BMW water pump replacement

DON

MEMBER
1998 BMW 540I
V8
2WD
AUTOMATIC
164,000 MILES

I have replaced my aftermarket water pump and am getting a leak from one of the seal between water pipe tubes that mate with the back side of the water pump housing and the o-rings. I have attached this a few times (4) and am getting the same leak. The pipe, after torquing the assembly to the block, appears only to butt up to the o-ring and not seat properly. I have just purchased, from the dealer, a new set of o-rings and gasket, but, in viewing the o-rings, they appear no different than those that came with the water pump. Is there something I am missing? Should I lube the o-ring with anything? Should I use gasket sealer when inserting the o-ring in the housing?
I am frustrated having done this many times over the last few weeks. There is nothing obvious as to why it's failing.

3 Replies

DOCHAGERTY

MECHANIC
9,601 POSTS

I usually chuck the aftermarket o-rings in favor of an original equipment units, they may look the same. Grease the O-rings with silcone grease.

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Saturday, January 29th, 2011 AT 5:02 AM

DON

MEMBER
2 POSTS

Dr. Hagerty,

Thank you. This worked for eliminating the leak from the o-ring. Everything is now nicely attached to the block. However, the temperature gauge is climbing still, then springing back to mid place. This was the reason I changed everything in the first place, and, I had a sneaking suspicion that what I was changing wasn't the source of the problem. Now, nothing makes sense. I still get a low coolant level warning, even though the expansion tank is full. When cold, it doesn't appear to need filling. Perhaps, it drains when the engine first starts then drops the level indicator to issue the warning. I am afraid of over-filling. I am bleeding the air periodically from the radiator and engine, but there doesn't seems to be much bubbles coming out. I am changing the FCU because the blower fans aren't working (Fuse is ok), but I can't see this being the source of the problem.

Anyway, thanks again.

Don