Anti-Lock Brake System Accumulator Ball

1990 XJ-S Coupe (US Spec, 5.3L V12)



ABS Accumulator

5/16” Allen (Hex) Wrench



My ABS light was taking a little longer than normal to turn off after start-up, and I could hear the ABS pump running longer as well.  This is nothing to take chances with, so it was time for a new accumulator ball.


The ABS accumulator ball is a hydraulic accumulator used to store pressure for the braking system.  It’s that black ball under the hood on the right side near the firewall.  The Service Manual has quite a bit of information on the system (Volume 4 and its Supplement)…


The GM Part #25528382 is an exact replacement.  I bought mine from for $85.16 plus shipping.


First, with the ignition off, discharge the pressure by pumping the brake peddle hard.  The manual says to pump “(approximately 20 times) until the pedal travel goes hard”.  Having read about fluid squirting out when the ball is removed, I pumped at least 50 times.


I then put some towels around the area where the ball threads into the pump to catch any fluid.  Using the 5/16” hex wrench right into the top of the ball, I slowly unscrewed it.  Luck me, absolutely no fluid came out.  The new ball came with a new washer/seal and I simply screwed it into the pump.  Supposed to torque it to 40-46 Nm (about 29-34 Ft-Lbs).  Next project…



Questions/comments: Email me.