Loose, floppy brake pedal

[Granthar]

Hello all.

I just collected my dream car this weekend (since 4 years old) A 1965 series 1 OTC. Drove with my son from Geneva through the Alps back to Basel Switzerland. Wonderful!

Anyway, my brake pedal is loose with a good 2-3 cm of free play before the brakes are applied. I don’t mean the brakes are spongy, rather the spring is not taking up the slack. I read in the manual that you should adjust the clutch pedal to create 1/2” slack, but there is much more than this on the brakes. In fact I can rock the pedal to and fro with my finger from the pivot under the bonnet. As mentioned the spring looks in good condition and assembled correctly. Any advice or re-direction to previous posts are much welcomed

Regards from Switzerland

Rob

[abowie]

Which pedal box do you have? The early 4.2s like yours have one that is different from the later ones.

A picture would be ideal.

[Granthar]

Here’s a photo. I have also shown the attachment of the spring. You can also see where brake fluid has leaked from before my ownership.

[Tony]

Does the pedal have side to side movement. Mine had this.The pedal I think is on a spline and the nut holding holding it on came lose. I applied the brakes and the brake pedal jumped the spline giving me a loses peddle feel. Eventually the pedal slipped the spline completely and hit the floor with no brakes what so ever.
Just worth a check.

[abowie]

That is the early pedal box.

As Tony says the pedal is attached to a splined shaft and held with a pinch bolt (#2 in diagram).

Lying upside down in the footwell you can loosen that pinch bolt. Then use a screwdriver as a lever and you can open up the splined section on the pedal enough that you should be able to rotate it. You should then be able to adjust your freeplay.

If on inspection it seems that the pedal is correctly positioned you may be correct and you have an incorrect pushrod (#48) fitted. This can be removed with a little difficulty by removing the clevis pin (#49) and replaced as necessary.

Finally there may be some sort of problem with your master cylinder sticking and the piston (#29) not fully withdrawing.

[Granthar]

Tried today to tighten the pinch bolt as it seemed loose, not too successfully as it turned out, very hard to access. Not sure this is the cause of the problem. I have attached a couple of videos, one indicates the movement is coming from the master cylinder, not a loose pedal on the shaft

I can’t upload a video. But the master cylinder piston shaft is oscillating in the cylinder when viewed from above. Should this happen?

[lopena]

The push-rod that goes into the master cylinder should not be very loose and rattling around (what you call ‘oscillating’) but should be snuggly held in place by the pressure from the MC piston. So, you either have the wrong (too short) push-rod fitted or, more likely, the master cylinder piston is not rebounding fully...I experienced this same condition and a quick rebuild of the MC cured it.

Good luck,
Alan
New Jersey

[baldyz1]

Not wishing to hijack the thread but maybe same problem.

My newly rebuilt car has a pedal that is really loose at the top of the travel and seems very high. If you catch your foot under it the pedal lifts about an inch so you could easily get you foot trapped the wrong side and lift it an inch making it even higher. The movement is fine but I just cannot see me safely driving like that when I do complete it. Do people think it has been wrongly put together. 1966 box same as above.

[politeperson]

Maybe Part labelled no 9 on the diagram is missing?

This stops the pedal rising too high.

[Heuer]

First thing to check is that the brake pedal return spring (#4 in the diagram) is present and correct. They can break which means the pedal will drop.

[caveman]

If you catch your foot under it the pedal lifts about an inch so you could easily get you foot trapped the wrong side and lift it an inch making it even higher.

My pedal has done this for many years, I just thought it was supposed to be like this. Brakes operate fine but I can hook my foot under the pedal and lift it up towards me if this isn’t correct I’ll need to investigate further.

[caveman]

Think I may need one of these, thanks James

[baldyz1]

Sorry for the late thank you for information here.

How difficult is it to remove the pedal box once everything has been fitted around it?

I very soon have to get all four wheels off the ground and remove the sump so this would be the time to inspect this also.

Many thanks
Chris

[baldyz1]

Just revisiting the topic as I am ready to do this job. As a reminder my brake pedal can be hooked up by your foot so that it becomes really high. The actuation is fine although the brake pedal starts high.

I have to take out the driver seat and also attend to some issues with the steering rack and a broken choke cable. Carbs and manifold are out so its a good time to sort everything.

Question then;

Am I going to be able to tackle the introduction of the stop plate marked (9) from inside the car or will I have to remove the pedal box to fit it. Same goes for if the spring is incorrect or broken. Can I basically see everything when lying on my back in the footwell?

Many thanks
Chris

[caveman]

Chris,

Fitting #9 can easily be done from inside the car with no removal necessary.

[baldyz1]

Fabulous just the answer needed.

Many thanks
Chris

[baldyz1]

So spent the afternoon looking at this, crawling in the footwell.

Turns out my pedal box is probably a 65 crossover so has the L shape body and a framework for the brake master cylinder as highlighted by the diagram above.

I now understand where the stop plate fits.

Question: does the stop plate fit to the outside of the bodywork / pedal box sandwich, i.e. literally bolt in place to the fitted pedal box or do you have to unbolt the pedal box body to raise it enough to get it between car body and the pedal box and onto the studs. Hope that makes sense. The bodywork has a lip all around the aperture so that's why i am unsure, as the plate would have to be angled somehow to clear the lip.


The brake pedal height will improve with the stop plate fitted but it will still be probably a cm or 2 higher than the clutch, is that normal? I cant push it further down with the stop plate as its at the start of its travel already. A shorter rod would probably work but I am not sure what the length should be.

My pedal box is C24649 as far as I can tell from other photos.

All help gratefully received.

Many thanks
Chris

[bitsobrits]

Chris,

The stop plate is fitted to the inside of the car, not sandwiched between the pedal box and body. There should be two approx 1/4" spacers between the plate and the bulkhead sheetmetal (stacked washers will do), otherwise it can't sit properly due to the flanges on the bulkhead sheetmetal.

Once you have the stop plate correctly mounted and therefore the brake pedal in it's normal resting position (install a pedal arm return spring if the one in the pedal box is broken, which is common), you may need to make up a new adjustable pushrod set up to give a very slight amount (about 1/16") of free play (at the rod to MC interface, not at the brake pedal) when the pedal is in it's 'at rest' position. A new pushrod can be made from a common bolt of the correct size/length (5/16" coarse thread?) with the head cut off and the cutoff end rounded with a file or sander. Starting with a high strength stainless bolt (ARP) is a nice, but unnecessary touch.

If the pedal height differences are troubling (the variance you mention is in the normal range), you can adjust the clutch pedal height by both/either making up an adjustable pushrod or removing/replacing the spacer between the clutch master and the pedal box with a thinner one.

In my own car, I instead made up a new stop plate and moved the brake pedal forward to approximately the clutch pedal level to facilitate heel/toe operation. That does require removing the pedal box and re-positioning the brake actuating arm on it's splined shaft, so it's a more involved process.

[baldyz1]

Steve, that's brilliant. I think the stop plate should get the pedal down a bit and maybe I can eat into the first part of brake application without applying the brakes.

So grateful for all the help.

Chris