1991 850i Unidentified leak on the Manual Transmission

[Marc850]

Hi,

I was changing the spark plugs on the 8 earlier in the day, so I've put it in my garage. I've changed them in about one hour and a half and then backed the car out of the garage to find a big amount of water/oil under where the transmission stood. The stuff was transparent or extremely lightly green coloured and felt like water but a bit greasier. The car doesn't seem to miss any fluid.

Having parked the car outside, I then went to check under it and it was still leaking and already made a puddle. I've put it on stands and went under it.
The leak definitely came from the front of the transmission, but seemed to come from upside the transmission. But what is exactly up there ?
Also the transmission normaly runs on ATF so if it did came from the transmission, should'nt it be red ?

It was dark when I went to check under the car, I might find more tomorrow but if anyone has any idea of where/what I should look for, it would be much appreciated !

PS: I've thought about water condensation, but the AC was not on and the temperature outside was normal.

[cartoonz]

Green would indicate that's Pentosin, i.e. the power steering fluid.
Start there...

[Belgiumbarry]

yes, there's a Pentosin metal tube that go's around the engine ( with filter in front ) , having a flex hose at the gearbox before going up … probably this one is leaking.
Mine leaked at the front flex hose …. had to replace it a year ago. ( expensive… )

[Marc850]

Thanks for the replies,

I've now checked the Pentosin level (Engine off, depressed the brakes 10 times) and it was almost all the way up to the top of the container. Does that mean it's not coming from that then ? Or does it just pressurise and gives a false positive ?

It's not coming out for now, I will do a 15km warmup to do an oil change this afternoon and will give it a more thorough look when I'll get it on jack stands.

Belgiumbarry, this hose, was it serviceable without having to take the transmission out ?

[ByMW]

Is your coolant green? Could be hoses around the aux heater pump.

[Marc850]

Yes I think it could very well be coolant. I thought it was yellow but it may have gone a bit darker or have been mixed with darker product.

I drove the car today and didn't have any leaks.
What's the role of the aux heater pump ? Is it a common part to fail ?

[Belgiumbarry]

yes , it's the hose for ( Pentosin) pressure feed to the AS+T unit , going all around the engine. We even discussed what could be the reason , as a much shorter route could have been taken. Think it is to level out pressure pulses from the pump.

Aux heater pumps have a bad reputation in leaking ( coolant ) , as the hose nipples can crack.... but than the leak wouldn't stop ….

If it is coolant it can come from the big steel tube in the valley , mounted front ( waterpump) & rear ( water bridge) with O rings …. i had to replace mine as it was leaking due corrosion at the O ring spot … that could be , imho, a place that could leak or not from time to time... as the coolant pressure "sets" the O rings to seal ... bad news "if" , as for replacing that tube the inlet manifolds have to be removed….

[ByMW]

While we're discussing potential badness...
The drip pan for the A/C evaporator exits into the transmission tunnel. That would just be water, but a leak from the heater core will also produce fluid running over the forward transmission; you can usually smell it inside the cabin.

[Marc850]

I will let the mechanic have a look, I think this is a bit too much for my mechanical skills. I haven't had any leaks since then tho...
Thanks to everyone for their input,

PS: I will do a follow up on this when I'll know more

[Timm]

Are you sure this is not condensate running from the evaporator - the evaporator drains exit above the gearbox.....

[Marc850]

Hi again everyone,

I've recently had a look at the final stage unit (the final fantasy sword thing).
In the process, I had a look at the evaporator cover, it looked a bit greasy
IMG_5644.jpg
So I opened it to find a bunch of greasyish liquid covered metal tubing
IMG_5645.jpgIMG_5646.jpgIMG_5647.jpg
I Think that the problem here is the inferior front O ring not the whole thing. Can I replace this part (all the o rings) only or do I have to remove the complete evaporator ?
Do I have to completely drop the dashboard ? (please say no...)

Anyway, I think it explains why I was loosing liquid (So coolant right ?) from under the gearbox since the evacuation is juste down there. If I can just replace the O rings, do I risk loosing any R12 ? Because I can't find it anymore and my AC still works so I would like to keep it in.

Thanks
Marc

[cartoonz]

Far more likely the heater core and crossover pipe are bad. Leave the AC alone

[Marc850]

Here's an update on this:
I got fed up with this leak and finaly took apart the center console to check the heater core: absolutely dry.
Then I took out the microfilter case and had a look behind the engine and finally found it, however I don't think it comes from the crossover pipe but more from the central cooling pipe or one of its O ring.
IMG_9839.jpg
Also, my car is steam boating from the passenger side exhaust and a little from the driver one. This is most noticeable when at a redlight where it looks like my car is casually having a hookah. The smoke is white, but it looks more like water than coolant (I could be wrong). There is what seems to be water coming out of the exhaust tips.
Those two issues are not linked right ?

I bought a CO2 tester to check for head gasket failure and will post an update as soon as I'll get a moment to do it.

[rjjablo]

Coolant has a distinct smell, sweet and produces white smoke. What does your Oil look like? Milkshake is head gasket

[Marc850]

My oil is really clean, so is my coolant. The CO2 test was completely negative.
It doesn't really smell like coolant I think but there is really a lot more (let's call it steam) coming from the passenger side than from the driver side

[Marc850]

Just to close the thread up: the leak was actually coming from the central plate that comes between the V. In order to access it you have to take the intake and the crossover pipe off. The intake removal is well documented but the crossover pipe isn't.

It is very difficult indeed (specially for the driver side) and if you can do it with the engine out of the car it's ideal. Otherwise you will need a 10mm flex tool like this one

Attachment 666237
After removing the intake manifold you should
1° Remove the left tube going from the water pump to a water hose next to the right side of the engine
2° Disconnect all three hoses going to the aux heater + the actual hose that's connected to the crossover pipe
3° Remove the six 10mm bolts holding the crossover pipe to each head (the 3 bolts on the driver side are definitely the hardest)
4° Remove the crossover pipe along with the central tube by gently prying it out of the water pump and of the central plate
Then it should look like this:
IMG_6341.jpg
From there I gave the cover a good clean because of the amount of coolant, grease and dirt that stood there.
IMG_4891.jpg
I've then uncovered the V12's own personal swimming pool
IMG_6342.jpg
And found the culprit
IMG_6343.jpg
I've vacuumed the coolant, cleaned what was left of the old gasket, sand the all thing with 400 then 600 grit and voilà
IMG_6345.jpg
I've poured some fresh coolant, closed it back and got back to the crossover pipe

5° Sand each part that will be in contact with the gasket (400-600 grit)
6° On the pipe itself I've used Reinsozil to maintain the gasket otherwise it kept falling down during install (but NOT on the head side since it hardens too fast)
7° Replace all 4 O-rings on the tubes (One on the left one and 3 on the Right one)
8° Grease the O-rings and the ends of the tubes
9° Re install the crossover pipe (Putting back the bolts is even harder)
10° It's a good idea to then pressure test the coolant circuit to make sure you have no leaks, because if that's the case, it's back to square one.

Mine didn't leak but I still have to finish my valve stem seals in order to fire up the car (Only 7 cylinders left...)
Thanks to everyone who helped