No play in brake pedal - what a drag?

[Dougs_LBC]

Just rebuilt the front brake calipers ,turned rotors, and new master cylinder, but the brake pedal has what feels like little to no play before it gets tough to depress.

A local Triumph Guru helped me with the rebuild a few months ago, and mentioned that there was a valve in the brake system in the later TR3A's that may need a rebuild?
The brakes were hanging up, and would release when we loosened the fitting on the master cylinder, which is why I replaced it. Has anyone experienced this type of problem with their brakes, and could this valve be the cause?

 

[Merlin63Tr4]

He might have been talking about the "Restrictor Valve" (P/N 116197). It's function is to keep some residual pressure in the calipers so as to reduce the pedal travel. It is no longer available and I believe most TRs have had it removed over the years. It is located at the five way fitting (the same fitting where the hydraulic brake light switch is located). /bcforum/images/%%GRAEMLIN_URL%%/hammer.gif

 

[rooster]

I don't know about a TR3, but it's possible that your old mater cylinder's plunger had worn at the contact point where it gets pushed by the brake servo. The brake servo could have been adjusted for that, then when you went to the new master cylinder, which does not have any wear, there isn't enough "slack" and so the brake shoes hang up.

I say this because I've been going through a similar problem on my TR6. My brake servo died, and I put a Nissan servo on it. The Nissan servo had to be adjusted to make sure that there is enough slack in the system or the brakes hang up. The adjustment is very very sensitive, to the point that even a 1/4 turn of the adjustment will make the brakes hang up.

Hope this makes some sense.

Cheers

 

[Dougs_LBC]

Thanks guys. I'll try adjusting it again(let it out a few turns last night), and if that doesn't work maybe I'll just need to remove the restrictor valve as well. Not having looked at it, what do you put in place of it, or how do you connect the hard brake lines once removed?

 

[Geo Hahn]

...maybe I'll just need to remove the restrictor valve as well. Not having looked at it, what do you put in place of it, or how do you connect the hard brake lines once removed?

Rather than removing it altogether, the usual 'fix' is to remove it, open it up and remove the innards. Then close it up and reinstall. All it is is a check valve, removing the inside pieces keeps it from working, the empty shell then goes back on to fill the gap to the hard line.

I removed mine some years back but I may just clean up the insides and put it back together. Without the valve there is more pedal movement than I really like, may jsut have been ginked up before and needed a cleaning.

 

[trrdster2000]

Doug, if all this does not work, have a good look at all your brake lines and see if someone along the way used a pressure fitting to join two lines and they tightened it up so tight it will let pressure go to the brakes but will not have enough to press it back out. After a couple of braking stops they are stuck on. Seen this a few times of the TR4A's and 6's on the rear wheels were there a a quick turn that brakes in half when getting it loose from the wheel cylinder. Works OK, unless you get it too tight.

Wayne

 

[YankeeTR]

The 'restrictor' valve is a residual pressure valve which keeps the brakes line pressure up to allow the instant application of the brakes instead of having to pump them once before full braking is applied.

The disc brakes would have a 2 lb. valve...the drums a 10 lb. valve. I really never had a TR with one installed but old TS 74011 would have benefitted from one.

 

[sp53]

Hi Eric make sure that the end play is adequate at the end of the master cylinder rod. The end of the rod actually needs to have slop in it or the peddle stays on a little and gives that hard feeling right at the top. You want about a half inch of free play. The problem could be in the rod adjustment screw on the rod or the little stop thingie at the bottom of the bracket is turned up to close and will not let the master travel its complete cycle of disengagement.

Sp53