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

Sun Mar 02, 2025 5:37 pm

At the end of last season i was getting some brake fluid on the floor, so i pulled the pan and the seal was leaking into the pan. I ordered a new master from Jbugs and installed it:

1st master from Jbugs: leaked out of brake light switch when i went to bleed the brakes after install, tried a couple different crush washers and a different switch, still leaked. Finally said its going to stop leaking or strip...and it stripped.

2nd master: ordered from bus depot, installed, went to fill and it started leaking out the bleeder on top of the master, tried to tighten with a 10mm shorty and it just kept turning, tried swapping the bleeder with the one from the old master and same thing.

Are these chinese castings that junky? Is there another option i can order?

Sun Mar 02, 2025 6:56 pm

going from memory here, but I think you need a 211611021T

Look out for an ATE, but welcome to shitty parts. now try and do this for a living with todays offerings

Sun Mar 02, 2025 10:19 pm

Worth looking around for a decent reconditioner if you still have the original. Just had mine sleeved and new seals, can't remember the cost but significantly less than a new one of any flavour. Obviously no worries with rerouting brake lines to fit either...

Good luck!

Sun Mar 02, 2025 11:17 pm

you may be getting someone else's returns the way things are these days. I dunno but stripped holes sound more than a defect. I know that there a lot of people out there who return things they break. It doesn't have to be the seller either. If they order it from the warehouse, it could be at a higher level.

Did you buy the ATE one or the aftermarket one?

also - I think we go thru the issue of what master works best for a 1970 so check with Robbie. He as a 1970 and usually knows what works and what does not.

Mon Mar 03, 2025 10:37 am

i have been looking at brake booster /master cylinders for newer cars looking for a set that could be easily adapted to the bus,it looks very doable and the quality of the parts should be much better,.I don,t expect the blue nut booster that i have will last very long,in fact the front boot is rotting away sitting in the garage ,i installed it a couple of years ago and the bus has not been driven,
Summit racing has a selection of cardon boosters kits that could work,but i think i would prefer a oem part ,possible scrap yard find,
has anyone done this?

Mon Mar 03, 2025 11:32 am

lil-jinx wrote: i have been looking at brake booster /master cylinders for newer cars looking for a set that could be easily adapted to the bus,it looks very doable and the quality of the parts should be much better,.I don,t expect the blue nut booster that i have will last very long,in fact the front boot is rotting away sitting in the garage ,i installed it a couple of years ago and the bus has not been driven,
Summit racing has a selection of cardon boosters kits that could work,but i think i would prefer a oem part ,possible scrap yard find,
has anyone done this?

Brake booster from another car?...not too hard to do. Look at the shape/size, look for a power ratio that is similar (not less but not greatly more either). Make sure it operates at thesame throw/stroke length....because many modern car boosters have far shorter MC throw.

But....using another master cylinder from another car...not so simple. At minimum most important (more important than diameter but piston diameter should be close)...you need to have the same fluid VOLUME output.

So by whatever combination of stroke and diameter, a standard pedal stroke should put out very close to the same volume in each circuit as your existing stock unit does. And....very importantly....the inner spring for each circuit should be the same "ratio" of difference to each other....because.....the spring on each circuit governs which circuit piston starts moving first or if they start moving together. And, the springs on each circuit have a stroke limiter pin or thimble that prevents the piston in each circuit from travelling too far and moving too much fluid volume.

Its not simple to swap around master cylinders rfrom other vehciles.

You can do it fairly well among most non-boosted acvw. For example while there are some differences in dual circuit MC's between types 1,3 and 4....you CAN swap them a bit if you bruing the springs and limiting stops from your existing cylinder to the donor cylinder. Pistons must stay with cylinders because the piston head position matches up with fluid inlet and compensation ports.

All of this is tedious work with a lot of test driving and pulling the MC in and out.

Ray

Mon Mar 03, 2025 11:55 am

lil-jinx wrote: i have been looking at brake booster /master cylinders for newer cars looking for a set that could be easily adapted to the bus,it looks very doable and the quality of the parts should be much better,

you're going to find sealing the vented part of the booster from the elements to be virtually impossible on any other booster than the one that was factory issued.

just get the OE rebuilt. it's 100% the way to go

Mon Mar 03, 2025 2:05 pm

Rebuild. Rebuild. takes you off the road.... but it IS Winter 2025. Still.

Mon Mar 03, 2025 2:50 pm

lil-jinx wrote: i have been looking at brake booster /master cylinders for newer cars looking for a set that could be easily adapted to the bus,it looks very doable and the quality of the parts should be much better,.I don,t expect the blue nut booster that i have will last very long,in fact the front boot is rotting away sitting in the garage ,i installed it a couple of years ago and the bus has not been driven,
Summit racing has a selection of cardon boosters kits that could work,but i think i would prefer a oem part ,possible scrap yard find,
has anyone done this?

Someone in this thread just had their master cylinder bored and sleeved. There is no reason that would not work. In the past it was not worth it. As for other cars, what a pita that will be. As Ray said, the diameter and stoke have to be the same, the clearances and mounting need to be the same. And, my guess is that the casting already fits other vehicles. The issue for you will be that the whole system was engineered by either ATE or Girling as a system, and not an individual part.

Last time I checked. Ate and Girling had better reviews that Cardone.

Mon Mar 03, 2025 6:08 pm

yes the system was made by ate as a system,but it seems that parts to maintain that system falls well short of original ate parts,the main obstacle would be the push rod from the pedal and access to the mc resovoir to fill it,neither one is insurmountable,as for balancing the hydrolics front to rear ,there are adjustable proportioning valves available.

Mon Mar 03, 2025 7:15 pm

lil-jinx wrote: yes the system was made by ate as a system,but it seems that parts to maintain that system falls well short of original ate parts,the main obstacle would be the push rod from the pedal and access to the mc resovoir to fill it,neither one is insurmountable,as for balancing the hydrolics front to rear ,there are adjustable proportioning valves available.

No.

That is NOT how adjustable proportioning valves work. I have been researching this for years because WE type 4 car people have far more brake parts availability problems that any of the buses do.

Brake proportioning valves do not adjust up or down the volume. They adjust the "onset of pressure". NOT the same thing. They are NOT for balancing front and rear. Yes they work enough that on a low center of gravity car with not a huge difference infront and rar you can get away with it.
The problem is that they start reducing by a percentage across the entire pressure spectrum.

They can help stop skidding to a degree but they do not allow full factory control of all pressure modulation across the board.
What you require is a volume regulator to be able to reduce stroke volume if you install an MC of higher volume per millimeter of stroke output.

American cars all the way through the 60's 70's 80's...maybe even now...use what is called a "combi-valve".
They look something like this and are usually mounted on the firewall near the master cylinder

A REALLY good paper on the difference in regulator, proportioning valves and combi-valves is on Wilwoods site.

These valve are what allowed American car companies way back...to pretty much use the same master cylinder for dozens of different chassis. These valves are flat out ingenious.

They regulate volume. They regulate pressure onset and cut off....they can be set up to be biased one way or the other or equal. Virtually all of them are set up at the factory and I have not yet seen an adjustable one but I am sure they are out there...but setting one up would be a LOT of testing

See...your buses have a rear brake pressure REGULATOR. Its not a proportioning valve. It really is a crude but effective anti-skid device. When the enertial shift of hard braking causes enough of a forward tilt to take too much weight off the rear wheels and possibly cause locking and skidding...the ball travels the incline and taps a differential pressure valve that limits the pressure to where it is at when that happens.

The 411/412/914 and many BMW and some Mercedes have a very different one. With ours, it allows rear braking up until the pressure hits 523 psi. You can only hit that pressure during panic braking. When that happens....it locks the fluid passage and keeps that 523 psi on the rear wheel cylinders but will not allow it to rise. The second you releae the pedal it releases the lock. Ingenious. Early anti-skid.

You need a volumetric adjuster and not a pressure adjuster. A dial type proportioning valve has no idea how much fluid volume is required to create what pressure in your system. It just starts dialing it back proportionally as you apply pressure. Not saying they are not useful...but I would say they can be dangerous in a bus.

Ray

Mon Mar 03, 2025 7:48 pm

yeah probably more effort than it's worth,hopefully what i have now will stand up ,i have another bellows seal to replace the rotten one.

Mon Mar 03, 2025 8:10 pm

Apologies to Hatrack for highjacking the thread
Thanks to raygreenwood for the education.

Mon Mar 03, 2025 10:27 pm

lil-jinx wrote: Apologies to Hatrack for highjacking the thread
Thanks to raygreenwood for the education.

But...hang in there...there are solutions. Yes, you can sleeve a cylinder, plate a cylinder etc. There are even ways to limit volume in a stroke from a larger MC....and in reality they are simple but take tedious testing on the bench. Not expensive....a couple of gauges and syringes but you first have to know what volume yours puts out and then tweak a larger volume MC to duplicate that. More to come. Ray

Mon Mar 03, 2025 11:57 pm

The proportioning valve in a bay (1971 and 1972 -79) turns off pressure to the rear brakes when the nose dives.* They do not cut pressure to the front discs. As the car heavily brakes the weight transfers forward as the nose dives. That dive takes weight off the back and transfers it to the front. Anyone who designs racing suspensions knows that the grip a tire has is related to the load on it. As the weight transfers forward, the rears lose their ability to grip and the fronts get more grip. If the pressure were not reduced on the rear, the rear tires would skid. The braking transfers forward more with discs than drums, due to the ability of the discs to do a better job at braking than the front drums of older bays.

To shift the balance between front and back, race cars, sand rails etc., they often use a two master cylinder system. The balance is set up on a skid pad until the braking is where the crew wants it.

* if you jack up the rear of a 1971 or later bus and try to bleed the rear brakes, it is very hard to do because the flow to the rear cylinders is reduced.

raygreenwood wrote: lil-jinx wrote: Apologies to Hatrack for highjacking the thread
Thanks to raygreenwood for the education.

But...hang in there...there are solutions. Yes, you can sleeve a cylinder, plate a cylinder etc. There are even ways to limit volume in a stroke from a larger MC....and in reality they are simple but take tedious testing on the bench. Not expensive....a couple of gauges and syringes but you first have to know what volume yours puts out and then tweak a larger volume MC to duplicate that. More to come. Ray

with the level questions constantly asked on this forum Ray, IMHO, expecting anything more than a bolt on solution in this area is pissing upwind.

Tue Mar 04, 2025 9:41 am

SGKent yeah I have installed a new (blue nut) booster and a brazil master cylinder,a few years ago,hopefully they will serve the purpose,
at this time the brakes are working well ,as far as a driveway test shows.

Tue Mar 04, 2025 9:44 am

SGKent wrote: The proportioning valve in a bay (1971 and 1972 -79) turns off pressure to the rear brakes when the nose dives.* They do not cut pressure to the front discs. As the car heavily brakes the weight transfers forward as the nose dives. That dive takes weight off the back and transfers it to the front. Anyone who designs racing suspensions knows that the grip a tire has is related to the load on it. As the weight transfers forward, the rears lose their ability to grip and the fronts get more grip. If the pressure were not reduced on the rear, the rear tires would skid. The braking transfers forward more with discs than drums, due to the ability of the discs to do a better job at braking than the front drums of older bays.

To shift the balance between front and back, race cars, sand rails etc., they often use a two master cylinder system. The balance is set up on a skid pad until the braking is where the crew wants it.

* if you jack up the rear of a 1971 or later bus and try to bleed the rear brakes, it is very hard to do because the flow to the rear cylinders is reduced.

raygreenwood wrote: lil-jinx wrote: Apologies to Hatrack for highjacking the thread
Thanks to raygreenwood for the education.

But...hang in there...there are solutions. Yes, you can sleeve a cylinder, plate a cylinder etc. There are even ways to limit volume in a stroke from a larger MC....and in reality they are simple but take tedious testing on the bench. Not expensive....a couple of gauges and syringes but you first have to know what volume yours puts out and then tweak a larger volume MC to duplicate that. More to come. Ray

with the level questions constantly asked on this forum Ray, IMHO, expecting anything more than a bolt on solution in this area is pissing upwind.

:lol:

Yes....that may be true. However, it does not change the fact that EVENTUALLY all acvw owners will have to look for more than a "bolt on" solution....if you plan to keep driving. We as as the acvw community in general and lately (as we can see) the bis community in specific.....are starting to see the first signs of what we in the type 4 car community have been putting up with for brake part issues for decades. It goes like this kind of in order:

Parts are not common but can be readily found at dealers and specialty parts houses.
Parts are no longer at dealers, are at specialty houses but are expensive
Parts are nowhere and have to be ordered and are more expensive.
Parts are now only NOS (which we are seeing issues with from age) and the "re-man" houses have stepped up work.....and we have failures from both
Parts OEM'S started making factory rebuild service (we saw this in early through mid 2000's) quality ranges from great to spotty....cost is very high
Parts being made by foreign subsidiaries and branded as OEM'S. Cost is moderate but not good but quality shows failures of about 50%

The last part of that list is where I am seeing bus brake cylinders now.

We in the type 4 car community have been one rung lower than that for about 20 years now:
Parts no longer made by anyone.

So what are going to do? It becomes time at some point to work out ....non bolt on solutions to preserve and rebuild quality original cylinders and pistons.

The active point here is that with proper due diligence and regular bleeding.....there is no reason for a brake master cylinder or it's pistons to EVER rust. That means this can and will last forever. From that point onward, it's just replacing seals at intervals.

Ray

Tue Mar 04, 2025 10:00 am

I considered building a system from modern oem parts,and if this was a forever vehicle I probably would,but I will likely part with it after a season or two of running it,and anything I build could be a real headache for the next owner.
it,s a good thought experiment,keeps the old gray matter from solidifying

Tue Mar 04, 2025 11:04 am

lil-jinx wrote: I considered building a system from modern oem parts,and if this was a forever vehicle I probably would,but I will likely part with it after a season or two of running it,and anything I build could be a real headache for the next owner.
it,s a good thought experiment,keeps the old gray matter from solidifying

Which is exactly why I started a project quite some time ago....and last month I got one step closer fo pulling the trigger (all of my parts are now prepped) .....on a project to nickel plate the bores of a group of type 4 brake master cylinders (i have 10 of them), about four clutch master cylinders, and 10 clutch slave cylinders.

This will bring them back to absolute best factory diameter and surface profile specs and male the bores 100% rust proof permanently.....unless someone does something stupid with steel tools inside and scratches through the bore and vent then they will only rust if you let them rust. Just keep them bled regularly if that happens.

The pistons will never wear out unless you park the thing and neglect it for a decade and let them corrode.

These will use all stock seals, pistons and springs.

The outside of the cylinders will be grit blasted and painted with master series silver and polyester clearcoat.

I will have about $650 in the project when done. That's about $27 per cylinder.

The other thing is that yes, you can have your master cylinder sleeved. That works superbly and CAN make for a lifetime cylinder but there are some rules to live by when you do this.

1. It's very rare to find anyone who is Sleeving cylinders in stainless steel anymore. It's more work and cost and can be a lot of work to hit exacting bore tolerances. So most people do this with brass.
The problem is that to hold the sleeve in, its a press fit and not a shrink fit. They use either a special epoxy or a sleeve loctite. The adhesive has to be properly coated and installed because brass against iron causes galvanic corrosion. While it may take many years or decades to develop a problem where brake fluid starts leaking between sleeve and bore....it can happen. I call that very minor.

The real issue is that with brass bore sleeve and the zinc pistons our earlier MCs use.....any free water gets in there and it WILL cause galvanic activity between the brass bore and zinc piston which does not corrode the bore....it corrodes the piston.

This means you need to be religious about bleeding/flushing your brake fluid say....every two years even if you have 0 miles. You should be doing that anyway.

It's even more critical with DOT 5 brake fluid because it tends to keep water in micro bubbles that get larger with time. That is "free water". If these bubbles bridge the 0.003" gap between piston and brass bore....the pistons corrode.

Lastly, if you have a bore sleeved....first measure your pistons. Then tell the shop to either lap the bore to that exact tolerance....or tell them to make the bore 0.002" to 0.003" undersized so you can do it yourself.

To many nicely sleeved bores I have seen that come back with alippy tolerances. Ray

Tue Mar 04, 2025 1:16 pm

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.