Brakes seized on

[Raggles]

Been away for 3 years due to life. Trying to get the van back on the road. Its been parked up under a tarpaulin fo 2 1/2 years. Fired up beautifully but the brakes are siezed. Am used to this on the rear drums with the parking brake ... have freed these up and the rears are turning fine. However, the front discs are locked and the brake lights are permenantly on ... there is no travel in the brake pedal which is firm. Any thoughts/advice welcome before I pop the wheels off tomorrow.

 

[davidoft]

sound like the master cylinder may be seized, but most likely the front pads have stuck themselves to the discs, a whack of the caliper usually frees them off

 

[Raggles]

The plot thickens ... All wheels are now turning freely when the negine is off and the brakes working fine. Engine on ... brake lights lit and brakes locked on - assume it must be something to do with the servo? Vacuum return valve? If so can it be temporarily disabled ... ie disconnect the hose and plug to allow me to move the van to a garage whilst waiting for the part? I have changed nothing since it was parked up and that was after a +2000 mile road trip where it travelled fine. If I disconnect the hose on the cab side of the non return valve will this deactivate the servo whilst ensuring no vacuum leaks at the manifold? The engine is not idling as well as it did - hunting a little - could that be linked?

 

[Raggles]

Well ... disconnected the vacuum hose and plugged. Brakes now work fine but no servo assist. Engine runs smoothly without hunting. I assume this means the servo needs a recondition/replacement? Can you get rebuild kits?

 

[W1K1]

you need to send it to someone that rebuilds them, or source a new one. it's not a simple "repair kit" job

 

[ozziedog]

Well ... disconnected the vacuum hose and plugged. Brakes now work fine but no servo assist. Engine runs smoothly without hunting. I assume this means the servo needs a recondition/replacement? Can you get rebuild kits?

First thing I’d try is really have a good look at any hoses or connections to your servo . Possibly just try another pipe too especially if it looks a bit ‘original’ not sure how you’d test a servo but I bet you can.

Ozziedog,,,,,,,,,, Google is your buddy too.

 

[Raggles]

First thing I’d try is really have a good look at any hoses or connections to your servo . Possibly just try another pipe too especially if it looks a bit ‘original’ not sure how you’d test a servo but I bet you can.

Ozziedog,,,,,,,,,, Google is your buddy too.

Curious as to why it would lock the brakes on if it was a hose issue? ... I don't fully understand the servo, but I thought when you depressed the brake it closed equalisation ports creating a vacuum and on release opened them creating balance? If that is the case wouldn't it suggest that for some reason you had a constant vacuum in the servo creating constant braking pressure? if a hose was leaky wouldn't it just release the vacuum giving no braking ... or have I got that completely wrong? Having said that, there must be some air leakage to effect the idle/mixture?

 

[ozziedog]

Curious as to why it would lock the brakes on if it was a hose issue? ... I don't fully understand the servo, but I thought when you depressed the brake it closed equalisation ports creating a vacuum and on release opened them creating balance? If that is the case wouldn't it suggest that for some reason you had a constant vacuum in the servo creating constant braking pressure? if a hose was leaky wouldn't it just release the vacuum giving no braking ... or have I got that completely wrong? Having said that, there must be some air leakage to effect the idle/mixture?

I’m in the same boat as you here as in not fully understanding the systems workings. My thought pattern was along the lines of the hydraulics and in particular the flexi pipes that have a nasty habit of collapsing internally and locking the brakes on. So leading on from that I thought it may be possible for a hose from your servo to collapse internally or have some sort of blockage that may allow you to create vacuum but possibly not let it go again for a while causing the brakes to stay firmly on for a while. Either a hose or any valves in the servo.

Ozziedog,,,,,,,,,,, just thoughts bud and ideas

 

[Raggles]

I have got this excellent explainer from The Samba -

The booster has internal valving that, when you press the pedal, simultaneously admits fresh air into the space in front of the diaphragm and shuts off the vacuum connection to that front area. That leaves atmospheric pressure on one side of the diaphragm and engine vacuum on the other; the difference in pressure is what moves the booster rod rearward to push on the master cylinder pistons. If that booster valve only operates partially, it will both admit air into the front of the booster and allow that air to pass into the rear vacuum chamber, which is connected by hose to the intake manifold. This will give both brake operation and a vacuum leak that adversely affects idling.

 

[ozziedog]

I have got this excellent explainer from The Samba -

The booster has internal valving that, when you press the pedal, simultaneously admits fresh air into the space in front of the diaphragm and shuts off the vacuum connection to that front area. That leaves atmospheric pressure on one side of the diaphragm and engine vacuum on the other; the difference in pressure is what moves the booster rod rearward to push on the master cylinder pistons. If that booster valve only operates partially, it will both admit air into the front of the booster and allow that air to pass into the rear vacuum chamber, which is connected by hose to the intake manifold. This will give both brake operation and a vacuum leak that adversely affects idling.

Blimey, I might be very very close indeed. There are some very clever peeps on the Samba and that’s a fact.

Ozziedog,,,,,,,, might get something right one day

 

[milfredo]

Blimey, I might be very very close indeed. There are some very clever peeps on the Samba and that’s a fact.

Ozziedog,,,,,,,, might get something right one day

Pretty much bang on chap

 

[naskeet]

Keep in mind that apart from the special 1•2 tonne payload model, with special concentric suspension dampers & helical springs, British specification 1971~79 VW 1600 Type 2s with front disc brakes, did NOT have factory-fitted vacuum brake-servo units.

VW OEM, heavy-duty rear suspension damper with concentric coil spring (VW part No. 211 513 031 M), as fitted to 1972~79 VW Type 2, uprated delivery vans, with 1•2 tonne payload. In the early-1990s, the list price for these was about £500 for a pair!!!