Brake Pedal Loss

[Mk1-nightmare]

Hello gents
I wonder if you could help me
I have a camper van twin wheel with brake pedal on the floor and remote servo
I’m trying to get it roadworthy after being stood idle for a few years
I’m not a trained mechanic but do have some knowledge to help me along
I’m currently having issues where the brake system won’t hold pressure
I can pump the pedal and obtain a firm pedal with brakes applied but when I release the pedal, after 10 seconds the pressure is lost And the pedal goes to the floor
I have replaced all flex hoses and ensured there are no leaks on the brake cylinders etc But I can’t see how or where I’m losing system pressure. I have replaced all seals on the cylinders
I have purged the system of old fluid and bled the brakes correctly

I’m stuck and don’t know how to resolve this, other than assume the servo is faulty and replace it

Does anyone have any ideas

Thanks

[Neil]

have you changed all the flexis ?

[Chug]

If it pumps up and pedal goes hard then it probably just needs shoes adjusting, or you've got air in the system somewhere...master cylinder seals?

[Stumble]

If it pumps up and pedal goes hard then it probably just needs shoes adjusting

Seconded

[Mk1-nightmare]

have you changed all the flexis ?

Yes all flexi hoses replaced

[Mk1-nightmare]

If it pumps up and pedal goes hard then it probably just needs shoes adjusting, or you've got air in the system somewhere...master cylinder seals?

Master cylinder seals replaced
Pedal pumps hard and if you hold pedal it stays hard
When you release pedal and wait 10-20 seconds, it loses its pressure and goes to the floor
You need to pump it again to get the pedal hard
Pretty sure it’s not air. Have bled each corner in order, multiple times

[Mk1-nightmare]

Removed the servo today
Have found that the vacuum inlet washer/seal has perished and separated
Does this maintain the vacuum and if failed could be the source of the problem. See picture

Also the pipe from cylinder block to rear of servo, the rubber elbow connection has also perished and split.
Explains why it was taped up by the previous owner
I broke the connection to the servo when trying to inspect condition

Does anyone know where I can obtain spare seals etc

Thanks

41901AC5-C8DA-4FD1-9B09-241DB431292D.jpeg

[Ralph.9]

I might have what you need, I will have a look.

[Neil]

get the servo reconditioned

[conrod]

servo is not the source of your problem, although should be repaired anyway. Sounds like you have air still trapped in the system. Do your front brake calipers have multiple bleed screws? (the 4 pot calipers can have 3 bleed screws per side) Did you bleed from all of them? Borrow a vacuum bleeder and try it with that. They connect to an air compressor, and basically suck the fluid through the system. Great for problematic systems.

[Mk1-nightmare]

get the servo reconditioned

Hello Neil. I have sent it away to be reconditioned

[Mk1-nightmare]

Do your front brake calipers have multiple bleed screws? (the 4 pot calipers can have 3 bleed screws per side) Did you bleed from all of them? Borrow a vacuum bleeder and try it with that.

Hello Conrod. I don’t have callipers I have drums on the front. I will take your advice though about using a vacuum bleeder.

[Neil]

get the servo reconditioned

Hello Neil. I have sent it away to be reconditioned

IF ITS BEEN ON FROM NEW ITS TIME

[steve williams]

Hopefully you have sorted your problem by now, If not try clamping off your flexi hoses, this will eliminate adjustment on the shoes, If it still goes to the floor its master cylinder,

[fortyeight]

hi i had a similar problem on a mk2 the compensator was sticking