1990 Jaguar XJS Brakes progressively lock up after 1-2 kms!

Tiny
TBUCKLER
  • MEMBER
  • 1990 JAGUAR XJS
  • V12
  • 2WD
  • AUTOMATIC
  • 25,350 MILES
I switch on my ignition - the ABS warning light is illuminated. I start the engine and the ABS light goes out.
I drive 1 - 2 kms and the front brakes are gradually applied until the car stops. With the car stationary and the engine still running, I test the brake pedal - it's solid and it vibrates under my foot.
I switch off the engine and wait up to an hour for the front brakes to cool and gradually release - then the process repeats itself. What is the problem?

Thanks

Tim
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Saturday, May 30th, 2009 AT 9:00 PM

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Tiny
BMRFIXIT
  • EXPERT
Check brake pads 1st and if any abnormal wear
check caliper and hose
also try B fluid flush

Brake fluid takes in moisture from the air. Water contaminated brake fluid has a reduced boiling point and may lead to brake system corrosion.
ACTION:
Brake fluid must be changed every two years or 30,000 miles, whichever occurs first.

Check rear braks TSB

ISSUE
Premature rear brake pad wear (in less than 3000 miles) is due to the brake pedal sticking and applying continuous low pressure to the rear calipers. Brake pedal sticking can be caused by over-tightening the pivot bolt or incorrect setting of the brake light switch.
ACTION
Use the procedure below to correct the problem.
SERVICE PROCEDURE
Loosen the nut for the brake pedal pivot bolt 1/2 turn.
Re-set the brake light switch as follows:
Loosen the switch and adjust switch position so that when the plunger is fully pressed in, there is at least.025 clearance between the plunger and brake pedal.
Inspect the rear discs for excessive wear and calipers for possible heat damage. Replace components if necessary.
SYSTEM OPERATION
The initial movement of the brake pedal (3/16" travel) applies 2 bar (29 psi) pressure to the rear brakes only.
The pressure delay valve (located on the L/H inner fender on 89-91 MY vehicles and on the R/H inner fender on 92 MY vehicles) then holds this pressure until the front brake line pressure has reached 8 bar (116 psi).
When the front brake line pressure reaches 8 bar with continued load on the brake pedal, the pressure delay valve opens and increasing pressure is then applied to both front and rear brakes.
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Sunday, May 31st, 2009 AT 6:55 AM

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