Master Cylinder Piston Removal

[KenF]

Well, so far the rebuild of the brake and clutch master cylinders isn't going very well. Pistons are stuck. Soaked overnight in Kroil penetrating oil, no luck. Tried air pushing from inside, nope. I'm hoping I can save these, even if they need to be sleeved. I've seen others use a grease fitting on the outlet and pushing grease through it, might work, idk. Any tips? Thanks!

 

[Forrest39]

if the pistons are not all the way at the bottom ob the bores, perhaps you could using a press or a c-clamp to get them to migrate even a little? Aerokroil is good stuff. It usually will allow some kind of motivation. I'd be hesitant to use heat on aluminum, but maybe others could comment on that approach...
-Kevin

 

[steven]

If the lady doesn't mind, put the master in the freezer overnight. Then try air or brake fluid in the cylinder to push the piston. The alum of the cylinder and steel of the piston expand and shrink at different rates

 

[HolyCat]

Be Careful with Air

If anyone else out there has a similar problem, please do be careful if you try to use air to push out a stuck piston. Unlike the grease mentioned, compressing air stores energy in the compressed air. Should the cylinder break (if there is an unknown crack or weak point), all that pent-up energy will be released suddenly, in an explosive-like manner. Liquids (or semi-liquids, like the grease) do not compress very much and do not store energy the way a gas like air does.

I think the poster is wise to not push it with compressed air and consider using grease.

You might also try a few solid "raps" with a rubber mallet to the aluminum while you have some pressure on the piston. However, do be careful doing so. For safety's sake, be sure to wear eye protection whenever trying to get a piston out with pressure.

Good luck in freeing that piston!

 

[KenF]

If the lady doesn't mind, put the master in the freezer overnight. Then try air or brake fluid in the cylinder to push the piston. The alum of the cylinder and steel of the piston expand and shrink at different rates

Okay, I snuck the MC's into the freezer, next to the frozen salmon that's probably too old anyway.

So, I think I read here Girling used bubble flares on the tube fittings. Will an AN-3 male fitting and some adaptor work temporarily for a hydraulic sealable connection without messing up the threads?

 

[steven]

If you are rebuilding the system why not use an existing brake line and seperate at the booster or the three way brass joiner. That way the threads will be right and have a brake shop make a adapter to pump brake fluid into the master or I picked up a brake pump off ebay for $30 that should allow fluid into the line with a narrow pipe.

 

[Hoghead]

Buy a bit of bubble tube, cut and install a 1/8 NPT compression union to a zerk fitting. Push it out with grease
Works everytime - almost

 

[KenF]

Well, I'm thinking of setting these aside for now, and just use the ones from SS. These will likely need to be resleeved anyway, around $100 each from Karps Power Brake Service and he said he could get the pistons out for me. Probably have to replace the innards after he does that, the non-rebuild kit stuff.

 

[spmdr]

Think about this...

...Unless you are in love with the Girling bits, I would think about replacing the masters with new parts, at least the clutch master.

Wilwood has a Girling repo 5/8" master (that bolts right in, using the old rod) for around $50 and it even comes with a Moisture barrier.

https://www.summitracing.com/parts/wil-260-2636/overview/

If you want it to look like an old part, put on the old cap...


The Brake master is a bit harder to replace. The 7/8" size is not a common part in the Girling style.

However, the smaller sizes are (3/4", .700") are common, but not great to use with a booster.

 

[Tiger]

Think about this...

...Unless you are in love with the Girling bits, I would think about replacing the masters with new parts, at least the clutch master.

Wilwood has a Girling repo 5/8" master (that bolts right in, using the old rod) for around $50 and it even comes with a Moisture barrier.

https://www.summitracing.com/parts/wil-260-2636/overview/

If you want it to look like an old part, put on the old cap...


The Brake master is a bit harder to replace. The 7/8" size is not a common part in the Girling style.

However, the smaller sizes are (3/4", .700") are common, but not great to use with a booster.

Dan, Regarding the Wilwood 360-2536 Clutch Master. I see it comes with a pushrod although not the OEM Tiger style. Can the OEM Tiger rod be used with the Wilwood without modification?

 

[Austin Healer]

Think about this...

...Unless you are in love with the Girling bits, I would think about replacing the masters with new parts, at least the clutch master.

Wilwood has a Girling repo 5/8" master (that bolts right in, using the old rod) for around $50 and it even comes with a Moisture barrier.

https://www.summitracing.com/parts/wil-260-2636/overview/

If you want it to look like an old part, put on the old cap...


The Brake master is a bit harder to replace. The 7/8" size is not a common part in the Girling style.

However, the smaller sizes are (3/4", .700") are common, but not great to use with a booster.

The Austin Healey used a 7/8" diameter master cylinder for the brakes... alloy body identical to the Alpine/Tiger. Moss part # 581.100 (TRW/Lucas) retail $74, or part # 581.102 (generic/repro) for retail $35. As a practical matter, only cast iron master cylinders can be rebuilt. Cast aluminum master cylinders have anodized bores, which will be destroyed if honed. Once the anodized coating is damaged the steel piston will react with bare aluminum and quickly cause problems (electrolytic corrosion)

 

[HolyCat]

The Austin Healey used a 7/8" diameter master cylinder for the brakes... alloy body identical to the Alpine/Tiger. Moss part # 581.100 (TRW/Lucas) retail $74, or part # 581.102 (generic/repro) for retail $35. As a practical matter, only cast iron master cylinders can be rebuilt. Cast aluminum master cylinders have anodized bores, which will be destroyed if honed. Once the anodized coating is damaged the steel piston will react with bare aluminum and quickly cause problems (electrolytic corrosion)

Can the aluminum master cylinders be sleeved to eliminate the electrolytic corrosion? Or can the corrosion happen in areas other than the bore, such as the passageway between the reservoir and the bore?

 

[Austin Healer]

Can the aluminum master cylinders be sleeved to eliminate the electrolytic corrosion? Or can the corrosion happen in areas other than the bore, such as the passageway between the reservoir and the bore?

Yes, the alloy cylinders could be sleeved, but as the new ones are so cheap it makes little economic sense. I have had nothing but problems with brass sleeves (Apple Hydraulics), stainless would be the way to go. If you are concerned about absolute originality, then sleeving would be the only way to properly rebuild an alloy master cylinder with any bore damage/wear. As the masters are visible, this might be of concern for someone who was after a "day one" type restoration, the rear wheel cylinders should just be tossed... these are so cheap ($15 retail) that it doesn't even make sense to expend the labor involved to rebuild them. Electrolytic corrosion only happens when two dissimilar metals are in direct contact. You can have regular corrosion (appears as a white powder.. aluminum salts) in the passage ways due to water in the brake fluid, but this usually only appears in severely neglected cars.