The Stovebolt Site Forums The Shop Area Driveline Master cylinder rebuild question

I just received my master cylinder rebuild kit.I removed the mc and carefully disassembled it taking a picture between every step. I have the old parts laid out in order wit the new parts from the kit. The only difference I see is a snap ring I’m assuming to take the place of the clip. I’m 95 percent sure, but don’t mind bouncing it off of others. I’m getting a cylinder hone from HF and will probably throw a little paint on the outside of it as well before reinstalling.

For me - I would just use my old clip. But that's me.

I can definitely do that.

I found the old clip to be an aggravation to reinstall...

If the snap ring seems to be correctly sized to do the job, I would go that way - especially if you have snap ring pliers in your tool box.

Bill, I had issues with my master cylinder after I rebuilt it. My by-pass hole was clogged. So be sure yours is open to allow your brakes to release properly.

Nick does mention the one frustration with the original clip. It can be a pain to get re-installed.

Either will work, but Nick's suggestion, if you have snap ring pliers, will make it easier to install.

Some thoughts on honing and steps to do before reassembly:

- Before starting to hone, clean the bore thoroughly and look closely for pitting in the cylinder wall. Minor surface rust can usually be easily cleaned up with a hone, but any pitting that you can catch your fingernail on may not be fully removed with just running the hone. Such pitting, if they are in the range where the cup/piston seal ride will more likely than not lead to cylinder leakage and premature failure of your rebuild. Been there, done that, having almost put my truck into the garage door after taking it for a state inspection. My rebuild lasted less than 10 miles. Just enough to get it to the station, pass inspection, then drive it home and have to stop the truck with the parking brake because my brake pedal went straight to the floor when trying to stop.

Can you say - YIKES!

- If your cleaning/honing is successful, be sure to thoroughly clean up the cylinder and all ports in the reservoir to be sure that fluid flows from the reservoir out and back again. A blocked return port can cause your brakes to stay partially or fully applied leading to possibly overheated/locked up brakes and some serious head scratching to figure out why.

Let us know how the work progresses.

Edit note: John "Utah York" made the point about the return "by-pass" hole being clogged before I could hit the post button - lol.

Don't be alarmed if you do see some pitting in the bore. It invariably happens. These master cylinders are open to the environment via a small hole in the side of the cap. Make sure that hole is open even though it will allow humid air in. The master cylinder won't function properly over time if that hole is clogged.
As far as inevitable pitting goes, most of the time it is not located where the cups ride in the bore which is all that matters.

A timely post this is. My truck gave me a hint several weeks ago with the pedal being a bit soft and going down a little more than normal. A few drives later, started to leave the shop and zero brakes. Topped it up with new type 4 fluid (that just happened to be on the shelf) and all's good for the past couple hundred miles but the seal at the brake rod is damp, just barely weeping.

So, time to pick up a seal kit. Anyone have a recommendation on a kit?

Thanks,

I ordered mine from Classic Chevy and GMC Truck Parts.
Less than $25.

Ron (and others), part of the new Chinese/Brazilian/Egyptian/African/Mexican master cylinder problems is if you press the pedal all the way down you also can subject the internal rubber "cup" (the one furthest from the push rod) to the threads that are cut in for the end cap. At least that's what I learned after messing a couple of these up, because the threads go in too far now. The trick is when you're bleeding your brakes to put a piece of wood about 3/4 or 1 inch thick under the brake pedal so when your wife, son, daughter, homeless person is helping you they can't push it all the way down. The process will still work fine and this is less messy than bench bleeding and crawling under while the MC dribbles on top of you. You just can't hit the threaded part and you won't get the leak that tearing the rubber cup provides. Good luck!

The small hole was stopped up. Thank you UtahYork and 52Carl! Definitely saved me some aggravation.