Most problematic area for S38 oil leak

[Kurt Beitler]

The S38 has a reputation for being an oil leaker. My M5 is a leaker and happens to be getting new oil pan and valve cover gaskets right now.

Have other owners found their cars to be leaky in these same areas? What tends to be the most common point of leakage? Are BMW seals and gaskets crap?

[Mel A]

My '91 has had a very slight leak near the front,passenger side,for about 5 months now-a few drops on the garage floor the next morning.Haven't lost enough to add any oil between oil changes.My mechanic suspects a front crank seal but can't tell for sure until he gets in there-it's difficult to tell without taking some parts off.Anyway,it's gotten worse recently and I am taking it in next Tuesday to have it repaired.I hope it's only the crank seal and not something more serious.

[dominik]

Kurt

Which year is your M5? My '89 model loses quite much oil. Not viewable on the ground but if you look under the car you can see it.

Also oil consumption is quite high. My car burns about 1l on 1500-2000km.

[Markus Kits]

I have the same oil leak in the front right side of the engine in my -90.
It,s not much,but you can see it if your under the car.
The oil cosumption is still low(about 1 litre
for 3000-4000 km).
This seems to be a week spot of the engine,but if you stay under 1 litre for 1000 km in a old car i think it,s ok.

[dominik]

The leak I have is in the middle of the engine. It's difficult to find the leak as the engine is quite dirty (seems nobody washed it there in the last 11 years) and the oil is distributed until the gearbox.

Enginge has 123k now, I think @150 I'll do a complete rebuild. Or perhaps upgrade to the S38 3.8 engine (someone from the E34 mailing list plans to do this at the moment).

[raymondw]

Last year when I replaced the etire clutch, my dealer also replaced the cranck-hub seal at the back of the engine. The problem was that this seal leaked small amounts of oil into the clutch.

I had the problem that after driving about 500km continously in the Alps, the clutch started to fail. Next morning when everything was cooled down, the clutch was working good, untill the next 500-600km.

My mechanic said that the leaking cranck hub seal caused the clutch falure.

Last October when changing oil my dealer used Shell Helix 5W40. But soon after this, oil was leaking from the front side of the engine. I switched to Castrol RS10W60 last march when an Inspection II was done, but when checking the valve clearances, the mechanic spoiled some oil on the right side of the engine. I cleaned the front and right side afterwards to check where the leak came from. After about 1000km the engine is still clean and dry.

With best regards,

Raymond

[Mel A]

Ok-I'm using Redline 10W30 synthetic...do you think if I switched to a heavier regular oil my oil leak may go away?I've heard of synthetic oil causing seals to leak.How much heavier is Castrol RS10W60 than 10W30?

[raymondw]

Hello Kurt,

10W60 means that oil keeps it's viscosity over a wider temperature range. After this limit, the oil will become thinner.

Thin oil is good for cold starts. The oil flows better, but at higher temperature, the oil get's thinner. The thinner the oil, the easier is can leak through the seals, especially the hub seals such as on the cranck shaft.

The most important reason the industry is switching to thin oil (0W or 5W) is to fullfill the demand of the consumers for a larger service intervall of about 30000km. Another reason is that with cold start engines with hydrolic valve adjusters are sooner supplied with oil and therefore stop making noises sooner.

But the S38 does not have any hydrolic valve adjusters and we don't mind oil change intervals of 7000km-10000km which in the end is better for the engine since the oil becomes less contaminated. Since the mechanical clearances in the S38 engine are higher than for the M30 engine, thinner oils are not that suited for the S38.

I think I have been lucky since I used the 5W40 oil for only 2500km and only in winter on short ranges. The oil still had a brown tint in it when it was tapped of. I cannot garantue that using 10W60 oil will solve oil leaks automatically, but Castrol RS 10W60 is much better for the S38 engine.

In the end it will depend on the condition of the seals if thicker oil will be the right answer. But with my car allways 10W40 Mobil 1 was used untill my dealer switched to Shell Helix 5W40. After only a few 100km I noticed the leaks. Coincidence? I guess not, so I switched to Castrol RS10W60 after the positive experiences of Chris et al. After this, I cleaned my engine to find the leak but untill today I could not find any.

I hope I have clarified myselfe a bit,

With best regards,

Raymond

[Ronin]

Known oil leaks areas for the S38 include:

*front timing case cover (upper and lower)
*oil pressure sender (O ring failure)
*front crank seal
*oil pan gasket
*rear crank seal
*rear upper cam housing cover plate
*oil return tube at lower right rear of engine block
*oil recovery system at bottom of air accumulator housing

These leaks tend to develop over time as a result of heat cycling, which eventually shrinks the gaskets. The cylinder head cover gasket shouldn't leak since it ought to be replaced at every valve adjustment.

[jrmicha]

Has anyone tried to replace the rear upper cam housing cover plate? I have a small leak on my 91 M5 from this gasket. I tried replacing it, but the firewall prevents the bolts from being removed. I tried moving the engine around a bit and could not get enough clearance. Anyone have any ideas short of removing the engine. I agree with the list below as I think I have fixed about 3/4th of these leaks so far.

Joe M.

Known oil leaks areas for the S38 include:

*front timing case cover (upper and lower)
*oil pressure sender (O ring failure)
*front crank seal
*oil pan gasket
*rear crank seal
*rear upper cam housing cover plate
*oil return tube at lower right rear of engine block
*oil recovery system at bottom of air accumulator housing

These leaks tend to develop over time as a result of heat cycling, which eventually shrinks the gaskets. The cylinder head cover gasket shouldn't leak since it ought to be replaced at every valve adjustment.[/quote]