Westerbeke W30 (4-91) rear oil leak - SailNet Community
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post #1 of 11 Old 07-03-2011 Thread Starter
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Westerbeke W30 (4-91) rear oil leak

Hello-
I have a fairly significant rear oil leak in my W30 engine. This is a slightly newer version of the 4-91. The motor starts promptly even without glowplugs (in Florida) and the crankcase breather is not clogged. My working diagnosis was a leaking rear seal. As Westerbeke no longer carries this part, I ordered one for a Leyland 4/25 tractor which has the same engine, but it has not arrived yet.
I have disassembled the back end- reduction gear/bellhousing/flywheel and backplate. I was initially expecting to find a lip type seal in a carrier based on the Westerbeke parts diagram, but I have the older round style rear plate and the parts book does not show a seal anywhere. I have also looked at the Austin FX3 (London Taxi) parts diagram and the Nash Metropolitan (same block) parts diagrams and don't see where the seal is. I am not able to identify a seal on the crank by looking at it. I believe I am looking at the back of the rear main bearing at the back of the crankcase.
Anyone familiar with this engine?
John Churchill
NURDLE
1979 Bristol 35.5
Sanibel FL
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post #2 of 11 Old 07-04-2011
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Pretty sure there has to be a seal where the shaft exits the housing. Suspect its under the coupling you uncovered. Not clear how that is held on as I don't see a nut. Press fit?
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post #3 of 11 Old 07-04-2011 Thread Starter
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The hub with the bolts sticking out is the crankshaft. That part does not come off, so I don't think anything goes in behind it. Could there be something built into the main bearing?
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post #4 of 11 Old 07-05-2011
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Might be a rope type seal. Google "rope type rear main seal." It requires removal of the crank shaft to replace. Not saying its a good idea, but a long time ago, I changed half of one by pulling the pan and last bearing with modest success.

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post #5 of 11 Old 07-05-2011
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I suppose this would mean "London Taxi engine" is now the largest known member of the "British Sports Car" engineering school. (Said with some fondness for both.)

No doubt someone will come up with the definitive answer for you, or Westerbleak perhaps can be, ah, extorted out of it?

Rear main seal is very much what comes to mind when someone says "lots of oil from the back of the engine" though.

Can the folks who sold you the tractor part, put you in touch with whoever supplies it? Is that a "British Leyland" engine actually?
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post #6 of 11 Old 07-05-2011 Thread Starter
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ENVELOPE PLEASE! - The Answer

Called Westerbeke's phone tree which sent me to my distributor who sent me to a guy at a different branch. He was very helpful and familiar with the later W30's with a lip seal in a carrier, he reviewed with me common causes of leaky seals- piston blowby and clogged crankcase vent systems, but did not know about my engine. He called Westerbeke and based on my serial number, he found that there is no rear seal. Apparently it is just crankcase pressure against the crank that keeps the oil in, there may be a spiral groove cut in the crank that wicks the oil back into the crankcase. Judging by the amount of oil my guess is that it is the gasket that seals the distributor gear area from the backplate. I know diesels don't have distributors but this engine originated as a gasoline engine.

Made by British Motor Company, later became British Leyland

Read about its history here BMC B-Series engine - Wikipedia, the free encyclopedia

Tractors were the Leyland 4/25 and 154 models

The Westerbeke 4-107 had the rope seal.
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post #7 of 11 Old 07-05-2011 Thread Starter
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the London Taxi model was the Austin FX3. Same engine.
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post #8 of 11 Old 08-26-2011 Thread Starter
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Finally got her all back together. Delayed by tons of "as long as I am at it" projects - redo dipstick/wiring harness/repaint/fuel filter relocate/waterpump/clean heat exchanger/new exhaust, etc.
Took oil pan off as well. Replaced the gasket between the rear block and the motorplate, suspecting that was the leak source.
Engine is in much better shape now than when I started.

Somewhat distressing that the thing still leaks.
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post #9 of 11 Old 08-29-2011
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Brings back memories. I had a Westerbeke 4-107 in my P39 for years, then re-powered with a brand new Perkins 4-108. Both were great engines and neither one ever let me down. But you know what? They both leaked oil constantly from the bottom of the bell housing, which I assumed was the rear main seal. I just lived with it and kept fresh oil absorbers beneath the leaking spot all the time. Guess the Brits just can't keep oil in an engine. Sounds like yours might be a bit more though. Good luck with the fix.
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post #10 of 11 Old 11-05-2011
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Find any good suppliers for your engine? ($) I have the same.....and .....the same leak. However, it was leak free the first fifteen years. I am going to try the rear seal again this winter, and would appreciate any tips.
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