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Brake Pedal Travel


NevSpit
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Spitfire MKIV 1300

 

Morning all, went to take the Spitfire out for a drive after about 3-4 weeks sitting in the garage. However, when I press the brake pedal it travels further than normal (it does stop the car) each successive press firms it up a little and after 3-4 all is back to normal but when rested for a few seconds the processes is repeated.  Having had a look around the forum I have left the pedal wedged down for now but am wondering is this a master cylinder seal issue?  At present I can see no leaks around the master cylinder or calipers (not checked rears) and the reservoir is full as normal. I have not carried out any work on the braking system for some time so nothing changed in that respect that could have introduced a problem.

 

Any wise and wonderful words from you knowledgeable folks appreciated as always.

 

Thanks Paul.

 

 

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Hello Paul.

 

Until the wise folk pitch-up, I will throw my pennies in to the hat !!

 

Are you running an after market servo or is there any servo fitted ??

 

I would check the rear wheel cylinders to ensure all is bone dry there and worth pulling the rubber caps back to check it looks okay. Whilst there ensure the shoes are free to move about and that they are adjusted properly - quite often the fault can be this.

 

If they appear okay I would visually check along the brake line for any brake fluid around the unions.

 

If all okay there we are dealing with either the caliper, flexi brake pipes and the master cylinder.

 

How old are your flexi pipes ?? They can collapse slightly and when you drive and brake with earnest, does the car the car pull up in a straight line without pulling of fish-tailing ?? If that test proves all fine then we are probably left with the master cylinder.

 

Even though you can see no fluid, it does not mean all is okay and it only takes a minor escape of fluid to experience what you are currently finding; in fact the drop in the master cylinder fluid may be so slight it can go unnoticed by the naked eye.

 

In addition the spring and or seals in the master cylinder could be sticking and this might also create the current situation

 

Any ingress of air anywhere in the system will cause a weak pedal, which is rectified by pumping a couple of times but of course is no cure !!

 

If you are methodical in your approach, I am certain you will identify the fault.

 

Check everything and leave the master cylinder strip down until last.

 

Hope the above assists ??

 

Good luck.

 

Richard.

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Hi, 

 

It does sound like a classic case of air in the system.  Obviously one can't diagnose how the air got in without seeing the vehicle.  Do you know someone at your local area meetings who you could call on to assist?

 

I am not sure why you'd leave the pedal wedged down (some do this for the clutch, to prevent seizing) but for the brakes, you don't really want the pads and shoes sticking to the discs and drums (thats why you shouldn't leave a handbrake on for extended periods).

 

One thing's for sure though, as it's your brakes, on a safety note, please don't drive the car until it's fixed!

 

Let us know how you get on.

 

Tom 

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Hello Tom.

 

The idea of holding the pedal down for a period of time is so that the pressure applied gets rid of the last few microscopic air bubbles; although this technique is normally only deployed when the system has been bled - be it brake or clutch.

 

That said, 12hrs is normally sufficient but certainly no longer than 18hrs. Without a doubt the technique definitely assists the firm pedal goal.

 

I think in Pauls case, the application of such will not assist the current dilemma.

 

Regards.

 

Richard.

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Hi

 

I had similar symptoms in a that the brakes were soft until pumped with no obvious leaks anywhere. I tried all the methods above. Slowly it developed into a leak around the master cylinder so I changed the seals.

 

All was great for a short while but then the soft pedal problem returned and a month ago over Christmas I noticed another leak around the master cylinder.

 

I don't know if it was poor quality seals but decided just to replace the master cylinder.

 

Brakes are firm once more. I guess I will see if they deteriorate now

 

 

Hope that helps a little

 

Aidan

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Aidan.

 

I had a slight problem with fluid loss on the clutch master. last year.

 

In my younger days I would strip the master cylinders down and do all that was required; now I just replace the unit and get on with my day !!

 

You are spot-on to highlight poor quality items; there are some excellent suppliers out there so worth making enquiries to establish such. Needless to say the Club Shop is an excellent outlet to start with.

 

Regards.

 

Richard.

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as the travel increases when parked for a period its a classic case of excessive front hub bearing end float, the weight of the car with too much float gets the brake disc to push back the caliper pistons , so every time you jump in you get a low pedal, pumpt hthe pistons out and hey presto its fine ...till you leave it for a while   put your knees against the  tyre and press/knee the wheel inward there should be a small dtectable shift , not a good rock  on the wheel.  if it feels positive its too much 

 

spec is 0.002" - 0.008"  but  best  jack it up  take the cap off , remove the split pin  nip the nut to light hand tight nip,  and back it of 1 full flat refit the pin and grease cap

 

Pete

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Thanks for all the replies, much appreciated.

I un wedged the pedal and will try again to see if the issue persists - expecting it to. Looks like a full review is on the cards as Richard suggested, apart from replacing both calipers and master cylinder seal kit about 3-4 years ago nothing else has been replaced so new flexi pipes could be on the cards. There is no servo fitted and don't worry it's safely tucked up back in the garage as i prefer the brakes to stop me rather than anything else.

Paul.

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  • 2 weeks later...

This ​may be​ is a bit long-winded, please bear with me. I changed my brake calipers before Christmas and have had problems since with brake pedal travel. On the first push of the pedal, the travel was too much but they did bite and have a solid "feel" to the pedal. Give the pedal another push and it was spot on, however the next time the brakes were used it was the same again, too much travel. I tried bleeding the brakes with a vacuum bleeder; I found that it was drawing air in around the bleed nipple and need a smear of silicone grease around the nipple to stop it. I then tried a standard one-way bleed valve, got over adventurous and clicked the brake valve out of position. While putting this right I decided to replace the rear drums, there was a good degree of ovality. Success there, handbrake fine but still the dreaded excess travel. I've tried checking the wheel bearings and leaving the pedal under pressure overnight but no joy.

So today I thought I'd try a different approach, have a look and see if there was anything obvious. The first thing that I noticed after taking the wheel off was that the pads were clear of the disc, half a millimetre maybe? Pumping the pedal while watching the pads, I could see the pistons easing back. Taking the pads out one at a time, I've pumped the pedal, nice and easy, to move the piston in and out, to get a bit of fluid on the bores and further in to the seals and it has worked, we now have a fully solid pedal and the brakes are superb, problem solved at last. All that grief and it ended up taking an hour to sort...

A few thoughts though...  I wondered if anyone has come across this before? Perhaps the calipers had been assembled with very little lubricant on and the seals were rolling instead of sliding  in the bores? Could this be another reason why leaving the pedal under pressure works for some, lubricating a dry seal where it contacts the bore? I made the big mistake of getting stuck on one line of approach. My apologies for the length of this but I did want to pass it on and any comments would be interesting.

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Interesting so it is pad pull back but not end float

 

are you realy sure the disc had not pushed the pads back so when jacked the gap appears

the piston seals should give some retraction but not enough to give a gap

 

all very useful next time this problem pops up

 

nice to have a solution

 

pete

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Going back to the original question, I'm a bit surprised to be the first to suggest rear brake adjustment might be in order. It's easy and cheap, and need for adjustment can cause the very symptoms described. If that doesn't work (all of 10 minutes' work), then by all means start checking the rest of the system for leaks and/or other faults.

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Yes very valid many a car has the handbrake cable snarled up which opens the shoes away from the wheel cyl pistons and gives lost hydraulic travel .

 

the base setfing is to disconnect the cable from the cyl levers then fully lock the square expander up to

lock the drum , reconnect the cables with the wheels at ride height , not left hanging adjust the cables to a nice but not taut fit then back off the expander to free the drum .

always best done with the wheels on to get a better feel of free.

 

pete

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Hello Herald948.

 

I mentioned your point on my first reply #2.

 

I would check the rear wheel cylinders to ensure all is bone dry there and worth pulling the rubber caps back to check it looks okay. Whilst there ensure the shoes are free to move about and that they are adjusted properly - quite often the fault can be this.​

 

​Needless to say it is worth mentioning again because excessive brake pedal travel can occur from out of adjustment shoes.

 

Regards.

 

Richard.

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Hello Herald948.

 

I mentioned your point on my first reply #2.

 

I would check the rear wheel cylinders to ensure all is bone dry there and worth pulling the rubber caps back to check it looks okay. Whilst there ensure the shoes are free to move about and that they are adjusted properly - quite often the fault can be this.​

 

​Needless to say it is worth mentioning again because excessive brake pedal travel can occur from out of adjustment shoes.

 

Regards.

 

Richard.

Indeed you did Richard; my apologies! It's just that I read so many plausible yet (IMO) less likely subsequent explanations and fixes for same (no offense to anyone; they were all logical possibilities!). I suspect you and I might be alike in trying first to address the most logical and/or least expensive fixes! :D

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Sadly work and life (as well as the temperature) have gotten in the way and I have not been able to investigate to date. However, the comments on front disks looks interesting so will probably take a look at that first then the rears - the latter were all adjusted last year when I finally got the handbrake to work better so would hope they are ok but you never know...

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Dave.

 

Personally, any fluid no matter how little or much that appears on the outside of where it should be in the hydraulic system has to be viewed with suspicion. If fluid can exit incorrectly then one must assume that air can enter equally.

 

As I mentioned earlier in this thread, I no longer bother with replacement seals and just get a new unit. Safe brakes or no brakes - it's non-negotiable for me.

 

I accept fully that many owners do use rebuild kits and all is fine, it's just a personal choice, that's all.

 

Part of the problem also lays with the quality of significant components these days, which may accelerate seal wear if the bore is below par as a result of sub-standard manufacturing.

 

Regards.

 

Richard. 

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Its the wiping effect of the seal lip there has to be some film left to lubricate or the seal wont last long

 

On warranty examination any wet was normal and expected, if removed from the truck for this damp

easilly seen residue under the boot the claim was thrown out by the manufactures

 

So you can blame the experts Ha!

 

If it spills out you have a problem

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  • 1 month later...

Well I finally managed to get some time to look at the Spitfire brakes today, sadly the Mini has been the priority lately given it is the daily driver and was calling for the welder and spookily some brake attention (brake gremlins have it in for me lately...)

 

Anyway, I went round the whole system checking the points that people had suggested: rear brake adjustment, front pad movement / gaps, weeping seals etc and nothing obvious. At the last MOT the tester suggested I nip up the n/s front bearing so given that and the advice above I did so by one flat, as I said though there didn't appear to be any pad movement evident and it wasn't a problem before. I also enlisted the wife and bleed the brakes as well.

 

End result - problem has gone away !  Not sure if it was the brakes being bled or the nipping up of the bearing reducing movement but at least for now it seems to have done the trick.  I will leave it a couple of days and see if the problem returns or not as originally I put the car away fine one night and the next time (not too long afterwards) I had the problem.

 

I also took the opportunity to wield the grease gun at the back and oil the trunnions at the front so another couple of good jobs ticked off.  Feeling pleased with oneself I had a play with the wiper motor checking connections and then taking the motor off for further inspection - I think I might be back later for some help on that one....

 

Many thanks as always for all the help and advice.

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