Brake imbalance

[stretoo]

My car pulls right on braking (and only when braking). The 4 pot calipers are 1 year old, the hoses and the dampers are new. What are the potential causes of this imbalance and how to fix it? Thanks in advance for your advices.

[christopher storey]

The first and obvious candidate is a seized piston, and unless the pedal is soft this is the first thing I would check. If, however, there is softness or long travel of the pedal, then I would suspect air in one of the left hand circuits, and would try bleeding which particularly at the front is a five minute job

[PeterCrespin]

As Chris says, try bleeding, but with one year old calipers I'd first satisfy myself it wasn't steering alignment. Of course if you have to pay someone to check your tracking but can bleed your own brakes for free, then Chris's advice makes more sense.

If you can't practice E-type abstinence during the winter months (you wouldn't be the only one) then it could well be a sticking piston. I don't enjoy car-use interruptus, and the poor dear has the scars to show for it.

[stretoo]

When I take my hands off the wheel (and not braking) the car goes straight so can it be bad tracking anyway?
The pistons are in stainless steel and the fluid is 8 month old so I don?t think they could stick, could they?
I?ll go for bleeding the brakes first as recommended by Chris and see what happens. I noticed that when pumping a bit the pedal becomes harder so there is probably air in the circuit and I?ll have also to check where the air can enter it.
Pete I totally agree with you so I drive my cars all year long to avoid such problem. I experienced sticking pistons once when driving to Le Mans Classic 2004 with my AM DBS because I hadn?t been able to drive it for 6 months and forgot to change the brake fluid (punishment: front brakes rebuilding) that was a good lesson learnt.

[Heuer]

Have you checked the pads? If one side has become contaminated for some reason you will get an imbalance. Worth taking the fronts out and check the state.

Have you checked the front wheel alignment? This can cause all manner of odd behaviour as Angus can testify with my car. The toe-in was way out on one front wheel (after it had returned from service ) but we all thought it was a rear shock absorber at fault.

Have you checked the front ARB bushings? If one side is perished or damaged braking will cause the car to dart to one side.

Have you checked the front shock absorbers? A faulty one will cause havoc under braking as well as in corners.

[stretoo]

Have you checked the pads? If one side has become contaminated for some reason you will get an imbalance. Worth taking the fronts out and check the state.

Have you checked the front wheel alignment? This can cause all manner of odd behaviour as Angus can testify with my car. The toe-in was way out on one front wheel (after it had returned from service ) but we all thought it was a rear shock absorber at fault.

Have you checked the front ARB bushings? If one side is perished or damaged braking will cause the car to dart to one side.

Have you checked the front shock absorbers? A faulty one will cause havoc under braking as well as in corners.

Thanks David
I will not take the bushing and the shock absorbers (mentioned as dampers in my previous post) into consideration for the moment as they are all new.
You may be right about pad contamination; I have ordered a new set of Kevlar pads I wanted to change them anyway.
I had the front wheels/direction serviced not a long time ago but I do not trust the result (your experience shows there are some good reasons to be suspicious). My problem is to find a trusty classic Jaguar mechanic in my region.
As soon as I get the new pads I will bleed the circuit with new fluid, change the pads and then I?ll check whether it solves the problem. If there is no improvement I will have the front wheels alignment checked (if I can find someone to do so the proper way...). Would you also consider a faulty track rod end as a potential cause?

[Heuer]

Faulty or badly adjusted could do it. You should be able to take the car to any modern garage and get a laser wheel alignment done or do it yourself with one of these: http://tinyurl.com/bnaynxs

[stretoo]

I started with the simplest and the most obvious potential cause as stated by Christopher: air in the circuit.
I have bled the circuit. Imbalance now cured. I have also tighten a little bit more the pipe junction on the caliper hoping that it will be enough to avoid air coming back in the circuit.

[christopher storey]

Glad it's cured. Those pipe fasteners have to be astonishingly tight!