Wear on crank pulley oil seal surface diagnosis (1 Viewer)

baldilocks

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1993 with 302k miles - I replaced the front crank seal about 4 years and 30k miles ago but it has begun to leak again. I had suspicions of the possibility of wear on the pulley/dampener. The isolator rubber is firm and shows only tiny superficial cracks. A new oem unit is north of $300 online.

In your expert opinion backed by real experience with this engine, should the wear in the photo be an issue? Thanks

8BD1FFB2-AD46-4E5C-BB8F-015B003D8F6A.jpeg
6A6B8BD1-DD5A-4561-B28E-A22523D2BD64.png
 
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If its not grooved, just too rough I wonder if you could spin the shaft while holding a strip of Crocus cloth on the wear band?

Observed a rotating shaft seal engineer colleague doing that on a lab seal test rig.

The surface finish in contact with a rotating shaft seal needs the valleys to hold oil to lube the rubber seal lip but you have to git rid of the surface finish peaks. And the surface finish cannot have any lead - the finish direction must be in line with the shaft rotation. If the finish has a lead it will "screw" oil out from under the seal lip.
 

Dave 2000

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I would replace the seal and sleeve the pulley, it would be easy enough to drop the pulley into an engineering works and have them fit the sleeve.

regards

Dave
 

baldilocks

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If its not grooved, just too rough I wonder if you could spin the shaft while holding a strip of Crocus cloth on the wear band?

Observed a rotating shaft seal engineer colleague doing that on a lab seal test rig.

The surface finish in contact with a rotating shaft seal needs the valleys to hold oil to lube the rubber seal lip but you have to git rid of the surface finish peaks. And the surface finish cannot have any lead - the finish direction must be in line with the shaft rotation. If the finish has a lead it will "screw" oil out from under the seal lip.
What do you mean by a “lead”?
 
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What do you mean by a “lead”?

Think screw pitch. Blueprints for shafts and such that were lathe turned or ground often had a requirement for "no lead" (that's as in lead vs follow as opposed to lead bullets).

Say in a lathe turn op the cutter was left against the shaft as it was withdrawn. The cutter would leave a spiral groove in the shaft - that is lead.

If a rotating shaft has lead it can slowly transfer oil past the seal lip to the outside.

My colleagues who worked with rotating shaft seals were real particular about the surface finish on the shafts they were supposed to seal. In a contest between steel and rubber, always bet on the steel.
 
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Think screw pitch. Blueprints for shafts and such that were lathe turned or ground often had a requirement for "no lead" (that's as in lead vs follow as opposed to lead bullets).

Say in a lathe turn op the cutter was left against the shaft as it was withdrawn. The cutter would leave a spiral groove in the shaft - that is lead.

If a rotating shaft has lead it can slowly transfer oil past the seal lip to the outside.

My colleagues who worked with rotating shaft seals were real particular about the surface finish on the shafts they were supposed to seal. In a contest between steel and rubber, always bet on the steel.
The end of the crankshaft on my Studebaker has an intentional "follow" cut into the shaft because the crank seal is only felt. It's designed to auger the oil back into the pan. It does not protrude past the felt seal.
 

baldilocks

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I went out this morning and took a long, hard gander at the seal surface through a magnifying glass and used a scribe to palpate. There is definitely a groove where the seal has ridden for 27 years and 302k miles. In general the surface is very pitted but no high spots could be seen with the level of magnification I have available. This pulley had a good run but its replacement has been ordered and is inbound from the UAE. P/N 13470-66020 superseded by 13470-66030

@NMC_EXP Thanks for the expert level info.
 
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The end of the crankshaft on my Studebaker has an intentional "follow" cut into the shaft because the crank seal is only felt. It's designed to auger the oil back into the pan. It does not protrude past the felt seal.

That's interesting.

Modern shaft seals rely on one or more rubber lips and may have a garter spring to keep the seal tight on the shaft. The rubber seals must have a very thin oil film between the lip and the shaft. A rotating shaft seal running dry will wear out quickly.

Common practice is to specify a shaft surface finish where the peaks have been removed but the valleys are still there. The valleys in the steel act as an oil reservoir for the seal lip.
 
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My colleagues who worked with rotating shaft seals were real particular about the surface finish on the shafts they were supposed to seal.
Common practice is to specify a shaft surface finish where the peaks have been removed but the valleys are still there.
What that's called is turned, ground & polished shafting.
Modern shaft seals rely on one or more rubber lips and may have a garter spring to keep the seal tight on the shaft. The rubber seals must have a very thin oil film between the lip and the shaft. A rotating shaft seal running dry will wear out quickly.
That's one of the reasons why i always pack a little grease in around the garter spring when I'm installing new lip seals, just to make sure that they don't run dry.
 
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What that's called is turned, ground & polished shafting.
Thanks for the info.

Rubber was my area. The little bit I knew about the metal side of the business I picked by working with the folks who had design control for the metal parts my rubber parts mated up with.

Almost 100% of the time if a part with a seal in leaked, the seal got blamed. Thing is the seal or o-ring is only 1/3 of a seal joint. There are two metal parts with the seal sandwiched between. A perfect seal or o-ring mated to an out of spec metal part meant a seal joint leak.

I spent a lot of time figuring out what actually caused a leak. So I had to learn something about the metal parts. As often as not it turned out to be a metal part.
 

baldilocks

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Thanks for the info.

Rubber was my area. The little bit I knew about the metal side of the business I picked by working with the folks who had design control for the metal parts my rubber parts mated up with.

Almost 100% of the time if a part with a seal in leaked, the seal got blamed. Thing is the seal or o-ring is only 1/3 of a seal joint. There are two metal parts with the seal sandwiched between. A perfect seal or o-ring mated to an out of spec metal part meant a seal joint leak.

I spent a lot of time figuring out what actually caused a leak. So I had to learn something about the metal parts. As often as not it turned out to be a metal part.
Which is why I coughed up the coin for a new metal part. The seal I removed looked And felt like it did the day I installed 4 plus years ago.
 
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Which is why I coughed up the coin for a new metal part. The seal I removed looked And felt like it did the day I installed 4 plus years ago.
Good call.

Most of the leaking seal joint post-mortems I did were on new equipment still under warranty. When I was working seals I had "static seals" such as o-rings. My coworkers had rotating/dynamic seals so I never saw a grooved shaft on the job.
 

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