Serious oil leak

[arceye]

Ok, needing some second opinions, thoughts much appreciated....long story I'm afraid

At the garage my lad has got a start at they have a Minor 1098 in, which came with an oil leak of biblical proportions from the rear. Because the boy was charged with putting some things back together and getting it running he's been picking my brains as the original problem is still there.

A previous (now left)mechanic had pulled the engine and done several things including replacing sump gaskets, and head gasket, someone else decided it was leaking from the back plate so that had been off aswell and new oil pump and gaskets fitted.

Anyway, back together and now running it still leaks majorly from the area around the rear "seal" . So I've been to take a look and this is where it stands.

under normal running there was a steady run of oil coming down the engine side of the back plate and also out of the little hole in the bellhousing, the engine breather was actually blocked so I cleaned that up... not much different.

With the engine breather doing its job and plumbed into the air filter, and the rocker cap removed there is a slow down in the leak but still a steady trickle, it drips at first and as soon as revved it runs down the engine side of the backplate, but no longer from the bellhousing.

There is a little more breathing from the rocker cap than I would normally like to see on an a series engine so suspecting blow by and crankcase pressure as the cause we did a compression test on a hot engine which gives between 170 and 180 psi on all cylinders, which is actually higher than I would expect on a standard and slightly worn engine, so I don't think the crankcase is pressurising from blowby.

I suppose one possibility would be the rear sump cork seal was fitted wrongly, but given the problem is that that the car came in with I think thats unlikely, which leads me to this thought....

The engine to my ear has a bottom end grumble when the revs are applied, not terrible but enough and generally sounds a little harsh, so if the main bearings / crank are worn to some extent especially at the scroll "seal" end could this allow the oil to escape at a rapid rate of knots from the rear of the block? , and is it likely as a cause.

My own thoughts are the engine is goosed, and needs at least a bottom end rebuild, but I'd like other peoples thoughts, I'm only involved as an act of goodwill via my lad and as I probably have as much an idea with an a series engine as anyone there, so it would be nice to lay it to rest.

[rich.]

is it possible for the oil pump to overpressurise?

[arceye]

I'm not sure Rich, but the fault has been present both with the original pump and the new one, I suppose a passage / feed could be blocked somewhere and put extra oil toward the back main bearing, but it appears to be getting around, I think there is also a pressure relief valve, though I don't know if it could cause a leak of this type?

[mr rusty]

It's got to be coming from either the rear crank seal or the oil pump, there's nowhere else it can come from at that end of the motor. I reckon the only way to find out is to have the 'box and bellhousing off and eyeball it, and check the crank for play and ovality. Just because someone's been over it before replacing bits it doesn't mean they did it properly! I think if the pressure relief valve isn't working all that happens is that the oil bypasses the filter, I can't see the pump developing enough pressure to push oil from the rear seal- if however the pump is faulty or cracked or most likely not fitted properly it would come out of there under pretty high pressure!

[arceye]

I know what you mean, one problem is the main possibilities have already been done twice with no change, the back plate has just gone back on along with the new oil pump, with me checking what was done before the gearbox went back on. It all looked good.

Which gives me another thought , it was ran a little while with the gearbox off and no real sign of oil leakage, though we didn't run it very long, and the rocker cover was off waiting for a fresh gasket. Now when they ran it with the gearbox on the leak was immediately present, so I advised draining the gearbox oil just to exclude the box. So the box having no oil it can't be the fault, but the problem seems to have worsened with the fitting of the box and clutch. The oil looks to run directly from the area where the crank exits the rear of the engine, is it possible the fitting of the clutch and gearbox could exasperate any movement in the crank due to wear and make the leak worse?

At this stage I think the only bit that hasn't been gone over twice is the sump seal, which I've suggested doing again just to be sure even though I don't think it will make a difference. The problem hasn't altered whatever they have done and I would have thought there would be some change for better or worse as a result of the work done whether done right or wrong. I'm quietly confident it is coming from the rear of the crank, so if not crankcase pressure, then what could throw it out so bloody fast. From the grumble at the bottom of the engine I reckon they will find play when it gets checked again, so would this do it? Given the grumble is it even worth checking?

[SirTainleyBarking]

The last engine I had in the Series LR had a shot bottom end, although you wouldn't know it. The crank was whipping around very nicely thank you very much and the rear oil seal stood very little chance. Before it was swapped out, you could lose a gallon of oil very quickly indeed

[arceye]

An update on this saga, which believe it or not is still continuing

As no one could figure it, and as we didn't know what previous mechanics had done, and the engine sounded rough on the bottom end they decided to change the engine (partly as I couldn't come up with a better plan)....which is where it gets bad for me..

I had a Marina 1275 engine at the back of the garage, 40k miles and running nicely with no signs of trouble when removed a couple of years ago. So we "donated" the engine for what it owed us, now with conversion backplate and flywheel fitted I have made engine mounts and gone down to help the boy do the final set up now the engine is in.

Great, play with points, fiddle about, and she cracks up and runs as quiet as the day we dropped her from the marina.

Switched off, looked under car, and there is a puddle of oil, up on ramps, run engine, looks ok, turn off, and a stream of oil as bad as before runs from the rear crank area.

So, upshot is, no improvement despite an engine change, I don't think we could be so unlucky as to be faced with the same problem twice and it be the engines, especially as the low mileage 1275 was ok when removed.

So, is it possible that some pudding working on the car earlier (before our involvement), who removed the gearbox could have bent the input shaft, and could this cause the symptoms. Its definately a leak from the engine as the box is drained to be sure.

I'm tearing my hair out over this, only got involved to help the lad who has only inherited the bloody job cos previous folk have failed, and he aint even doing it in works time

[JPB]

This is bizarre. For one thing, does the Marina-spec A-series not have a lip seal at the back of the block where the Minor engine relied upon an oil scroll on the engine side of the flywheel boss?
A damaged 1st motion shaft shouldn't make a difference as it locates downstream of the oil seal or scroll, in the spigot bush on the gearbox side of the flywheel. If it were bent, then it wouldn't enter the bush and the clutch would be difficult - impossible even - to align and even if you did get a bent 1st motion shaft entered, that wouldn't damage a sound rear main which would need to have some massive amount of wear on it to cause the end of the crank to compromise the oil seal.

This only leaves the attachment of the rear bearer plate to the block. Could one or more of the setscrews that attach it be too long and if so, did you use the same screws to fit the Minor plate to the Marina block? If so, it could cause a leak by over reaching and piercing the sump.
I've seen that only once in 32 years of buggering about with engines and that was admittedly in an all aluminium engine from an OHV Reliant.
Can't think of anything else but hey, you never know.

[arceye]

Thanks John, I'm probably clutching at straws but was wondering if the input could waggle the crank, as the fault seems the same despite the engine change.

Trouble is I didn't change the back plate or flywheel (the boys getting too bloody independent, not a boy now really I suppose) and only got back involved to make the engine mounts and get it running. The boy did comment that he struggled to get the engine onto the gearbox as if it was "tight".

I think I'm going to have to get more involved perhaps best way forward now is gearbox off, run engine and see if the leak is still present, what is getting me is with the original engine I was present when it was run without the gearbox the first time and there didn't seem to be a leak, gearbox on and fault was present, now what I thought was a good engine shows the same bloody leak .

So, gearbox off, run, and see if it leaks ? if it does I can take a look at what they have done with the back plate etc, but if it doesn't I'm stumped as to what to suggest they try next.

[JPB]

Well admittedly the fact that an engine didn't leak with the gearbox not attached, but did when they were connected, would tend to make the gearbox the common factor in the two leaking engines so fingers crossed that it's something to do with that, but for a main bearing to be so worn as to allow the crank to whip about that much, I'd expect the engine to rumble from cold and the Marina engine is sweet so it's even possible that two separate faults exist here. Not that I want to be unduly pessimistic you understand.