TheSamba.com :: View topic

Tue Nov 30, 2021 8:23 pm

Hey guys, hows it going?

My MC is having an issue. The plunger/piston wasn't coming out after being pressed in. So i took it all apart, it was really dirty and i was surprised that the seals are in good condition and that theres no scoring on the walls. Under the reservoir are two holes, one is pretty tiny, that appeared clogged up so i was hopeful that was the issue. I cleaned it all up, gave it a very light hone, cleaned it again, dried it all off with compressed air and put it back together with fluid.

Its much better but its not right. The plunger/piston doesn't always come back out all the way and then, when i went to bench test/bleed it, the first stroke is solid with pressure through out the stroke, then the next will only build pressure at the very bottom of the stroke, regardless if the piston comes all the way out or not. But if i wait 20 seconds, it'll give another full stroke with full pressure.

Anyone got any ideas?? I'd like to understand whats happening before i make a decision about rebuild/replacement.

Cheers.

Wed Dec 01, 2021 8:09 am

adjust your brakes, bleed out the air

Wed Dec 01, 2021 7:12 pm

jmmj wrote: Anyone got any ideas??

Part 7, 13, or 10 might be not doing what they are supposed to do.

Before the 20 seconds is the pushrod against the piston or is the piston still in?

Thu Dec 02, 2021 10:57 am

western auto wrote: adjust your brakes, bleed out the air

Yeah its still in the vise so thats not related thanks...

Cheers!

Thu Dec 02, 2021 11:10 am

BarryL wrote: jmmj wrote: Anyone got any ideas??

Part 7, 13, or 10 might be not doing what they are supposed to do.

Before the 20 seconds is the pushrod against the piston or is the piston still in?

Ahh thats a better diagram than the one i found. Cheers Barry. I was suspecting the check valve even though its so simple and seemed ok. But then i remembered that i lent the kombi out to a friend a couple weeks ago, turns out that he may have helped out by topping off the fluid.... with ya know... ATF oil!! So i'm guessing the primary cap swelled up.

Anyways, i went all round town looking for a rebuild kit but to no avail. Ended up buying a replacement MC. Annoying because i didn't want to spend money on this because i'm saving to go the way of disc brakes, new lines with double circuit MC. Oh well. Such is life.

The new MC is in the bus and its breaking better than ever.

Cheers!

Thu Dec 02, 2021 6:40 pm

jmmj wrote: Ahh thats a better diagram than the one i found.Cheers!
Borrowed it without permission from The Bentley Manual 1963-1967.

Fri May 23, 2025 6:38 am

I removed and inspected my 15 year old Varga master cylinder and found a ring of pitting at the very beginning of the bore at the seal (near the push-rod) that seems to be suborn to remove with a hone. Other than this half ring of pitting the bore is really nice. The part of the bore the main seal rides is perfect so I have confidence it will function OK, but may leak, or develop a leak at the end seal. The pitting rust ring MAY be just ahead of the end seal, so it may possible not even come into contact with the seal surface. I'll need to do some careful measuring to confirm.

I know is not standard practice, but is it possible to get a little more aggressive in this one inch of bore where the end seal would ride?

Normally I would replace it, but Varga Brazil parts are not available (or cheap) like they used to be. It's going back onto the bus regardless, and will be using all the original parts, other than the cracked reservoir and dust boot. I refuse to used a new Chinese junk cylinder.

It's getting old (and expensive) replacing all these brake parts simply because they have some minor rust pitting in the bores. This is the last bus I'll be using DOT 3/4 brake fluid. DOT 5 silicone fluid from here on out.

Anyone sleeved any master/wheel cylinders?

Fri May 23, 2025 7:10 am

ATF messed the cup and seals up. Might be a good time to consider doing a dual circuit conversion. It’s worth the time money and effort especially since you’re halfway there. That’s the second thing I do to any VW I get. The first thing is fix / adjust the emergency brake system. If originality is your primary concern no one can see it and a crinkled nose is not very original looking.

Fri May 23, 2025 12:37 pm

pondoras box wrote: ATF messed the cup and seals up. Might be a good time to consider doing a dual circuit conversion. It’s worth the time money and effort especially since you’re halfway there. That’s the second thing I do to any VW I get. The first thing is fix / adjust the emergency brake system. If originality is your primary concern no one can see it and a crinkled nose is not very original looking. Having a working hand brake is the first thing I do too; as a matter of fact I used it to drive the bus where it could be worked on easier. You know, it would have been nice if VW would have continued using mechanical cable brake for a little longer; they last indefinitely with little maintenance.

Fri May 23, 2025 5:05 pm

Stocknazi wrote: Having a working hand brake is the first thing I do too; as a matter of fact I used it to drive the bus where it could be worked on easier. You know, it would have been nice if VW would have continued using mechanical cable brake for a little longer; they last indefinitely with little maintenance.

Having a good working parking brake is a must, but one needs to keep in mind that if one of the rear wheel cylinders blows out, that brake drum is instantly lubricated up. So one looses half of the rear brakes which is only about 40% total braking power to start with, now one is down to about 20%..... Plus the VW will pull in the direction of the still working rear parking brake. Meaning suddenly heading into the ditch, curb, or off the cliff, or in the other direction into the oncoming traffic.

Fri May 23, 2025 6:24 pm

Stocknazi wrote: Anyone sleeved any master/wheel cylinders?
I'm currently having my 1953 Packard master cylinder sleeved at White Post Restorations. They told me 4-6 week turnaround. You get it back rebuilt too.