Oil Leak from rear of engine.. advice

[BenM635i]

Question for you good people... its a long shot but I suspect that you may be able to take an educated guess as to the cause of my woes.

I have been under the car all morning and got properly filthy and messy (its great and the lady will kill me when she sees whats in the washing machine!).

Scenario:

1) M635 engine
2) Oil leak from rear of engine
3) took off the exhaust shield to get a better view from below, cleaned the old leaked oil and had a good look with torch to try to ID where the mess comes from. Not able to identify the source (its from rear of engine, not near exhaust outlets or anywhere i can see despite mirrors and great investigation). No oil leak apparent from cold un-run engine i.e. leak does not happen cold and stopped.
4) Ran engine up to temperature and got back underneath, oil dripping and it runs along the union of the gearbox / block... looks to be coming from above but i cant see due to no access.

Any idea what this could be? What would be 'avove' the gearbox, at the back of the engine, hidden from view from the below? Oil is not coming from the top of the engine i.e. cam cover or anywhere i can get access to. Its a fair leak, after 2-3 minutes warm up then switching engine off its dripping visibly from the bottom of the gearbox casing where its run from the top. If estimated would say loses 100-200ml each time car gets warm then sits parked.

Realise its a long shot to ask for diagnosis based on the above and i was hoping to get some photos to post here... the camera came back unused though as no way i can see the issue.

Has anyone had this, what could be causing it? Big question, is there any way to get to area short of head off / engine out?

Right now priorities are getting a bit of bodywork done - until then ill live with the leak and keep a pan under the car. Curious as to what i am likely to have to do to stop this though.

**edit, this is the best photo i can find of the rear of the engine - marked where i suspect it might be leaking from, feasable, is this an oil pipe? **

[hornhospital]

I think your circled item is a coolant return fitting. I don't know about the S38, but on the plain old M30s, the oil sender switch is at the back of the head, and is notorious for leaking down the joint between the block and transmission when the seal in the switch fails, making it appear to casual inspection that the rear main oil seal has blown. I've related elsewhere how we all but pulled the transmission to replace the crankshaft seal, when someone noticed the oil was coming around the transmission-block joint. $20 for a new sender and the leak was gone.

[BenM635i]

Thanks for the quick reply Ken - so the pipe seems to be a non starter.

I was hoping that it might be the oil pressure switch as had read about that in various posts.. however I am not 100% sure where the sender is on the M88 engine and the various manuals i have dont specify the location. Reading them all again now to see if i can fathom what it might be.

Access to the area is nigh on impossible though.

** update ** sadly i dont think the leak can be from the oil pressure sender manual says that the sender is towards the front of the engine... back to scratching my head rather sad...

[Brucey]

IIRC there is an oil return pipe elbow that is just below #6 exhaust port on the M-engine. This is sealed via flange and gasket at one end and via an 'O' ring at the other. This is the most common source of oil leaks in this part of the engine.

This won't leak oil when standing but when the engine is running the oil can wee out of it if the seals are bad. Most commonly the 'O' ring is the cause of the problem; to change the O-ring the fitting has to come off the block.

By all accounts this fitting is a PITA job when the manifold is fitted -if it is possible at all, that is...- but when the manifold is off, it is a doddle....

cheers

[BenM635i]

IIRC there is an oil return pipe elbow that is just below #6 exhaust port on the M-engine. This is sealed via flange and gasket at one end and via an 'O' ring at the other. This is the most common source of oil leaks in this part of the engine.

This won't leak oil when standing but when the engine is running the oil can wee out of it if the seals are bad. Most commonly the 'O' ring is the cause of the problem; to change the O-ring the fitting has to come off the block.

By all accounts this fitting is a PITA job when the manifold is fitted -if it is possible at all, that is...- but when the manifold is off, it is a doddle....

cheers

Cheers Brucey, this was the pipe i was hoping was the cause of the leak. When the manifold heatshield is removed you can see the pipe in question from below the car (at least i think this is the one you are referring to).. it comes down from the head via a connection i couldnt see clearly (likely O ring) then drops down to go into the lower of the block via a connector with 2x ?10mm? bolts... this looked to be the culprit. However i cleaned it up then ran engine and couldnt see the leak coming from this pipe, seemed to come from above the gearbox so that the oil ran down the union of block and gearbox.

To replace would be horrible. Much knuckle skin would be lost. Much pain. The manifold is massively in the way of any kind of access to the whole area.

Nightmare.. i think the next course of action is to order one of those mirrors on an extendable stick then try to get a view behind the block somehow.

Thanks for assistance so far, know its a random and likely silly thing to be asking but all efforts are appreciated x10.


** update **

Brucey, you are a wonder! Just found another of your posts via the Googleweb and a diagram you posted, i believe item 20 might be the culprit. As you said "The picture above also has the external oil return pipe, with item 20 a ten pence item that can cost hundreds to fit properly.... " - i think you are right.

Now to work out a way to remove and refit this pipe without manifold fun'n'games.

[Pod]

You could get hold of one of those endoscope cameras. Snap-on do one, but there are probably others on ebay for less cost

[BenM635i]

You could get hold of one of those endoscope cameras. Snap-on do one, but there are probably others on ebay for less cost

Seems like a good excuse for a new gadget, fleabay do them for £18.90 delivered

Buying this: http://www.ebay.co.uk/itm/USB-Endoscope ... SwPhdU-Ixm

Plan is to get this in place where i can watch the O ring... then run engine and watch. That way i dont have to lie under the car with the engine going while hot oil drops on my face. If its the ring, then i do the fix somehow. Plan approved?

[Pod]

Wow! Prices have dropped. I presume you need a PC or laptop to use this!

Just be careful you don't melt the lead on the manifold

[BenM635i]

They seem to be as cheap as £6 or something silly if ordered direct from Hong Kong / China... mad world we live in.

Ill do best not to cause meltings and fire (and not destroy the company laptop too).

Thanks all, i now have a plan. Will report back in a week or so as to success or failure.

[baders]

Are you absolutely sure the problem is not the rear cam cover and gasket ? I've read that this can be a problem on the M88. Item 1 and 5 here;

http://www.realoem.com/bmw/enUS/showpar ... Id=11_0251

[sansouci]

Harbor Freight has two fiber optic inspection cameras. One with recording capability.

[Brucey]

Are you absolutely sure the problem is not the rear cam cover and gasket ? I've read that this can be a problem on the M88. Item 1 and 5 here;

http://www.realoem.com/bmw/enUS/showpar ... Id=11_0251

If you can't see oil coming out of the 'usual suspect' (oil return elbow) you definitely want to check the other possibilities out before tearing into anything.

If you want to pin the leak down, clean everything and dust the area with talc. That way you'll see the oil creep across any surfaces more easily; a thin film of (clean) oil can run across a surface and be difficult to see; often it will appear to be coming out of wherever it finally decides to pool/drip off.

If you have dye-penetrant developer (which is basically talc + solvent in a rattle can) it is a good -if expensive- alternative to the above.

cheers

[hornhospital]

If you get one from HF, get the one with the smaller scope. The one I got works great, but it won't go through a spark plug hole.

[BenM635i]

Thanks for all the advice gents.

Definitely doesnt look to be leaking from the rear cam cover gaskets Baders - can actually reach behind there and it all seemed very dry to touch even after running the engine.

Brucey i hear and heed your words sir and will resist the urge to pull pipes off till i know they are the cause.

Ordered the little endoscope cam for the princely sum of £18.90, once it comes ill jack the girl up again and get her on stands. Then clean up the best i can and apply some Cussons talc to the area somehow (imagine most of it will go on me as when lying down under the car, the area in question is maybe 50cm above my head... still at least i will come home to the lady smelling fresh rather than 'you stink of oil and what have you done to your trousers?!').

Then run her for a minute or 2 and check for leaks, then repeat till i see the cause.

I believe it would be possible to swap out the O ring and gasket on the elbow using a 1/4" ratchet and a bucket load of patience, there is not a lot of room but with the exhaust shield off its probably just doable.

[BenM635i]

Summary:

1) Winning
2) got under her this morning (managed to get some time off work aka WFH)
3) Looked all around the rocker cover, rear rocker cover gasket - 100% sure no leaks from this area
4) Brucey's idea of using talc to spot leaks work very nicely.. i fashioned a James Bond type contraption with a piece of tubing and then dart gunned the talc out all around the area of the oil return pipe O ring.. no way to reach up to do it any other way
5) Ran her a bit, pretty sure the leak is from the O ring join..
6) Working on Sherlock type theory that if all other possibilities are excluded then whats left must be the one.. also working on the theory that this pipe is all i can fix myself before calling mechanics + the O ring + gasket are £5.10 i decide to crack on
7) 2.5 hours later, very dirty (she will kill be again) and with manifold heatshield off and cross member off i confirm that it is possible to get the oil return pipe off, not easy, not fun but possible

The hardest bit of the job was getting the old O ring out of the recess as i couldnt reach by hand with a tool in hand, so i again bodged using duck tape and 3x screwdrivers a special 'O ring removal tool remote operated'.

So then trot to BMW to get the O ring and gasket, they have thwarted my plan by not getting the gasket in. So i have an O ring and will resist reassembly until i can replace the gasket too. Gasket looks like it will work again however i dont want to bolt her all up then find it leaks.

A gamble gentlemen. However i dont see what else it can be apart from this pipe and it is something i can do myself for minimal £.

Battle is won, war to follow Saturday AM:

[Brucey]

good work fella!

cheers

[wattsmonkey]

Good work indeed! I was convinced there wasn't enough clearance to get the bolts out with the manifold installed.

I don't think you've taken a gamble at all: you've replaced a part which is well known for leaking AND you checked that it was leaking first!

Rob

[Da_Hose]

I have seen recommendations to be sure and put some sealant on the tube, before pushing it into place. That ensures that there are no micro gaps which allow oil to seep. Since the oil system is pressurized and you are pushing the fitting up into the seal, that seems like a decent idea. I would also be sure the new seal gets some oil on it before you install and push the tube on.

Jose

[Brucey]

it is an oil return pipe, so it is at crankcase pressure. I have always supposed that either the crankcase ventilation system doesn't work as well on an M88 or when these fittings leak, the seal is completely jiggered.

If you have a comparable potential leak on an M30 cylinder head (eg on the distributor housing to head gasket) it can be a sizable hole before it causes a really bad oil leak; normally when the engine is running there is air being sucked in through the hole and thence via the crankcase vent into the inlet. This means that usually, relatively little oil comes out.

cheers

[Da_Hose]

The M88/S38 is quite temperamental about crankcase pressure leaks. It will surge and refuse to idle/spool up when you apply throttle.

I believe that is why the S38/M88 are so prone to niusance oil leaks. The constant positive crankcase pressure just pushes oil out of any area that isn't completely sealed.

Jose

[88m53453]

If you ever need to replace the gasket on the rear of the head, it's not that bad....

Remove fan clutch as you will need all the clearance everywhere that you can get
Floor jack under the trans
remove lower trans mount nuts
carefully raise the floor jack and that will raise the rear of the engine enough to get to the offending part
Snap on makes a nifty 10mm offset box wrench that makes the job easier

Cheers

[BenM635i]

Morning gentlemen - not forgotten this however got the keys to new house on Friday so this weekend has been rather chaotic. Been at current place for 19 years so forgot what a shambles of a life moving house causes!

Anyway, pipe went back on easily enough.. always amazing how once you suss something out it then becomes easy. Thats the good news.

The bad news .. well i started her for 2 minutes on Saturday just to see and i think she is still bleeding however cant be 100% sure. Might possibly be old oil from top of transmission getting warm and running down but thats likely just me being hopeful.

However my new £18.90 gadget arrived on Saturday and will be easier to use than the mirror on a stick which i already had:
http://www.ebay.co.uk/itm/Rolson-3pc-Ki ... Swd0BVv~eb

Its amazing that you can buy an endoscope with LED lighting for the price of a pizza! So today in among moving stuff ill try to get to the garage and have a proper run and get the camera back there.

If its still leaking, i dont believe its the gasket on rocker housing, or the cover. The pipe has now been excluded. Scarey thought i cant get out of my head is head gasket... however only way to find out is to get probing. Ill report back tonight. Ill either be happy, or rather sad (but whatever i am, ill be really oily again ha!).

[88m53453]

My M car had a leak I chased for a while, probably not your problem, but you'll enjoy the laugh at my expense. Had oil at the trans/engine joint at the bottom...Rear engine seal, drat, but I have a lift at the shop, so new seal and new clutch , why not ?? All buttoned up and a week later dreaded burning oil smell... Well, I have installed a ton of rear seals, but maybe , just maybe, I messed this one and better on mine than on a customer car , right ?? Well pulled it back apart and seal looks fine, but what the heck, they are cheap, New seal...one week later and the burning smell is back.....

Further investigation.. and I find it, hydro brake booster is leaking and running down a circuit that kept it hidden until it dropped on the rear of the engine/front of the trans . Problem solved

[BenM635i]

Cheers for the moral support 88m53453 :) - it helps.

Today I got up to the garage with my endoscope. My baby is still leaking, not from rocker case rear gasket and not from the oil return pipe but definitely from somewhere. Its so dark and murcky and oily back there though i cant see where the mess is coming from. Once up to temperature the oil drips from the transmission / block interface + surrounding area - its not a small leak.

For now I am demoralised (well not really but am tired) and decided to concentrate on moving house + decorating then renting out old flat for the next week or so. Not enough hours in the day.

The problem is that access is so restricted back there, they really did cram the M88 engine into the front. Will find the leak and hope fix it myself. Somehow. The only option might be a steam clean, then the mother of all bright lights coupled with a good poke around with the endoscope.

Verdict on today, i detest oil leaks!!

[BenM635i]

Quick update, by some miracle i seem to have fixed it!

Have taken the old girl out a couple of times in last month... seems dry... took her for MOT yesterday and she passed with no advisories whereas for last 2 years they have taken exception to the oil pool on the floor under their inspection ramp :)

So result!!! Must have been the oil return pipe after all.. all i have to remember the saga by is some scars on my knuckles and an old oil mark on the garage floor.

Thanks to all who helped with advice on this. Now i can start on the next thing on my 'to do' list.