1850 severe engine oil leak

[Dunhookin]

My 1980 automatic 1850 has had a litany of endless snags and component failures this year, its' been one thing after another. It's latest issue is a huge engine oil leak.

The engine has had a major overhaul, new bearings, piston rings, all oil seals and gaskets - and a new engine block. The engine runs really well, apart from this really serious oil leak.

The leak is from the back of the engine/gearbox bellhousing area, dripping off the bottom of the engine back plate where it bolts to the gearbox. Thinking the new crankshaft rear seal I'd fitted was causing the leak, I removed the engine again to investigate.

There were signs of oil escaping past the seal in the 6 o'clock position, but given the severity of the leak, there was less oil visible in the area than I expected. I could see no other possible sources of the leak.

I fitted another new rear crank seal supplied by Robsport. I noted that the new seal went into the seal 'horseshoe' housing easier than I expected, needing just thumb pressure to push it into place. I fitted the seal housing to the engine, refitted everything removed for access - then put the engine back in the car.

Ran the engine for about 10 minutes - and with massive dismay watched oil leaking out exactly as before - all that work for nothing - clearly the oil seal itself isn't the cause of my problem. I'm wondering whether I'm missing something - hence posting this to see if anybody on here has seen this before.

Could the rear crank seal housing be the cause of the leak? It's a piece of aluminium, so I think that very unlikely - but with the engine having to come out again, I want to be 100% sure I cover everything. Could the seal housing be porous?

Could the problem be the flange at the rear of the crankshaft that the seal sits on?

Any shared experiences, intel or advice greatly received. Thank you

With best regards

Andy H

[new to this]

Hi when you took the rear crankshaft seal out,were there any wear marks on the end of the crankshaft,may be you may need a speedi sleave,it fits on the end of the crankshaft

Dave

[matt of the vivas]

Is it definitely the rear crank seal or could it be the oil pump O rings - they often make a mess in the same area. Did you fit a new old stock pump - if so I often find the o rings are perished. I make it my policy now to replace all the pump rings any time I touch the pump - they are very cheap and it's simple to do.

[BobM]

Hi Andy,

I had exactly this experience when recently fitting a reconditioned engine, which I had bought many years ago.
I suspected all the causes mentioned above. Finally, the culprit was the sump pan. The gaskets available
will not crush to seal a pan with any distortion to its flange.

Place the sump pan face down on a flat surface and test for gaps with a feeler gauge. Minor distortion around
the bolt holes is very common and caused by over tightening. This can be corrected. However anything more
is going to be difficult and finding a better sump pan is going to be a better course of action.

Best of luck.

Bob

[Dunhookin]

Fellas, thank you for your responses.

Matt, the oil pump leaks you've experienced, was the oil leaking at a substantial rate? The leak I have is very severe, within 10 minutes of starting, when the oil thins down, there's a dinner plate sized oil puddle on the floor dripping rapidly.

Bob - the sump hmm - that has me wondering. I did have a good look all around the area where the sump bolts to the engine - no leaks were visible. In my case, the oil is running off the bottom of the engine back plate where it meets the gearbox bell housing in the 6 o'clock position. I've got the engine almost ready to come out again - but I will check and re-check the sump again.

Dave, the speedi sleeve - I've never seen before. I will be investigating that today.

Thanks again guys - I will post further updates shortly

[yorkshire_spam]

Just to add.... I had an oil leak on the 1850, I didn't have a puddle but in 500 miles I went from high mark to low mark on the dipstick - it was the o-ring seals on the pump/cover plate.
I found it by thoroughly cleaning all the oil off to the point where the engine/sump/backplate were all DRY and then running the engine. It was so obvious I didn't even have to resort to the "talc trick" (where you dust the suspect area with talc and watch the oil appear)

[matt of the vivas]

Yeah the O rings on the pump can leak really well... But it should be obvious where it's coming from. It is definitely engine oil that's leaking and not ATF from the gearbox nose seal?

[Dunhookin]

Thanks Matt. I will carefully check the oil pump, the seals are new, but I need to eliminate it.

It is definitely engine oil, the gearbox is a reconditioned item that I was very kindly gifted...thanks to you.

One thing to mention, when I fitted the latest new rear crank seal (supplied by Robsport) it pushed into the horseshoe housing with thumb pressure only. I wondered about that at the time, but fitted it anyway. It made no difference to the oil leak, which is just as bad as with the previous seal.

Has me wondering whether the horseshoe is suspect - have you ever known it? What is your view on the seal being pushed in with thumb pressure?

[Magenta Auto Sprint]

Pleased to hear that it is definitely engine oil and not ATF.

When replacing the seal, have you applied a smear of engine oil to the seal lip before fitting it on the crankshaft? also ensure that the 'horseshoe' seal housing is flat and free from the smallest of burrs before fitting, a light touch with a smooth small file will show up any issues.

Does the crankshaft journal have a wear grove or other imperfections on it?

Malcolm

[Dunhookin]

Thanks Malcolm. I checked the rear crankshaft journal where the seal sits. I cleaned all visible marks off it carefully and gently using a scotch bright pad and GT85. There is a very slight 'ding' mark in the journal, it's very small and easy to miss.

The ding is located on the outer part of the crank journal, the lip of the seal rests on the inner part. I simply cannot imagine that it would cause a leak of this magnitude. Yes, I did coat the seal in a film of engine oil before fitting.

I'm going to lift the engine out again tonight, see if there are any clues this time...

[matt of the vivas]

There was a bad batch of rear seals, the internal spring was too long so it didn't clamp round the shaft enough. The fix - I think Jeroen on here came up with it - was to shorten and rejoin the spring. Maybe a message to him might be useful? I can't believe the seals are still being supplied like that though, it was a lot of years ago that it was first raised as an issue.

[matt of the vivas]

As for fitting - I usually use a smear of loctite round the edge of the seal where it fits into the housing. Can't move outwards then, even if it's a slightly loose fit, and the loctite fills any scratches in the housing from previous oil seal replacements.

[Dunhookin]

Hmm, thanks Matt - I think I'll adopt your Loctite method when it goes back together. Next step is to get the lump back out of it, which is happening tonight. This time, I'm hoping to see evidence of the source of the leak with the engine on the bench

[Magenta Auto Sprint]

There is also a blanking plug on the back of the block part number 154561 and a copper washer, this may be for a oil gallery, check that it's tight etc.

Malcolm

[Dunhookin]

Thanks Malcolm. I checked the gallery plug you mentioned at the first oil leak investigation, there was no evidence of oil escaping from there. The new block came without dowels, etc. the gallery plug came from the old scrap engine and went in with a smear of sealant.

It sits in a recess in the block - and it has to be tight otherwise the engine back plate won't sit in position. I will be checking it again though - thank you for the part number - may come in handy.

I'm thinking that I may need to get the engine to somewhere with a test rig where it can be run out of the car - the leak will then be readily visible