Sump Gasket

[David53]

I've decided that along with the front end rebuild I may as well tackle a few other little jobs that are needed. One is to drop the sump and fit a new gasket set to (hopefully) eliminate an annoying little oil leak which is coming from the rear of the sump where it joins the block.

Does anyone have any tips regarding firtting the new gaskets, especially the cork strips at front and rear? I have read the manual and am aware you need to leave them about a quarter inch protruding each side and tighten evenly. Any other tips from someone who's done it would be very welcome. Would really like to sure that leak!

[bmcecosse]

General feeling is that rubber end joints as used on the 1275 engine are much better. But the leak is usually caused by crankcase pressure - and the advice as ever is to ensure the fumes are sucked away and burned by the engine. If you continue with the cork - some say soak in water before fitting.

[David53]

Thanks Roy. I think the leak is really just oil seeping past the cork gasket at the back. I have the rocker cover outlet connected to the carby so crankcase pressure should be OK. In any case, not a huge job to drop the sump and fit the new gaskets.

Can anyone confirm that the 1275 rubber gaskets are superior, and will they fit an 803?

[Kevin]

Yes the rubber ones are superior but I dont know if they fit an 803, could be worth contacting one of the spares specialists.

[Declan_Burns]

I agree they are superior and it was the only thing that stopped my oil leaks. They have to be cut back slightly with a hacksaw to fit as there is a metal reinforcing inside-a 10 minute job. They are becoming diffucult to source but I think you can buy them from Moss. I don't know if they fit the 803CC. If you are having difficulty sourcing, I have a few spares.
Regards
Declan

[IslipMinor]

They have to be cut back slightly with a hacksaw to fit

Why? They have a sealing face on each end and are designed to be fitted 'as is' I believe? There is a reference in the workshop manual about trimming the cork gaskets, but not the rubber ones as far as I know? Afterthought - is that only for the 1275? Are the 803/948/1098 main bearing caps the same size as the 1275? If smaller, then they would need to be trimmed???

A small dab of instant gasket on each end and along the back where they sit in the sump recess to help them seal, and then grease on the lips that seal against the main bearing caps. The sump gasket then goes over the ends of the rubber seals, and the sealant and grease allows the seals to find their own best location as the sump bolts are tightened. If fitted 'dry' they will not locate as well, so as a minimum I would suggest grease on both sides of the seal (rubber or cork).

Then of course the usual debate about whether to use any sealant on the sump gaskets themselves? I do use a sealant (instant gsaket) on the sump side of the gasket, then grease on the block side of the gasket. Seals very well and allows the sump to drop very easily, should the need arise in the future!

Same principle for the rocker cover gasket! Saves hours of scraping!!

[Declan_Burns]

Richard,
They are too long when you fit them on the 1098cc and need to be cut back about 5-6mm. I think the bearing caps are smaller on the 1098cc.
Regards

[IslipMinor]

Declan,

Thanks, I shall remember that if I decide to rebuild the original 948 engine before selling it.

[bmcecosse]

1275 has 2" mains - all the others 1.75" . So the 'humps' are larger on the 1275 - it uses a different sump to suit. I really do think the 803 sump was unchanged for 948/1098 use.

[David53]

Thanks for the responses. I will look into the rubber, but it does sound like the 1275 gasket might not be ideal for the 803.

If I use the original cork strips at each end any tips on fitting? Should I use a sealant as well?

Thank you

[Declan_Burns]

Thanks Roy,
I wasn't sure on the bearing cap sizes. I take it you are right so it should also work on the 803cc. Worth a try-as on the 1098cc it works a treat. The seal fits quite well, having been cut back and dressed with a file, although having said that, I did smother it with high temperature silicone to be on the safe side-who knows-may have been unnecessary? Richard's advice on the gasket fitting with grease on one side and goo on the other exactly my opinion-that's what I do and has never failed. I have never had any negative feedback on this mod.
Regards
Declan

[Declan_Burns]

Double post-sorry!

[bmcecosse]

Just soak in water and leave over length. A 1275 sump gasket may not be the correct shape to suit an 803 engine - not sure - but certainly on Minis the 1275 block is slightly differently shaped - they widened the gearbox casing and the block slightly to allow for the larger diameter big-ends on the non-S 1275 cranks.

[Declan_Burns]

Here's a drawing of the synthrtic rubber seal just for info. I did make a sketch of the sump at the time and will post it up when (and if) I find it. if I recall correctly the aperture for the seal is slightly V-shaped.
Regards
Declan[frame][/frame]