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Morris 6 Cylinder engine, oil leak ?


thedawnpatrol

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Hi Guys

 

i know this is not easily answered but just wanted to gauge peoples thoughts.............

 

as some of you are following my thread on the restoration of my MCC PU you will know that the engine is the same as the MCC CS8

 

i'm still in the early stages of running the engine and checking the carb setting etc, However, every time i run the engine, i get a lot of oil dripping out of the bell housing weep hole, now i'm told there is no seal ? but only an 'Oil Thrower' ?

 

i did not actually rebuild the engine, it was done for me earlier in the year, but of course until it had oil and ran, it did not present a problem.

 

so my question is, should there be a seal ? could the 'thrower' be faulty ? but more importantly, can this be remedied from the bottom end, i.e. not having to take the engine out ?

and no, i have not over filled the oil, i have good pressure when running ( only run it for 4 - 6 minutes at a time)

 

Jules

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Jules I had exactly the same issue with my PU8/4 engine. The rear crankshaft oil seal is basically a machined hole with a small clearance for the crankshaft to turn in. A spiral groove is cut into the hole which is supposed to wind the oil back into the sump.

 

Apart from any normal wear that might take place to the seal. The big problem is that as the crankshaft white metal main bearings wear the crankshaft will be pushed down and wear the bottom of the seal making it oval.

 

This is what had happened to mine, and the engineers solution was to machine it out bigger and remake the seal with part of a piston liner, which I think was pressed and or loctited into place.

 

It all sounded fine, until I actually reinstalled the engine and ran it. Literally 2 minutes and the engine stopped with a thud. Allowed to cool and restarted, this time 1 minute. I had no idea what the problem was, so the engineers had the engine back for strip down and found that the crank was picking up in the seal and seizing. I guess they really didn't know how much clearance to give it.

 

The seal was inside a sandwich casting between the back of the engine and bell housing and fortunately for me I had spare engine which I don't think could have had much use, so we swapped the casting. So as far as I can remember, you won't have to dismantle the engine to get to it, but of course you will have to remove it (or the gearbox?) from the chassis to remedy the problem.

 

Again from memory, My PU8/4 sandwich casting is unique to the vehicle as it incorporates the rear engine mountings, which are different from yours. So it could be that yours is more readily available (Rory?)

 

As it happens, this was only part of the saga with my expensive rebuilt engine ( for another time) Ron

Morris PU 84 052.jpg

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Jules, as Ron suggests this type of sealing arrangement is very common with older vehicles - often known as a labyrinth seal. They normally work fine, but any problem quickly finds them out. You see them a lot on gearbox input shafts.

 

Before panicking, you might check that you are running the correct grade of oil and that you don't have excessive oil pressure for some reason.

 

I can't speak to the Morris as I'm not familiar with them, but typically you'd expect a drain hole in or near the rear main bearing cap so that the oil coming from the rear main bearing has an easy escape route. If that hole is partly blocked, say with a bit of sealant, it'll give you problems.

 

If you do have a problem with the seal being damaged and it is a separate part (not part of the block casting) perhaps it could be machined to take a modern seal?

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On a Bedford 28HP we had (back in my vintage bus days), the engine consistently leaked from the rear labyrinth seal. Not a proper engineering fix I know, but i put a ring of some proper gasket paper around the journal which cured it, enough to satisfy MOT testers anyway! The paper was the stuff that swells slightly when impregnated with oil. I think I had to drop the gearbox and flywheel off to do it though. Budgetary constraints and vehicle use precluded a more permanent solution.

 

We had tried fitting a NOS oil scroll, but it leaked just as badly so we suspected ovality somewhere.

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I have no experience with these engines but if the 'seal' is part of / retained by a housing that bolts onto the back of the block behind the flywheel, is it possible that the oil is not getting past the seal but is getting between the housing and the block or even past the threads of the bolts that hold it on ? I had a leak from a Bedford gearbox once which was oil getting past the threads of properly tightened bolts. A good clean and some Hylomar stopped it.

 

As Sean said there must be a drain hole between the main bearing and the 'seal' to return oil that comes out of the rear edge of the main bearing (quite a lot) back into the sump. Even a partial blockage of that will result in oil in the bell housing.

 

These laberinth seals usually give no trouble at all as long as the main bearings are in reasionable condition. I would definately not try to 'modernise' it as it is a perfectly good design but there is another problem.

 

David

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