modified rear crankshaft oil sel

Post by **annechas** » Thu Jul 23, 2009 8:20 pm

Anyone out there fitted a modified rear crankshaft oil seal? Believe one is available to cure the common problem of oil leaks there.[/b]

Post by **rayofleamington** » Thu Jul 23, 2009 8:26 pm

Have a good look at the fitting instructions before you decide to get one. They do work but not always easy to justify a full engine strip and some machining work.

Post by **annechas** » Thu Jul 23, 2009 8:29 pm

Thanks for that. Sounds like a bit of a job, but does it work and what about the cost?

Post by **Declan_Burns** » Thu Jul 23, 2009 8:46 pm

I fitted it last year and it does work. You do get the odd drop seeping through but I mean a drop or two a week. This is because the seal is not fitted over a machined surface. Don't underestimate the work. It means gearbox, clutch, flywheel and backplate out-or engine out or both and there are so many other parts worth replacing simultaneously that it all adds up. I can send you the fitting instructions if you want. I think the seal kit was about 52 GBP at the time.

Post by **bmcecosse** » Thu Jul 23, 2009 9:05 pm

The rear 'seal' on the A series engine leaks because there is excessive internal pressure in the block. Cure the pressure - and there won't be any leak! Take the oil filler cap off when the engine is hot and idling - if there is a plume of smoke/fume - the bores/pistons/rings are badly worn - the engine needs overhauling. If there is no excessive plume - then check the breathers on the engine are clear - and make sure one of them is plumbed into the intake system to draw away the fumes.
If there is a slight suction in the block - there won't be any leakage.

Post by **rayofleamington** » Thu Jul 23, 2009 9:22 pm

The rear 'seal' on the A series engine leaks because there is excessive internal pressure in the block

any engine will leak if it has blocked breathers and pressurises itself.

The rear scroll seal is marginal at best and will not cope with pressure, but if the crank / bearings are worn it'll leak far more.

Post by **simmitc** » Thu Jul 23, 2009 9:38 pm

The modified kits are a complete waste of time and money. As noted above, there is precision machining required. Moreover, they require that the flange at the rear of the crank is perfectly round and smooth, and also matches precise dimensions. The slightest mark on the flange will wreck the rubber seal. I've found only one crankshaft out of many that meets the required dimensions; and after running the modified kit for 500 miles found that it leaked worse than the original.

Having driven from Essex to the Isle of Man (yes, via a ferry!), Edinburgh, Cornwall, and various other long distance runs using standard engines, I can state that an engine in good condition does NOT leak vast quantities of oil. You'd be better off reconditioning the engine properly.

Post by **bmcecosse** » Thu Jul 23, 2009 9:57 pm

Indeed - I was going to add that - but felt I had typed enough! Yes - if the rear main is badly worn the oil will flow out excessively and flood the scroll seal - AND if the crank bearings are so worn that the crank has been jumping about (rumbling) - then the labyrinths in the 'seal' can be damaged - and will never seal properly again. Then it will be necessary to resort to the external rubber lip seal - which as pointed out elsewhere -requires a smooth surface on the outer edge of the crank flywheel flange to have any great hope of success - and even then seems to be doubtful.

Post by **annechas** » Thu Jul 23, 2009 10:47 pm

Thanks everyone for the feedback. The engine is is pretty good shape as it has been totally rebuilt. No smoke from the rear end or mayonnaise. I think I'll forget the new seal and look at the crankcase pressure. I'll update later. Cheers

Post by **Declan_Burns** » Fri Jul 24, 2009 6:32 am

I totally agree with the breather issue as mentioned above. I've done about 3000 miles since I fitted the seal and as I mentioned very very little oil seeps through. Although we couldn't machine the flange surface professionally in-situ we did smooth it off as best as possible. A belt from a belt sander turned inside out and a cylindrical grinding stone as a cam shaft in an electric drill, while an assistant slowly cranks the engine with the plugs out. It calls for elbow grease but we got it fairly smooth. Perhaps that's why it worked in my case. It is a last resort job.

Post by **bmcecosse** » Fri Jul 24, 2009 9:05 am

Ingenious ! I was thinking it would have to be done with strips of emery, partially wrapped around - and back and forth arm action. That would be a LOT more elbow grease than your powered device!

Post by **mike.perry** » Fri Jul 24, 2009 10:38 am

I fitted the rear seal to my 1275 Midget engine a few years ago plus the mushroom valve on the manifold, I do not have breather pipes on the carbs, and the system worked fairly well. Lately, despite cleaning the valve it is becoming anti social with the amount of oil it is dripping.

Post by **bmcecosse** » Fri Jul 24, 2009 12:23 pm

Reflects the amount of pressure in the block i'm afraid.

Post by **RobThomas** » Sun Jul 26, 2009 8:35 am

How about drilling the rear main cap for a tiny bore capilliary pipe so that it runs into the gap round the scroll seal. Connect it up via a collector canister and a tapping right into the intake manifold so that it draws the oil off under any light throttle loading?

Post by **bmcecosse** » Sun Jul 26, 2009 11:30 am

Sounds like interesting machining - go for it!

Morris Minor Owners Club

modified rear crankshaft oil sel

modified rear crankshaft oil sel

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