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MG MGA - Serious Oil Leak 2007

Some of you may or may not recall a trip I took last year around this time when I discovered a serious oil leak when driving my A at highway speeds.

Well, after working with Barney, I found that the oil filter adapter housing was the cause. At least a major cause. Fixed that and for the past year have had no serious leaks. I thought all was well. I was wrong.

I just returned from a wonderful 300 mile trip through the Izu peninsula. Famous for warm weather, great winding roads, and hot springs. Of course it snowed, rained, was foggy, and was bitter cold. The forcast said clear and warm.

That didn't stop us. Tops down, heaters on and off we went. Let me say that the MGA has proven itself to be one of the funnest sports cars I have ever driven. We did sharp ess turns at almost 50 mph with no problems. It drove like it was on rails. Let me add that the sway bar is a must. A fellow A owner and I swapped cars and there was such a difference that the other owner thanked me profusely for letting him experience what an MGA should drive like. Fortunately, I had an extra pair of shorts. Both cars are otherwise pretty much the same.

Sorry for that sidebar. Anyway, after some sprited driving we often stop to give the cars a rest and have a drink or a snack. At each stop I would peek under my A and could see a steady stream of oil from the gearbox weap hole. It looked like a Mr. Coffee machine. This is something that needs attention. I am sure the oil is from the rear of the engine as everything else including the oil filter area is dry.

Last year I kind of jumped the gun and was preparing for the rear seal conversion. I think it may finally be time. Any thoughts?
Tommy

Tommy,

The first thing to do if you have oil coming out the clutch bellhousing drain is to determine if it is engine oil or gearbox oil.
Just let it drain on to some white cloth. Even though you use engine oil in the gearbox, the color of the leaking oil will be different when from the engine or gearbox. Engine oil becomes very dark after little use and gearbox oil tends to retain the original color.
If it is engine oil I would check the crankcase ventilation system before pulling the engine to replace, or modify, the rear crankshaft seal. With negative pressure in the crankcase you should not get a leak at the rate you describe, even with a poor seal.
Check that the hose and fittings from the air cleaner to the valve rocker cover are clear. The side cover and tube should also be removed and checked. Does the side pipe extend down to the level of the oil pan gasket?
Is there any sign of emulsified oil on the inside of the oil filler cap?

Mick
Mick Anderson

Mick,

Thank you for the information. I am certain it is engine oil as the level drops consistently with the leak. The tranny has never leaked any significant amount of oil and the level stays consistant.

As for the ventilation system, I am pretty sure that the pressure is OK. I recently removed the engine side cover and venturi pipe and it was clear and it does extend to the proper location. I also ensured that the tappet cover vent and hose were clear to the air filter housing. There should be enough negative pressure. No signs of emulsified oil anywhere. It would be nice if that is all it is!

Tom

How's the summer in Sydney this year?
Tommy

Mick,

Come to think of it, I had some correspondence with Barney lasy year and went back and re-read everything. He too mentioned the crankcase pressure problem. I ruled it out after finding the oil adapter leak and the lack of oil leaks after that fix. I think I may re-visit it and consider adding a PVC system BEFORE trying to add a rear seal. Now, off to Barney's site for more info! I think he just did an update on PVC systems.

Tom
Tommy

Tom,

I would not bother with a PCV system, a lot of work to get it right, for no real return on investment. These systems are only part of the "anti-pollution craze", the MGA system is all you really need. Barney has an article on the PCV system, but why turn your car into a MGB for no gain? You would really need the full MGB system.

In Sydney it was 45 degrees C (113 degrees F) in the Western suburbs yesterday. Forest fires all over the place.

Mick

Mick Anderson

Tommy,
If you do the rear main seal conversion, the key to its success is exact and precise machining of the engine backing plate. The machinist's challenge is to make an existing hole larger. It has to be spot on center and the machine screw holes that will hold the seal in place must also be precisely placed around the enlarged hole. If either are even slightly off-center, the seal won't sit properly around the crankshaft and you will be out the money and still have a leaky rear main. The first time I did this procedure, I used a local machine shop with sorry results. The second time, I had University Motors do the work. The result is excellent. The moral of the story is to use the best machine shop you can find. While I have to believe you will be able to find a craftsman machinist in Japan, I suggest considering finding a backing plate in the U.S., have it shipped to University Motors and let them do the work and ship it to you in Japan. By the way, the MGA backing plates are getting scarce now. It took me a while to find the second one, and when I did it wasn't cheap (US$125 as I remember). Was it all worth the expense? To me, absolutely yes. It's great to have an MGA that leaves the garage floor dry and does not have an undercarriage coated in 20w50.
Frank
Frank Nocera

Thanks for the heads up, Frank. I sent an e-mail to University Motors and hope to get a reply soon. I also have a post asking for a swap out rear plate. That may be a good alternative. Were they also able to source the correct viton seal, prep it and install it as well? I think I could do it, but maybe its best to leave that one to the pros as well!

Tom

Tommy

Tommy,
Since you are overseas, University Motors should be able to source the proper Chicago Rawhide seal (the part number is on Barney's site) from a local (Michigan) truck parts supplier. The seal ain't cheap, either; about $50 each, as I remember. Installing it is not difficult; just a few machine screws and a curved plate over part of the seal.

The other precise machining is on the rear flange of the crankshaft where a VERY round and smooth bearing surface must be pinned onto the rear flange. That is probably do-able in Japan, but no doubt pretty expensive. (It seems everything there is.) It actually may be cost-effective to ship your crank to University, have them install the bearing surface, measure it for fit against the installed sealand then have it shipped it back to Japan. It would be worth doing the math both ways to see how the costs compare. Again, the goal is exactness and precision. In for a penny...
Frank
Frank Nocera

The curved plate over part of the seal is a standard 5-main bearing engine part but is not used for any 3-main bearing engine installation.

The flange on the modified seal used for my 3-main installation overlaps some of the rear plate attachment bolts, to the seal has to be installed after the plate is attached to the engine (and requiring caulking).
Barney Gaylord

Barney,
Thanks for the correction and keepping the thread accurate. That's what I get for going on memory. I just hate this early onset of Alzheimers.
Frank
Frank Nocera

I agree that a clean floor, and dry undercarrige is desireable. But, this seems like a lot of trouble and expense in order to contain the small amount of oil that drips from the rear of the crankshaft when all else in in good condidion. If you are getting a stream of oil, something else is wrong somewhere that is contributing to the amount of oil leaking out. These engines have run for over 50 years, and if that amount of oil leaking was normal, things would have changed long ago. I suspect you have a secondary leak that is combining with the crankshaft normal drip. Perhaps you should investigate where the other leak is comming from before going to all the trouble of installing a rear seal. When all else is OK, the amount of oil dripping from the rear of the crankshaft is hardly enough to justify all the work involved to contain it. However, it would be nice to have a clean floor. What is that worth in time and money. Only you can answer that question.
Ed Bell

Ed

The Japanese authorities are completely nuts about oil leaks....

dominic clancy

Ed,

Dominic is correct. He must have a similar experience in Switzerland.

As for the leak, I can loose several ounces of oil each time I stop. For this past trip, a little over 2 qts. in 300 miles. It can easily be seen pooling and running from under the car. If you peer under the car, it clearly comes from the gearbox weap hole after the car stops. It seems as the scroll cannot keep up with the drainback from the engine after some hard driving.

If it was only 10-15 drips I wouldn't worry. I would just wipe it away or park it for a while before it goes in for its Japanese inspection. At this rate it will fail and I will be out a day of work plus my car will not be street legal and will be impounded until it can be fixed. The irony here is that I can't fix it while it is impounded.

The timing is good. The engine will be pulled for some maintenance anyway. Why not try to fix it?
Tommy

If you are pulling the engine you might as well take it apart for a complete inspection. Check the bores, rings, valve guides, etc., anything that could cause an increase in crankcase pressure. Inspect the scroll and flange area of the crankshaft, block, and rear main cap for damage. While a few drips is common, the amount of oil you are using is way past normal. Running at 65 mph for a thousand miles I use one quart of oil and most of that is due to cylinder wear as the car is still stock bore, leakage is minimal
John H

Hi John,

I plan to do an inspection while the engine is out. It was rebuilt about 2000 miles ago and I had an anal retentive machinist check, double check, and triple check all the specifications. He even went as far as balancing the con-rods and pistons. It has new pistons, rings, bearings, etc and the head had new valves, seats, and seals installed. At some point the guides must have been replaced as they were fine.

After a little thought (mostly by Barney) I don't think I have a crankcase pressure problem as oil does not leak while driving, only after stopping and only from the gearbox weap hole. Of couse, I still plan to check it out.

THe damage is probably around the rear bearing cap and/or scroll seal area. Either way the seal setup is going in! I may not have another chance.
Tommy

This thread was discussed between 22/01/2007 and 25/01/2007

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