid Transfer Pump and just go to town pumping it into the diff, with no mention of anything else (i.e., extracting the previously used oil). Is the concept here that I should be pumping the new oil in at the lowest point I can get to in the diff and trying to displace the old fluid into leaking out? I don't see how it would be extracting fluid directly with the pump, or am I missing something?

Seems like displacement of the old oil wouldn't be the most optimal way to change it, aside from it being easy, as wouldn't there be a ton of contamination to the new oil? Hoping I missed something, don't really want to buy any more tools atm. Thanks!
You definitely want to pump out the old oil first. Just switch the in/out hoses and pump out as much of the old fluid as you can. Then pump in the new fluid until it just starts to trickle out of the drain hole, that's when you know the differential case is full.
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