Jump to content

Excessive travel on brake pedel


Andrew
 Share

Recommended Posts

Here is my tail of woe (why do I bother sometimes working on my beloved car) when I bought my Herald about a year ago I was informed that the brake fluid had not been changed for some years. And as we know it is good practice to change the fluid every couple of years or so I though. As I was going to have to bleed the system I thought I would replace my flexi hoses so bought four new ones. Replaced the two rear hoses no problem and bled the read two brakes. Proceeded to the front callipers both bleed nipples sheared off so bought two new callipers from the club shop. Fitted the callipers bled the front brakes and here is my problem. The brake pedal travels almost to the floor before any braking takes place but when you get there it is a solid pedal but if you pump the pedal it bites about a third of the way down and it is a good solid pedal as it was before I messed with anything. So I made sure the rear brakes are adjusted correctly which they are bleed the system again no air found in the system but the pedal is no better. Any suggestions please cannot figure this one out

Regards from a Frustrated Andrew

Link to comment
Share on other sites

are you sure the master cyl is in good order,  worn seals dont like the extra travel when bleeding.  the small end seal which covers the reservoir port is very important when recuperating the cylinder , , does the pedal return fully , there must be some play/ slack on the push rod ,with foot off, it should be a rattle fit if its not returning you dont allow the cyl to refill after an application and get a lost pedal

 

excess front hub end float can push the pads back when standing

 

when adjusting rear brakes dont let the  axles hang this tensions the cable and you get a false result. jack the upright to raise the wheels

if you dont know how the handbrake has been set up you must disconnect the cables , then firmly lock up the adjusters then reconnect the cable to suit the new position of the cable lever,  this error will give low pedals. as the cables are holding the shoes open .

 

make sure the reservoir cap breather hole is clear

 

just some thoughts  Pete

Link to comment
Share on other sites

Hello Andrew.

 

I renewed all my flexi hoses on the Vitesse last year so I can appreciate your question.

 

The manual says always start at the furthest away bleed point from the master cylinder.

 

However what I have found and helps immensely is to bleed the fronts first so that there is some fluid in that section. 

 

Then go to the rear bleed points and THEN follow the WSM guideline. The rationale behind bleeding the fronts first is to limit the amount of air in the pipes being sucked back & forth as you do the correct circuit for bleeding.

 

The rear shoes MUST be adjusted in to the locked position fully - that is to say that the drum cannot move.

 

This prevents fluid being used to move the piston back & forth and as such the fluid then goes to where it is required, the nipple. 

 

Ensure you do not let the master cylinder go beyond 1/3 full or you may / will start to draw air in. If that is the case you will need to start all over again. 

 

When locking the nipple down, ensure the brake pedal is FULLY DOWN and held in that position whilst the nipple is locked off and THEN let the pedal come up slowly. You will be surprised how much the level in the master cylinder goes down, so as already stated keep your eye on it.

 

Finally ensure you buy a one way valve bleeding kit and that the bleeding tube is below the level of the waste fluid in the jar.

 

If you do the above, you will find a spot-on pedal.

 

You can buy the one-man bleeding kit but I personally prefer the help of an extra pair of hands. 

 

My final tip is that when the bleeding is done and you are happy with the pedal pressure, keep the brake pedal pushed down for about 24hrs by using a stick wedged against something. The reason for this is that the pressure exerted will allow any trapped tiny air bubbles to be expelled via the master cylinder.

 

Hope that assists ??

Good luck.

 

Richard.
 

Link to comment
Share on other sites

Thank you to all I think I will start with a new master cylinder and then take your advise regarding the hand brake cable set up and locking the rear wheels and jacking up under them rather than let them hang. I will report back so all can see my solution

Regards

Andrew

Link to comment
Share on other sites

  • 2 weeks later...

Hello to all

As promised I said I would update everyone with my brake pedal travel issue. Did every thing that was advised by classiclife and also fitted a new master cylinder. Now my pedal travels about half way and is solid. On dismantling the old cylinder found the bores quite rough so this could have been part of the problem, but once again thankyou to all (now all I need is a dry day to road test my car)

Regards

Andrew

Link to comment
Share on other sites

Add to the list check the end float on yoir front hubs, if its excessive it will push the pads back and you gain pedal travel

light spanmer the castle nut to nip , not wraunch it up, then back off 1 or 2 flats of the nut

so its almost loose refit the pin

 

spec is 0.002 to 0.008"

 

With the wheel on you should feel some rock at max you get about 3mm rock at the tyre periphery

aim for the min but must never have no play, or the outer bearing will sieze on the stub

very quickly.

pete

Link to comment
Share on other sites

Andrew.

 

1/2 way is okay provided that the car brakes properly and does not pull to the left or right - if that does occur there is an imbalance with the system. If the car "fish-tails" on braking that can be a sign that one of the flexi-hoses / calipers has a problem. I had this on my Vitesse when I first purchased the car; on replacing the flexi-hoses and both calipers this disappeared, so one or the other was at fault but probably a mixture of both due to age and the likelihood of the parts being past their best. 

 

You may well find that the new wheel cylinders will give you a better pedal and of course you have nothing to lose and can only gain in replacing them. Some folks overhaul with kits, but personally I'm not a fan of that - that is purely personal choice.

 

Ensure that the rear shoes are adjusted properly, it does not take much slack in their movement to exasperate pedal travel. 

 

The information given by Pete is sound and worth bearing in mind should you still not be happy with pedal performance. You have to balance good braking in classic cars with pedal travel and if you are getting that and are happy, then that is job done.

 

Many classic car owners believe that adding a servo will improve braking by stopping quicker and in a shorter distance - that is not the case at all. The job of the servo is to make the effort of braking on using the brake pedal a more positive action and less strenuous on your leg.

 

Good quality brake pads / discs and rear shoes go a long long way to provide efficient braking; once the braking system is set-up properly and you are certainly on way to achieving that. Well done.

 

Just some ideas for you.

 

Good luck.

 

Richard.

Link to comment
Share on other sites

I agree with Richard as I have a servo fitted to my MK1 Vitesse but made sure brakes were as good as can be before I installed it. Fitted it just to reduce the pedal force needed, could lock the wheels before fitting but am a lot happier with the servo.

 

Regards

 

Paul

Link to comment
Share on other sites

"Many classic car owners believe that adding a servo will improve braking by stopping quicker and in a shorter distance - that is not the case at all. The job of the servo is to make the effort of braking on using the brake pedal a more positive action and less strenuous on your leg."

 

Yes, I've heard this chestnut before. "The servo doesn't improve braking it just makes it easier". Well, no! If you have thighs like a sumo wrestler you CAN stop the car as quickly as a servo but who of us has that physique?  

 

The servo WILL help the less well endowed stop their car quicker and in a shorter distance.

Link to comment
Share on other sites

Sorry Doug, but if the master cylinder size is correctly matched for non-servo use, then you don't need to be muscle-bound.

 

My wife can drive non-servoed cars with no issues. Bith my daughters, one of whom is tiny and 7st drove a classic mini, again no servo and she could stop it PDQ.

 

The problem arises with larger bore, sometimes incorrectly refereed to as uprated, master cylinders are fitted.

 

And the servo -assisted factory GT6's had a bore master cylinder. So yes, if you wanted to lose the servo then a change to a smaller master should see the balance restored.

 

Of course, some people do need extra assistance, but Richards statemaent is correct, the brakes will not work better, it just requires less effort.

 

(and the typical problem is with dolomite etc brakes, nice servo, tiny (spit sized calipers, smaller discs, even on the sprint!!) brakes. Feel great, until they have had enough, which can be easy to do especially on downhill stretches)

Link to comment
Share on other sites

Clive, my servo didn't work for years, I wasn't bothered. My brakes seemed OK. Eventually the servo started leaking brake fluid into it's vacuum chamber and I was forced to replace it. What a difference! Wow! Astonishing. To get the same braking effect without a servo requires a Very heavy foot and I mean stamping on the pedal. It's not until you have the servo you realize how efficient the brakes can be and what effort is required to replicate servo braking.

 

I have the larger bore master cylinder, it's only a fraction of an inch bigger. At one point I thought I had a problem and replaced it with a friend's smaller bore spare, there was little difference except the action point was further down the pedal.

 

All this is sharper in my mind as the servo on my modern has failed :( leaving the car almost un-drivable, until the garage can fit it in.

Link to comment
Share on other sites

I like a servo i can drive in me slippers  

 

on the 2000 its std.  it failed on its first weeks outing but managed to miss the bus on the roundabout

 

 on the Vit6  1600  we had  GT6 calipers, mintex 1144 pads and a servo ....  impressive,  tenacious and effort less

 

its all down to preference  

 

Pete

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share

×
×
  • Create New...