Starting From Scratch – Diagnosing an Oil Leak on the 1963 Jaguar MkII 3.4

By Craig Ranson
By Craig Ranson

Managing Director – Bridge Classic Cars

Our in-house engine builder at Bridge Classic Cars, Ady, has been working at trying to get to the bottom of the oil leak with the 1963 Jaguar MkII 3.4.

At idle, the engine would behave itself perfectly. Not a spot of oil but any higher in the revs and it would begin to leak. Ady has spent countless hours hanging over the engine bay of the MkII trying to get to the root cause of the issue. He believes he has found the cause.

Upon inspection for the oil leak, Ady has found the bores in several cylinders to be heavily scored.

With some of the pistons, the rings have too much play in them and allow a lot of the cylinder head pressure to escape past the rings, down the cylinder and into the crankcase. With this added pressure, it begins to push the oil out to any opening that may have a weakness.

The rear main seal on the MkII 3.4’s is a split seal design. Meaning at the bottom engine they are cut to allow them to be slipped into place during installation. This, with the added crankcase pressure, has been pushing the oil from the crankcase through the rear seal and out. So a combination of pistons slop, ring movement and too much crankcase pressure have been causing the leak we have been searching for.

The only remedy for this in Ady’s experience, is a full engine rebuild with new parts including a rebore to clean up the cylinder walls.

Keep an eye on the Bridge Classic Cars blog for more updates on the MkII 3.4.

Share this post
Enjoyed this article by Craig Ranson?
Email Craig Ranson