Clutch master cylinder rebuild frequency?

I was returning to New Jersey from an event in Pennsylvania and the GPS, in its infinite wisdom, decided that the best route home on a Saturday afternoon would be straight through the middle of downtown Philadelphia. Under normal circumstances that would have been merely annoying, but on this trip the clutch master cylinder decided to stop holding pressure, so it alone was deciding when and how fast the clutch would be released, independent of my foot position. I managed to struggle through the bumper-to-bumper downtown traffic with as little clutch usage as possible, and when I got home verified that the problem was indeed in the MC, since it was still full of fluid. When I poured the normally clear fluid out it was a black color, which told me that there were tiny pieces of the rubber seal suspended in the fluid. This adventure made me wonder if there was any time schedule when the rubber seals in the hydraulic systems should be renewed. I never gave it any thought before, but a failure of either MC could range from annoying to disastrous, especially when on a trip away from the shop. How about the brake caliper piston seals? I haven’t seen them for maybe 30+ years, when I had the cylinders sleeved. They don’t move much, but might they deteriorate with time? Has anyone else experienced this type of problem?

Are you using DOT5 (silicone) or DOT 4 fluid?

Dot 4 synthetic brake fluid.

In my S3 E-type I went the way of Stainless Steel after it failed a couple times with the standard cylinder . I used Hye-Dra-Cyl I know he moved to Fla. but Greg still had what I needed. Greg Hagopian - good luck !

So synthetic is different than silicone??

IMO not really Mike. I don’t think that failure of seals is likely to be a predictable event.

I flush the brake systems on my cars every year or two when they get a service.

I used to swear by silicone fluid but more recently I’ve taken to using mineral simply because it’s easy to get.

In case of DOT4 you have to replace the fluid every few years, as DOT4 is hygroscopic.
If not several Brake parts will oxidate because of the moisture.

Mike, rebuilds of the hydraulic systems should last many, many, years! That being said, I rebuilt brake and clutch hydraulics a year ago on my E Type over one winter. Long story short, by spring and with about two miles on the car, the clutch fluid was black and I was having trouble getting pressure. Took the master cyl. apart and the seals (aftermarket looked like they were a hundred years old! New aftermarket kit installed (from the usuals, reputable) more issues, (leak)! I found and bought an NOS Lockheed/Girling kit and it’s been good ever since! Not sure what a good answer is! No more black fluid either, which I had with both aftermarkets!

My clutch m/c started leaking the day I was selling my S Type, I stared at the fluid running down the footwell and took $1,000 off the sales price. I told the buyer he could drive it home, over the Sierras to San Francisco, but he sent a transporter instead.
Glad to see you guys still keeping up the conversation. I am driving an XF now instead. A very different world. I have never seen the engine, it is covered to protect it from people like me. Us.