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MG MGA - Engine Rear Seal

I know that Barney has outlined a method for installing a rear seal (MGB type) in the MGA engine. Does anybody have an alternative method? What is the latest thoughts on this modification? (Improvement?)
James Johanski

I read in a recent Practical Classics about an aftermarket rear seal for an A-series engine that fitted behind the engine backplate. I wonder if there is something similar for a B-series and whether they really work.

Dan Smithers

Apparently my engine has a Teflon seal fitted there, but I have no details and it stil drips a bit
dominic clancy

James,

I am about to install the rear seal on my A. Barney has been very, very helpful (anything new?) in guinding me along with all my questions. Besides, it was a modification he himself did and met with success. That is a positive endorsement.

The seal was easy to find but was expensive. I had a bit of trouble finding an extra rear plate as MGAs are rare in Japan. I posted a message here and Brian sold me one and shipped it to my machine shop. I also had the machine shop make the crankshaft ring (I may have a spare). Everything arrived in the mail last week. Pricing was reasonable.

The installation looks to be straighforward sans any broken bolts or unforseen problems. I am pulling the drivetrain anyway to add a B clutch, a revised oil pump, rocker pedastals, and a sweet Crane cam, as well as changing the gearbox layshaft.

My plan was to do this this weekend but our MG classic car club (a bunch of guys with convertible cars of any make or year who just want to have fun) are having a night tour of Tokyo. I can't pass it up so the engine removal will have to be next week.

I will keep you posted if you like.
Tom Baker

The idea of creating a rear main seal is curious to me. I know that there has been much discussion on the matter for years now but if all things are correct with the engine then it should only leak a couple of drips per parking session.

I have two A's, one a restored road car that I drive occasionally, the engine was outsourced for it's rebuild. I don't know the condition of the reverse scroll on the crank or the rear main/block that it passes through. I do know that the engine runs very well, but it leaks like a PIG! The other car has been converted into a purpose built race car. I buildt the engine myself and sourced the machinist and the crank shop. I was very clear that the area the scroll runs near in the rear main cap and block not be touched other than cleaning, and when the crank was ground .010, that the scroll journal not be touched other than cleaning. This car drips about 2 drops per parked session.

My questions are these- Are the scroll journals being ground or polished along with the rest of the crank?

Is the area where the scroll runs near being bored along with the rest of the rear main/block?

It seams to me that if you can live with a 50 year old car leaving a couple of drops on your garage floor, then the original design isn't so bad. But that's just me.

JohnB

JohnB, For me the key word is couple of drops of oil. I would like it not to leak at all. As a previous owner of MGB's with five main engines and what might be in more modern terms, a proper lip type seal, I was able to achieve no leaks, not a drop, nothing. That pleased me. I just would like my MGA engine and transmission and rear axle not to leak any thing also. Maybe I should just use an MGB 5 main engine, but then I would loose the mechanical tach drive and the car would not be original, or at least appear original.
James Johanski

Hey Barney, I thought you would have chimed in by now. How is your rear seal holding up? Would you do it again. Is it worth it?
James Johanski

I ran my rear seal for 40,000 miles before retiring the engine for other reasons. I little drip doesn't bother me, so I wouldn't bother with the seal unless you have a real "pig" of an oil leak there.

If you want your MGA engine not to drip at all, you also have to get rid of the draft tube and install the PCV system to pipe crankcase blow-by into the intake manifold and draw a "slight" vacuum on the crankcase (but retain crankcase ventillation).
Barney Gaylord

Other options for a rear seal are a company called True North in Allendale MI. Got the name of the company from John Twist. John also suggested using a 1800 five bearing crank in a 3 bearing engine block. Off course the back plate would have to be machined, but that would have to be done anyway. Now, the MGB lip seal could be used. Any comments?
James Johanski

Oink-Oink.

Barney helped me analyze the situation on my car. There is no considerable oil loss at speed and only a drip or two after normal around the town driving. If I don't do any high speed driving I would not be so concerned with a couple of drips.

The problem surfaces AFTER driving the car at speed in which case the oil literally pours out, right at the gearbox weap hole. I often leave a nice long trail of oil as well when pulling into parking areas and such. Apparently, the scroll just can't keep up with the returning flow of oil back to the pan from the top end.

When I bough the car the engine had been, uhum, rebuilt complete with RTV to seal the head gasket and about a tube of the stuff to seal the oil pan. Of course all of that RTV was IN the oil pan, not on the outside. Couldn't see it through the paint. I decided to disassemble the engine, measure EVERYTHING, replace parts and assemble. Amazingly, most internal parts were new and showed little wear and the machine work done to the block was fine.

However, when I removed the crankshaft we noticed a sliver missing from one of the bearings. To be safe I took the crank to a local very reputable machine shop, who builds both NASCAR and very expensive stred rod engines, to have a look. He is little known for his work an vintage British engines, but he has been doing those as well for at least 30 years. He even rebuilt the spare motor I gave to my friend. I should have kept that motor. It's been 5 years and it still runs like a top and it is amazingly oil-drip free.

Anyway, I had the crank polished and informed the shop to be careful with the scroll (read it somewhere before taking it in). The shop owner gave me one of those looks and said not to worry as he has been doing these engines for a long time. I felt like an ass.

I assembled the car, shipped it to Japan. I tinkered around town for several months getting things sorted out. No real oil leak. I was then invited on a tour with a local classic car group. They drive really fast (for Japan 60 MPH through the mountains is fast). After my first run I was checking the oil and it was really low. Looked under the car and a steady stream of oil just poured out. This was scary. I am in the mountains, in a foreign country, there are NO MGAs here, no Moss Motors, and did I mention I am a foreigner? I kept an eagle eye on the oil level and pressure and made it home safe.

It has been almost 2 years since then and it only leaks after that kind of driving. I consulted Barney several times and through the magic of common sense and logic-both Barney's-it was decided that the rear seal may be the best alternative.

We will know in a couple of weeks.....
Tom Baker

I just had the engine and gearbox out to rebuild the gearbox. Seals at both ends were brittle and craked and I hoped that was the source of my oil leak. Wrong - rear of engine still leaks like a "pig." I am OK keeping a pan under my A at home but hate taking it anywhere that I can't park on asphal or gravel. Friends don't seem to appreciate a puddle of oil in the driveway after I leave.
Is there any sort of magnetic pan that can be attached to catch the drips and then dumped out later? (And won't get blown off while driving at speed?)
Steven B

Maybe someone can come up with an MGA "diaper". It could be fashioned after the devices used to catch horse dung for parade and police horses. The addition of a drain cock, would allow the release of fluid without removing the diaper. There seams to be enough folks with the leak problem, that this may be a viable commercial offering.
James Johanski

A old mechanic who once worked on B series engines told me to never let the oil in the sump exceed the dipstick level if you want to control the oil leak. There is no merit in being 'safe' with the oil level and topping it up a bit higher.
J H Cole

I'm new to this site.. I too have developled a oil leak and took it to my mechanic, he is going to put a new clutch,pressure plate and throwout bearing but he then said that I need a rear main seal so I notified Moss motors and they stated that there was no such animal... I now read that Barney has installed one... Could you tell me where I can locate one and what is the proceedure to install it... Thanks any info would be great.. Tom
Tom LeRose

Steven
I have made up a tray that bolts to the bellhousing. I stuff a rag in it to catch the drips then replace the rag as required.
Kris
Kris Sorensen

Tom, -- The special rear seal design is here: http://mgaguru.com/mgtech/engine/cs202a.htm
Barney Gaylord

My 2 cents, make sure you confirm the problem is your engine and not your font seal to the transmission. I just pulled my motor again because of leaking and sure enough, I failed to replace a 5o cent seal around the front spline of the tranny. If your oil from the leak appears "Clean" chances are it's you gear box!
Bill R

re reverse scroll

the groove has to be clean no carbon build up (cleaned with paint stripper)
and no wear on the rear main bearing this result in oil leaks
not polished with any wet and dry or ground .

jb alexander

This thread was discussed between 28/06/2007 and 12/07/2007

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