[robb100]

I just replaced the oil filter housing gasket due to it leaking oil. I also replaced the mickey mouse flange since i was there. The flange wasn't leaking but it sure was breaking down. I also replaced the serpentine belt. I drained all of the coolant and it was not blue! It was kinda brown/yellow in color. Got everything put back and filled with blue euro coolant, bled the cooling system, started it up and now there is a coolant leak somewhere. It''s not coming from any of the hoses I disconnected, or the flange. I can't seem to find out where it is coming from. But it is blue so I know it's coolant. The car sat for 3 days with no coolant inside. Could a seal have dried up or something? Could it be the water pump? It's hard to tell where it is coming from but the drip is quite large and right in the centerline of the car. Not towards the passenger side where the water pump is. Any ideas? Thanks.

[jsunma]

OK...lots of missing info here.

First, have you started the car and looked under the hood while it's running to SEE if you see any leaks? Possibilities would be at the hose connection between the flange you replaced and the hose. You don't note whether you changed the whole hose or just the flange, and if the latter (or I guess the former), what sort of clamp did you use.

Second, do you still have the under-engine shield installed? If so, then it's hard to tell where the leak is actually coming from as many things will end up dripping out in the "centerline". Again, LOOK and see if you can tell what's leaking.

Third, start to check back from the hoses you might have disturbed (touched) when doing this work. Often on an older car, leaks will appear on the opposite end of the hose's connectors. Just moving stuff around will cause leaks. You need to look.

Fourth, your comment about the change in color of the coolant. Any idea when the coolant was last changed? If you don't know and it's old, then a change in color is normal. Good thing you changed it.

So, the upshot is that you need to investigate some more before jumping to any drastic conclusions like "could it be the water pump?" (when was that last changed?...how many miles on your car?). Cooling systems on these cars are fragile and doing just about anything results in additional issues. But these are all manageable with a bit of methodical trouble-shooting.

[robb100]

Thanks for the reply. It has 112k miles. I’ve had it about 6 years. No coolant change in that time or water pump replacement. I only changed the flange, not the hose. I used the worm clamp that came with the new flange. The under tray is still off. Yes, i bled the cooling system, started the car, let it warm up them looked under the car and noticed the leak. I have looked around the flange and the other coolant hose that I disconnected from the oil filter housing. No leaks there. I will get under the car while it is running to see if I can find the source. I only looked under while it was off. I will follow the hoses I messed with and check the opposite ends. Thanks.

[jsunma]

Originally Posted by robb100

It has 112k miles. I’ve had it about 6 years. No coolant change in that time

So, fwiw, I'd put money on the fact that your recent coolant change was the first coolant change that the car has had. Good thing that you did it. As much as I feel that it should be done more frequently than every 112K miles, your car is probably fine and the old coolant is not the source of any current issues.

A worm clamp is not the best clamp for that flange connection. Better to use a constant tension clamp. IMO.

[Serf27]

Where does the coolant leak onto the ground?
Driver side, passenger side?

[robb100]

It’s more in the middle. And I can see some on the steering rack also. Everything is quite greasy from a valve cover leak ( fixed earlier this summer) and an oil pan leak (not fixed yet).

[robb100]

I will recheck everything this afternoon. Yes I removed all of the hoses from OFH. The flange took a while but I got it to seat. It is made by Dorman. Had to dig out a lot of the old plastic one. I will also look around the OFH, especially the back side. Didn’t see any leaks from the front side but didn’t really think of the back side. I will clean up the oily stuff and let it dry and take a look again. Thanks.

[crashoverride]

If you still have the belly pan undercarriage plastic cover the leak can start in one spot and follow the pan to a convenient opening.
Also don't rule out that coolant was spilled, it pooled in pan and is now running out of pan. With no leak.
Finally BMW doesn't play well with old fasteners they really are a one time use. With the occasional "you can get lucky and reuse" So always replace bolts and hose clamps.

[whyzee125]

Very good chance it's your water pump. They fail randomly and often and will spill water somewhat from the middle if your belly tray is still installed. Did you replace the whole hose attached to the mickey mouse flange or cut the hose and just replaced the flange itself?

[robb100]

I only replaced the flange. Crushed the one one to remove it. Prised the old clamp band off and reinstalled on new flange with new clamp.

[jsunma]

Originally Posted by robb100

I only replaced the flange. Crushed the one one to remove it. Prised the old clamp band off and reinstalled on new flange with new clamp.

Yeah, I've done that. Getting at the other end of that hose is a p.i.t.a for sure.

[bosstones]

N55 (E84) but I had a coolant leak after replacing my OFHG, VCG, mickey mouse flange, upper radiator hose, and overflow hose. Drove me nuts since all the hoses and joints were dry. I had my underbody tray on but saw nothing underneath on the floor.

In my case, the leak turned out to be the underside of top seam of the expansion tank. Never had a leak before I did the aforementioned work and it was not an obvious leak to find.

Check for coolant on the body/frame under the expansion tank. If you see signs of 'wet' (or dried coolant), check under the top seam of the tank w/ an inspection mirror. In my, case, I could see a glistening from coolant.

[robb100]

Sorry for the long delay in updating. Had some things come up. Turned out the MM flange gasget had torn when installing. Also one of the bolt holes was stripped. I re-threaded the hole, installed a new gasget and bolts and tightened everything up. No leaks now. The new gasket allowed the flange to seat much easier.

[Bmw1939]

Yep. You have to lube up that o ring real good on the mm flange or you may have problems. My very reputable parts guy said they went away from the aluminum because they had some failures. I figured it was due to the lack of lube. I installed the aluminum with plenty of lube and haven't had a problem.