So

The problem child.

Total mileage 37,000. The last three years it didn't move an inch. 

It has a problem, heavy traffic and the brakes pedal goes solid, the brakes come on, let it cool and they're free again. I've gone over the calibers, all good. I've replaced the brake servo and master cylinder (used unit)

I've even followed the recommend bleed the brakes procedure.

I've run it up to Glasgow, 800 faultless miles, but a day in London and it gets defeated by traffic on the Chiswick roundabout.

Don't think it's a faulty vacuum hose & I've cleaned the gunk from the pedal rod, fluids all clear (and new) system all flushed through and filter good.

Only recent work was two new cables for the handbrake, but it managed fine for 150 miles before the Chiswick incident.

I've replaced a few age related issues; new belts, new radiator, new air condenser, new tyres, plugs and packs, so it owes me a few quid, I don't want to give up on it yet. 

Any ideas?

 

 

Hi Tim

Found this on the jaguarforum.com site:

"There is a common fault with the X Type that follows a brake bleed using the manual pedal pumping method. When the brake pedal goes to the floor during a pedal pump bleed, damage to the brake booster (servo) normally results. I personally suffered this following a full service at a garage that I had requested a complete brake fluid change be included. I specifically told them about the manual bleed problem and asked if they had a pressure bleeder. Although they did, the boss forgot to tell the mechanic and he manually bled them and detroyed the servo.
One of the members here posted that adjustment to the push-rod between servo and master cylinder is possible and successfully cured his fault by winding in the push-rod to give some slack. Other members report putting a block of wood under the pedal to restrict pedal travel when pedal pump bleeding method is used. "Never allow the pedal to go all the way down."
Symptoms include solidly locked on brakes and brakes that slowly begin to bind as you drive before locking up completely (like mine)."

Not sure how that would damage the servo though.......

Have you tried turning each road wheel when the brakes are locked on to see if it is all 4 or just one, or one circuit which is at fault?

Good luck
John

Thanks John,

Very helpful, also not sure how the servo would get damaged by bleeding, maybe it's a Ford/Jaguar thing!

Hadn't thought of an each wheel test. I'll give it a go. Might also find my BBQ thermometer and check the heat of the discs.....

Hi Tim

This might help:

https://autotechnician.co.uk/brake-servo-fault-finding-guide/

Good luck
John

On 5/22/2025 at 6:34 AM, Big John said:

Hi Tim

This might help:

https://autotechnician.co.uk/brake-servo-fault-finding-guide/

Good luck
John

Thanks John, should have a chance to get to it this weekend, it's running fine at the moment. annoyingly. At least if it just broke I could fix it.