I can't believe this. So a mechanic replaces the rear main seal then runs the car and it starts leaking again.
Not as bad but a slow drip. He gets another rear main seal and puts it in and same thing.
So now he tells me this must mean the crankshaft is not running true.
Because after an hour of running that leak starts. He's guessing maybe the crankshaft bearings are worn causing some wiggle.
Engine has 198,000 miles. Anyone else experienced this issue?
My engine is noisy and I have had the cam chain replaced.

My regular Jag mechanic has a lower mileage engine out of a '96 that he can put in my '95.
It's a car he has maintained so he knows the engine is good. I've heard it run and driven.
The car it's coming out of has been neglected and is red and faded with expired registration.
I looked into buying it but going to cost a lot to get it registered and it wouldn't be as nice as my car.
The interior is in crap condition too. I've kept mine nice.

 

When the Technician replacing the rear main seal had the seal out, did he or she inspect the area of the crankshaft the seal lip runs on for any wear?

 

Didn't appear to be excessive wear.

 

Did the Technician set up a dial indicator to measure the crankshaft for distortion as it rotates by hand. That is the best method to determine if the crankshaft is somehow distorted.

 

I'm leaning towards the engine swap I mentioned in the OP.
My engine's been noisy for some time now.

 

So the mechanic called yesterday and says that the recommendation from the seal dealer is to also replace the front main seal which they say will help the rear seal function properly.
Doesn't make sense but they say it will work to stop the drip leak from the brand new rear main seal.
He's charging me $150 to change the front seal so it's worth a shot.

 

Is it possible there is a problem with the crankcase breathing system and the crankcase pressure is positive instead of negative?

A pressure transducer and scope would be the most accurate way to measure it, but a vacuum gauge connected to the oil dipstick tube would give you a basic idea of whether crankcase pressures are elevated.

The fact that your engine is noisy is a clue. Jaguar AJ16 engines are famous for their smoothness and quietness. Has your mechanic probed around with a stethoscope?

Cheers,

Don

 

Have put 100,000 miles on my AJ16 and can confirm quiet and smooth.

Wouldn't pulling the breather hose immediately show if the engine was positive, as it should be. I'm wondering whether the steel mesh in the camcover, by the breather hose, can be completely clogged up causing overpressurization, pushing oil out of the seals?

 

Update: My mechanic called the seal dealer to report the rear main seal leakage. I also told him to make sure the crankcase breather system was not clogged. So the seal dealer told him that replacing the front main seal would fix the rear main seal leak. He installed the front main seal and it actually did fix the rear main seal leak. He also replaced the oil pan gasket. So I know have no leaks.

 

That's good news, but I'd love to understand the science of why that would work?

 

May be the front seal as not worn acts as a locator and if loose lets the crankshaft migrate fwd coming off the rear seal seat , I understand the crankshaft lateral migration is a minor forces compared to the rotational forces

This is only in effect for a face seal seat vs. circumfixal

Along the length of the crankshaft there should surely be a locator bearing as have not opened a X300 engine lower half myself

I have a amazing story on someone erroring on a crankshaft brass journal that actually did fly and fail , but this may not be the place