After-market rear crankshaft seal

[chris_bates]

I've always hated these after-market crankshaft seals; they only work if you have a perfectly round and smooth rear crankshaft bush (the bit that you bolt the flywheel on to). I've had them on three engines now and all have caused real problems and I have vowed to replace them whenever I have the engine out.

Well, not only do they not keep the oil out of the gearbox bell housing, the one I have been working on this evening wouldn't come off. It is held on by allen bolts (ie you need an allen key to remove them) and needless to say the heads of two of these bolts rounded off so the only solution was to drill them out I now have a garage floor covered in aluminium swarf and needless to say there is a bit of a risk that some of the swarf has found its way into the engine no matter how careful I have been. Aluminium swarf is not magnetic so I have used my trusty old vacuum to get up most of it.

This post is a warning to any out there who might be tempted to "invest" in one of these expensive and useless good ideas, not to go anywhere near them and stick to the tried and tested BMC solution. The full desription of the offending item is "crankshaft oil seal conversion kit" (part number is MGS108322 in the Moss catalogue) and they cost just shy of £100!

There are two things that you can do to reduce rear end oil leaks, The first is to ensure you have negative pressure in the crankcase by keeping the vents clear. The second which I intend to try is a tip from a member from somewhere in Africa who sent this suggestion into the letters page of Minor Matters. He swore by wrapping the end of the crank on the outside of the rear main bearing in hemp and maintained a zero leakage over many years experience! I'll report back on that one once I have got this engine back in the car.

Chris

[bmcecosse]

Hahahaha - this has been discussed to death... Yes - the external seals are pretty hopeless, and quite unnecessary. The solution IS negative pressure in the crankcase (or at least - no positive pressure) and unworn main bearings. If the rear main is worn - excessive oil pours over the labyrinth seal and it just can't cope. DO NOT try the hemp idea - it's madness - you will end up with bits of hemp through the oil ways blocking the flow. And it won't work anyway! I have to ask - where has the aluminium come from? Surely the Allen cap screws securing the hopeless seal are high tensile steel? I think unlikely to be aluminium......

[simmitc]

I can only endorse the view that these kits are a complete waste of time and should be avoided. They are sold by a number of parts suppliers, who really should know better. Many years ago I bought one after the supplier assured me that you had only to drop the sump to fit it. Rubbish! Engine out and flywheel off - can't recall whether the backplate comes off as well. The instructions provide very precise dimensions for the flange on the end of the crankshaft, and caution that if they are not matched, then the seal should not be fitted. Out of 20+ flanges that I have measured, only 1 met the requirement. Even then, the rubber lip seal is expected to run on the narrow edge of the flange, which was never designed or machined to accept such a seal - any roughness will rip the rubber to pieces. The instructions also recommend adding copious amounts of sealant "gunge" - always a sign of good engineering

The aluminium swarf to which Chris refers will have come from the bracket used for mounting the seal - virtually impossible to drill the allen screws out without touching the ally.

[bmcecosse]

And hard going to drill Allen screws at best of times ! So - the hopeless seal retainer is made of aluminium???

[chris_bates]

The half circle pieces which form the complete circle to hold the "rubber ring" are made of aluminium. There is a half circle which replaces the BMC part above the main bearing and this is held in place with large allen cap screws to replace the BMC bolts. This in effect completes the circular baseplate on which the seal holder is bolted. The top half of this seal holder is secured by 3 small allen headed screws which are accessed through the bolt holes of the crankshaft flange. The bottom half of the seal holder is held to the top half by long allen headed screws fitted perpendicular through the edges of the two circular parts. I got the perpendicular screws out but trying to remove the screws holding the top half of the seal holder to the baseplate through the bolt holes was a no go. The heads are simply too small to take the torque required to do them up tightly (or else they were put on too tightly in the first place. The only solution was to drill a series of holes around the offending seal holder to expose the large allen screws underneath. Lots of swarf and colourful language And being aluminium, the swarf is not magnetic meaning relying on the vacuum!

I'll have another look at the original article concerning the hemp wrap. The idea as I remember it is that the hemp is greased and wrapped around inside the groove on the outside of the main bearing and its top counterpart. It is of course imperative that it is wrapped in the right direction like putting ptfe tape round a plumbing joint.

I know this after market solution has been mentioned before but I was so angry at being confronted by yet another of these pesky things that I thought another warning to any readers who might yet still be tempted by this rip-off would do no harm!

Rage now suitably vented

Chris

[philthehill]

As a picture tells a thousand words this is the type of seal kit discussed above.
You are most likely right in that the three Allen headed screws were done up too tightly and possibly Locktited in place. They should be done up no more than 9lb ft and Loctited in place. When I removed the seal kit fitted to my 1275cc engine I had no problem removing the three screws even though they were Loctited in place. I did use a nice tight Allen key though. [frame][/frame][frame][/frame]

[Berniewade]

When overhauling my 1960 Morris 1000 Convertible a few years ago I tried one of these crank seals but had no luck with it only to find it was leaking oil very badly so resorted to the original seal and never had any further problems with oil leaks .

[M25VAN]

I wonder if there is a size of speedi sleeve that would fit over the rear of the crank and give a better surface for the seal to run on?

[bmcecosse]

It's too narrow... But the point is - it's completely unnecessary! The labyrinth seal works perfectly well !!

[ribs]

I took the 950 engine out of my minor to change the clutch - and while I was at it attempt to stop a couple of oil leaks one from the timing case and the other at the rear of the crankshaft. Reading that one of these oil seal kits would;'do the job once and for all' I bought one. On getting it home, I read the instructions - and found that I am supposed to get the rear main bearing cap machined! Belatedly, I looked on this forum and found this thread - ho hum....

Suffice to say, the kit will be returned - but what goes in it's place? bmcecosse mentioned that the labyrinth seal works fine, but what labyrinth seal? The Haynes manual (and Moss catalogue) shows the rear cover (half round, held by 3 wired bolts) and a gasket - but no seal. This cover has a groove around the inside as if some kind of seal locates there, but when I removed it there was only the gasket - as per the book. Am I missing something here?

The timing chain cover had a felt seal in a groove. I was going to soak the new one in engine oil before fitting it to the cover - is this correct - or should it be fitted dry - or with grease? The Haynes shows it laid on the oil thrower, (?) but apart from this says nothing about how it should be fitted.
Regards to all.

[philthehill]

I was not aware that the rear main bearing cap has to be machined! Perhaps you would be so kind as to post the fitting instructions for the 948cc kit on here. Are the parts similar to the ones in my post picture above.
The MOSS kit Pt No: MGS108322 to fit the 948cc is exactly the same as the kit which I fitted to my 1275cc Midget block and for which I had mixed success and finally went back to the normal oil return arrangement. I suspect that only the dimensions to suit the particular crankshaft rear end are different. You just remove the top oil thrower ring cover Pt No: 2A51 (that which is held by three wired bolts) and replace with the similar alloy part from the kit.
There is NO seal at the rear of the crankshaft just a oil thrower ring which is part of the crankshaft and which fits inside of the cover Pt No: 2A51 and the rear main bearing cap. The thrown oil is returned to the sump by a oil return drain and the scroll (labyrinth seal) cut into the rear of the crankshaft.
As regards the felt seal fitted into the timing cover yes it should be soaked in engine oil before fitting. Much better to fit the later lip seal and associated timing cover and oil thrower ring though.

[bmcecosse]

As Phil describes...the rear seal is simply a scroll running within a labyrinth. The fact that your engine was leaking at both ends suggests excessive crankcase pressure....forcing the oil out past the seals. Remedy is an engine overhaul......although some success can be gained by increasing the suction on the crankcase - through the breathers.

[ribs]

Sorry, but my computing skills are not up to posting the fitting instructions, but here is the relevant paragraph verbatim.

Remove the main bearing cap, take out the shell and clean it all thoroughly. Looking at the the main bearing cap you will see that the end face (fig 2) is not flat, it having been left "as cast" from manufacture; consequently the height of this end face from the block will be uneven and variable. The triangular alloy packing piece supplied fits above the main bearing cap, against the block and is exactly 11mm thick. To ensure an oil tight seal in this area and for the oil seal to run square to the flange, the end of the main bearing cap must be machined both flat and square to the block and at 11mm from it.

The components in the kit look identical to those of the 1275 kit posted. Whatever, it is not the simple 'fit and forget' item as described in the catalogue. The engine doesn't seem as if it needs a rebuild - It has ample power for it's size, doesn't smoke or use an excessive amount of oil. Whilst it is out I decided to remove and clean out the sump (judging by the amount of sludge in the bottom of the oil filter canister, this seems like a good idea) and paint it. The latter means that I will be replacing all the gaskets - except the head gasket. hopefully this should help to make the engine a little more oil tight. The leaks at the ends of the crank weren't particularly excessive and I would have left it if the clutch hadn't gone, but point taken, I will make sure all is clear in the breather department.

[philthehill]

ribs
Many thanks for the reply.
As regards the machining of the rear face of the rear main bearing cap. The 1275cc rear seal kit does not need any machining so much easier to fit. That kit has only sealant between the bottom half of the seal carrier and the main bearing cap so if you are handy with a file you can soon reduce the Minor 948cc rear main bearing cap to the required 11mm - finishing off on a sheet of glass with some wet and dry. The sealant will take up any imperfections between the lower half of the rear main bearing cap and the back face of the bottom half of the seal carrier. The requirement to reduce the rear main cap would not put me off in fact it would be more of a challenge. Measure constantly and use a engineers square to ensure the rear face of the rear main bearing cap is square to the rear of the block and the crankshaft. The alloy top half spacer (with 3 holes) when fitted can be used as a datum.
Fitting new sump cork seals and sump gaskets should stop any leaks from the rear of the sump. Worn main bearings especially the rear main bearing can exacerbate the problem of oil getting past the scroll/labyrinth.
Personally I would send the kit back and just get what you have right. My 1275cc (which in the area of the rear main /sump seal is similar to the 948cc Minor engine) does very well without any expensive seal kit being fitted to the rear main because I take time to ensure that it is assembled correctly.
Make sure that you not have any leaks from the oil pump cover where fitted into the rear engine plate. Even BMC recommended soldering the cover into place to remove any possibility of oil leaks from between the oil pump cover and the rear engine plate.

[ribs]

Yes, I'm going to stick with the original set up. The oil pump cover is soldered, so should be ok. I assume that the tappet cover bolts are loctighted (Haynes states 2 ft/lbs) with a smear of Hylomar on the fibre washers?

[philthehill]

The tappet cover securing bolts do not need to be loctited just nipped up. Over tightening just results in the cover being pulled into towards the block. A smear of Hylomar around the bolt washers (both metal and fibre) will not go amiss. If you are fitting cork gaskets smear them (both sides) with grease. If using the polythene gaskets leave bare when fitting.
Best of luck.