Replace brake servo and pedal still hard as a rock

[Dave Wood]

I had a hard brake pedal on my 73 bay window so I thought replacing the booster/servo would fix it. I took off the old servo and it was full of brake fluid and totally shot. I think the brake fluid was leaking in the servo from the bad filler line from the brake fluid reservoir.

Anyways I replaced the booster and bled all brakes in proper order and I still have a rock hard pedal. the vacuum line seems to be working fine as when I removed it from the carb I can hear the suction and the engine will stall.

I seem to only be able to push the pedal an inch or two and thats it. the bus will stop but its not a good feeling. Can anyone recommend where I should look from here?
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Dave
87 Vanagon GL

[1967250s]

What about when you remove the vacuum line from the servo? Could be the one way valve is backwards....
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'72 Elm Green Deluxe

[Dave Wood]

I'll give that a try although I have a suspicion my check valve is missing. the vacuum line has a splice in the engine bay where I would imagine the check valve should be located. If I'm missing the check valve would that cause this? I thought the check valve was just in case a engine stall and you would still have brake assist?
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Dave
87 Vanagon GL

[kreemoweet]

A missing check valve will not affect the operation of the brakes, while the engine is running. A backwards check valve would
be the same as no booster action at all (very hard pedal). The Bentley manual has the orientation of the check valve BACKWARDS,
so pay no attention to what is says about that. Are you just assuming your "new" booster works correctly? Where did it come from?
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[old DKP driver]

Is the engine in your 73 like the one in your (old) 72 that you had a few years ago or, is it an upright bug style engine?

You said it has 1 carb

also since this is a 73 it should have a small barb (plastic) coming off the booster hose (5mm dia.) that was used for the egr system when the bus was new.

these get broken off and aren't easy to spot sometimes resulting in a vacuum
leak.

If you have the green Bentley look on page 27 at the bottom drawing. it's
#8
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V.W.owner since 1967

[skills@eurocarsplus]

new or used booster?

I have 3 power brake buses. one will throw you thru the window with a sneeze on the pedal

the other is stiff, but has assist

the 3rd is in the middle of the first 2. all systems in like new condition

check to make sure you don't have a stuck wheel cylinder or caliper issues. all of mine stop great, it's almost like they have different valving.
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[Dave Wood]

Thanks for all the replies. This bus has just one carb that is not stock. This is the flat pancake type engine (1700). The booster vacuum line is attached to the back base of the carb. As far as I can see there is only the vacuum line, no check valves. I bought this new booster from JBugs http://www.jbugs.com/product/211611905.html

I have not been able to have someone push the brake while I'm under it yet so I don't know if there is any leak type noise from the booster.

There are two lines on the booster. One on the rear side that goes to the engine. Where does the front vacuum line go?

I did have a problem today after I bled the brakes. The front driver side caliper was sticky enough that it over heated on the x-way today. I took the side roads home and will look at the caliper tomorrow.
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Dave
87 Vanagon GL

[skills@eurocarsplus]

you need a good sized vacuum source, say 5/16-3/8.

if you have old hoses, replace them. if the calipers/wheel cylinders do not move freely, this will give a stiff pedal
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[Dave Wood]

Thanks, the vacuum line is normal size and should be good. The front caliper might be the culprit. This bus did not get used much and it would not surprise it me driving it around town is the most use its gotten in years. I'll look at it more tomorrow and try to free up the caliper
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Dave
87 Vanagon GL

[1967250s]

You really need to trace the whole vacuum line, from back to front, checking it all, including the metal tube. The rear line on the booster is obviously the vacuum from the engine, so the front one should be the vent. There is a rubber line coming from the left wheel well in the dogleg that should connect to the front of the booster.
But it sounds like is the calipers are also binding, either the pistons are seized, or the rubber brake lines are clogged. First, make sure there is adequate play in the brake pedal by adjusting the push rod. Press the brake, then loosen the bleeder. If it squirts out, then the brake flex lines do need replacing. Then see if the calipers pistons can be pushed back in. Make sure the booster seal to brake master cylinder is not leaking either.
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'72 Elm Green Deluxe

[Dave Wood]

[skills@eurocarsplus]

don't adjust anything till you solve the root cause. make sure all the calipers/hoses etc are ok and go from there. very seldom do they need adjustment.

was the booster new/used/rebuilt? I don't recall you answering that.
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[TomWesty]

Could a bad master cylinder cause this? It doesn't sound like he replaced that. I thought that's what causes the boosters to die is a bad M/C.
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If you haven't bled on them, you haven't worked on them.
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[Wildthings]

[Dave Wood]

[FlatfourFrenchy]

Brake fluid in servo from reservoir? Maybe but only via bad master cylinder.
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1971 Tin Top Westy Campmobile 70

[kreemoweet]

It's possible the new booster from Jbugs is from the same source as the new boosters that Wolfsburg West has
recently begun to offer. I got one of those WW boosters, and the pushrod in the booster, that goes into the
M/C piston, was too long. Fortunately, that pushrod was adjustable, by means of a threaded tip with locknut.
WW said they made the pushrod the same length as on a new ATE booster, which is true, but the ugly fact is, ATE is also making
their pushrods too long for use with the M/C's used on VW busses. I have a new ATE booster, and the pushrod
interferes with the piston on both ATE and Varga/TRW M/C's.
_________________
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'68 bug: seized by the authorities
'71 kombi: not yet seized by the authorities

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[Dave Wood]

thanks all, I'm going check the pushrod to the master and also check and see if the master leaking into the booster. I've got a lot to learn about these older busses. I pulled the wheel because the drivers side caliper seems to be stuck a little and its like no other caliper I've seen before. Ive seen dual pistons but neer dual bleeder valves! When I said I bled the system before I did it with the wheels still on and did not notice the second lower bleeder on the front calipers. I need to go back to my bentley and read up on these suckers.

I'm thinking my calipers need rebuilt and I've never done that before, So it looks like I'll be learning something new this week
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Dave
87 Vanagon GL

[Tcash]

I pulled the wheel because the drivers side caliper seems to be stuck
As posted check your brake hoses. They can look fine on the outside, but they collapse on the inside. Crack one of the bleeder valves and if the caliper releases. The problem is the brake hose.
The brake hoses have a date stamp on them.

Good Luck
Tcash

[Dave Wood]

Wanted to give an update. The brake hoses were 7 years old so I replaced them. I was able to free up the stuck caliper and I plan on rebuilding them this winter to fix them properly.

The problem with the booster was a simple one. I figured the vacuum was working because when I removed the hose from the carb there was vacuum and the engine would stall. BUT if I removed the hose from the booster nothing!. I think I previously mentioned the PO removed the check valve and spliced the hoses together. When I checked this splice I found, A BOLT!! So I'm guessing the booster went bad and the bus would not run because open vacuum hose. Instead of fixing the booster they removed the check valve and blocked the line. Sheese.

All is well now and he stops on a dime
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Dave
87 Vanagon GL