Hi All 914 owners,

I'm finishing up my complete restoration of a '73 only only to find a rear caliper LEAKING through the outboard Adjuster. A rebuild was Mandatory!

From Auto Parts Warehouse I found a pretty fair price for the Centric 143.37017
rebuild kits, about 1/2 the price of some "name" parts providers:

http://www.autopartswarehouse.com/search/?...mp;addfitment=1

To do the rebuild, the calipers must be "split" which scares some folks since they don't understand the sealing technology between the halves. ATE used 2 simple
"O" rings in the caliper design, a technology which has worked for well over 50 years. So NO WORRIES! If you think about it the "O" ring is the same technology that seals the caliper pistons.

The next step is IMPORTANT TO UNDERSTAND: The caliper pistons must be UNSCREWED to remove. Do NOT try air pressure nor ESPECIALLY hydraulic pressure to get them out. To get enough piston out of the body to grab, turning
the adjuster screws on both side will help. The task was a bit hard, but using small Channel-Lock pliers I was able to turn the pistons and thread them out.

Then things are just an issue of cleaning off all the rust: A wire wheel did a great job on my pistons and 600 grit wet & dry cleaned up the bores. Then CLEAN, CLEAN, Clean.

Assembly is the simple reverse procedure ensuring that the piston seals are properly fitted in their channels and the Tiny "O" ring (the cause of the whole rebuild) is carefully installed in its grove. For piston re-install, I lubed everything
with fresh brake fluid and for the Offending "O" ring I used axle grease to ensure
it would slide into the body and net get cut by the sharp edge.

After bolting the halves back together, I cleaned the casting with solvent and painted them with Rust-Oleum black paint. No I didn't use the expensive
high-temp caliper paint since from my experience, street driving never gets
calipers that hot.

As an example, my last 914 had a 500 HP Chevy with Wilwood brakes and after hammering a track session, the fronts only got to 400 degrees while the rears were a cool 300 degrees. At those temps, some brake pads won't even start to work! That's the car's photo on the left.

Hope this helps!
Terry

Eric at PMB has a how-to video on YouTube, very in depth

https://www.youtube.com/watch?v=dm_DnizKOZM


I don't recommend Chinese seal kits or paint. The plating on the "inside" of the bore is the most important part of any caliper rebuild.

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Eric,
Thanks for the great rebuild video! That shop is certainly thorough!

I'm interested about your comment on the "plating" on the piston bores. When
I cleaned mine I found nothing but cast iron. Of course there is nothing wrong
with a cast iron bore and most Engine bores are cast iron and it seems to work.

Currently there is a whole new technology of surface coatings varying by the application. However, 40+ years ago, I don't think VW/Porsche paid for any kind of plating on the 914 calipers. The more I work on 914s, the more is see that the goal was Low Cost!

What can you share on these calipers that was not apparent? I love all the tech details.

Cheers,
Terry

That would be an incorrect assumption. "All" ATE calipers were plated with yellow zinc dichromate. You may want to look at the caliper 1/2's where they bolt together. You will find a deep yellow iridescent zinc finish.

Engines generally get heated up to temperatures that will burn off the moisture that will accumulate within. They are also immersed in "oil" something that will basically harm the rubber seals in a caliper. Regardless, you wouldn't want your engine to sit for any appreciable amount of time without running either.

The reason you didn't find it in the bore is because it's worn off. The reason you need to rebuild the calipers is because it's worn off. Brake fluid being "hygroscopic", it pulls water into the system from the atmosphere (small hole in the res. cap). That water tends to gather around the rubber seals. Once the protective plating has worn, and the car sits for any appreciable amount of time, rust forms and brake calipers stick.

Factory assembly line pictures circ. 1970:

Click to view attachment

Thanks for the daily car porn Eric