Brake Servo is always engaging Master Cylinder
Turbo Mini Forums

It appears that the push rod between that directly connects with the master cylinder is sticking out an 1/8th to a 1/4 inch too far. If I attach the master cylinder to the servo it engages the brakes. In order to keep the brakes from engaging I've had to leave a gap between the two. The push rod does not appear to be adjustable as it is a single piece and I am not sure what could be happening with the master cylinder as an alternative.

Any ideas?

Does the end of the push rod extend past the opening where the master cylinder connects?

Thanks a lot,
Jeremy

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'91 ERA
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The rod inside the servo housing screws in.

I tried that again with no success. I may not have been as clear as I could of been. Attached is a picture showing specifically which rod I am talking about. When I spin it and check it for play it moves quite freely on it's own. The rebuild kit indicates this rod sits up against the push rod from the other side. I have not been able to find a drawing of the internals, but attached is one from a Triumph.

The other odd thing is that prior to yesterday I had never taken the master cylinder off of the servo. As I am putting them back together there is resistance and it is as if I am compressing the piston in the master cylinder.

Thanks,
Jeremy

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'91 ERA
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what about the pedal assembly? is it returning to the correct position? there is adjustment in the linkage as it goes from the bracket to the servo

Everything is returning to the correct position. If I take the servo complete out it is not possible for the push rod to go any further back.

'91 ERA
http://turboera.com/

have you replaced the master cylinder or is this the one that was originally fitted to the servo?

This is the original one. I was considering rebuilding or replacing it, but wasn't sure what would be going wrong with it.

'91 ERA
http://turboera.com/

I'll take some measurements from some spares I have and see if I can work it out

Thanks a lot.

'91 ERA
http://turboera.com/

So this was working fine, you took it apart, no changes were made and now it wont go back together ?

And you're saying it is when you are trying to bolt it together with all hydraulic system intact, it locks the brakes ?

Have you tried allowing the pressure in the system to release to allow the MC to bolt up, the closing up the bleed nipples again ?

The internal piston could end up in the wrong place if it's locking up now...but if it worked before, it should work again.

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

I didn't make any changes and it does lock up the brakes. I did bleed them when I originally put everything together and at that time the problem was intermittent. Since separating the master cylinder and servo and trying to put them back together the problem has now become consistent. Leaving the space in essence makes the servo useless, but the brakes no longer lock up. Just slow to the stop.

I will get back at it this weekend and will see if this makes a difference. I was thinking that if the piston was too far back that pushing it forward would just force the fluid back into the reservoir. I am game to try anything before I grind down the push rod a bit as that isn't really dealing with the issue.

Thanks.

'91 ERA
http://turboera.com/

It's hard to imagine needing to machine anything if it worked before.

And as you say, if the piston was too far back, it could move forward filling the reservoir before brakes started to activate.

I guess another option, make up a small spacer between servo and master ? At least there is no permanent damage done that way

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

I've pm'ed you with measurements however looking at your photo below, the nose of the pushrod you have highlighted in the photo on mine was fluch with the servo casing; yours appears to be projecting and I assume that's what the issue is

I compared my servo to Rob's and it appears that the entire push rod setup is 10mm out of alignment. sticking 10mm out the front of the casing and as a result the long threaded rod on the back is 10mm short. I have no idea how this would of happened, but definitely explains the issue. There doesn't appear to be anyway to fix this, but if anyone has an idea I am all ears otherwise it is off to get a new one.

'91 ERA
http://turboera.com/

Take it apart - will probably be quite obvious once it's split

I got it apart and it looks like there was some significant corrosion built up on the back of the servo that appeared to be blocking the diaphragm plate from fully returning. As well as the neck of the diaphragm plate was not sliding smoothly through the seal. Cleaned up everything and it seems to be working well. I was never able to get the key out to take the whole booster apart although this was not necessary.

I am sure it is on the site here somewhere else, but for anyone interested the following link to overhauling a triumph servo is quite helpful. http://www.buckeyetriumphs.org/technical/B...Servo/Servo.htm I also found that it was easier to take apart then described here and as I am not able to quickly weld up tools to support this I drilled wholes in a spare piece of plywood to hold one half still and used a second board to twist it open. First time took a bit of force, but afterwards it was easy enough to take apart and put back together by myself. This happened more than once as it needs to go back together the correct way or your master cylinder won't be able to mount properly.

Thanks again for the help!

Jeremy

'91 ERA
http://turboera.com/