Excessive intermittent pedal travel

[dieselpower]

Hello all,

My 1983 V12 has an intermittent problem. When you start off driving all is good and the brakes are positive and pull the car up in a nice straight line. After driving around for a while, maybe 20 mins or so all of a sudden you come to use the brakes and there is a massive travel in the pedal before the brakes bite. This is most disconcerting and is making me a little nervous of driving it. Any advice much appreciated. I must add that after driving for awhile further the problem can vanish as mysteriously as it appeared. Only to reappear again later.

[ptjs1]

Diesel power,

It could be a number of things. However, XJS cxn be prone to knockbck of the pads which then needs a bigger pedal movement on first application again. I would strip the front pads out, and ensure that the caliper pistons are fully moving, then check for any distortion of discs using a simple run-out test.

Remember, under NO circumstances, let any fluid get pushed back in the system if you remove the pads and exercise the calipers. Undo the bleed valve, and connect a pipe to let any fluid bleed out. Top up the reservoir as necessary.

Good luck

Paul

[dieselpower]

Thanks for the advice. It's all a bit beyond my simple capabilities I think. The car is going in to Surrey Jag Centre in a few weeks for HT leads, dizzy cap, rotor arm and new plugs. I think I'll ask them to give the brakes a once over when it's there.