Is my oil pump output compressible seal the wrong size

DennisMo · Dec 20, 2023

Hello all from Vancouver!

I opened my timing cover to fix a leak and am replacing the oil pump output rubber seal that seals between the pump and the outer timing cover case by compression.
The outer diameter of the small oil pump output pipe is .260 inches. The inner diameter of the new compressible seal is .200 inches.
I can put the seal onto the output pipe by stretching it, but it is quite a stretch. Using (my rarely used) high school math, the stretch increase of the new seal along its inner circumference is from .062 inches to .082 inches which is about 33% stretch

I wonder whether the seal inner diameter might be wrong and whether the seal may split one day ...
If anyone has a new seal in their inventory and could measure the inner diameter I would be grateful

Looking forward to your comments with thanks

Dennis

hybridracer · Dec 20, 2023

Weird, the seal can be a loose fit on the pump, it doesn't need to be tight at all! But then again, I haven't seen a new one since about 1980.

jimbo · Dec 20, 2023

FYI, MKIII and pre MKIII oil pump seals and seal landings are different

DennisMo · Dec 20, 2023

I have a 1973
Dennis

marshg246 · Dec 20, 2023

DennisMo said:
Hello all from Vancouver!

I opened my timing cover to fix a leak and am replacing the oil pump output rubber seal that seals between the pump and the outer timing cover case by compression.
The outer diameter of the small oil pump output pipe is .260 inches. The inner diameter of the new compressible seal is .200 inches.
I can put the seal onto the output pipe by stretching it, but it is quite a stretch. Using (my rarely used) high school math, the stretch increase of the new seal along its inner circumference is from .062 inches to .082 inches which is about 33% stretch

I wonder whether the seal inner diameter might be wrong and whether the seal may split one day ...
If anyone has a new seal in their inventory and could measure the inner diameter I would be grateful

Looking forward to your comments with thanks

Dennis

Assuming the original pump and the part the seal goes one is original:

Should be: https://andover-norton.co.uk/en/sho...ming-cover-oil-pump-oil-pressure-relief-valve

Not: https://andover-norton.co.uk/en/shop-details/16729/oil-pump-seal-mk3

ILLF8ED · Dec 20, 2023

I just measured one of my new seals. I can slide a 13/64 drill snuggly into the hole (.203”). You might check if the pipe on the pump is correct. It is a push in fit….maybe in backward?

DennisMo · Dec 20, 2023

The little output stub that comes out of the pump (to the timing cover) is the same outside diameter on both sides at .260 inches
Thanks
Dennis

marshg246 · Dec 20, 2023

DennisMo said:
The little output stub that comes out of the pump (to the timing cover) is the same outside diameter on both sides at .260 inches
Thanks
Dennis

Which seal do you have?

DennisMo · Dec 20, 2023

marshg246 said:
Which seal do you have?

The old one that came off it is now .260 hole diameter (It was likely less that than when installed)
The one I got in a complete seal kit for the engine is .200 hole diameter
Dennis

marshg246 · Dec 20, 2023

DennisMo said:
The old one that came off it is now .260 hole diameter (It was likely less that than when installed)
The one I got in a complete seal kit for the engine is .200 hole diameter
Dennis

Please see the two pictures in my post #5. You may have a MKIII gasket set!

ILLF8ED · Dec 20, 2023

The correct seal is conical. The 850 MkIII is a flat rubber disc with a slight cone in the middle.

Tornado · Dec 20, 2023

Also, confirm if you have a mkIII timing cover installed, as they are sometimes retrofit to mkII engines b/c they have anti wet sump check valve and timing chain tension check opening. It would ththen need the mkIII oil seal, not the mkII seal.

Is my oil pump output compressible seal the wrong size

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