Technical Punto TD60 Brake Binding Problem

[lionsden]

I have a problem with brakes on a Punto 60 TD 1998 (Mk 1). The car is a diesel, and the brakes I gather are not the same as the petrol model.

When pressure is applied to the front pads, (brake depressed), the brakes operate, but pads do not release pressure when pedal is released. Rear brakes operate normally, releasing pressure on drums when pedal is released. (Note: the car is on axle stands for these tests). Handbrake appears to be OK.

The front flexible hoses to the brake callipers have been replaced, and one of the brake callipers (left – passenger) has also been replaced (due to possible wrong diagnosis of this problem by a local garage). Due to various work done, the brake fluid has effectively also been renewed.

Before I commit to replacing the brake master cylinder, does anyone have any suggestions as to what might be causing the problem, other than the master cylinder?

There does not appear to be any problem with clearance between the pedal/pushrod and the cylinder plunger/pistons – the pedal appears to be releasing correctly. Tapping the master cylinder when the pads are locked on, has no apparent effect. (My master cylinder happens to be the not so popular stubby Bosch one I believe – not cheap to buy – quoted €170 + VAT here in Ireland - hence my concern re correct diagnosis.)

Question: if the problem is with the master cylinder, why do the rear brakes not bind also? BOTH front brakes bind – given the split diagonal pipe layout, I would have assumed that a binding front left would have given rise also to a binding rear right?

Any advice?

Thanks in advance. Aidan.

 

[Ziggy122]

Strip the whole front brakes down
Clean those sliding areas where the pads sit in the calipers
Put some Copper grease or a lubricating grease on these sliding pins

The cleaner they are the better the grease can work

See if the Brakes release better
Failing that - there is a problem with the Return with the piston seals
or as said the master cylinder isn't sucking back the fluid as such.....

Ziggy

 

[lionsden]

Thanks Ziggy

The current pads are new and fitted only a few days ago - due to the binding, one set (passenger) were "burned away" - so both sides replaced, and copper greased - I don't think they are the problem.

You mention seals - do you know is it possible to get a seal kit for these cylinders? I suspect not, as the Fiat dealer never mentioned it.

Looks like Master Cylinder then ....

Aidan.

 

[Ziggy122]

if the Piston Seals are hard and aren't retracting the pads that could be the cause of the problem
As pads always sit just Ever so slightly against the disc, hence when you put your foot on the brake its instantly there

If the master cylinder is shot, it'd hardly apply the brakes for you

The Slider Pim / Pins definatly Not bent and free to slide?

Ziggy

 

[lionsden]

I don't think it is the slider pins - I replaced the pads (new) myself a few days ago, with a smear of copper grease, and before applying brake pressure, checked that they (callipers) moved freely. One side (passenger calliper) is new (reconditioned, fitted by garage a few weeks ago) and should not have any problems. Also, BOTH front wheels are binding - what is the probability of TWO faults on front wheels simultaneously?

What continues to puzzle me is the fact that rear wheels do not bind. If it was the master cylinder, why are there no problems at the back?

Will go out again this morning to re-investigate.

Thanks again Ziggy .....

 

[fingers99]

May be worth investigating the interchangeability of master cylinder/servo units. The ones used on the petrol cars are very cheap (you could get the whole unit from a scrappy, bin the master cylinder and buy a new one). Last time I bought a master cylinder, albeit one for a Cinquecento -- it cost less than 20 quid.

Big Mick at eurocarcare in Derby (they're on Google) or brakepartsUK (likewise) may have ideas re. a master cylinder rebuild.

 

[thelad]

Has it go ABS?