TheSamba.com :: View topic - 1970 Westy master cylinder woes

Tue Mar 04, 2025 1:30 pm

lil-jinx wrote: no one fixes anything any more ,it,s all replace the component,I recall the day when every mechanic that worked on brakes had a wheel cylinder hone in their tool box,and you could buy cylinder seals,and boots at any parts outlet.

yes. It just seems like yesterday, but really it was a long time ago.

We lost a Scottish terrier to cancer last spring. He was almost fourteen years old. I remember taking him up to the snow when he was about a year old, and he did not know what to do with it - he was like, "Is this stuff safe to walk on? Seems pretty weak to me." I remember standing with a girl friend in that same parking lot in the snow way back about the time someone's 1970 bus in this thread was a year or two old. That girlfriend has already lost her husband to heart failure, and I have my heart issues. I also lost two close cousins to diseases last year. Both were in their 70's. I remember playing with them when we were kids in 1954 VA. We are really lucky to have any parts for these buses due to their age and uniqueness. Did you know that thesamba is almost 30 years old now, not quite there but closing in on it?

Wed Jul 23, 2025 9:32 am

Has anyone got any more information here?
Ray mentioned that an NOS master that has sat on a shelf for years will not pump. Does that mean that I should not bother with the ATE one that VW NOS sells for $385?

Others mentioned rebuild kits. Is there any chance these are available?
My googling brings up nothing.

I currently carry around the Chinese one that the usual suspects sell for around 40 bucks.
Really tho, it doesn't inspire confidence in the hand.

Wed Jul 23, 2025 9:46 am

jakokombi wrote: Has anyone got any more information here?
Ray mentioned that an NOS master that has sat on a shelf for years will not pump. Does that mean that I should not bother with the ATE one that VW NOS sells for $385?

Others mentioned rebuild kits. Is there any chance these are available?
My googling brings up nothing.

I currently carry around the Chinese one that the usual suspects sell for around 40 bucks.
Really tho, it doesn't inspire confidence in the hand. depends when it was made. If it has been sitting in a hot garage for 50 years then it will probably not work well. If it has been sitting 4 or 5 years in climate control since manufacture then you would be Ok. Anything needed for these 40 - 60 year old buses requires some research. Asking Robbie for help picking one out is what I might do. He has a 1970 bus.

Wed Jul 23, 2025 10:10 am

Thanks, I wonder if anyone knows if ATE is still making these, I suppose that I should contact VW NOS directly.

Wed Jul 23, 2025 12:10 pm

read this 2016 thread. It may answer questions. https://www.thesamba.com/vw/forum/viewtopic.php?p=8278155

Scott at German Supply has the 1970 /T variant for sale, empi made. Airhead shows out of stock on the ATE one. NOS VW has an old stock ATE for $385. Rock Auto has an IAP /T variant for $43.79. The /T variant is 1970 ONLY.

Wed Jul 23, 2025 12:38 pm

I got a response from VWNOS, I asked if they have a date of manufacture, they answered "None that I know of".
I'm going to assume this means OLD.

I see a few sellers with the EMPI brand ones, a few years back that meant junk.
Still so?

Wed Jul 23, 2025 1:37 pm

here is also a good read https://www.thesamba.com/vw/forum/viewtopic.php?t=771189&highlight=iap+brake

Wed Jul 23, 2025 2:23 pm

I bought a German ATE from Scott at German Supply for our
69 Bus about 3 months ago. The price was far less than $385.

Fri Jul 25, 2025 6:52 am

kits can be had from your flaps, bore size and MC brand would get you the replacement seals , sometimes the piston is correct too.

I had to go this route with my Type 3 master, after buying an expensive one from CIP that wouldn't build pressure. i pulled an original FAG from a junkyard car, blasted it, pulled the piston/seals, swabbed the inside out, new seals and we were on the road again in the afternoon

Fri Jul 25, 2025 8:14 am

W1K1 wrote: kits can be had from your flaps, bore size and MC brand would get you the replacement seals , sometimes the piston is correct too.

I had to go this route with my Type 3 master, after buying an expensive one from CIP that wouldn't build pressure. i pulled an original FAG from a junkyard car, blasted it, pulled the piston/seals, swabbed the inside out, new seals and we were on the road again in the afternoon

Really, this is the way to go....rebuild what you have.

If you have bought an NOS cylinder and are running into the no pressure or impossible to bleed or the most common.....stiff U-cup syndrome....
.....Meaning, it bleeds decent, builds pressure if you pump a couple of times and will hold that pressure indefinitely if you keep pressure on the peddle....BUT....as you begin to release your foot pressure, say to half of what it is....the pedal does not even have to start moving upward.....back pressure against the pedal inside the cylinder just disappears and the pedal may drop halfway to the floor or all the way.

This is because on cylinders that have been sitting on a shelf for years....typically more than about 7-10 years (and ambient temps do not really matter)....the natural aging of the EPDM rubber that the seals are made of causes them to harden up by a factor usually (from what I have measured) of about 10 durometer.

This hardening by itself....is not a huge problem. But if the master cylinder sat on the shelf fully assembled with its seals constrained to the shape of the bore, they take on "compression set". This causes them to require pressure to inflate the seal lips outward like when you pump it up and hold pressure. But when you release pressure they go back to their constrained/compression set shape and the seals bypass internally.

If it's bad enough, this internal bypass between circuits and back to the reservoir can keep you from bleeding the system.

But NOS cylinders DO have some points in their favor. If they were stored in a dry area they have brand new unpitted bores and uncorroded pistons and springs. If you are lucky, the brass flap valves will be fine as well.

Go out and find a rebuild kit....even if it's not for the same exact cylinder/year. If it's the same diameter, brand and has dual circuits....about 90%+ of the time the seals will drop right in.

Just replace the seals and inspect or replace as needed, the flap valves ...
And you have a brand new cylinder.

Ray

Fri Jul 25, 2025 2:20 pm

Maybe I should just rebuild the one in my bus with the seals from that
Chinese one that I can't stand to look at.

Thanks all for the great information!

Ray, your excellent description helps to understand what may be going on
with mine.
When I adjusted the brakes, they were fine for a while, then it seemed as if I lost pressure in the front circuit. We pulled it and broke it down to find everything looking fine. We were on the road, so we put it back together and it has been fine, until I adjusted, the brakes again. I know suspect hardening seals.?

Fri Jul 25, 2025 2:42 pm

Understanding the reasons a master fails is the answer here.

Brake fluid is hygroscopic, it pulls moisture from the air. That moisture then causes corrosion inside the line, wheel and master cylinders. This can happen even with new fluid every year. They make inexpensive testers that will tell you the percentage of moisture in the fluid, and when it it time to change it.

The area of the master cylinder that gets swept typically does not get the corrosion. That comes in the un-swept area. As those pits grow from rust and electrolysis they undercut the seals, which then leak. When brakes are bled after sitting a long time without service, the pitting can be jagged. When the brakes are bled the master cylinder pistons and seals end up traveling into that jagged area. It can tear the seal, causing it to leak, or it can tear small pieces off that block the compensation ports.

If the pitting is not too bad, the master can be honed on the inside to good metal, and new seals put in. But, if the pits are too deep, then the honing may require too much metal being removed. Some rare and hard to find master cylinders get resleeved when new ones are no longer available. It really all comes down to what is available.

When the master is apart, shine a bore light in the bore and look for dark spots to find the pitting. That will tell you whether a master is a candidate for rebuilding. Then the next step is finding the correct rebuild kit. They are not as common as they were 50 years ago. Labor rates to rebuild a master make it more expensive to rebuild one than replace it - unless it is rare and new parts are not available.

Ray's techniques are excellent for anyone wanting to rebuild one, and he will tell you, as he has, it really depends on the quality of the core whether it can be rebuilt. They can look great on the outside and be crap on the inside. Most times I have been here the inside pitting was too deep to rebuild them, and as long as new quality ones are available, it was easier to replace them. Manufacturers used to make oversize bore kits to deal with having to hone one oversize to get rid of pitting, but that is uncommon now.

Fri Jul 25, 2025 6:32 pm

SGKent wrote: Understanding the reasons a master fails is the answer here.

Brake fluid is hygroscopic, it pulls moisture from the air. That moisture then causes corrosion inside the line, wheel and master cylinders. This can happen even with new fluid every year. They make inexpensive testers that will tell you the percentage of moisture in the fluid, and when it it time to change it.

The area of the master cylinder that gets swept typically does not get the corrosion. That comes in the un-swept area. As those pits grow from rust and electrolysis they undercut the seals, which then leak. When brakes are bled after sitting a long time without service, the pitting can be jagged. When the brakes are bled the master cylinder pistons and seals end up traveling into that jagged area. It can tear the seal, causing it to leak, or it can tear small pieces off that block the compensation ports.

If the pitting is not too bad, the master can be honed on the inside to good metal, and new seals put in. But, if the pits are too deep, then the honing may require too much metal being removed. Some rare and hard to find master cylinders get resleeved when new ones are no longer available. It really all comes down to what is available.

When the master is apart, shine a bore light in the bore and look for dark spots to find the pitting. That will tell you whether a master is a candidate for rebuilding. Then the next step is finding the correct rebuild kit. They are not as common as they were 50 years ago. Labor rates to rebuild a master make it more expensive to rebuild one than replace it - unless it is rare and new parts are not available.

Ray's techniques are excellent for anyone wanting to rebuild one, and he will tell you, as he has, it really depends on the quality of the core whether it can be rebuilt. They can look great on the outside and be crap on the inside. Most times I have been here the inside pitting was too deep to rebuild them, and as long as new quality ones are available, it was easier to replace them. Manufacturers used to make oversize bore kits to deal with having to hone one oversize to get rid of pitting, but that is uncommon now.

No....hate to disagree but actually it's cannot cause corrosion even if you change fluid once per year.

Unless your business is on the rock of Gibraltar in constant sea air and gales....there is just no way you can pull in over 5% moisture BY VOLUME just from the small air pocket in the top of of your reservoir. That's where ALMOST all your moisture comes from.

If owners would simply flush a quart through using a bleeder on each corner....you would never get any rust in these systems.

BUT.....as Mercedes and others have found, once a year is "tropical" climate rate of change. About two years is the limit on four seasons systems.

People finding rust inside of their systems....either you waited a lot longer than two years or the rust was already in there from a previous owner.

Moisture under 5% by volume causes"0" rust. Its only when it's 5% by volume or higher that the fluid can no longer absorb any more and you get free water in the fluid. Ray

Fri Jul 25, 2025 9:59 pm

unfortunately Ray I have been there too many times with pitted brake systems on my car and others I have worked on. There are a lot of factors at play including the type of brake fluid used. The CJ7 I had was a biannual thing on the rear wheel cylinders. Sorry but I speak from experience. Just because you may not have seen it doesn't mean it can't exist.

Sat Jul 26, 2025 5:42 am

Quote:
If owners would simply flush a quart through using a bleeder on each corner....you would never get any rust in these systems.

Every time I touch a bleeder, 250 ml of fresh brake fluid gets pushed. I can up the old, amd return it to FCP for future store credit. The only caliper problems I get are new to me cars.

It helps to buy new bleeders and trade in the old ones, too.

Sat Jul 26, 2025 9:52 am

SGKent wrote: unfortunately Ray I have been there too many times with pitted brake systems on my car and others I have worked on. There are a lot of factors at play including the type of brake fluid used. The CJ7 I had was a biannual thing on the rear wheel cylinders. Sorry but I speak from experience. Just because you may not have seen it doesn't mean it can't exist.

I speak from experience as well. A LOT of experience. I will give one point of agreement...depending on cylinder design.

However for the vast majority of ACVW....this problem is a non problem unless the owner is lazy :wink:

On virtually all acvw....you are bleeding every year....WITHOUT FAIL....and it does not matter which fluid.....its either mineral based or glycol based if it's in a factory system. Neither one of those are actually capable of creating corrosion with water content under 5%....period. That's the chemistry and physics.

But....as you note..., if you are bleeding all the time YEARLY at a minimum....and STILL getting cylinder pitting, you are either using a system that has some kind of stupid piston material that is electrolytically incompatible with the bore material (possible...jeeps have been junk for decades)....or you are not getting the fluid that is contaminated....out of the system even if you are bleeding yearly.

Make note of what is in your system for piston material. Virtually all acvws before the lats 70s used nearly pure zinc for MC pistons. Later they switched to aluminum. Anodized aluminum. That last part is important. I have seen some few car models and some early in the "aluminum piston" era aftermarket kits that were NOT anodized....which means there will be galvanic action if moisture is present.

And...what you are stating about corrosion still happening even with high frequency bleeding, can happen with some older or crappy master cylinder designs....which is exactly why on a yearly flush, it's better to completely drain the system and then refill and pressure bleed.

The problem (when it happens) is that long, dead end MC bores that are fed, vented and angled incorrectly....yes....can possibly have areas of fluid that do not "play" during normal bleeding. Not common....but it's there.

An example of this is the clutch slave cylinder on VW golf and jetta my 4, 5 and 6. It's long and dead end. The pressure line is at one end and the bleeder valve is right next to it and the cylinder needs to be bled on a slight right to left incline.....to get out the air. But, that does not ever change out the fluid.

The method the world has come up with is to disconnect the line and syringe out the fluid, reconnect and pressure bleed.

Ray

Sat Jul 26, 2025 10:03 am

Abscate wrote: Quote:
If owners would simply flush a quart through using a bleeder on each corner....you would never get any rust in these systems.

Every time I touch a bleeder, 250 ml of fresh brake fluid gets pushed. I can up the old, amd return it to FCP for future store credit. The only caliper problems I get are new to me cars.

It helps to buy new bleeders and trade in the old ones, too.

Yep, agree. My brakes get bled in a similar way and never have an issue.

Too many times, owners of older cars that they bought and were not ever bled because the bleeder screws were rusted in or broken off.

I have a little rigamarole with my bleeder screws I learned years ago and it never fails.

1. A very fine smear of anti-sieze on threads only if they are normal breeders.
2. Once I finish a bleed, I use a garden hose to rinse out the bleeder.
3. Then use an air hose to blow out the rinse water.
4. Always cap with the rubber cap.

These bleeders will now never rust in or break off.

Whenever possible I install Speed Bleeder valves. Ray

Sat Aug 23, 2025 7:39 pm

Anyone try the Wagenswest Rabbit conversion? Looks to be an answer to our 70’s woes but I need to do more research. Pricey at $295.

https://wagenswest.com/product/1968-70-disc-brake-master-cylinder-conversion-kit/

Sun Aug 24, 2025 4:06 am

raygreenwood wrote: Abscate wrote: Quote:
If owners would simply flush a quart through using a bleeder on each corner....you would never get any rust in these systems.

Every time I touch a bleeder, 250 ml of fresh brake fluid gets pushed. I can up the old, amd return it to FCP for future store credit. The only caliper problems I get are new to me cars.

It helps to buy new bleeders and trade in the old ones, too.

Yep, agree. My brakes get bled in a similar way and never have an issue.

Too many times, owners of older cars that they bought and were not ever bled because the bleeder screws were rusted in or broken off.

I have a little rigamarole with my bleeder screws I learned years ago and it never fails.

1. A very fine smear of anti-sieze on threads only if they are normal breeders.
2. Once I finish a bleed, I use a garden hose to rinse out the bleeder.
3. Then use an air hose to blow out the rinse water.
4. Always cap with the rubber cap.

These bleeders will now never rust in or break off.

Whenever possible I install Speed Bleeder valves. Ray

Let’s cut this keyboard mechanic meme off at the pass. Using anti-seize on bleeder threads won’t contaminate your brake system leading to fiery death.

The bleeder threads don’t seal, the taper on the end does. I’m sure some British cars will use a flare brake bleeder where this isn’t true, but ATE stuff can have a slurry of antiseize. You can loosen it and push a few mil up the threads if you are really paranoid.

Mon Aug 25, 2025 6:48 am

Wow! PincheOso joined just to post up that Wagons West solution,
nice work!

I hadn't heard of this before and am planning to go this route, thanks.

With everything, including the machined bracket, I don't think that price is
too out of line. When you consider that they put together this system and made the adapter, all to solve a one year only issue, I see little profit for them.