Hello all,

I brought my Series III out for it's first drive in a long time, and I immediately remembered why I chose this car for my upcoming grand tour. Even after languishing for six months, it still ran strong and rode soft. It even feels like it has better cornering ability than my XJ-S. Anyway, as the title of this thread implies, the one area it let me down today is braking. It has developed an issue where, when breaking, the car will brake, then lurch forward, then brake again, and so on. I can feel a rumbling in the brake pedal when this happens, as though the car was going over loose stones. The firmer I press the pedal, the less jerky but more rumbly the braking becomes. At first I suspected that one of the tires had gotten out of round, as the front right loses air over a few days and has been flat for months. However, at all speeds the car rides smooth, with none of the up and down or rumbling associated with out of round tires. It's only when braking that this occurs. The car also doesn't wander, and it steers just fine. Any ideas on the matter?

This problem and all others the car has will be tackled in a few months when I have my Jag man go through the car inside and out, replacing, repairing, and/or refurbishing anything that has failed and/or could fail in the next 25k miles, along with correction of all paint and body imperfections and a thorough rust removal and prevention. However, as I wish to use the car in the interim, I'd like to sort this problem now. It's not disconcerting, as the car does actually stop. However, it is quite annoying.

 

My gut feeling is that you have a leaky caliper. Brake fluid on the discs and pads can cause what you've described. A visual inspection should be enough to tell in this case.

Warped brake discs or irregular friction surface of the discs can cause a shudder or pulsation in the brake pedal. This would not be something you can visually inspect for

Friction material transference from the pads to the discs can be mistaken for a problem with the rotor as the pedal pulsing/shuddering is the same. Sometimes you can actually see evidence of this on the disc....looks like dark splotchy marks

Cheers
DD

 

I see some speckling on the front left disc. I haven't jacked up the rear to check the rear discs yet. I don't think the discs look warped, and I can't think of anything that would cause them to warp. I pressed hard on the brake pedal several times, and I didn't see any fluid on the discs. In addition, the brake fluid reservoir is full. I'll check the rear discs soon, though I had the rear brakes gone through only a year ago.