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MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGA - Rubber seal for three bearing engines

Update:
A few weeks ago I completed the mod found on Barney Gaylord's MGA web site (http://www.mgaguru.com/mgtech/engine/cs202a.htm). This mod allows the placement of a rubber seal over a modified rear crank flange, thus adding the benefits of a rear seal to these engines.

All was well for a short while. Then it started leaking oil like a sieve through the rear main. Yesterday the engine came out again and was taken to the machine shop to consult with the machinist. The machine work on the rear engine backing plate appears to be spot-on.

The mod calls for cutting away the seal casing so that only a flat metal case surface remained to be bolted to the rear engine plate. It appears that in my application, the loss of strength in the cut-away seal casing caused the seal to twist from the torque of the crank flange on the seal surface. The twisted seal was thus out-of-round and created the new leak. The crank flange is within .001" of round.

Today the machinist is making a flat, round plate (drilled to match the seal bolt holes) to fit over the cut-down replacement seal. This should add strength and hopefully will keep it from twisting. I'll update later this week on whether it works.

I need to get this fixed in time for the NAMGAR Key West trip April 20!
Frank Nocera

Hi Frank. Sorry to hear about your rear seal problems. It seems even when you try to improve know MGA rear seal problems, that it creates new headaches. Good luck with the fix! Please let us know how it all works out. Cheers! GLenn
Glenn

Hi Frank, this all seam familiar, I've just done the same to my 3 brg engine, I modified my engine 2 years ago ( my own idea ) but I had a seal made for the job, I didn't drill the main bearing cap as per Barney's intructions. It wasn't a sucess, I recently redone the mod as per Barneys website, After 15 minutes of running it leaked like a Texas oil strike!! Luckily I had the car in the garage ticking over, the only thing that was different was the holes in the main bearing cap. I think the crankcase compression pushes the oil out as they are only a couple of inches above the oil level. Out with the engine and several ours debating what to do next, I dragged a 5 bearing engine out from under the bench and am now building a new engine. Sadly I've admitted defeat, I've been told that the 1800's leaked worse that the 1500 and 1600 with the scroll type crank. Typical Austin/Morris mentality to carry on with the same poor design for more than a decade, I bet the Japanese are still laughing, (all the way to the bank) Sadly MG Rover are in trouble again. Now then what about K series head gaskets!!
Terry Drinkwater

Frank,
I have used Indian Head gasket shellac on the outer ring of main seals for years to hold the seal from spinning. You may want to do that in addition to your rear plate.
Good luck.
mike parker

Hi again Frank I've just re-read your thread, I failed to say that I fitted my cut down seal with a metal ring around the outside to help keep the seal against the plate Sorry for this news!
Terry Drinkwater

Terry - "...carry on with the same poor design for more than a decade..." I would hvae to say for MUCH more than a decade, since the same scroll seal was used in the Morris X series engines that are used in the T series engines since somewhere in the mid to late 30s. There are several different approaches to providing a positive seal for the XPAG engines used in the T series MGs over the years, all of which have met with varying degrees of success or failure. Some of them have worked well in some installations but not all. The one consistant thing about all of them is the high rate of failure. On the other hand, a well set up scroll seal seems to work well all the time (when I say "works well", I am refering to no oil pouring out while the car is being run, only the few odd drips when the engine is shut off). I don't knowwhat the secret is, other than a large amount of luck. Our TD is one of those that has performed well over the past 30 years with just the scroll seal. luck of the draw I guess. Cheers - Dave
David DuBois

David - you're quite right to correct me, I thought about this afterwards and remember owning a 1622cc Leyland Sherpa van (sad, I know) 1978 vintage and this has the same crank scroll ( I've kept the engine - residing under my bench with other 1600/1622/1800 B series engines, I like to think they keep each other company, even more sad). Why change somethink that doesn't work!
Terry Drinkwater

I just had an 18V, 5-main, installed with an MGA backingplate machined-out to accomodate the MGB rear seal. Within 50 miles,... like a sive. The seal 'twisted-out'. The engine is going back-in in a couple days, we'll see what happens, I'm concerned. Steve
Steve Meline

Hi Everyone,
I have been considering "fixing" the oil leak from the rear main of my newly acquired MGA for a while now. This thread does not make happy reading!! There appears no positive solution from very experienced people. Are there oil additives that may help to reduce the leaks in both cold and hot conditions?
Regards, Dave, Gold Coast, Australia.
Jim Paul

I added an O ring seal to my 1500 3 year/ 9000 miles ago. It has worked well. I did it by machining the engine side of the flywheel, making an .25 in thick aluminum ring with an L shaped notch to hold a standard 1/8" cross section O ring aginst the rear of the engine. This piece replaces the alum factory scrap/ shield, and is spigoted into the rear most bore of the block. If you have autcad, i can send a layout, but after 18 april. Happy motoring to all, bill.
w.g cook

I have thought this over, and have to ask a question. What is the machined diameter of the oil seal seating area? What is the outside diameter of the oil seal that you are using, as measured with a micrometer? It seems to me that the oil seal should be .002-.003 larger than the machined seat. If you are too closely matched, the seal will slip. If you haven't checked it, maybe you can go to the local bearing/seal shop and find another seal that may fit better.
FWIW
mike parker

Hi Steve, re - your 5 bearing oil seal conversion, I looked at my 1600 backplate with regards to machining it out but where the recessed holes for the bolts are you end up with very little metal for the seal to fit against. I phoned Peter Gamble of Hi-Gear Engineering
here in the UK who makes the bellhousings etc for the 5 speed conversions and found out that he has backplates made out of aluminium without the recessed holes so that you can fit the retainer as fitted to MGB's. If you want his contact number please email me

Terry
Terry Drinkwater

Terry, Thank you so much for your time and effort, very much appreciated. I had heard of, and thought about getting, that pre-fabed alternative backing plate. Now wish I had. If it dosn't work this time I may call you for that number.

Jim, I had my a serious rear seal leak in my 1500 for years. I had the engine built twice, wrong, before someone finally properly mic'ed the crank and found that the journal in which the inverted/Archemeades' screw [the MGA's excuse for a real oil seal] is housed was worn. The fix for me ultimatly was a new crank, but I understand they can be welded up to increase the diameter then machined to spec. Tricky since the screw then has to be somehow implanted. Other readers here know much more about this than I. G.W.'s fix sounds well thought out. Wish you the best. I'm "across town" if I can help.
Steve Meline

Greetings, -- I am not a member here, but someone called this thread to my attention and asked for my input. In case anyone in this discussion hasn't seen it yet, my seal installation is detailed here: http://mgaguru.com/mgtech/engine/cs202a.htm

I have no idea why Frank's seal might have twisted out of shape to cause the leak. I can only speculate that it may have been damaged somehow in the process of modificatoin during installation, but just a guess.

My career experience as a machine designer leads me to think that the added steel ring on top of the seal flange is probably a waste of time. When the seal flange is attached to the block and bearing cap with screws and adhesive it is much more ridgid than it would be in the original unmodified seal configuration, where the face flange is only held at the edge by the outer shell. From Frank's description it didn't sound like any problem with distortion of the face flange on the seal.

The rubber seal is vulcanized to the steel shell (molded in place), so it should never be able to tear loose from the metal face. If the seal lip was distorted as much as was reported, this would likely have been the same whether it was modified or not. Modification and mounting method likely had nothing to do with it, unless it was damaged in the process of being modified.

I have installed three of these modiied seals in this manner and have never had any "mechanical" problem with the seal itself.

During the learning curve, the first one leaked immediately because of the accumulated oil puddling around the crankshaft flange with no provision for drainback. The bolt heads milling around in the oil puddle would mechanically force the oil right past the seal. Drilling the drain-back holes in the bottom of the bearing cap solved that problem.

A second leak occured after a few days of running when the press fit slip ring worked loose from the crankshaft flange. A new ring with tighter press fit plus a little drilling and installation of the roll pin solved that problem.

A third leak occured after a few weeks of heavy running time, a couple thousand miles. This was because the new rubber seal runs dry at road speed when the mechanical scroll seal is doing its job properly. Friction when running dry creates a lot of heat. The ($16) silicone rubber seal I was using had perished from the heat and had gone brittle and developed lots of cracks in the seal lip. The fix for that was to install a new seal with a more heat resistant Viton seal lip (a $48 seal).

After that, no problem, and the thing worked well for 60,000 miles with the same seal until I retired the engine for other reasons (gone through too many wars by 250,000 miles, one total rebuild and many interim repairs). I still have the slip ring and Viton seal which I removed and saved after 60,000 miles of operation. The seal lip is still flexible and still in servicable condition. It looks like it could have lasted a lot longer.

Best regards,

Barney Gaylord
1958 MGA with an attitude
http://MGAguru.com
Barney Gaylord


Update:

We replaced the seal, following the original engineering guidelines, per Barney's recommendation, and not using the reinforcing ring made by my machinist. The engine was reinstalled earlier this week. 50 miles later it is working well; no oil drips. So what was the problem? I am not sure. It may have been an issue of mis-alignment of the mounting holes drilled in the first seal. It appears, on very close inspection, there may have been some damage to the first seal when the steel case was cut down. The car will continue to be driven this week. If anything changes, I'll let you know. If you don't hear from me on this issue, assume the Case of the Errant Rear Main Mod is solved.
Frank Nocera

This thread was discussed between 05/04/2005 and 14/04/2005

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