Slow oil seep from front of engine

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PTFunk
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Slow oil seep from front of engine

Post by PTFunk »

Hi all - I did some searching on this without success. Also, please forgive my ignorance of S38 front-engine anatomy!

My '88 M6 has had a slow oil seep from the front of the engine for a while now - slow enough to rarely collect on the floor, but definitely noticeable as grime or sludge in lower areas like the A/C compressor (which I recently removed & re-installed). Before I dive into trying to solve this, I thought I'd glean some knowledge from those of you who have dealt with this issue.

I'm pretty sure the valve cover gasket (the usual suspect!) is O.K. in front, but will confirm. Besides that, could one of the round gaskets on the front of the valve housing (#18 on the attached schematic) be a problem area? If so, any precautions about removing these end caps, which I believe are for the cam sprockets?

How about the timing case cover(s)? RealOEM indicates a few gaskets for the lower timing case cover, as well the main crankshaft seal (?!?).

I was also eyeing the distributor assembly drawing, but does it have any penetrations into the valve housing through which oil could seep?

Thanks in advance for your help in tracking down this annoying problem. In a way, I'd be happy if it were just the valve cover gasket since that's 'easy' to replace...
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"Sabine": '88 M6 Royalblau/Silber
SLS delete, Wizard Cooling radiator, BavAuto Strut bar, M-Technik steering wheel, Conforti chip, Bilstein B8s / H&R Lowering Springs, BBE stainless cat-back exhaust
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Da_Hose
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Re: Slow oil seep from front of engine

Post by Da_Hose »

The crankcase has a lot of positive pressure, so it's not unusual for the valve cover seal to leak. Next up is possible leakage from a failing main seal. Last, and least likely is a leak in the cam chain tensioner. I think that is least likely, because if it were leaking then the high engine oil pressure would cause a BIG mess. Have you tried cleaning up the whole front with soap/water, and then checking daily?

Jose
1987 M6 - My dream car
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PTFunk
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Re: Slow oil seep from front of engine

Post by PTFunk »

Da_Hose wrote: Fri Jul 27, 2018 8:25 pmHave you tried cleaning up the whole front with soap/water, and then checking daily?
Hi Jose - I think a general cleanup is a good place to start since there's a lot of grime/sludge everywhere. What components should I learn how to remove in order to get "full" access? Fan? Radiator? Distributor assembly?

Thanks,
Paul
"Sabine": '88 M6 Royalblau/Silber
SLS delete, Wizard Cooling radiator, BavAuto Strut bar, M-Technik steering wheel, Conforti chip, Bilstein B8s / H&R Lowering Springs, BBE stainless cat-back exhaust
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Da_Hose
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Re: Slow oil seep from front of engine

Post by Da_Hose »

Depends on how aggressive you want to be. If you have time and space to do it, removing the radiator and fan will give maximum access. Although, if you get a decent assortment of brushes and a foaming degreaser, you can get things well cleaned up.

Jose
1987 M6 - My dream car
Canadiane24
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Re: Slow oil seep from front of engine

Post by Canadiane24 »

My '88 M6 came with several oil leaks which I painstakingly tracked down and repaired. +1 on thoroughly degreasing the engine to start. Hard to spot the source otherwise. The biggest leak and easiest fix on my car was a loose clamp on the power steering return line at the reservoir.

Sounds like you've repaired the usual suspects. Here's a couple other areas mine was leaking.

The original cam chain tensioner is a multi-piece unit sealed with aluminum crush washers that leak over time. I replaced the entire tensioner with a one piece unit from a later M50 engine. The write up is on Bigcoupe.

After I replaced the tensioner there was still oil dripping from that area. I tracked it down to the point where the top edge of the timing chain cover meets the underside of the cylinder head on the passenger side. The head gasket runs the length of the cylinder head and extends over the top of the timing chain cover. It seals poorly at this junction because the head gasket is metal and sandwiched between the head and timing chain cover by three 5mm bolts snugging the cam chain cover to the underside of the head. They can't apply enough vertical pressure to hold a seal properly, especially against the many horizontal bolts holding the cam chain cover to the engine block. Unfortunately there is no way to re-seal this area without removing the oil pan and cam chain cover. My oil pan was also leaking so I took the plunge and removed the oil pan and cam chain cover and replaced the timing chain, crankshaft sprocket and chain guides at the same time.

After 190,000 kms it seemed like cheap insurance. In hind sight I'm not sure it was necessary. There was very little wear on the guides and sprocket and as precisely as I could measure it with digital calipers, the chain had only stretched 1mm over it's length. If you go this route use the guide on Bigcoupe that explains how to replace the timing chain and guides without removing the cylinder head. Also replace the distributor seal and o-ring, front crankshaft seal and water pump. This is a job you don't want to do twice.

Just before re-installing the timing chain cover, I used a razor blade to gently pry down the end of the head gasket so i could clean underneath with brake cleaner and shop air and apply a quality gasket maker to both sides of the head gasket. I then tightened the three vertical bolts first before the horizontal ones. It's now been two years and the engine has not leaked a drop. The SLS pump is another matter...
'88 M6 Canadian Version
'06 Cayman S
'18 Honda Clarity PHEV (Forgive me. It's my pass to the HOV lane)
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sansouci
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Re: Slow oil seep from front of engine

Post by sansouci »

Another less likely culprit is the A/C compressor which can have a seal failure dumping the lube.
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PTFunk
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Re: Slow oil seep from front of engine

Post by PTFunk »

Canadiane24 wrote: Mon Sep 03, 2018 8:58 pm My '88 M6 came with several oil leaks which I painstakingly tracked down and repaired. +1 on thoroughly degreasing the engine to start. Hard to spot the source otherwise. The biggest leak and easiest fix on my car was a loose clamp on the power steering return line at the reservoir.
...
Thanks for your very thorough response! I am concerned about the timing chain cover (which likely has original seal), but as you & Jose pointed out, I need to clean the area thoroughly to better localize the leak. I'm not 100% clear on your description of the head gasket situation, but it would probably be obvious if I were looking right at it.

With the amount of work you did, I'm assuming you took out the fan & radiator? Or were you able to get in there without getting these out of the way?

Thanks,
Paul
"Sabine": '88 M6 Royalblau/Silber
SLS delete, Wizard Cooling radiator, BavAuto Strut bar, M-Technik steering wheel, Conforti chip, Bilstein B8s / H&R Lowering Springs, BBE stainless cat-back exhaust
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PTFunk
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Re: Slow oil seep from front of engine

Post by PTFunk »

sansouci wrote: Tue Sep 04, 2018 7:50 am Another less likely culprit is the A/C compressor which can have a seal failure dumping the lube.
Hi Sansouci - I can thankfully take the A/C compressor seal out of contention, since I had my unit rebuilt by Jay. The oil drops that show up on the compressor are definitely coming from above... that much is clear.
"Sabine": '88 M6 Royalblau/Silber
SLS delete, Wizard Cooling radiator, BavAuto Strut bar, M-Technik steering wheel, Conforti chip, Bilstein B8s / H&R Lowering Springs, BBE stainless cat-back exhaust
Canadiane24
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Re: Slow oil seep from front of engine

Post by Canadiane24 »

PTFUnk - Yes, removing the timing chain cover to repair the oil leak requires removing the rad and alternator. Power steering and a/c compressor can be unbolted and moved to the side without removing the hoses. Don't need to discharge the a/c system or remove the a/c condenser but would recommend placing a piece of 1/4" plywood in front to protect it during surgery to the front of the motor. Thick cardboard will do in a pinch.

It's a big job but not particularly tricky or hard. If you don't also need to replace the timing chain or guides you might just want to live with the oil leak.
'88 M6 Canadian Version
'06 Cayman S
'18 Honda Clarity PHEV (Forgive me. It's my pass to the HOV lane)
Canadiane24
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Re: Slow oil seep from front of engine

Post by Canadiane24 »

PTFunk - Just re-read the thread. You don't mention the mileage so I assume you don't need to replace the timing chain. If so, do the chain tensioner first. I recall I had to remove the original in sections because there wasn't enough clearance to unscrew it from the block in one piece. $6 for three aluminum crush washers if you want to re-use the stock tensioner. $60 if you want to replace it with the one-piece unit.

Again, start with a thorough cleaning. Helps to isolate the leaks and makes subsequent repairs much easier.
'88 M6 Canadian Version
'06 Cayman S
'18 Honda Clarity PHEV (Forgive me. It's my pass to the HOV lane)
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PTFunk
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Re: Slow oil seep from front of engine

Post by PTFunk »

Canadiane24 wrote: Sat Sep 08, 2018 7:47 pm PTFunk - Just re-read the thread. You don't mention the mileage so I assume you don't need to replace the timing chain. If so, do the chain tensioner first. I recall I had to remove the original in sections because there wasn't enough clearance to unscrew it from the block in one piece. $6 for three aluminum crush washers if you want to re-use the stock tensioner. $60 if you want to replace it with the one-piece unit.
I'm at ~120,000 miles, so technically I'm (over)due for timing chain service. According to the conservative school of thought, this would include the chain and all ancillary components. However, when I had the valves re-adjusted ~4 years ago the mechanic did a borescope inspection down the timing case and was surprised at the excellent condition of the rails/guides, at least cosmetically. It'd probably be wise for me to attempt a tensioner change as a preventative measure. This was one of the first things I did on my E39, since it's easily accessible via its own externally sealed opening.
"Sabine": '88 M6 Royalblau/Silber
SLS delete, Wizard Cooling radiator, BavAuto Strut bar, M-Technik steering wheel, Conforti chip, Bilstein B8s / H&R Lowering Springs, BBE stainless cat-back exhaust
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