Starter Motor Oil Seal

[Bloggs]

Hi All,

On stripping the starter motor to check brushes I find its rather well 'Oiled'!
The front oil seal has worn and must be letting in oil from main engine casing.
PO (one of them!) has stripped it and fitted new brushes no that long ago, but now the brush gear is full of stickly gunk.

So has anyone changed this seal and can you suggest a source?

Trying to measure in situ I get 24 OD, 6 or 7 think and the shalf measures 13.46.
Plenty of 13x24x7 oil seal about but concerned they will be tight on the shalf.

Bloggs

[Oddjob]

Are we talking about the seal inside the front housing? where the shaft of the armature sticks through?

If so that's not exactly a normal oil seal, is more like a forward facing lipped seal.

[Matt_Harrington]

I've just replaced mine with an o-ring (that was what was in there) - I'll fish out the size tomorrow morning

[Oddjob]

Oring is on the outside, the seal is on the inside Matt.

[Bloggs]

Yes it's the seal in the end cover. I have not yet removed it as I wanted find replacement 1st, if possible. The amount of oil inside was considerable. Surprised no short circuit to date.

[Oddjob]

I think the question you should be asking is WHY has it failed. To fail I'd imagine the bush in the outside of that part of the casing has worn, this allowed the shaft to oscillate, this must have worn the seal away.. So IF that's happened fixing the seal is just a band aid. Maybe think more about replacing the end cap on that end. Fix both problems at the same time

[McCabe-Thiele (Ted)]

Just my thoughts on the matter. The starter motor shaft is stationary except when you press the starter button. Iirc the starter motor shaft is a pretty snug fit when the external O ring is in place. So how is oil getting past the first line of defence when the shaft is mostly stationary?
I can imagine that if the starter end plate/ bearing is worn then an oval orbit might cause seal wear in the long term so what has caused the starter wear?

[Oddjob]

There is another possibility which has just occurred to me, the seal is a forward facing lip seal, IF the seal has flipped in that the lip is now facing into the motor that may allow oil to get past it. I think you need to remove the end cap and check.

[McCabe-Thiele (Ted)]

Is it possible that the starter clutch has not been working correctly causing the starter motor to rotate with the engine for prolonged periods before disengaging?

That might explain why the brushes have been replaced recently and why the end plate has worn or is this not possible?

[Matt_Harrington]

Oring is on the outside, the seal is on the inside Matt.

Oops!

[Bloggs]

Thanks for the thoughts to date.

Just measure shalf with the 'Best' micrometer, 13.47 Diameter.
Front bush has a small amount of wear but not very much as is the original.
Seal lip is the correect way around but seal is letting quite a bit of oil past.
Looks like a standard single lip oil seal.
Starter has been 'opened' before and the brushes are quite unworn, one almost new length.
So I guess someone fitted new brushes not that long ago.
The seal has made a very slight mark on shalf but only just detectable.

As expected it not a standard sized seal, shalf size nearest seal is 17/32" : )

I'll keep on looking.

[Oddjob]

The seal looks to me to be a metal cased seal. The single lip is also quite large considering it's size.

I'll see what I can find.

Maybe whoever opened the starter last time ripped the edge of the seal?

[Bloggs]

HI,

Thanks for you reply and looking for spares.
The exisitng seal Looks OK, maybe just wear on the lip and as you say it has a longish lip.
Yes it does seem to be a steel backed version.

I remember seeing ads for a Goo you added to engine oil to swell engine oil seals on older engines. Does it work and would just painting it on the seal lips add that little bit extra to seal?

[Oddjob]

Easier and cheaper to just replace the starter motor

[McCabe-Thiele (Ted)]

HI,

Thanks for you reply and looking for spares.
The exisitng seal Looks OK, maybe just wear on the lip and as you say it has a longish lip.
Yes it does seem to be a steel backed version.

I remember seeing ads for a Goo you added to engine oil to swell engine oil seals on older engines. Does it work and would just painting it on the seal lips add that little bit extra to seal?

I think you are talking about seal Plasticisers - imho not a long term fix.
Modern ATF contains such additatives as standard.