Technical Newbie With Brake Trouble

[speedydan]

Hi all,

Firstly my name is Dan (speedydan) and I am the owner of a Stilo Abarth,
a blue 2002 model.

I bought the car as a daily fun runabout and really do enjoy driving it!

Now the problem! Sorry its a bit of a story but need to try and explain it the best I can.

I developed a problem with the n/s rear caliper, it had seized, so I decided to have it replaced.
This was fine, he said he bled the system for ages as they are notoriously awkward to bleed and all appeared to be fine.

I then drove it home, and the brakes seemed ok initially but then the pedal pressure started to fade spiradically, usually at the most inconvenient time possible.
I took the car back as i assumed it had not been bled properly but after having another go, the guy at the garage confirmed that no more air came out.

I have read somewhere that the car needs to be bled using a diagnostic machine, is this correct? If so, will this lead to brake pressure fading until the pedal is re-pumped?

Also, will this trigger the ABS/ASR linked fault or is this a separate issue entirely?

One possible explanation I have heard although can't really see as likely is that the master cylinder is on its way out? This was perfectly fine before the caliper replacement so think its unlikely.

Any help greatly appreciated as I am only a very amateur mechanic and being based in Gibraltar, there seems to be very few garages that can do more 'specialist' work and I seem to be being fobbed off!

Many thanks

 

[jim cooper]

First step is to bleed the whole system, not just the line leading to the replaced caliper. It is done in the order starting with the rear caliper farthest from the fluid reservoir, then the other rear caliper, then the front caliper farthest from the reservoir and lastly the front caliper nearest the reservoir. You don't need a diagnostic machine to do this but a garage with a pressurized fluid supply to the resevoir should be able to do the job quickly. If a problem still exists then another cause is evident. Did the guy fit new rear pads? If these are hitting a rust ridge on a worn disc outer edge you could get a spongy pedal.

 

[speedydan]

Hi Jim,

Thanks for taking the time to write a reply to my problem.
The whole system has been bled, he said he started at the rears and worked round to the fronts. He said he used a pressurised bleeding system and I have no reason to doubt him but its a possibility I guess.

That's interesting about the brake pads, they are not new but still lots left on them, the rear discs I know are getting worn, I remember looking at them a short time ago when I took the wheel off. I will check this out.

Assuming that the pads are ok and the brakes are properly bled, what other possibilities are there?
Could it be a faulty master cylinder or abs module?
Both sensors on passenger wheels have been changed due to the warning lights coming on but it now comes on and off intermittently and the brake pedal fault is always there so I wouldn't think they were linked?

Many Thanks

 

[saw]

should the hydraulic clutch be bled at the same time? just wondering (hoping its NOT the clutch) as its my first hydraulic clutch i have nfi

 

[Daveystrings]

Maybe one of the rubber brake lines got damaged and is bulging now and again, get a friend to pump the brakes hard whilst inspecting the rubber hoses at each wheel. Start with the one that the caliper was changed, maybe the mechanic damaged the line or something. While inspecting look for any traces of fluid either just in casey.

Alternatively the caliper slides along the 2 bolts that hold the carrier, this means that as the pads wear each pad (either side of the disc) wear evenly, however if this isnt sliding properly on a caliper then it could be causing the piston to extend further and give the feeling of a spongy pedal. This problem could be a bit trickier to find tho but its probably the caliper that was changed. That said if its a new caliper thats prob unlikely unless it was fitted incorrectly.

Just a couple of things to consider

 

[jim cooper]

Just one more thought. When a rear caliper has been replaced it is important to press the brake pedal hard quite a few times with the engine running and with the handbrake cable fully loosened. Afterwards tighten the handbrake cable (under a flap behind the brake lever) so that the required travel, say 5 notches, is achieved.

 

[speedydan]

Thanks for the replies, I have a few things to try from your suggestions so will have a go when i'm off work next week.
I still believe its a simple problem rather than something too complex so hopefully I can sort it!