FE-FC Holden Discussion Forum

Gday all,
I am after some advice, with regards to, a VH40 brake booster I have just plumbed into my EJ braking system.
I am running a grey and have sourced the vacuum from the inlet manifold via a 25mil heater hose, going straight into the diaphragm housing, the VH40 is mounted in the engine bay on the RH side, diaphragm housing pointing FWD, vent facing down. The Master cyl is plumbed into the fitting closest to the diaphragm on top, the next fitting on top moving aft is the bleed nipple, the horizontal one at the end goes straight to the brakes.
The problem I am having is that with the engine running and vacuum connected to the VH40, the brakes are permanently on. Disconnect the vacuum and the brakes come off. With vacuum disconnected the brakes work as an unboosted system. Connect vacuum brakes are on.
I did put an “O” Ring kit through the VH40, have I done something wrong? and which bit would I look at first.
Can someone also advise on the correct method of plumbing in a VH40, and also the basic principals of operation of the VH40.

Regards
Scotty

Hey there Bent...mate,it seems you have it plumbed in correctly,i have a similar setup on my FE and what you describe looks ok.I can only think that the booster is somehow working in reverse,and it may well be that you screwed up somehow when you did the o ring kit.Ive never actually rebuilt a booster before however,so i cant offer too much more help.Someone in here will know,however.       Good luck...jimmys57

Just scratching my head i am sure you have to pull a valve or something out of the slave cylinder- other wise the brakes will stay on- i can't remember off hand butgive Rare spares acall and they should tell you wjat to pullout.
Cheers

Thanks Jimmys57, at least I’ve fitted it correctly.
Vinnie, yeah I've been scratching my head too, but I've been thinking more that the small diaphragm is stuck in the “actuated” position closing the atmospheric vent and keeping the main diaphragm “SUCKED IN” permanently, thus applying the brakes.
Any other thoughts???

Scotty

OK
i don't know  if you are running drums or disks however on my FC when i installed a VH 40 i had to remove the valve in the master cylinder as the valve keeps some pressure in the line "Hence" the pressure is increased whilst  going through the booster.
Might pay to have a look if there is one in there.

Scotty,
          Hi there, it is definately the master cylinder, for drum brakes they have a valve which needs to be removed, or replace with a master cylinder from a model with disc brakes.  I know this as I was in the same boat as you once before.

Michael

Thanks, Michael and Vinnie,
I think you blokes have nailed it, as I have just retro fitted a HR disc brake front end to my EJ utilising the original master cylinder.
I also gave my VH40 the once over last night, and apart from finding out it is actually a VH44-4; everything looked to be serviceable. So tonight I will go looking for the valve in the master cylinder.

Scotty

Gday all,
     Well I spent quite a bit of time over the weekend on my brake problem.
     Firstly, I had replaced the front drum brakes with discs, so thanks to Vinnie and Michael I located the check valve in the master cylinder and removed it, NO CHANGE.
     Then I bit the bulled and pulled the booster out, and opened it up to check the main diaphragm. What I found was, when I originally had the booster disassembled for stripping and painting I put masking tape over the little tube that gos to the atmospheric valve (inside and out), and didn’t remove the tape on the inside before reassembly.
     The human factor.

Scotty

P.S. I picked up a nice straight EK yesterday.

Well there you go!....Glad you sorted it out finally mate...you must have been pulling your hair out trying to figure it out....Cheers jimmys57