HELP! M20 leaking oil from the wiring loom!?

[Mungo1337]

Hopefully the idiotic title has got someone's attention ... but its true!

Over the weekend the oil pressure light came on on my touring. I checked dipstick and it was below the bottom mark. 1.5 litres later all was fine. Next day, oil pressure light was back on. Another 1.5 litres went in and by the following morning it had lost it all again.

After prodding about we found the wiring loom that runs along the block high up on the inlet side under the manifold was full of oil, but the block is dry up there. The loom was sopping between where it curves off the bulkhead to just behind the alternator - either side of this it dries up.

My mechanic is guessing it might be leaking back up the oil pressure switch into the loom, but he isn't overly familiar with e30s. His next step is to steam clean the block to get a better look, but if anyone knows the most likely source I'd appreciate it.

[BenHar]

Maybe the breather pipe between the manifold and the block?

Ben

[maggspower]

First of all which light came on, the oil pressure light in the dash cluster, or the low oil warning light in the overhead check panel?

They are very different.

[lamby]

thats a lot not to see,dipstick tube in?rocker cover gasket? doubt it,s leaking a litre and half up the switch more running down.is the engine covered in oil?

[Brianmoooore]

Very common fault! It will be the pressure switch.

[Mungo1337]

Thanks guys. It was the low oil warning light in the overhead panel that came on. The lower part of the engine block was covered in oil, but above and around the loom was dry, as was the breather pipe and rocker cover.

It does seem a lot to be coming out of the switch, but it seems like the best place to start. Didn't know the dipstick tube came out! I'll check that too

[eko]

As Brian says above,oil pressure switch is likely suspect.

[Mungo1337]

Oil pressure switch was indeed the culprit. I didn't think oil went up, but it was pumping it right up the wire into the loom. Put an oem rplacement in and all sorted - but now there is a steady drip from the back of the engine gearbox off next ...

[SGP]

With any luck the sump bolts under the bell housing cover may simply be loose.

[aimlessrock]

Mungo, i suspect the pressure may have blown the sump gasket...not a bog job..but very messy.

I replaced mine about 6 months ago and got covered...i also change the oil pump while i was at it.

best of luck

[Mungo1337]

hmm yeh I think fixing the first leak upped the pressure causing the sump gasket to give way.

There was a litre of oil in the bellhousing and a slight weep from the rear main seal, plus hotspots all over the clutch adding to my woes.

I think I'll replace the oil pump while the sump's off too. Any recommendations welcome

[BenHar]

Is it possible that the oil pressure relief valve is stuck shut?

Ben

[Brianmoooore]

Whatever pressure is in the oil gallery of the engine has absolutely nothing to do with the pressure in the sump!
Sump gaskets deteriorate with age and heat, and leak spontaneously, but gaskets and seals can be blown by badly worn piston rings and/or bores, allowing the crankcase to become pressurised.

[BenHar]

Sorry if it was a stupid question, Brian. Just thought that the pressure going to high might be what caused the pressure switch to fail.

Ben

[mark_i]

how can an M20 crankcase pressurise? i thought it was vented through the 1" steel tube that connects to under the inlet manifold...

[Suki_BiH]

M20 crankcase can't be pressurize !

1.5lit in one day is a lot of oil linkage...most likely gasket,o-ring and other failure if your car doesn't smoke at exhaust like a steam locomotive.

[Brianmoooore]

1" steel tube only goes from the top of the engine to the bottom. The only vent is the rubber hose from the rocker cover to the throttle body.
On a 'good' engine, this system maintains the crankcase at slightly less than atmospheric pressure, but on a badly worn engine, piston blow by can overwhelm the system, and also causes sludge to form and be pushed into the breather pipe, partly blocking it, further increasing crankcase pressure. This is more a comment on engines generally, rather than specific to E30s.

[Suki_BiH]

for that... engine has to be a wary wary wary baaaaad

[Mungo1337]

The sump gasket looks like it might be original. Is it possible the sump and main rear seal have been leaking slowly for a long time allowing it to build up in the bellhousing?

The old bus has only done 76k and seems fairly well looked after - it certainly doesn't smoke, so I'm hoping this is just serial seal failure and nothing more serious.

[Brianmoooore]

Won't be anything wrong with the rear main seal - I've yet to see a failed seal on M20s with more than 250,000 miles on the clock, so it's very unlikely to be giving problems on an engine like yours, that is barely run in.
On the other hand, M20 sump gaskets are just thin paper ones that go brittle with age and fail regularly. The gasket will be the problem.

[Mungo1337]

Okay thanks Brian The thought of worn bores was starting to give me a nosebleed

[SGP]

With any luck the sump bolts under the bell housing cover may simply be loose.

Very easy to check.