TR2/3/3A TR3A Brake Pedal - Too Much Travel

[Vince]

I had rebuilt both master cylinders last year, and ever since the brake pedal has a lot of movement while the clutch seems to work fine. The pedal will "pump up" a little bit (ie. has some air in the line), but not much. I did re-build the calipers and replaced all three rubber lines. There is no loss of fluid at all.

Is it likely that my rebuild of the brake master cylinder has a problem? Or is there another cause? The pedal goes almost all the way to the floor. Car stops just fine.

 

[Andrew Mace]

At risk of restating the obvious, have you checked the rear brake adjustment?

 

[Geo Hahn]

A quick & dirty check to see if a rear brake adjustment is in order can sometimes be had by putting the handbrake on just a but and seeing if that gives you a firm pedal. Use caution and don't drive far like this but it does momentarily take up any slack in the rear brakes if it is there to take up (or else you feel a lot of drag).

 

[Vince]

I adjusted the rear brakes, tightened up three clicks on one side and four on the other. Both are just one click away from locking up. Helped some, but still seems like the pedal travels too far. I also tried the handbrake idea, thought of that myself, and it did not make much difference. Raining here, so did not get the car out and drive it. Will have to see how it does on the road.

 

[bgbassplyr]

You might also check the the pedal where the M/C actuating rod pin attaches. The hole is probably worn to an oval shape, allowing for some free play before getting the rod engaged.

You must get as much of the mechanical 'slop' out of the system as possible.

 

[Vince]

Mechanical slop not an issue, hole nice and round in pedal/bracket and very little slop. I am becoming convinced there is something not quite right with the master cylinder. Can get a new one for about $51, so I think I'll just go this route to eliminate that root cause.

 

[TR3driver]

I am becoming convinced there is something not quite right with the master cylinder. Can get a new one for about $51, so I think I'll just go this route to eliminate that root cause.

Unless of course you get one of the defective ones that was making the rounds a few years back.

I'd want to pull the existing one back apart and at least try to see the problem. Only possibilities I can think of are that the return spring is broken, or the 'leash' for the foot valve is hung up or out of place in some fashion. Anyway, it should be trivial to work out a bench test to see how far you can push the piston with the outlet blocked with a bolt & nut (and the cylinder full of fluid of course). There should be a very slight movement possible (as the valve closes), but not much.