JHG

2008 535i.The fan failed spectacularly.
I have a leak I cannot identify.
The oil cooled has been pressure tested and does not leak.
I also removed and pressure tested the oil cooler lines. They are solid.
The fan has been out several times. I cleaned and dried everything each time, even putting it up on my lift to check.
Today I removed the fan, put the oil cooler back in and ran the engine for a few minutes until warm.
I still cannot see an oil leak. The car can be driven and of course the front of the motor is oily after a while.
What other lines carry oil besides the ones from the filter housing to and from the cooler?
I cannot find a diagram of the oil flow anywhere. Anyone have a link? Any ideas?
I'm going insane!

habbyguy

Not sure about the connection between the fan and the oil leak - did the car overheat, and the oil leak start then?

Anyway, the oil filter / cooler housing (or actually, the "o-rings" behind it, which are not shaped like "o"s at all), or the alternator bracket (also has a similar set of seals / o-rings) are common sources of leaks on the I6 BMW engines.

With any oil leak, the common method for IDing it is to clean everything up and then watch for the first trickle of "new" oil, and follow it up (always up) to the source. The other option would be to add some UV dye to the oil and look for the telltale streak of bright when you apply the UV light.

JHG

The fan failed in the driveway and the car was immediately parked, so, it did not overheat.
The fan failure caused all kinds of carnage in the shroud. It actually destroyed the shroud. It damaged the oil cooler, which leaked. I repaired and pressure tested it. It's good to go.
There were no leaks until the fan failure, so assuming no incidental leak at exactly that same time, I'm looking at anything in the area of the fan that carries oil that could have been damaged.
I haven't tried dye, which is a good idea, but I have cleaned everything up spotless a few times, but can't locate the leak.
The o rings on the oil lines are good, I've inspected them but the sharp plastic flying around couldn't have affected them,
What about the alternator bracket?
And by the "oil cooler housing", what do you mean? The heat exchanger?
I've idled it without the fan in place twice today and still can't see a leak.
I've turned wrenches for decades, but BMWs are new to me. Thanks for the help!

habbyguy

FWIW, I can't imagine the fan's dance of destruction causing one of the "O-rings" behind the filter / cooler housing to leak, but I can imagine it creating a fracture in the housing itself that might expand under heat / pressure.

Those "O-rings" are behind the filter / cooler housing, and behind the alternator bracket.

I think the dye might be your best bet, since the "new oil" will be very obvious.

And yeah, I've been a DIY mech for decades, and BMWs (particularly this one) never ceases to amaze (and surprise) me. But I'm learning to never assume things work like "lesser cars". BMW never misses an opportunity to over-complicate, over-engineer, and over-price things. ;-)

twh

Two other things to check...
The radiator could be damaged and leaking in the oil cooler passages.
There is a transmission cooler and power steering cooler under the radiator.

JHG

How could radiator be damaged to be leaking oil? The the oil heat exchanger is separate from the radiator.
I tried dye today. No luck. It was 30 cc of dye and I was in darkness when I looked.
Keep in mind, I have it on a lift also, so I looked everywhere.
I made sure the oil cooler housing is definitely not leaking.
It is definitely oil as the level will go down when driven for a day or so.
I put the fan back in and warmed it up and it seems like it had more oil everywhere than when I ran it without the fan.
Not only blown around, but more in general if that makes any sense.
What other lines carry motor oil?
I made sure I have a tow hook today. It's the kids car, so I guess when something really blows, I'll be able to fix it.

twh

Yea, forget that statement about the radiator -- I've seen cars with oil coolers integrated into the radiator. Was just thinking about how a disintegrating blade could munge up the works.

Have you had a look in the coolant reservoir? Is it milk-shakey looking? Oil and coolant mixing looks that way.

kd7iwp

Have you got any photos to help us perhaps see where it's coming from? So you can't see the leak, but oil is appearing all over the place? Sounds like it's going through the fan to be blown around then. If you run it for a bit without the fan do you get oil anywhere?

twh

Also could be refrigerant oil from the A/C system. That radiator is up front also. That won't be dark, but it will be oily.

habbyguy

I'm confused though - the OP added dye, and THEN had oil leaking out everywhere, but no sign of the dye? Maybe it's not oil (power steering fluid?). If there's dye in the oil, and it's leaking out, it WILL be visible.