Hi! Ive been down the rabbit hole of all 4 rotors seizing up, and after changing out pads, rotors, and all calipers, I've landed on the brake booster shaft adjustment or replacement option. I am currently in between the first failed test after adjusting the brake booster shaft and the second adjustment, and I am looking at brake boosters for sale and seeing very expensive new options, and I am generally distrusting of anything used due to the possibility of just ruining the 'new' one like my original. Are there any brake boosters from other models / brands that I could try swapping in, or am I pretty mush stuck? So help me God.

 

No and it's not a reported problem? If yours is bad I would get a used one.
Can you make sure you have a booster problem? It should set a code but maybe not?
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I had exactly the same issue. Fixed after I changed the flexible hoses to the front calipers. Although they looked fine, that fixed it. Note that my brakes were stuck on symmetrically, not just one caliper, so it didn't intuitively point to the flex hoses.

Its diagonally split so maybe the fronts can impact the rears?

Still a mystery, but solved over three years ago and hasn't returned since.

HTH, Dave

 

 

Good point from DaveAllen about collapsing rubber brake hoses. I had a rear hose do that to me years ago on another car. I had almost zero rear brakes as the line was pretty well blocked. It also looked fine from the outside.
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Update: 2004 x type, standard as far as I can tell. I replaced all the calipers and rubber hoses.
Some relevant threads for the uninitiated:
https://www.jaguarforums.com/forum/x...roblem-285899/
https://www.jaguarforums.com/forum/x...oblems-141632/
https://www.jaguarforums.com/forum/x...eeding-204673/
TLDR, its the brake booster, and they are expensive as hell here in the US. I was hoping this issue was common enough for someone to have done some experimenting but i suppose not.

 

The car blew a brake line and the extra travel for those few miles destroyed the Vacuum booster. I bought one rebuilt from O'Reilly auto for around $200 i think.

Just keep in mind, that you may have to adjust the rod in the booster that you are installing. It is basically hit or miss.