Hello all.
My brakes were working very well 2 days ago. Yesterday, I took the car out and the brakes started acting up.
I have front brakes but no rear brakes.
The same thing happened to me about 8 months ago and I replaced the master cylinder with a new one; not rebuilt, bench bled the MC, bled the brakes and all was well.
I do not think it is the MC but not sure.
Today, I jacked up the rear to see if I had any leaks but it was all dry under there.
I decided to bleed the brakes and for all my efforts, I cannot get the bleeder nipples to loosen.
As a matter of fact, I think I stripped the driver side. Dumb of me to use the wrong wrench. I will go out and buy a wrench tomorrow. I also think I used the incorrect wrench. Is it a 7/16 or an 11mm wrench? On my car a socket does not fit because there is no room for the ratchet. How are you guys/gals doing it?
If I can't get the bleeder out, I guess I will have to drop the rear end and replace both calipers, brake pads and the brake hose at the same time.
Is it possible that when I replaced the MC and bled the brake there was still air in the system?
Any ideas?

 

Not sure about the root cause of the brake problem. Mine is an 87 model without ABS. Is yours the ABS version?

For bleeding the brakes I always use a 6 point wrench to loosen the bleeder before using a flare wrench for the actual bleeding.

7/16" is just larger than 11mm (approximately 11.1mm). If the 11mm fits - use that - its slightly smaller / tighter on the bleeder.

HTH, Dave

 

Sanchez
When you get it sorted, treat yourself to a set of these!
https://www.fossewayperformance.co.u...ed-easy-bleed/

 

How old is the flexible hose between the body and the IRS? They can collapse internally with age. Usually that results in the brakes sticking on, but could presumably prevent fluid flowing as well.

 

Sorry to all for not responding. Reason being that the expansion plugs on my '85 XJ6 started to leak. As a result I pulled the engine and tranny to replace all of the expansion plugs. When I am done with the XJ6 I will resume work on the XJS brakes. Until then, I will not post anything about my cars.

 

Hello all.
I finished the work on my 85 XJ6 today. The engine went back in with relative ease with the help of my neighbor and I am back up and running.
Back to the XJS, I decided to move the car outside of my garage to set it up to remove the rear suspension. I have a 15ft retractable awning in front of my garage, so I will be working in the shade. Anyway, I started to move the car and the brakes were perfect. What the heck! I drove it around the block and the brakes were good. I kept on driving for a few miles and as the overall vehicle temperature rose the brakes started to act up again. No rear brakes. It seems that the brake failure is temperature related.
Any reason why this is so? I don't want to remove the rear suspension unless I really have to.
Has anyone experienced something like this and if you did what was done to resolve the issue?
At age 74, I am not looking forward to removing the rear suspension. HELP! HELP!!!!. I am getting too old for this crap.

 

It has to be rubber related. I would suggest the master cylinder as the engine bay warms up
Re build or replace. I think the seals that do the rear are giving up.

 

@ Greg:The MC is just about a year old on my car. This MC was purchased new, not rebuilt, so the question is how long it was sitting on a shelf before I purchased it.
It was purchased from Paul's Jag in Florida and he is slowly going out of business.
I will take your advice and rebuild the MC. Where can I find genuine seals for the MC? Any recommendations?
I will research the size of the seals and see what I find.

 

I carefully read your full story. I’m inclined to believe the master cylinder isn’t your problem. I’ve never experienced a failure of something one year after installation. Too rare!
Another probability could be the brake booster system. ( power brakes). First check the vacuum line from the intake to the booster and if hard or brittle, that could probably be the issue.
If the line feels OK, pull off the booster and shake to hear if there is a fluid in there. The booster could still be defective if the rubber inside is cracked.
Regarding the brake bleeder. I don’t know what year the factory went from imperial to metric on the nipples. I always use a 6 sided box end to bleed. Plus I heat the nipples with my acetylene torch before attempting to bleed. I’ve tried. ( unsuccessfully ) to use penetrating fluids. But the localized heat of a torch has been the only way I’ve been successful if it’s been a while since I opened that bleeder.
If you are unsuccessful opening the bleeder. It’s probably time to remove the whole caliper.
I’d never try to do that job in place. Dropping the rear end is about an hour job if you know what you’re doing and the exhaust comes apart. ( a little longer at my age (76) but once out of the car I lift the whole rear end up onto my workbench using the engine hoist. Whatever you do, don’t re-use the nipple. Order a new one from Moss Motors

 

Well, that is unusual! I have a few more thoughts, FWIW:
Rebuild kits are stocked by Manners; but I think many places will have them. It always could be the single flexible to the rear cage, I suppose, though that sticking the brakes off is something I have not heard of.
How old are the calipers, as it could be that they are slightly sticking ON, when the brakes appear to be OK, and then the pads fade with the heat generated by driving with them slightly on, and that is the reason the brakes are not working. This could be caused by old and stiff cylinder seals or rusty cylinders/bores. So worth jacking the rear of the car up and applying the brakes and seeing if they release reasonably well (ie you can turn nthe rear wheels by hand OK).
How exactly do you know the rears are not working, by the way? Any particular symptoms?

 

Hi Sanchez

(1) Could be Water in the Brake Fluid if you have a Sticking Caliper, the Water will Boil First and you could/will lose your Brakes

(2) Might not be a Sticking Caliper! Might be a Sticking Brake Pad, which should slide in and out of the Caliper nice and easy when the Caliper Pin is removed

Hot Tip from 'Greg' which I've always used is to Shave off a 'Mill' with a Sander or Grinder from the Metal Edge of the Backing Pad so they don't Stick





(3) Might be a Sticking or Rusty Caliper Pin

(4) You Could try using (JB Weld) to Glue a Spanner onto the Bleed Nipple (Not Tried it myself but that might work?)

(5) A Rattle Gun, always seems to work best for Stuck Bleed Nipples, as there is less chance of Snapping it off

(6) Copper Grease on the New Bleed Nipple before you put it back (Tight but not 'Stupid Tight') @ Grant

(7) Dropping the IRS is nowhere near as difficult as many people think but you 'Must' have the Car Supported, so it Cannot Fall and have 'Fail Safes' underneath because dropping the Cage could unbalance it in a way that you may not expect

The Hardest Part is Convincing yourself you can do it!

How I dropped the IRS Cage on my XJS V12 Cherry Blossom

If you can afford it you could always buy a fully rebuilt IRS about $3000

Good Luck
Hope this Helps
Alex

 

I sure like hearing those encouraging words regarding dropping the IRS cage, OB! At some point reasonably soon, I will need to do so and have been dreading it tremendously.... Your comments make me feel so much better, along with comments from Mguar!
Thanks, Guys!

 

@Greg and Others: After doing some research, I believe I am totally mistaken about what I have been stating in my post. Research tells me the following:
"When you apply the brake pedal, the primary piston toward the back of the master cylinder, closer to the brake booster, operates the front brakes. The secondary piston toward the front of the master cylinder, towards the front of the car, is the one that works the rear brakes".
I HOPE THE FOLLOWING MAKES SENSE:
In my case, when I apply the brake and I have to go almost 3/4 way down before the brake works, that tells me that the rear brake is working, but the front brake is not.
My theory is that there is no hydraulic brake pressure between the primary and secondary piston so by pushing the brake pedal down I am creating a mechanical connection between the primary and secondary piston to get the car to stop. In other words I have no front brakes.
I was thinking that the problem I am having was with the rear brake but based on the quote above it seems that it is the front brake that fails when hot.

 

Here is a generic MC not Jaguar specific

 

Sanchez
On my car, which is RHD, the rear exit from the M/C works the rear brakes and the front exit the front brakes. I am pretty sure your LHD is the same. So your deduction above does not seem correct to me. Neither does the "mechanical connection" stuff, as I don't think the M/C works like that.
Are the symptoms that the pedal has normal travel and then, when the car is warm, longer travel and poorer braking? If so then it points to M/C rubbers again.

 

@ Greg: Being wrong and getting corrected by Gurus like you is what this conversation is all about. The above post was gleaned from the Internet and is the standard operation for most Dual piston MCs. That Jaguar being different is no surprise to anyone including myself.
So my original take was correct. When I apply the brake, the rear piston is supposed to activate the rear brake and the front piston activates the front brake.
As per your take on this, if the rear piston seal is bad, then I would have no rear brakes and as the pedal is pushed further, the front piston then activates the front brake.
Lesson well taken.
I ordered a NEW MC, a rebuild kit and the 3 flexible hoses. Should be here sometime next week. I will report after I have done the repair and if that fails I will drop the rear and replace the calipers. The front calipers are less than a year old. The flexible hoses are of an unknown age.
Cheers

 

@sanchez has there been any recent exhaust work or have the over-axle pipes been disturbed in any way?

 

@Mac Allan: The answer to your question is a big NO. I will have to cut my pipes out. Two years ago I had som exhaust work done and I am pretty sure the exhaust shop welded the over axle pipes to the pipe coming from the engine.

 

Good luck!