Back Plate Gasket

[ricombi]

After discovering that my wonderful moggy was losing oil at an alarming rate and the radiator was getting a distinctly oily mix in it, plus the wonderful sign of mayonnaise in the rocker box, i concluded that my head gasket had failed, and all this halfway to Newquay for holiday

After nursing the car through the holiday and getting it home, i set about changing the head gasket and cleaning the head etc. this absolved the problem with the radiator but after a quick blast to Ikea (about 60miles each way from my houes) i still lost approx. 2 pints of oil
Upon inspection of the underside of the car i found a line of oil approx. the same width as the engine all down the middle of the car.

After some discussion with my father, we concluded that the only gasket we hadn't changed, the engine back plate gasket, had created some kind of small leak which under pressure was allowing oil to spray from under the car and incidentally all over the floorpan.

I have the gasket already as i was going to change it, but was put off when reading the Haynes manual it says that this gasket cannot be changed without first removing the engine.

I would like to know if this is definetely the case or can i change the gasket without removing the engine?

I am off to university soon so if the engine does need to be removed then i'd rather get it out before i go and rebuild as a project while at uni.

[brixtonmorris]

dont think that gaskets the problem, it sounds like a worn rear main bearing. the faster you go the more oil you lose.

[rayofleamington]

you can do it without removing the engine, but you need to remove the gearbox instead!!
I've changed backplates a few times and it's only a 10 minute job, however removal of the the gearbox, clutch and flywheel made the job last a whole day
Make double sure that the flywheel bolts are torqued up properly and that the tab washers are locked onto the bolt heads.

I'm sure Chris wil wince when I mention this but even just a rocker cover gasket can be enough to drench the entire underside of your car and dump many pints of oil on that kind of journey - so make sure you know where the oil is coming from before you take anything apart!!

The usual way is to clean up all the mess then drive around and re-check to see where the path of fresh oil comes from. Be careful when doing this that you have checked all the way back up to the source - not just to the nearest gasket.
A backplate gasket is NOT a common failure (unless it was damaged on a previous dissassembly and not replaced). Sump leaks are much more common as the gasket is made up of seperate parts and the bit over the rear main bearing seems to be the most unreliable.

Also the rear crank seal (there isn't actually a seal) can leak a fair bit of oil. This usually dumps into the clutch bell housing so you would see oil coming from the drain hole (with the split pin in it) and also around the bell housing flange if it is a major leak. Leaking pints of oil is pretty unlikely from the rear of the crank (the clutch would be covered and you should have noticed it behaving wierdly) but not impossible.

good luck!

[Chris Morley]

I'm sure Chris wil wince when I mention this

I would have a few weeks ago ( ) but now I'm totally oil-tight . It's amazing how much oil was able to leak under pressure from one crack in the rocker cover cork gasket then drip down to cover much of the underside. A big clue was finding oil in the spark plug threads beneath the crack....

[Cam]

Ah! so that was it then!! I'm glad it was something simple and you are now oil tight!

[turbominor]

i had similar problems with my first 1300 minor, I changed every gasket except the backplate one and it still leaked oil badly, half way through changing the back plate gasket ( as this point I assumed the oil pump was leaking...) i noticed the rear bearing cap had cracked and oil was pooring out..

strange as engine ran fine...

small leak which under pressure was allowing oil to spray from under the car and incidentally all over the floorpan.

..... well at least you wont need to worry about rust

[ricombi]

i changed every other gasket bar the back plate one, and none of them are leaking, i checked them specifically after i put them in.

if it can be done then i will change it and see if the problem continues. if it does and the bearing is knackered i'll rebuild the engine anyway.

thanks for all the help you guys, dunno where i'd be without you

[Chris Morley]

Ah! so that was it then!! I'm glad it was something simple and you are now oil tight!

Yes, it's not often that an irritating problem is so easily solved & with so little expense involved! The gasket sealer cost 3 times as much as the gasket (and this was from Halfords!).

well at least you wont need to worry about rust

Not for about 5 years I guess...