Tacho woes

[Dick Weiss]

Stoddard's catalog shows 2-photos--#59 &/or #60 is the same seal and the shim is noted as #58.
If the seal's face (when seated/installed) doesn't protrude or it's too deep to be squeezed, the casting's
nose must be shortened so it does protrude; This is due from the hardened seal actually 'machined' the
depth (and diameter) so it'll allow oil to pass if it's not retained! I even add a little RTV on its diameter.
The correct installment is w/its lip pointing inward--to the pump.

[Mike Wilson]

Great explanation, Dick, of benefit to all of us.

Mike

[Mike Wilson]

Great explanation, Dick, of benefit to all of us.

Mike

[Mike Ruddy]

Thankyou Dick, that sheds new light on what's happening. Measuring the recess where the seal sits shows it to be 4.0mm deep. Both new seals I have are 3.9mm thick. Therein lies the problem !

Filing the nose whilst the pump is in place looks tricky and probably impossible for me to make a good job. My next thought is to pack the seal by first inserting a washer and making the seal sit a little proud. Hunting around in my small box of Porsche washers I've found a possible candidate, 11.7mm outer diameter, 8.2mm inner and 1.0mm thick, non magnetic, looks to be aluminium.

With the seal 12.8 OD, 7.0mm ID the washer will fit nicely in the bottom of the oil pump recess and perhaps push the seal out just enough for some compression. I'll give it a go and see what happens.

[Mike Ruddy]

Meanwhile, this is my tach. Is there anything a layman can do to open it up and clean out any oil that will be in there ?

[Dick Weiss]

Obviously the 912 doesn't use this seal due to having the electric tach unless thel tach drive
assembly is used for the 356 mechanical tach.

[Mike Ruddy]

Word back from Stoddard about their tach drive seals.

The 539-07-117-P seal is supplied by Porsche A.G. , less flexible composition and approx. 7 mm inside diameter.

The 539-07-117 seals measure nominally 7.3 to 7.4 I.D. .. more flexible. Height dimensions same for both seals.

[Dick Weiss]

Mike,

I neglected to mention the seal's retainment by your method of 'spacing out' the seal using a special washer/shim to protrude the seal's face would do the job.
Luckily, I never tried (or needed) to do that.

Dick