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Receding Brake Pedal

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I think so John. When I restored the car 3 years ago, I aligned all 3 pedals. The gas and clutch are still very close in height and the brake pedal is clearly recessed relative to the other two.

There is a nut on the rod connecting the pedal and the MC, that when tightened, fixes the overall length of the rod and fork, and I recall tightening it firmly when I installed the MC. When I looked at it a few days ago it was still snug against the fork, but I did not check that it was still tight - i.e. using a wrench. Could it be that the rod has been rotating - shortening the rod-and-fork assembly, drawing the pedal down, while still holding the nut against the fork giving the appearance of the nut being tight?
 
SteveHall64Healey said:
.... Could it be that the rod has been rotating - shortening the rod-and-fork assembly, drawing the pedal down, while still holding the nut against the fork giving the appearance of the nut being tight?
Click to expand...
That could be. So the fork is threaded too? The rod would eventually be stopped by the lever on the pedal surrounded by the fork.
 
Yes, the fork is internally threaded - the rod screws into it and fork clips onto the pedal. You set pedal height by rotating the fork around the pedal until height is correct, and then lock it in with the nut on the rod.
 
SteveHall64Healey said:
Could it be that the rod has been rotating - shortening the rod-and-fork assembly, drawing the pedal down, while still holding the nut against the fork giving the appearance of the nut being tight?
Click to expand...

Seems possible to me. You can adjust the pedal to where you want it again, tighten the nut and then paint stripe the nut/rod/clevis with any paint you have handy. Then, if it shifts again, a quick look will show if any part has moved.
 
SteveHall64Healey said:
Hi Bob,

There has been no loss of fluid - the reservoir has remained at the full level. If this were the case, I should see some drop on the reservoir...?
Click to expand...

Correct. But my (main) point is that your return spring should keep your pedal at full height (unless something is impeding its movement). It's a pretty strong spring.
 
The return spring is working and is pushing the rod out to the point where the rod is stopped by the washer-like stop that is held in by the circlip (is this the right term?). If the rod-and-fork assembly grows shorter by the rotation of the rod, it would pull the brake pedal closer to the MC.....
 
Two of us have suggested a bad return spring. It would be simple to check. Can you pull the pedal back to where you say it used to be? If the return spring is strong enough, there is nothing short of binding of the piston or some part of the linkage, that would keep it from fully extending and making the pedal as tall as it can be. Perhaps I'm not seeing something about this possibility.
 
Understood re the return spring. It's really not convenient to take it out, plus I'd have to bleed the system. It is clear from under the dash that the cylinder comes all the way out when the brake pedal is lifted. There is nothing binding it. When you press on it, the cylinder goes in several inches and when you release it, the cylinder immediately comes out: no binding, no delay.
 
You don't need to take the pedal return spring out to test it; you already did in post #26. It looks like the operating rod has been rotating. After adjusting the fork to the right height, put a drop of thread-locker on the threads and tighten the nut.
 
I'm stumped. I can't think of any principle of hydraulics that allow for a fluid to pull; you may have discovered a heretofore unknown natural phenomenon.
 
Hi Bob,

I wasn't suggesting that - not sure if anyone else was. The hydraulic side seems to be fine, with no leaks or loss of fluid and with the return spring in the MC functioning normally. I think what might have happened is that the rod rotated over time, continuing to thread into the fork, drawing the brake pedal to the MC. The retaining nut that fixes the rod into the fork might not have been sufficiently tight ...
 
SteveHall64Healey said:
... I think what might have happened is that the rod rotated over time, continuing to thread into the fork, drawing the brake pedal to the MC. The retaining nut that fixes the rod into the fork might not have been sufficiently tight ...
Click to expand...

That's the only thing that makes any sense (still pretty strange). I can't think of anything that would cause the rod to rotate; maybe the piston could, but IIRC the pushrod and piston only contact each other. Still, the jamb nut is there for a reason.
 
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