I HAVE A QUESTION ON THE ROTOR REMOVAL:
It seems that the three? or five bolts? attaching the rotor to the hub are difficult to remove initially. Do you recommend leaving the tire on the ground until you loosen the bolts or is their sufficient grip to loosen them on the bench?

 

Safety wire is normally used on aircraft because of vibration (It's also difficult to find or tighten a bolt if you are in flight.) However, if you intend to reengine your XJS with a RR Merlin 16 cyl I would suggest the use of safety wire!

 

Being new here, I hate to be a pain......but it's that ocd detail thing I've been cursed with. Did not the Merlin have 6 cyl in each bank ?

I shall now slink back to the shadowy part of the cave.

 

V12 the merlin was indeed, attention to detail is not a curse and there's a lot to be said for caves.

 

Yes, that was a test question! You passed:
The Rolls-Royce Merlin is a British liquid-cooled V-12 piston aero engine of 27-litres (1,650 cu in) capacity. Used in Spitfire. U.S. put it into the P36 (removed the Allison)and renamed it the P51!
Another question:

I HAVE A QUESTION ON THE ROTOR REMOVAL:
It seems that the five bolts attaching the rotor to the hub are difficult to remove initially. Do you recommend leaving the tire on the ground until you loosen the bolts or is their sufficient grip to loosen them on the bench?

 

The caliper does not have to be removed to slide the rotor out

Undo the bolts from the back through the dust shield with a flex socket and impact wrench.

Remove the hub and slide the rotor out with the pads removed.

I have had to grind a small amount of metal at times but I don't remember where. It has been a decade or so since I changed rotors on theses old cars but it beats trying to keep up with the shims.

The only time I remove the calipers is if I am going to work ON THE CALIPERS.

bob

 

Rotor and caliber out together by removing the wheel bearing nut. That sounds great and easy. But, I am going to replace the rotors. What I was referring to was the rotor bolts. There seems to be consensus they are hard to remove. My question was is it easier to start them when the tire is on the ground and will not rotate, like you do when you take the wheel off, or better on the bench?

 

The rotors are undone by removing 5 bolts which are accessible from the back of the rotor. If you still have the dust shields, then the bolts are accessible through an indentation in the shield, and to access each bolt requires the wheel to be rotated.
BUT the hub HAS to be removed to remove the disc, even when the disc is undone from the hub, as the disc mates against the inside face of the hub. The hub is removed by undoing the split-pinned nut on the end of the stub axle under the dust cap.
In theory, according to some, if the actual disc pads are removed, the hub and disc can be fiddled free without having to undo the calliper. I have never done this and I am not sure if it is true or not. My own view is that it is better to undo the caliper as that give far more room to do the job carefully, and if the discs are shot, a caliper rebuild is a good plan anyway, as is renewing the flexibles.
Hope this helps
Greg

 

If you have an impact gun/wrench then you can remove the disc-to-hub bolts on the bench easily. If not you can still do it on the bench with a bracing bar thru the wheel studs (and, ideally, an extra pair of hands) to hold the assembly stationary while the bolts are removed.

Lacking any of that, yes, break the bolts free before removing the hub-disc assembly from the car. The go to the work bench for full disassembly.

Cheers
DD

 

Or, since you are replacing the discs/rotors anyway, just clamp 'em in your bench vise and remove the bolts. This will almost certainly mar the friction surface of the rotors but since you are replacing them ....who cares?

Cheers
DD

 

I lost my place on this forum; will start over. 1993 XJS. I cant remove the right front, long, caliber bolt. Frozen solid. Used a four foot extension bar; no luck. Raised the car and had it rest on the extension bar; same!
Beginning to wonder if the bolt is removed by turning clockwise, left hand tread? I also would like to confirm size as 17 mm
Thanks for your info!

 

The bolt undoes normally, anticlockwise. An electric impact gun with at least 450Nm force will move it. Orangeblossom told me it would and it does. 17mm may fit, but I have a feeling it is an imperial size like 11/16ths. As long as the socket is reasonably tight, and certainly not loose on the hex, it will be OK
The bolt goes through the steering arm, then the caliper and into the upright. It corrodes and jams where it goes through the steering arm, and nothing but and impact wrench will do a really jammed one.
Greg

 

Greg: Thanks! That bolt is an SOB! I jacked up the car. Put the extension bar on the bolt then lowered the car so the bar supported the weight of the car and left it for a week. Bolt won! OB,s solution is good but as you know the UK is on 220vts and US is half that. Did use 100 lb. psi impact gun with no success. Had doubts that it removed clockwise and I was tightening and not loosening. It seemed like an 18mm socket fits tight, but all indicators on this site talked about 17mm. I just don't want to round the shoulders of the bolt. Will press on!

 

Use an impact socket regardless since it will be a 6 point socket, getting the best purchase and preventing rounding.

100 ft/lbs out of an impact is nothing. I'm surprised they sell such a gun. Borrow a bigger gun from someone or try a breaker bar with a 3-5 hammer and some penetrating oil 30 min. beforehand.

 

I considered 100 PSI on a gun formidable, but bow to your expertise. Starting over with PB Blaster and 6 point socket 17 or 18 mm, best fitting, and a four foot breaker bar. Will keep the car suspended on the breaker bar with PB Blaster until I am ready to introduce your solutions.
Thanks Sidescrollin!

 

There maybe some crossed wires between yourself and sidescrollin with one talking torque and the other air pressure. Don't mean to intrude just pointing it out.

 

from: Fastenerdata - Corrosion - Fastener Specifications

Fastener Corrosion
Fastener Corrosion is a natural phenomenon, as nature seeks to recombine elements which have been refined by humans into a purer form. Iron occurs naturally as iron stone, pure iron being unstable and wanting to rust in the presence of oxygen and water.
All fasteners made of carbon steels are an alloy of Iron, carbon and other elements; and stainless steel despite its various additions of Nickel and Molybdenum still behaves like steel, even 316/A4 stainless steel has around 60% content of iron.
The corrosion resistance of stainless steel is dependent on a thin invisible layer of chromium oxide on the steel surface. There are environments that breakdown this passive film and several forms of corrosion can form on stainless steel.
The passive film is self-healing if given a stable environment including oxygen.

Now in the process of determining the specification of the bolts for replacement because of the condition of the threads found on the left caliper bolt. The markings on the head of the bolt are "W" "E" and "M8.B" Not sure if it is Whitworth or metric and not sure of the "W","E" marking. The diameter of the threads is 12 cm, they appear to be fine and the shaft is 12 cm. Will press on and report back.

 

I think so too.

He said lbs. psi or something odd like that, but i assumed he meant the torque figure because psi doesn't tell anything about the gun. 100 psi in a gun that only puts out 50 lbs/ft isn't the same as 100 psi in a gun that will do 650 lbs./ft

 

Didn't mean to confuse you, My son has a heavy duty (What ever that means) impact wrench attached to a large tank compressor that is rated at 100 PSI. Unfortunately, he is out of town and I can't give you the torque rating of the wrench. But will get back on that!

BACK TO YOU: knowing where he bought it, the torque is between 750 and 1,000 lbs