Hi All -


Posting in general tech because I think this might be applicable to lots of models.


I just got started taking apart the brakes on my '94 XJ12, and right away, I'm wondering if I'm doing something wrong.


Full disclosure, this is my first Jag, and this is the first attempt to work on it. So, I have to presume that I'm missing something.


Here's the issue. The calipers are held onto the car by 2 bolts. Even after applying significant force, hammering on the wrench, and dousing them with penetrating oil, these suckers just will not budge.


Is there a trick or a technique that I'm missing?


FYI, once I get further into it, I'll post a thread in the XJ12 section about all of the stuff I'm doing to the car.


Thanks - BS

 

there is no trick, try to use a pneumatic impact tool with the relative socket to undo them

 

Just to confirm the model - it's the XJ40 with the V12?

One more question - are you doing the front or the rear brakes?

The basic setup is similar for front and rear:



The caliper Carrier (arrowed in blue) is secured to the vertical link by two bolts (circled in blue). It carries the Brake Caliper (arrowed in red) which is secured to it by two Guide Pins (circled in red).

When the brakes are applied the Caliper piston pushes the brake pad in front of it, towards the Brake Disc. This movement forces the caliper housing to move along the Guide Pins in the opposite direction of the piston to apply the second brake pad. The brake disc is therefore gripped between the two pads. As brake pressure is increased the grip on the brake disc is increased to slow down the rotation of the road wheel.

The Guide Pins must be removed first and the Caliper separated from the Carrier. There is no need to remove the carrier for a pad change unless you are also replacing the Brake Discs (rotors).

Graham

 

Hi guys -


Thanks for the responses, and the diagram.


Yes, the car is the V12 XJ40, the one with the single rectangular headlight on each side.


I am changing out the rotors as well, so I do need to take everything apart.


So the disassembly order is first guide pins, then the bolts, correct?


Two more questions - what is the source for that diagram?


And do you have any non-air-tool suggestions for the bolts? I suppose it won't kill me to buy a compressor, but I've got limited garage storage space for one.


Thanks again!

 

I took the diagram from the Jaguar Parts Catalogue and edited it to remove everything not relevant to the fixings.

Disassembly order is Guide Pins first, Caliper and Pads slid out then the Carrier bolts. This is the RH rear brake on my XJ40:



Have something available to support the Caliper to avoid straining the flexi hose. Here I have it (arrowed in red) standing on a block of wood. The Carrier (arrowed in blue) is ready to be removed and, as you can see, there's plenty of space to work with the Calip0er out of the way.

The Caliper bolts are often tight but I've never been defeated using a socket on a 2 foot breaker bar. Standing on the end of the bar cracks them loose.

Graham

 

First try to hammer the bolts, if you still cannot undo them, then put the socket (a black impact socket with six pockets) on and hammer the socket while you try to undo the bolt(s).
Axial hammering only.

 

Hey all -


I actually bought a battery-powered electric impact wrench.


Frozen bolts off in about 6 seconds, just like butter!


Now I know why pro mechanics use these things all the time. It's like a magic wand... Apply to bolt, press button, and PRESTO! the bolt is off.


I wish I had bought one of those YEARS ago...


So, anyway, the caliper is off, and I've started disassembling the suspension in order to replace the brake hoses, calipers, brake pads, tie rod ends, ball joints, sway bar end links and sway bars.


This car is going to drive like a new car once I'm done. At least that's the plan.


Cheers - BS

 

Electric impacts are great for home.

Don't forget the anti-seize so you don't go through this again.