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Old 29-07-2017   #1
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rubbish brakes---any sensible suggestions?

I could do with a bit of input please ladies and gentlemen. My 500 has been residing in a body shop for the better part of 6 months whilst incredibly bad previous work (can't really, in all honesty, call them repairs) was being rectified. Everything now put back together, but very poor brake pedal. Have subsequently renewed brake master-cylinder and front wheel cylinders as these ended up being drained and therefore 'exposed'--still rubbish brake pedal. then replaced rear wheel cylinders--still rubbish brake pedal. And yes, before anyone asks, I did run it up and down the road--ahead and reverse, stamping on the brake pedal. I even tried doing the same trick with the hand-brake in case poor adjustment of the rear shoes was the cause--still got rubbish brakes. I then tried another (also brand new) master cylinder--still got rubbish brakes. As it was 8.30pm by this time, 'er indoors decreed that it was a mite late to go blasting up and down the road (the exhaust is---'throaty!'), but the brake pedal is hardly any better. There does not seem to be any loss of brake fluid, but it is proving difficult to get all the air out of the system--particularly at the front brakes. I am wondering--as the front flexible hose were also drained of brake fluid and therefore exposed to the atmosphere, could these be the cause of the fault? I have checked the hoses for bulging etc. and there seems to be no external fault with them, but could they have been damaged internally by being exposed (with a residue of brake fluid in them?. I would be very grateful if anybody can come up with suggestions as to why I have this fault. I am trying very hard to have the car ready for the 'Festival Italia' at Brands on the 13th August where I have been invited to have it in the Middle Barton compound (and drive it round the circuit!)
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Old 29-07-2017   #2
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Re: rubbish brakes---any sensible suggestions?

I had similar problems with my brakes, difficulty in bleeding the air out of the system as the flow of fluid was restricted. Changed all flexi hoses and then perfect, the hoses can perish from the inside and close up restricting flow whilst looking ok on the outside.
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Old 30-07-2017   #3
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Re: rubbish brakes---any sensible suggestions?

Does the pedal pump up, indicating air?

If you clamp the rear brake hoses does the pedal feel any different?

If you clamp the front hoses does the pedal feel any different?

Have you tried bleeding the master cylinder on it's own by slackening the master cylinder pipe unions while a helper presses the pedal. Tighten the unions at the bottom of each stroke. Then re-bleed the whole car. You could also try jacking each end of the car up to help any trapped air reach the highest point (bleed screw).

Has any work been carried out that may have affected the pedal free play (unlikely)?

Are you sure your adjusters are working properly as they seem to be a weak point on these cars?

I've just replace all the hydraulics on my 500F including hoses and pipes. I haven't driven the car yet, but have excess pedal travel. I've determined that the adjusters on my new shoes will have to be set by driving the car and slamming the brakes on a few times. The master cylinder diameter is very small on these cars so any excess clearance at the shoes will lead to lots of pedal travel.

You may have a problem at the hoses, but in my experience any internal damage usually leads to the brake locking on as the pressure of the fluid returning from the wheel cylinder is less than the pressure going to the cylinder when you brake. The hoses are cheap enough so if they're past their best it's best to replace them.
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Old 30-07-2017   #4
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Re: rubbish brakes---any sensible suggestions?

Tom - you described a problem when you fitted the uprated master cylinder- that sounds similar to the problem you have now?
Have you checked the condition of the brake pedal pin? If its worn - you will not displace enough brake fluid....just a thought.....
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Old 31-07-2017   #5
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Re: rubbish brakes---any sensible suggestions?

Thank you Andrew, Hobo and Berkeleyman for your input and advice--much appreciated. I am going to start by renewing the flexible hose, and take it from there. With regard to the 'miniservo' master-cylinders Andrew, my colleage couldn't get any of them to work, including mine which I sent down to him to try and help out with a situation. I will be putting a thread onto the Forum very shortly, describing our experience with various companies, and our total lack of success!!
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Old 01-08-2017   #6
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Re: rubbish brakes---any sensible suggestions?

I had the same issue - rectified with an adjustable pedal pin.
I remember reading of others experiencing this issue that you have and the pin being the culprit
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Old 01-08-2017   #7
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Re: rubbish brakes---any sensible suggestions?

That is interesting to hear how you got the 'Miniservo' master-cylinder to work Andrew----did you make a longer pin or buy a 71mm (length of actual rod, excluding head) pin?
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Old 01-08-2017   #8
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Re: rubbish brakes---any sensible suggestions?

I bought a 10mm clevis pin and turned 10mm stud to a radius end following the profile of the master cylinder piston - and screwed it in to give the perfect pedal travel.
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Old 04-08-2017   #9
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Re: rubbish brakes---any sensible suggestions?

Hobbler,

I had this a few weeks ago, and couldn't for the life of me figure it out. I'd pumped about 2 litres of fluid through with no bubbles but the pedal was still on the floor.

I'm 99% sure this will sort your problem if you have fitted new pads and springs too.
The springs supplied are too strong for the auto adjuster to work, they just pull the pads back to the centre and this away from the drums.
Take each drum off, and using a workbench (or similar) stretch the brake springs - only say 2 inches - but enough to give them a slightly less bendy feel to them. Mine ended up circa 5-6mm longer than before. Refit the springs and pads as before, and using some grips on the circular adjuster you can turn this to push the pads out a little too. you should notice that they aren't pulled back fully to the centre now as there is less pressure from the springs. Keep checking with the drum to get the adjusters there or thereabouts so you can get the drum back on. Do this on each wheel and you will have super brakes
You can test if this spring issue is the cause just by checking one wheel first.

My brakes are great now - travel is about 1 1/2 inches in the pedal before it is solid!!!

If only my bloody engine worked....

I bet you a shandy this is whats causing it.

Chris
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Old 04-08-2017   #10
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Re: rubbish brakes---any sensible suggestions?

Quote Originally Posted by AndrewHarvey View Post
I had the same issue - rectified with an adjustable pedal pin.
I remember reading of others experiencing this issue that you have and the pin being the culprit
I had pretty much the exact same issue here. It was driving me nuts. I replaced basically the whole braking system and still had no brakes. I took the pin off the pedal and it was pretty worn. My friend welded a small piece of metal to the tip, ground it down a bit, then smoothed it out and my brakes came back. So now if I stomp on the brake pedal hard my wheels will lock up and I can go into a skid. This was not possible before I fixed the pin issue.
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Old 04-08-2017   #11
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Re: rubbish brakes---any sensible suggestions?

Lengthening the master cylinder pin is not good, as it will potentially push the valve carrier too far into the cylinder and cause damage.

It seems as though the newer brake pads and drums are a little further out of tolerance than the original parts, all made worse by the overly strong springs in the brake kits!

Its really worth checking this before doing any mods on the master cylinder / pin.
Mine is on the original pin and it has very little travel now to solid braking.

I was extremely sceptical about this too, but after wasting several weekends pumping fluid through, and trying everything I could under the sun to get the bloody things to work. I stumbled upon this somewhere on the net, and thought I'd give it a go. It took literally 45 mins and the brakes are now perfect!

Chris
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Old 04-08-2017   #12
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Re: rubbish brakes---any sensible suggestions?

I have no standard (everything)
There is two different length pins one for 500 one for 126.
My updated master cylinder would not work - I don't know if it was made for a 500 or 126 BUT with a lengthened pin all is good.
If the wrong mix of 500 and 126 parts are used the pin maybe too short.
Worn pins are another tale....
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Old 13-09-2017   #13
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Re: rubbish brakes---any sensible suggestions?

Chris and/or others

I know this is a slightly old thread but as I am now facing the situation mentioned I just want to ask a couple of things.

I have been round and replaced all the brake shoes, springs and wheel cylinders. Everything seemed to be back together OK but I was struggling to bleed the system (first timer!) so I got a local mechanic to check everything.

Anyway, as per hobbler's original post, the brakes are pants (apologies to non-UK readers...that may not translate ). Worse than they were before with long travel and poor stopping power (although no longer pulling to the side). There are no leaks etc and pumping the pedal makes no difference.

So I am interested in the solution proposed by Chris but...
(1) are you saying essentially to go back to removing the drums and shoes and try to stretch the springs? Considering, as a novice, it took me about half a day for each wheel I am a bit reluctant to do this but will if there is any way to check that the over-strong springs are the issue; also, removing the front drums again will require yet another new hub nut I assume
(2) How easy is it to stretch the springs? Especially for a home mechanic with limited tools/workbench.
(3) Fundamentally and for my education I am trying to understand why this would solve the issue; my simple mind says that if the springs are too strong and so pulling the shoes away from the drum, then their efficiency shouldn't be affected...it just requires a harder and possibly longer push on the pedal to compensate (i.e. I don't quite understand how it impacts the efficiency)

As a related question (and I know there are other threads on this)...in words of one syllable how easy is the disc brake modification (within the scope of a novice?)?

Any advice/help gratefully received as always.

Cheers

Andrew
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Old 13-09-2017   #14
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Re: rubbish brakes---any sensible suggestions?

I replaced my entire braking system and had the same long brake pedal problem. The car didn't inspire confidence, especially on the hills of South Devon where I live!

The problem is caused by a combination of poor quality adjusters on some of the replacement shoes and over strong springs. I carefully stretched my springs and was rather sceptical about the modification making any difference. I got into the car and the brake pedal was now nice and high with an inch or two of free play. I took the car for a test drive and the brakes are now great.

There's a link here to a posting on the Fiat 500 Owners Club forum

http://www.fiat500club.org.uk/clubch...php?f=1&t=7934

The springs can be easily stretched with hand tools. Clamp one end in a vice, place a screwdriver shaft in the loop at the other end and stretch. Take your time and don't over stretch them.

I agree with the comments in the link above, and have come to the conclusion that the weaker springs allow the shoes to adjust to give the correct drum to shoe clearance, and and less pedal pressure is needed to push the shoes against the drum.

Long pedal travel is an MOT failure and is dangerous. If a slight hydraulic leak was to occur you'd have no reserve travel on the pedal to bring the car to a halt.

You should replace the hub nuts, but as a temporary solution you could use a flat oil stone, or some Emery cloth on a flat surface to sand the back of the hub nut to remove a couple of thou. When the nuts are torqued down you should have a fresh section of the nut adjacent to the staking groove.

I can't comment on disc brake conversions, but have no plans to convert my car as I'm now very happy with the drum brakes and their stopping ability.
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Old 13-09-2017   #15
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Really don't know what is the problem but just want to mention that when I removed my aft flex hoses it was impossible to pass a piece of wire through the hose meaning that it was kind of blocked. So better start with a new set of hoses and then do any spring modifications. Just my two cents
Thomas
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