71 Transporter, brake problem

BTW: What's the can attached to the front of the booster?

Tom

Uh, I was with you right up to this question - the booster itself is a large "can" about a foot in diameter and mounted to the front of the master cylinder. It has two hoses - the vacuum hose and the vent hose which provides clean dry air for the other side of the diaphragm. Could it be, if you have vacuum all the way up there, that the vent hose is pinched off or clogged? Mine had a tiny hole in it and collected water which froze and busted the diaphragm!

The Proportioning Valve can be clogged up alright. If you open it up, be sure to open slowly and carefully with a good tray under it to catch the few parts that are in there, as you will be unable to buy replacements. After cleaning, flush the entire brake system with clean fluid (should do this every couple years anyway!)

There is a possibility the check valve in the vacuum line back at the engine is defective. You can tell by blowing / sucking on the line - you should be able to suck but not blow.

Another very common problem is that the flexible lines deteriorate inside and a "flap" closes them off effectively. If they haven't been changed for awhile, you might want to look into this investment. Try loosening a bleeder screw at a time and see if you get good flow and not much pedal resistance (refill MC often!) Let us know how it goes, please.

The can I was referring to is a attached to the clean air port on the booster. It's the size of a can of vienna sausages. There's a picture of it here (labeled mysterycan.jpg).

Tom

I'll try all of these things today and post the results. Thanks!

Tom

SIMPLE ENOUGH the brakes on that buggy are a cinch. easy as 1,2,3

1. look behind the wheels for leaky wheel cylinder. no leaks ok.
2. adjust your star wheel adjusters up tight but loose enough to turn the tire by hand. you will need a screw driver and a spray can of brake clean. now the pedal should come up 2-3 inches. if that dont fix it

3.remove the master cylinder and exchange it for a rebuild unit, $25-$40. make sure you bench bleed it, get a large economy size can of brake fluid, cut the top off of it with a razor, and completly submerge the unit in fluid, pump it with a wooden dowel till all the air bubbles are out of it. carefully put it back on the car without stripping the tubeing nuts. plug the holes with tissue paper so it dont drip fluid. ALWAYS USE A TUBING NUT WRENCH OR SMALL LOCKING PLIERS or you will bend the brake line tubeing.

1. no luck? take it to pepboys or kragens or costco or a grandauto and tell them you want a POWER BLEED ONLY

cant say a thing about the can... but trash that hose!

I'm assuming you got front disks - how worn are the pads? How long's it been since the brake pistons/cyls were cleaned up and the rubber piston rings replaced? When I got brake problems, I check this stuff first, then ditto the master cylinder, then look at other stuff.

PROBLEM SOLVED!

I checked the brake lines... rubber was new and flexible, steel lines looked good. Went to the booster and had a look at the breather hose. It was colapsed... ahhhhhh duh. I pulled the hose, heard it GASP for air, and like magic my brakes work great!

I think the can is a charcoal filter which has probably been there for

30+ years. I'm assuming it's not passing any air which is why the el-crappo hose collapsed (besides the fact that it's just a crappy hose). I'm going to try a new hose first, and if I still have problems, I'm going to disect the can filter, remove the crud, and fill it with some other filter material to make it reusable.

Since I had expected to spend more time breaking some stuff that wasnt already broken, I figured I'd make an attempt at cleaning out the Brake Pressure Regulator. It was easy to get out, apart and clean, but now I need to bleed my brakes and dont have anyone here to stand on the pedal so it'll have to wait until later. I took a spin around the block and even with the spongy brakes, stopping is 100% better than before removing the breather hose. The pressure regulator did have just a little bit of crud, but not enough to make any difference (the ball still moved freely). The only problem was the gasket. I had to re-use the old gasket which was in sad shape. I considered blue gasket sealer but figured the brake fluid might attack it so I passed. Is there a gasket sealer compatible with brake fluid? I'll search for a new gasket.

Thanks, Tom

steel lines

breather hose.

heard it GASP for

been there for

why the

a crappy

have problems,

fill it with

stuff that wasnt

out the Brake

clean, but now I

on the pedal

the block and

before

have just a

(the ball

had to re-use

gasket sealer

Is there a

for a new gasket.

Talked to someone at the local VW club tonight who says the can is not a filter but a vacuum reserve. If the engine stalls while at speed, there is enough boost to stop safely. I looked and it does have a one way valve. Unfortunately, it causes more problems than it solves so I just removed it. I'm going to run a vent hose up high somewhere to prevent water from getting sucked into the booster during heavy rain, etc.

Tom

If that was the case, it should be installed between the engine vacumn port and the booster....

Okay, now it's just spam. Stop please.

Yeah - If what he described is accurate, it's on the wrong side for vacuum! Now maybe later models are different, but with a check valve back at the engine and a non-collapsible tube all the way up front, there shouldn't be a need for a reserve. Mine works fine without it. That device warrants some more investigating.

,

behind

via a

able to

the can is not a

at speed, there

engine vacumn