Hi all

I store my 1993 XJS in Chicago for winter while we are in FL. It started up great but my brake pedal went to floor ! The brakes were fine and firm when I put her to bed.

Anyone have any ideas why the brake hydraulic pressure bled off while car sitting there ? There is no fluid leaks anywhere.

Many thanks for your help

Jonathan

 

My guess (because it happened to my azure and I guessed the same) is that the hydraulic accumulator ruptured and dumped a bunch of nitrogen in the system,

 

Jonathan,

It's not as simple as the "hydraulic pressure bleeding off". You have the Teves II system which is complex.

The symptoms of a pedal that has gone soft, could include an introduction of something into the fluid system, nitrogen (as mentioned), air or water absorption. It could also just be the pistons backing off (in which case, one or two presses would restore pedal pressure. It could also theoretically be seals in the Actuation unit having hardened (but I'd suspect not).

If it were me, I would do the following:

- Discharge any potential pressure in the accumulator. Turn off the ignition fully, press the brake pedal repeatedly 20-30 times. Note if the pedal is getting very hard by the end of this sequence.

- Make sure the bonnet is open. Don't put your foot on the brake! Now Turn on the ignition and see if the brake pump on the passenger side starts to run. Count how long it runs before cutting out. If it is still running after 1 minute, then turn off the ignition, as you will have a pump, accumulator or PRV problem.

- If the pump cuts out in less than one minute, try the pedal a couple of times. How does it feel? Press it 5-10 times, do you hear the pump cut back in, run then cut out?

If the pedal is still soft, do the "blink test" to see if the ABS unit is storing any fault codes.

Good luck

Paul

 

Thank you So much for your help ! I’ll try your suggestions and see what happens

 

Hi Paul

here is what I found:

- Discharge any potential pressure in the accumulator. Turn off the ignition fully, press the brake pedal repeatedly 20-30 times. Note if the pedal is getting very hard by the end of this sequence.

PEDAL GOT HARD AFTER ABOUT 20 pumps

- Make sure the bonnet is open. Don't put your foot on the brake! Now Turn on the ignition and see if the brake pump on the passenger side starts to run. Count how long it runs before cutting out. If it is still running after 1 minute, then turn off the ignition, as you will have a pump, accumulator or PRV problem.

PUMP CUT OUT AFTER ABOUT 50 SECONDS

- If the pump cuts out in less than one minute, try the pedal a couple of times. How does it feel? Press it 5-10 times, do you hear the pump cut back in, run then cut out?

PUMP DID CUT BACK IN BUT PEDAL SPONGY AND SOFT

If the pedal is still soft, do the "blink test" to see if the ABS unit is storing any fault codes.

CAN YOU LET ME KNOW HOW TO DO BLINK TEST ?

thanks a bunch ! JB

 

Jonathan,

When you say the pedal is now spongy and soft, do you mean that it has improved since you first started it up and it went to the floor? If so, go through the whole discharge and re-accumulation procedure again and see if there is any further improvement.

Drop me a PM and state your email in the message, and I'll email you the document that explains the Blink test procedure.

Cheers

Paul

 

Hi Paul

Sorry about that...there really was not any real improvement after start procedure. I’ll try it again.

Not sure how to send a PM ?

thanks

JB

 

Click on my username in my last post and then select "Send a private message to ptjs1" from the drop-down list

Cheers

Paul

 

Hi all…quick update and thanks to everyone’s help. I went ahead and bled the brakes and brakes are working really well now and have been going for a couple of weeks and pedal is nice and hard. I do still worry that if this is a closed hydraulic system why would would it bleed out after sitting for months ?