rothlane'68

So, a while back, I couldn't get my brakes to bleed and picked up a new master cylinder from AutoZone (with lifetime warranty!). That one held up until last year, when I pushed fluid back to the MC while installing new brake pads, it started to leak from the rear seal and the the brakes wouldn't bleed. I figured this was on me for taking shortcuts, swapped it out for a new one at AZ, got a firm pedal, and went on my way. A couple weeks ago, after short drive, I noticed a trickle of fluid coming from the back of the MC. No loss of pedal on the drive though. Front wheels were also hot while the rears were bone cold. Adjusting the rear drums seemed to fix that. Anyway, swapped the MC again, and this one leaks from the rear seal right out of the box (got firm pedal though?!).

This can't be right, right? Am I causing these to go bad somehow?

And, where can I buy Master Cylinder that won't crap out right away?

Any insight is much appreciated. This is a '68 442 with a power disc/rear drum combo, converted to single piston calipers up front.

classicmuscle442

Is it possible fluid got up into booster and is from an earlier failure

rothlane'68

Possible, but I'm inclined to think not. It was quite a bit of fluid and it kept coming.

The other thing is that I bled them with a motive power bleeder, and the leak was consistent as soon as I brought the pressure up.

Any easy way to test for that? I guess I could hook up the power bleeder, bring up the pressure, unbold the MC from the booster and slide it away from the booster to see if I can see the leak.

Fun71

Ever since the 80s I have heard about how folks have used the "lifetime warranty" on AZ parts many, many times. Do you really think the cheapest part available is also high quality?

rothlane'68

Well... No, I don’t.

I think the ones from AZ, NAPA, advance, o’rileys, rock auto, and CAP are all cardone remanufactured units. I think the “new” ones are probably also cardone remans.

I don’t like bleeding brakes. I’m ready to spend more.

Can you recommend a supplier that you think might be selling a quality part?

classicmuscle442

Could try using a vacuum bleeder, very easy to use and no mess. Is it possible the power bleeder is developing to much pressure.

FN723

Just the downfall of owning and maintaining an old vehicle, aftermarket parts. You soon find yourself making a list of parts manufacturers to avoid.

rothlane'68

I'm using a fairly low pressure (10 psi, motive recommends 14 I believe), but I think next time around I’ll try to bleed them the old fashioned way.

Yup, sometimes it feels like there isn’t anyone left! This warranty was the only thing that had me going back to AZ.


Well, it looks like I have a few options for new master cylinders from Summit: Raybestos, AC Delco, and Right Stuff.

Ive gotten some hoses from right stuff in the past and everything was on point.

If anyone has had success with my if these brands for a master cylinder let me know, otherwise I’ll probably pick one at random.

Fun71

Rock Auto has Centric, AC Delco, and Raybestos brands.

https://www.rockauto.com/en/catalog/...+cylinder,1836

oddball

Yeah, just the way it is. Even "new" units are questionable.

The units are very, very simple. Tear down a new one before installing it and take a quick peak at the seals, pistons and bore. I've seen brand "new" castings have deep scratches in the bore. Just use some brake fluid as lube.