924Board.org

[Smoothie]

After ordering once, reordering once and waiting 2 weeks, I just picked up a brake master cylinder rebuild kit from NAPA today (part #1317 United Brake Parts) for my '82 931. It's made in Germany and the company logo "Ate" is on the seals. Looking through it, I don't know exactly all that should be included with this kit, but one thing stands out - there are no new springs. Anyone with a lot of experience with mc kits in general know if springs are usually included (or if they should be included in this specific kit)?

[gohim]

How much was that Rebuild Kit?

When I was much younger, I used to rebuild the master cylinders of the cars that I bought instead of buying new, because the price difference was so great. I never had to rebuild a single master cylinder that I worked on, because the rebuild failed.

Over the years, the price difference decreased to the point where there wasn't enough of a difference between a new master cylinder, and a rebuild kit.

The last time I checked, the cost of a master cylinder rebuild kit for a 80 or 81 and later 924 NA was $120-$140 (same kit, for different master cylinders), and a new master cylinder was $140-$165.

The Kits that I have worked with often contain different parts, depending on where the kit was put together.

I would think that a kit from the original manufacturer of the master cylinder (ATE) should contain all of the parts that normally wear out.

I would hope to see all of the parts that fit inside of the master cylinder, but would not but unhappy if the springs were not included. Some kits that I have seen, and used, did not include the pistons, and that, I was not happy about. The cast iron body of the master cylinder wears very little, and unless the bore is damaged by moisture (you have been changing the brake fluid with a quality fluid on a regular basis right?) Then you should need the do anyhing to the bore except maybe remove any deposited material from the seals with a piece of a "dish scrubbing pad" (scotchbrite).

IMHO all master cylinder rebuild kits should include the pistons (the ones that I have seen have always been some sort of aluminum alloy and subject to wear).

The master cylinder, clutch master, and clutch slave kits from Lucas, and Girling, are usually just the rubber seals, and sometimes if you are lucky the snaprings. I guess they figure that the poor quality of their seals, and cars, in general would keep you from wearing out any other parts in the master cylinder, and cause you to eventually replace the entire part instead of continually rebuilding it.

[Smoothie]

Thanks Gohim. The kit was $58.19 and includes the 2 pistons (what they call "forward and rear valve bodies" in the Haynes book), 2 valve discs, 2 large seal cups, 4 smaller seal cups, 1 snap ring, 1 O-ring, 2 seal spacers (they go on ends of springs), 1 very small washer, 1 white plastic washer, 2 large metal washers. In other words, everything except the "shouldered bolt" and "limiting sleeve" and the two springs. That would be everything shown on pg.199 picture 3.11a in the Haynes except the 2 pieces just to the left of the right-most spring and the springs. One thing that's in the kit, but not shown in Haynes is the tiny washer.

I looked at http://www.napaonline.com and they give you the same MC kit (UBP1317) for a '78 928, an '80 924/T and an '81-'82 924/T.

I have a brake cylinder hone that I normally use on something like this. Will have to see what condition the inside of the MC is in and go from there.

[larso]

Well if you had some specs on the springs, you could measure their length, and see if they are to spec. But I don't think the factory manual has this info in it does it? You could even go as far as testing the spring to see how soft or hard it is by seeing how much mass it will hold compared to a new one and how much it compresses, but since you don't have a new spring to compare to that sucks. Do any of the manuals have any "wear limits" listed for the springs length? I only buy new master and slave cyls when the price is right too. The slave cyl that I last had was really weird, the bore had a rough look to it, but it felt smooth with my hand..must have been different minerals deposited on the metal...didn't take any risk with rebuilding that slave, was afraid that it would just POP again with new seals. Check the bore carefully. If the brake fluid was dirty when you took it out I'd check the bore really carefully if you haven't already. And if the brake fluid wasn't dirty, it's probably just as good to rebuild it as it is to buy a new one.