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Registered
Join Date: Jan 2013
Location: Mexico City
Posts: 295
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Help! 74 911s caliper piston pitting
After discovering one of my brake lines was broke i decided to replace all four and also do some maintenance work on the calipers since one of them was in rough shape, so when i took the pistons out i noticed they had some pitting in them, one has a lot the other three are pretty small pits but i don't know if i have to replace all four or just the worst one i hope someone can steer me in the right direction. My plan is to upgrade eventually to the big reds or brembo but right now budget is really tight and i would like to save as much as i can towards the upgrade.
I'm ordering rebuild kits for all four calipers but I'm lost with the pistons, if i have to replace one do i have to replace all four or just that one? is there a way to fix them? welding or brazing or something? i was looking at the DuroAno S-Caliper Piston sold here what do you guys think about these? this is how the pistons look like      thanks in advance best regards |
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03-30-2013, 01:25 AM
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not worth fixing, just replace them. Why do you need big red brakes? it won't stop any faster, unless your racing and you need a lot more cash than just brakes!!!
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08 Cayenne Turbo |
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03-30-2013, 01:34 AM
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Join Date: Feb 2012
Posts: 97
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I think you could get away with replacing the worst one and polishing out the others.
I used a small whetstone and oil on mine and was able to get rid of 99% of the rust. It's a judgement call on the pitting. I chose to reinstall all of my pistons, with very minor pitting and haven't had a problem. But I'm a cheapskate. I'm sure others will advise to replace no matter what. |
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03-30-2013, 06:41 AM
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Registered
Join Date: Mar 2010
Posts: 799
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My vote, go for the new piston upgrade (it's what I did). I also removed a set of Brembos on my car beacuse they were not only unneeded, but the pedal feel is terrible with the stock 19mm MC.
As for your existing pistons, the pitting is a breach in the plating and will only come back if you remove it somehow. As a bonus, the aluminum pistons save some weight too. Spend a little $ to get good pads (Porterfield R4-S or the like) and you'll be happy with your refreshed stoppers.
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1973 Coupe Projekt X (AKA bunch o' boxes full of parts) Last edited by kugelfischer; 03-30-2013 at 08:49 AM.. Reason: Error |
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03-30-2013, 06:59 AM
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Functionista
Join Date: Jul 2011
Location: CO
Posts: 7,717
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Obviously the best choice is new pistons.
But an interesting experiment might be to try some of the stuff guys use to repair pitting in hydraulic cylinders on large equipment until rebuilding is possible. These pistons (rods really) face the same types of stress if not more than brakes. The pits can cause seal tear and leaks so this substance fills the voids and stops further damage. A lot of work to do it twice if it doesn't work though.
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Jeff 74 911, #3 I do not disbelieve in anything. I start from the premise that everything is true until proved false. Everything is possible. |
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03-30-2013, 07:16 AM
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Registered
Join Date: Jan 2003
Location: Burford, ON, Canada
Posts: 2,321
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This is a known problem with S calipers. I always replace the pistons. Consider those from PMB Performance:
48mm Stainless Steel S-Caliper Piston or as you noted DuroAno S-Caliper Pistons Either are great solutions.
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Keeper of 356, 911, 912 & 914 databases; source for Kardex and CoA-type reports; email for info Researching 356, 911, 912 & 914 Paint codes, Engine #'s and Transmission #'s Addicted since 1975 |
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03-31-2013, 08:44 AM
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76 911S Targa
Join Date: Oct 2010
Location: Idaho
Posts: 1,150
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I agree with the others. Replace the pistons. I have reused pitted pistons in my Norton Commando but Norton parts are harder to find than the OEM Porsche parts. They worked OK. It's the rubber seals that need to work properly. The edges of the pits in the piston wall will ultimately score the rubber, the brake fluid will escape and you get to do it all over again.
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76 911S, 2.7, Bursch Thermal Reactor Replacements, Smog Pump Removed, Magnecors, Silicone Valve Cover Gaskets, 11 Blade Fan, Carrera Oil Cooler, Turbo Tie Rods. |
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03-31-2013, 09:14 AM
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