'71CS

Doing the front brakes today and took the cover off the master cylinder and found the front part full of rust. Should I replace the master or can it be cleaned up? Is the system contaminated with that amount of rust in there as in put a new one on and be done with it? Any input is appreciated. Thanks.

MDchanic

Wow. That's pretty crusty. I don't think I've ever seen one that bad that's still operating.

That being said, I'm pretty conservative, and if it's working well, I'd just flush it through with clean fluid.
I'd be inclined to pick up a spare and keep it close, for when this one finally goes (which could be next week, next month, or next year), but my bottom line is "if it ain't broke, don't fix it."

- Eric

jaunty75

I would take the opposite approach. In my opinion, it IS broken, and it should be "fixed." Replace it before it does more damage.

New master cylinders are easy to get, not expensive, and pretty easy to replace. With that much rust that you can see, how much is there internally that you can't see?

rustyroger

If it's just the reservoir that is rusty and the cylinder is undamaged then you may be OK. If rust has got to the actual cylinder then it's time for a new one.
I wouldn't be taking any bets on the rest of the system, if it has drained away because of a leak then you may well have internal corrosion of the steel brake pipes.

As Jaunty says, if a new one is cheap then replace it. Then you can have peace of mind about your #1 safety device. Brake pipes are cheap too, even if you buy ready made items.

Roger.

Octania

That looks more like spooge than rust to me.

I would disconnect the lines there at the MC
Remove all the juice and wipe out the spooge
Flush MC thoroughly until only clean juice comes out
re-attach lines
flush the rest of the system all the way using at least 1 Qt new fluid such that only clean juice comes out.

If it works fine then, run it
If not, then replace MC

If you want to go down the "what if stuff you can't see has taken place" road then you really need to replace everything
MC
Lines
Prop valve
wheel cylinders/ calipers
Booster

and that will add up to a good size bill even if you do the work yourself.

And remember that "new" is not necessarily better than working original GM

MDchanic

My thoughts exactly, Chris.

If the pedal is hard and doesn't sink, and if the M/C doesn't leak, then the pistons, rubber seals, and bores are intact, no matter what the reservoir looks like.

Master Cylinders do not fail catastrophically, they begin to leak past their seals slowly, so if it starts to go bad, then replace it (but, as you noted, you can never be sure what's inside the box when you buy a "new" one).

- Eric

'71CS

Thank you very much for the reply guy's..much appreciated!
I'm going to try MDchanic and Octania's approach and try cleaning up the spooge from the reservoir and then a thorough flush, can replace it if that doesn't do the trick.
Thanks a lot,
Trev

'71CS

I did end up replacing the master cylinder, the old one was done in the end, I pulled it away from the brake booster and there was a bit of fluid behind it, it was at the point where I would on occasion have to pump the pedal to get my brakes to work. I cleaned up the old one, did a good flush but could never get a good firm pedal back even after tons of bleeding so on goes the new M/C, bench bled it, install, quick bleed at all four drums and blam...nice firm pedal that doesn't need to be pumped to work. Done.

Don R.

Replacement was a good choice. did you check the wheel cylinders and the rest of the system? If the MC was that gunked up I would at least pull back all the wheel cylinder boots and be sure you do not have any leaks. If you see any replace ALL the cylinders.

MDchanic

You did the right thing.

You tried to salvage it, determined that you couldn't, and replaced it.

Now you can enjoy the summer.

- Eric

Octania

bleed it all the way out to the ends of all lines
inspect under wheel cylinders' boots as set forth above, no leakage is acceptable.

'71CS

Thanks again guy's for the input and comment's..alway's appreciated! Ya I thought there was nothing to lose by trying to get the old one working as was suggested but it turned out it had seen it's day..all good. I put new wheel cylinder's and shoes on the back last year and just finished replacing the front wheel cylinder's, shoes and drums and rubber brake lines and now the M/C so everything is in good working order and should be for a while hopefully. Thanks again.

rustyroger

I don't agree with Don, I don't see any need to replace wheel cylinders working perfectly well because another one is faulty.
Pretty much they work perfectly well until corrosion causes the seal to fail. Poor maintenance or lack of use can speed up the process.

Whenever I service brakes I peel back the outer cover to look for signs of brake fluid, and move the shoes to push the pistons in and out. A smear of lubricant before slipping the cover back on if all is well or if it has leaks or is siezed then I replace it.

Roger.

D. Yaros

Pray tell, what is "spooge?" Is that a technical term?

'71CS

Oh ya..definitely technical, so technical in fact I will defer what it means back to Octania. Thanks.

Koda

Yeah, definitely punting back to him on that one.

rustyroger

Spurious Poop On Oldsmobiles Generally Endemic?.

Roger.