Skip to main content

39 replies

Leaking Caliper Piston

bobhudsonbobhudsonMember
I rebuilt my front calipers approximately 18 months ago. Thought I had cleaned and polished pistons, bores and seal grooves sufficiently before reassembly.

Last week the car started pulling under braking and have now found a leaky seal at one of the small pistons.

When I removed the caliper I found hat corrosion in that piston seal groove apparently left impressions (similar to pin holes) in the upper and outer seal surfaces.

I cleaned up the groove with circular Dremel hard and soft disks. I guess dreaming that would work with the groove clean I reinstalled that seal and reassembled but it didn't seal.

Does anyone know the dimension of the seals so that I may search for a single seal rather than purchase a complete kit again. I suppose I could find a dial caliper and measure but thought maybe someone had that information available and the size was available as common seals through hydraulic parts.

I know it's a good possibility and best to again rebuild the fronts and purchase new kits but wanted to avoid that until necessary.

Thanks in advance for any suggestions and help,

Bob
Original Post

Replies sorted oldest to newest

bobhudsonbobhudsonMember
Good point. Actually the seal looked worse than the groove. I probably should have used a better word than pitting for the description. The seal looked as if it had been pressed into coarse grit on the outer surfaces more representative of contamination or bad molding.

Basically what I did to clean it was much milder than a typical honing process so I believe there's little if any change in the original dimension.

New calipers would be nice. Do you know if any Mustang or other calipers are interchangeable?

I'll investigate replacements but am considering selling the car want to leave those upgrades to the next owner.
bosswrenchbosswrenchMember
Bob, I found that almost ALL Euro cars from the '70s and '80s (Cobra, Ferrari, Pantera, Porsche etc) use nickel plated mild steel pistons instead of stainless like in U.S cars since the '80s. The pistons are magnetic. So the plating sometimes pits like a rusty bumper and will tear up new seals no matter how carefully you install them. If that's your problem, the fix is new pistons if possible or unpitted-used if new are unavailable.

Your calipers are English 4-piston Girlings and are no longer sold by Girling after 45 years. No known cross-reference. Someone in Europe advertised new pistons F/S at one time. I made some on a lathe out of stainless bar stock for my ATS rear calipers- also were unavailable. Mustang calipers aren't in the same league and will not bolt on.
deniscdeniscCaretaker of 8MA1244 '70 Euro Mangusta DRIVE THEM, THEY WERE MEANT TO BE DRIVEN, IF YOU WANT TO LOOK AT ONE, BUY A POSTER!
quote:
Originally posted by Bosswrench:


Your calipers are English 4-piston Girlings and are no longer sold by Girling after 45 years. No known cross-reference. Someone in Europe advertised new pistons F/S at one time. I made some on a lathe out of stainless bar stock for my ATS rear calipers- also were unavailable. Mustang calipers aren't in the same league and will not bolt on.



Boss tell y'a about your ATS. A rare car for sure
bosswrenchbosswrenchMember
Actually, those 'ATS' calipers are stock aluminum two-piston units for a 1970 911S. I adapted them to the rear uprights and balanced them against stock Girling front calipers first, then Wilwood Superlite 2s, both with a manual proportioning valve.

The Wilwoods went on after we lost the stock fronts on a 1000 mile Fun Rally round trip to 'Vegas & back. My wife drove the mountain route entirely on the rear brakes and said the brake pedal was 'a bit long in travel' but she had no trouble keeping up with the other dozen Panteras in the group. We trade off driving; I drove home the same way and also had no trouble.

I've since added Porterfield R-4S pads & Speed-bleeders on both ends, after the ATS sprung a leak. I used 312 stainless bar stock to make 4 pistons after I found both the Girlings and ATS calipers had plated pistons. I checked an aluminum Girling Mangusta caliper last year (same as big-block Cobras) and its pistons were also magnetic.... Change brake fluid EVERY year!
bosswrenchbosswrenchMember
No ss pistons that I know of. Simple to make but labor intensive. Roland in Germany said he had a few NOS pistons (unknown source). Girling sold off all their 40+ yr old patterns & tooling decades ago to private shops in England- for both early & late Pantera. Never heard anything more about spares. ATS did the same- last contact I had from them was a shop in S. Africa. VERY small market...
bobhudsonbobhudsonMember
That repair kit with new pistons is a possible option if I keep having issues.

Initial inspection does not indicate leaking fluid on that caliper now although I have not removed it.

The car still pulls left under hard braking after an attempt to bleed the brakes again. I used the do it yourself method using a hose on the bleeder submerged into a bottle with fluid. This time I'll get someone to pressure them when I bleed.

I will pull the caliper and check it again for leaking seals or sticking pistons. I can't imagine anything else would cause it to pull left. Any fluid residue on the pads should be gone by now after cleaning and running.

Seemed initially obvious why with the leaking seal but now am wondering if something else is causing the left pull.
rockyrockyMember
I had the same problem as you described, leaking caliper, started pulling to one side.

What I found was the fluid had saturated and swelled up the pad material on one of the pads, and I wasn't getting good braking power on the leaky side.

The one affected pad was swollen in the center, and you could tell that it wasn't gripping (engaging on the rotor) the same as the other three.

The leak was on my drivers side caliper, and the car would pull to the passenger side.

I was told that you can soak the pads in brake cleaner (and/or water) and get the fluid out, and then re-bed in the pads. I had a new set of Porterfield R4S pads, but I didn't try it.


Rocky
Last edited by rocky
bobhudsonbobhudsonMember
Rocky
Thanks for sharing that experience and information. That seems to be consistent with the chain of events with me thus thus far.

I attempted to clean the pad previously by just washing the face with gasoline but the fluid may have penetrated the pad so I'll inspect the pad and try the cleaning method you suggest after I remove the caliper and verify there is not leak.

Bosswrench
I have not changed rotors and agree that would cause an issue. I'm willing to attempt swapping rotors around if pad cleaning doesn't correct it in an attempt to discover the cause.

Thanks guys for the suggestions

Bob
Next

Add Reply

Views: 604
Post

Membership Required

We're sorry. You must be signed in to continue. Sign In or Register
×
Are you sure you want to remove from your Block List?
×
Loading...
×
When you block a person, they can no longer invite you to a private message or post to your profile wall. Replies and comments they make will be collapsed/hidden by default. Finally, you'll never receive email notifications about content they create or likes they designate for your content.
Note: if you proceed, you will no longer be following .
×
Link copied to your clipboard.
×