W203: Possible causes of the rear main oil seal leak
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Germancars
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What could be causing a minor oil leak from the rear main oil seal before I pay to have the entire gearbox, etc., removed?
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Germancars
- Senior
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- Joined: Thu Dec 24, 2020 11:25 pm
The vehicle has only travelled 42,000 kilometres.
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MercedesMan98
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Old age and little mileage could be the cause, but I'd be shocked if it had excessive crankcase pressure.
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matthewlightburn
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It's "normal"—a known weakness—and it's likely older than mileage on your vehicle. Mine was completed some time ago. Purchasing genuine MB parts—especially the plate with the seal already installed—rather than simply the seal alone is the only way to accomplish it correctly.
You don't mention which engine this is and how you diagnosed the seal as being at fault ?
You don't mention which engine this is and how you diagnosed the seal as being at fault ?
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Germancars
- Senior
- Posts: 80
- Joined: Thu Dec 24, 2020 11:25 pm
The 5.4 is it. I was informed by a professional garage that it was the seal. But they haven’t had the gearbox out to confirm. My issue is that I believe I need to remove the gearbox to make sure. Is there no other option?
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matthewlightburn
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No. By removing the tiny black plastic "inspection" covers from the bell housing's bottom, you can reach the torque converter, and you can typically identify the problem using a borescope or Mk1 human eyeball.
Another uncommon problem with the M113 V8 is that there are core plugs in the casting (also known as casting/welch/freeze plugs) in the valley of the V beneath the intake manifold. If one or more of these plugs rot out, engine oil will gradually fill the valley until it drips down the engine's back, around the gearbox bell housing and onto the floor.
Those in the "know" initially believe it to be the crank shaft's rear seal.
Yours knows better, though.
You can probably guess how I know this is a real problem rather than just something I saw online :doh:.
The cost of a new plug is negligible, but replacing it requires a significant amount of effort (££). It might also be a good idea to take a borescope look underneath.
If it's the rear seal, you might as well be ready to replace the gearbox mounts, flex disc and centre bearing on the driveshaft. Since the car has a low mileage, you might be able to avoid doing them.
However, I'm a "while you are in there" kind of guy.
Another uncommon problem with the M113 V8 is that there are core plugs in the casting (also known as casting/welch/freeze plugs) in the valley of the V beneath the intake manifold. If one or more of these plugs rot out, engine oil will gradually fill the valley until it drips down the engine's back, around the gearbox bell housing and onto the floor.
Those in the "know" initially believe it to be the crank shaft's rear seal.
Yours knows better, though.
You can probably guess how I know this is a real problem rather than just something I saw online :doh:.
The cost of a new plug is negligible, but replacing it requires a significant amount of effort (££). It might also be a good idea to take a borescope look underneath.
If it's the rear seal, you might as well be ready to replace the gearbox mounts, flex disc and centre bearing on the driveshaft. Since the car has a low mileage, you might be able to avoid doing them.
However, I'm a "while you are in there" kind of guy.