I am replacing the front brake pads and rotors on my 1990 Jaguar XJS V12. I removed the caliper and put on the new rotor but now cannot get the lower caliper bolt back in. I have tried everything to line it up but nothing seems to work. The bolt goes through the first mount and the caliper but does not thread back in.

After about 10 tries and several hours I give up and really want to finish the job.

HELP !!

 

Hi MIFoodie

Without knowing exactly the way you went about this, I'll have to Start from Scratch in the hope that you will get one of those 'Lightbulb Moments'

Where you go doh! I never thought of that, or else maybe you did!

First take off the Caliper and try the Bolt in the Threaded hole of the Hub

Screw it in and screw it out again, so that you know that the bolt will go in without any problem

Assuming it does, then put on the Caliper and very loosely put the bottom bolt in first, then just tighten it up a little bit (just nip it up)

Then using a feeler gauge, measure the thickness of the Shim or Shims, needed for the Top Bolt

Which could be One or Two Shims

If you did up the Top Bolt without inserting the Shims, that could be the reason why the Bottom Bolt won't Thread up and go in

Anyway back to the 'Plot'

Assuming you know how many of those Shims you are going to need, next take out the Bottom Bolt and replace that Bolt with a Screwdriver which should then be the only thing that is taking the weight of that Caliper

Then remove the Screwdriver that you put in the Bottom Bolt Hole of the Caliper and Replace it with a Bolt and then do it up a little bit

So it holds the Weight of the Caliper (it doesn't even need to be nipped up) just enough to pick up the Thread and a little bit more

Then put a Small bend in the Shim or Shims and Slot that Shim or Shims into the gap where the Shim goes at the Top Hole

Putting a little Bend in the Shim, will keep it in position and stop it falling out, where as soon as you see the Hole in the Shim, almost line up with the Hole in the Caliper

Put a Screwdriver through the Caliper, The Shim and the hole in the Hub and use the Screwdriver to 'Jiggle' the Shim into position

Then take out the Screwdriver and put in the Bolt, then 'Nip' The Top and Bottom Bolt up Tight and check all is OK

On the assumption that it is, then Torque up your Caliper Bolts as per the Manual and finally Wire them up

You can see how I did mine on Page: 85 of my 'Cherry Blossom' restoration thread

And here is a Link to that Page: https://www.jaguarforums.com/forum/x...122634/page85/

 

Thanks for the details. The shims (2) were in the bottom bolt hole and I cannot get both shims in there and lined up with the bolt using the screwdriver as you suggest. If I try ti get in one shim I can get the bottom bolt to bottom out to the threads but it seems to not line up and grab the threads (even with 1 of the two shims.

I can keep trying as you suggest but hoped that there was another way.

 

The BEST way to replace the rotors without needing to rebuild or repair the calipers is NOT REMOVE THEM!!!!!!!!!!!!!!!!!!!

I just remove the bolts from the back side with a FLEX SOCKET and maneuver the rotors past the spindle.

I only made the mistake of removing a caliper ONCE!!!!!!!!!

The shims and resetting the toe alignment convinced me to find a different way.

bob

 

Just to check, and please excuse me if you know all this: there are two bolts, not the same length to attach the calliper. The longer one goes at the bottom. The lower bolt assembly order is:
Steering arm; shims as needed; calliper; and the bolt threads into the upright.


The lower bolt cannot bottom out into the upright if the correct bolt and assembly order is in place.


I would ensure the calliper has no pads in it yet, then (very important) loosen the steering arm top bolt a but (the one above the stub axle fixing)and then get the lower bolt started with everything loose. Once it is threaded into the upright a couple of turns, start the top calliper bolt. Once that is done, tighten the top steering arm bolt and the top calliper bolt. Then proceed as OB suggested.

 

Hi MIFoodie

Having replaced the Calipers on Three of my XJS's

I have never considered this as being a difficult job, although it could take the best part of a day, what with all the Torquing and Wiring up of the Bolts

The only other reason why you might be having a problem (that I can think of right now)

Is that you haven't dropped the Track Rod Ball Joint on the Steering Arm before you started

In my own experience (though maybe not of others) This can make Changing the Calipers a lot easier, as you can then pull the Hub round to get a better look at what you are doing

Plus it also gives you a lot more room to work, as does doing this job outside in the open

 

Thanks all !! I got the right front done and now going to start the left front with all my new found knowledge of what I am doing. Also, can't wait to tackle the rear brakes!!!

 

I had this happen on my car and struggled getting the thing lined up. Turned out I had to move the steering rack a bit, it ended up in a position that made things difficult. Maybe worth popping the tie rods when doing this job.

 

I popped the tie rod and loosened a few other bolts to get it to line up, tehn tightened up the whole thing. It worked great. On the left side, which I have yet to do, I may try to change the rotor by not removing the caliper. I'll see how that goes.