Mac Allan,

You might want to check that all of the pads are able to move cleanly. The XJS is quite over-braked at the front end so even a sticking caliper piston can go relatively unnoticed and the car still pull up straight.

I had the "not quite right" feeling some years ago after replacing pads. I should have guessed as they were very tight to put in. After a while, I removed the new pads (with great difficulty) and realised one was really binding at the top and bottom of the caliper. I filed them down, cleaned up the caliper mount slot a bit better and normal service was resumed.

Cheers

Paul

 

This is a very good point, and applicable to all models with the Girling four-pot front callipers, regardless of engine size. I always ease the width of new pads on my band sander, as they are always too tight a fit in my view. I once had a friend's 3.6 which had been so badly and expensively looked after by a West London place it was shocking. The front pads had been knocked in place with a hammer as far as I could tell, resulting on no braking at all on one side of one disk, and very uneven braking on the others. It took a calliper off job and a watchmakers' tool (cold chisel) to get them out!
Greg

 

That's a good idea, I'll take a look later today.

 

I'm not nuts!

Wait, let me rephrase that... I'm not crazy on this particular topic. It turns out there were two contributing factors.

First, when I re-bled the brakes, there was a tiny bit of air still in the line, and I do mean tiny -- three micro bubbles on one side, and two on the other. Not enough to make the pedal squishy or effect overall stopping power, but enough to require a little more pedal effort to engage the calibers.

Second, was my idle was too high because my tachometer was off, something I've been trying to figure out for awhile but discovered the solution:

https://www.jaguarforums.com/forum/x...curacy-156808/

When I did the brake pads, it was the same long weekend that I had ventured into Death Valley and to do the plugs, wires, new disty cap, rotor, etc. So by the time I was ready to do the run-in of the pads, the engine was running smoother and better, and when I adjusted the idle to an indicated 700rpm, it was actually running closer to 1200rpm. I've been fiddling with the idle ever since, because I could tell it wasn't right, but couldn't figure out the sweet spot.

So the higher idle also contributed to the brakes requiring more pedal effort to come to a complete stop.

Thanks to everybody for your help and suggestions. The Bosch QuietCast pads still feel a little different than the prior pads, but I no longer have a funny feeling that something is wrong and should be figured out.

 

Mac , I'm glad it all worked out well for you , how ever I need to keep a commitment I made in post #20 , If that's OK with you .

Doug , I hope the pictures below explain better than I did how disc rotor lipping can affect pedal feel .

The first five pics show the top and bottom lip , curved
The square edge of the disc pad
The disc pad trying to sit flat , but can't because of the curvature of the lips .
















The next two pics show how the disc pad will sit flat on a new or machines rotor .







The second most common cause for disc rotor machining is to remove those lips , as long as they are with in specs .

Cheers Doug ,

Sid

BTW , these photos were taken this morning , they are not from any internet sites .

 

Thanks!

Now I get what you mean, and entirely agree. The pad is not sitting on a fresh, flat surface.

The part that had me confused was when you mentioned the pad was "...sitting on the lips", which isn't exactly the case. The pad sits on the uneven surface between the lips.

Cheers and thanks
DD

 

Quite OK with me. Particularly impressed with your third photograph and how it illustrates your point, so much so that I'd like to amend my last post to say that that there were three contributing factors, not two.



Thanks for taking the time to demonstrate your point.

 

I also see your point now and had the same confusion as Doug but, looking at the second picture the disc was probably junk anyway.

 

Well I'm glad that's cleared that up , thank's Doug and Mac
Yes Norri , you were spot on , those rotors were under size .

cheers