Hello Everyone,
I am lining up my winter projects and one of them is assessing/rebuilding the master cylinder on my 1970 Chevelle 2dr with power brakes, discs up front. Here's the short story. I replaced the master cylinder new in 1988 along with new SS brake lines, calipers, wheel cylinders, pads etc. I also used DOT 5 brake fluid in the system since it was replaced. I drove the car about 10K miles and then in 1998 I parked it waiting for the body work to get done. Now that the body is complete, I want to clean and evaluate the brake system. It has been removed from the car and had the lines flushed and capped. I want to know if the master cylinder is still ok and if necessary, rebuild it. Does anyone have:
1. A good procedure to check the master cylinder off the car.
2. A good procedure to rebuild the master cylinder.
Thanks in advance.
Dave

You're probably OK, but it wouln't be a bad idea to rebuild. Kits are available at Napa. You'll get conflicting info on this, but the Dot 5 probably helped a lot as far as any rust goes. I wish I still had the pictures of the wheel cylinders on a corvette with Dot 5 that was driven 500 miles a year for 21 years. It then needed a brake job and insides of cylinders were like brand new. As opposed to the same cars' wheel cylinders that had rust galore after 7 years with Dot 3.

The cost of a rebuild kit is probably the same or more than the cost of a rebuilt master cylinder.

The rebuilt master cylinder will have a warranty. The do-it-yourself rebuild won't.

It's gotten to the point where it doesn't make sense to rebuild it yourself unless you're saving an original or otherwise rare/special casting.

First Guess: Bolt it on and give it a "60-second" test. If it passes the test--drive it.