Hi all, need some help/advice.

Had the car on axle stands and was testing the gearbox by running through the gears etc. What I noticed was that when I put my foot on the clutch, the wheels stopped turning without me touching the brake pedal.

If I disconnect the vacuum hose from the booster, the problem goes away - wheels spin freely until I brake.

So the issue is with the booster, but I'm not sure where to start looking or what to test.
It has been rebuilt with all new seals, etc. It is also entirely possible I may not have re-assembled it properly or something is back to front.

Anyone got any ideas on what I should check before I pull it out and disassemble?

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67 Van, 1275cc

Have you read this?

viewtopic.php?f=25&t=90214

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ex-NSW Police 1970 MK II Cooper S
VMCI #43

Yep - got it printed out so I can compare how mine is out back together when I get a chance

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67 Van, 1275cc

It sounds like it's allowing atmospheric pressure air into the back of the booster before the brakes are pressed, I'd look at the valve that hangs off the side of the booster cylinder and for leaks in the hose to the back of the booster.

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Roads need more corners
A Deluxe(CG13DE), 2 Clubbies(998 and 1275) and 2 Morris 1100Ss

Not sure if this will be relevant or even apply to your problem but I have had 2 pbr boosters that would hang the brakes for a few seconds after the pedal was released. No amount of rebuilding would fix the problem and I eventually traced it to a lip or step that had developed in the bore of the main cylinder. It was almost imperceptable to the eye but I found it by a strong light and looking down the bore.
I assume it was a corrosion problem and honing to remove would make it too large for the seals.
One was a vh40 and the other was a vh44 and I came to the coclusion that they had sat in one position for too long with brake fluid in them and corroded.
Cheers

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Cheers Dave.

Glad to see my post is still being used.
Had the exact problem with my vh44. The diaphragm I had was two thick and was holding the brakes on. In my case locked up front brakes. If you pull the hose and it releases the problem is on the vacuum side
Some times if the diaphragm has been pinched in the housing this will happen.


Sent from my SM-J530Y using Tapatalk

Thanks for the help folks. Gonna pull the booster on the weekend and see what’s going on.

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67 Van, 1275cc

For those playing along at home, I had a valve back to front, and the elbow hose had a leak as well. Sorted those and working as it should!

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67 Van, 1275cc