OT: Need source for 1.75" (44.5 mm) OD master cylinder seal

MT6 · Jul 13, 2020

I'm trying to source a 1.75" OD seal for a brake master cylinder from a road grader. I can order a rebuild kit for around $300 or a new master cylinder for $700. I trying to fix this as a favor for a neighbor. The bore of the cylinder is pitted which wore out the seal that's in there now. I plan to bore out the cylinder and sleeve it with piece of 1.75" ID stainless air cylinder tubing. Already bought a cylinder and the ID is spot on.

I contacted MICO and was connected to an engineer. He was very help full but the cylinders are now assembled in Mexico and he has no access to any parts. Contacted a brake supplier in Florida and he was less than helpful.

The seal that's in there now was obviously modified as the ID of it was nibbled out to fit around the piston. It worked until it was worn by the pitting.

Ideally the seal would be 1.75" OD 1.35 ID with the lip about .45 high. 1.75" is close to 44.5 mm if that helps. My google foo has been exhausted trying to find anything even close. It does need to be rated for DOT3 brake fluid.

Yes I'm aware of the liability but I'm trying to get him some brakes and his budget is slim.

Thanks,
MT6

Limy Sami · Jul 13, 2020

Page 8 here? https://irp-cdn.multiscreensite.com/aa4b2dfa/files/uploaded/LOCKHEED HYDRAULIC CATALOGUE.pdf

and this - if you put your hole in the middle Lockheed Brake Master Cylinder Oil Seal Cup, 1 3/4 Bore

(only a quick goopgle search)

Hardplates · Jul 13, 2020

MT6 said:
I'm trying to source a 1.75" OD seal for a brake master cylinder from a road grader. I can order a rebuild kit for around $300 or a new master cylinder for $700. I trying to fix this as a favor for a neighbor. The bore of the cylinder is pitted which wore out the seal that's in there now. I plan to bore out the cylinder and sleeve it with piece of 1.75" ID stainless air cylinder tubing. Already bought a cylinder and the ID is spot on.

I contacted MICO and was connected to an engineer. He was very help full but the cylinders are now assembled in Mexico and he has no access to any parts. Contacted a brake supplier in Florida and he was less than helpful.

The seal that's in there now was obviously modified as the ID of it was nibbled out to fit around the piston. It worked until it was worn by the pitting.

Ideally the seal would be 1.75" OD 1.35 ID with the lip about .45 high. 1.75" is close to 44.5 mm if that helps. My google foo has been exhausted trying to find anything even close. It does need to be rated for DOT3 brake fluid.

Yes I'm aware of the liability but I'm trying to get him some brakes and his budget is slim.

Thanks,
MT6

I would try my local hydraulic shop if it were me.

MT6 · Jul 13, 2020

Thanks Limi, that was fast. Your goopgle search key words were obviously better than mine. I'll buy from the US site.

BoxcarPete · Jul 13, 2020

If that doesn't work out for whatever reason, send me a PM and I can try to find something here. If you send me the exact ID/OD and groove width I can take a look.

Mud · Jul 13, 2020

Limy Sami said:
Page 8 here? https://irp-cdn.multiscreensite.com/aa4b2dfa/files/uploaded/LOCKHEED HYDRAULIC CATALOGUE.pdf

and this - if you put your hole in the middle Lockheed Brake Master Cylinder Oil Seal Cup, 1 3/4 Bore

(only a quick goopgle search)

Will he need Girling fluid with the Lockheed cups? Seems like the British brakes always need Girling fluid.

john.k · Jul 13, 2020

If he cant keep water out,I suggest he uses silicone fluid ....anyway ,whoever heard of an old rigid frame grader with brakes ..... few years ago ,we could drive a grader on the road here without plates or rego......Used to drive the old Cat 12 all over ,wheels would fall off,steering fail ,youve always got the blade to pull you up.....or maybe the scarifier.One time the wheel lean broke ,and took off through a house yard,and we had to buy all new clothes for a woman that had her washing out.......Bill Perry Keene had a theory that a grader couldnt go faster than 25 mph ,cause the chains would throw out against the cases and drag .

MT6 · Jul 14, 2020

The classicandexotic.com owners have retired and straight-eight.com has taken over their remaining inventory. Luckily they had the 1.75 OD seals in stock. I contacted the owner and he says that the seals are compatible with DOT3 brake fluid.

I had never heard of Girling fluid so I was concerned that would be a problem. I know that at least some hydraulic seals are not compatible with brake fluid. The hydraulic seal supplier that I checked with was not able to supply the seal that I needed.

The road grader is either a Gallion or Dresser and is 40 some years old and the brakes have a power assist on them. Not always handy to just drop the blade to stop the machine.

BoxcarPete · Jul 14, 2020

MT6 said:
The classicandexotic.com owners have retired and straight-eight.com has taken over their remaining inventory. Luckily they had the 1.75 OD seals in stock. I contacted the owner and he says that the seals are compatible with DOT3 brake fluid.

I had never heard of Girling fluid so I was concerned that would be a problem. I know that at least some hydraulic seals are not compatible with brake fluid. The hydraulic seal supplier that I checked with was not able to supply the seal that I needed.

The road grader is either a Gallion or Dresser and is 40 some years old and the brakes have a power assist on them. Not always handy to just drop the blade to stop the machine.

Glad you found them. The reason hydraulic seals won't typically work is because they're usually either NBR (Buna-N, Nitrile) rubber or Polyurethane. NBR and Urethane won't work with brake fluid (Teflon/UHMW will). EPDM is another rubber which has similar physical properties and appearance to NBR, does just fine with brake fluid but cannot come into contact with petroleum products. So, you'd never see it used in a hydraulic system (with a couple exceptions: skydrol and brake fluid since they're not petroleum based).

Everything make sense? Make sure to squeeze 12-16% on the OD and stretch 1-2% on the ID!

Mud · Jul 14, 2020

BoxcarPete said:
Glad you found them. The reason hydraulic seals won't typically work is because they're usually either NBR (Buna-N, Nitrile) rubber or Polyurethane. NBR and Urethane won't work with brake fluid (Teflon/UHMW will). EPDM is another rubber which has similar physical properties and appearance to NBR, does just fine with brake fluid but cannot come into contact with petroleum products. So, you'd never see it used in a hydraulic system (with a couple exceptions: skydrol and brake fluid since they're not petroleum based).

What is in DOT3 brake fluid that Buna N and British rubber parts won't tolerate? There seems to be alcohol, but I've never heard it spelled out definitively.

BoxcarPete · Jul 14, 2020

Mud said:
What is in DOT3 brake fluid that Buna N and British rubber parts won't tolerate? There seems to be alcohol, but I've never heard it spelled out definitively.

I believe it's the variety of (Di-/Tri-/Poly-)alkylene and (Di-/Tri-/Poly-)ethylene glycols that make up the base of the fluid cause swelling, loss of hardness, loss of tensile strength, etc. in NBR but not EPDM. I'm not a compounder, so don't quote me on the chemistry behind it, but I believe it's got something to do with the polarity of the molecules in the fluid. EPDM just doesn't do well with completely non-polar stuff, but polar solvents like acetone and MEK don't bother it whatsoever. MEK will eat most rubbers for lunch.

jim rozen · Jul 14, 2020

Mud said:
Will he need Girling fluid with the Lockheed cups? Seems like the British brakes always need Girling fluid.

It'll be OK as long as he uses Whitworth wernches.

machinistrrt · Jul 15, 2020

jim rozen said:
.....Whitworth wernches.

Tough for us Yanks to speak with a stiff upper lip.

On another note, I found out recently that ATE Super Blue is now Unobtainium, and priced like it when you find it.
I found a gold ATE fluid that's supposed to have the same specs. Something about DOT said no blue brake fluid. You don't think some maroon saw the blue and topped off with washer fluid??

Limy Sami · Jul 15, 2020

jim rozen said:
It'll be OK as long as he uses Whitworth wernches.

Fords fitted a lot of Girling brakes and AFAIK Ford UK only ever used SAE threads & wrench sizes.

Oh and by the way - if you're talking British Standard Whitworth threads and hexagons, then they are spanners, and NOT wrenches

john.k · Jul 15, 2020

There used to be a local crowd making master cylinder and wheel cylinder seals of polyurethane so you could use mineral hydraulic oil in them..(.only for offroad.)...most old graders had brakes on only two wheels in the tandem ,because the wheels are rigidly connected by the drive chains......The only Galion/Dresser grader I 'm real familiar with are the small 503s ,although we did have a bigger Galion once with a 4/71 in it ..

Rob F. · Jul 15, 2020

Do you have a good NAPA store nearby? The one near me is good about that kind of thing.
They should have parts books that have all kinds of brake kits and parts in them, getting the right counter guy that knows where to look is the key here....

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OT: Need source for 1.75" (44.5 mm) OD master cylinder seal

MT6

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Limy Sami

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Hardplates

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MT6

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BoxcarPete

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Mud

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MT6

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BoxcarPete

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Mud

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jim rozen

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