i think pistons are just a little sticky as the car as not been on the road .. after few pumpin they seem to stick to plywood when pedal is pressed down and release plywood ( faxe brake pad) when we release pressure on pedal.

the thing is ive read that the test for the accumulator is to de pressurized system and count how many second it runs when you turn ignition on. this morning was 15sec which made me think it was dead. Now its 40s which is opposite conclusion.


https://www.xjsbanger.co.uk/jaguar-x...or-diagnostics

i dont know if any of you had the chance to read that article linked above.. i did but my english is soso ad the guy seem funny talking so im not quite sure i got all the meaning of his details. but it clearly state :

If brake accumulator's pressure switch fails – it will react to the pressure incorrectly or won’t react at all, that includes:
- switching the pump with every brake pedal stroke (switching the pump pressure accumulator sphere even if sphere is fully functional and loaded full),

so i dont know not really excited about changing the accumulator if it's not needed. ( indeed cost and hazard of operation if its juste the switch..


Any idea ? thanks a lot to every xjs masters out there

 

15secs seems quite quick to pressurise and then cut out. Mine has always run for longer than that when cold and first started. The cutout is caused when the pressure is "deemed" to be correct. So the implication is that:

- it is reaching pressure but really rapidly dropping without brake application
- it's not reaching pressure but it thinks it is (pressure relief switch or other signal problem)

So, it could be the accumulator ball but I'm not sure I'd thrown money at it and just replace it quite yet.

Paul

 

Hi gtv2c

Agree with Paul

From a first time Start up 15 Seconds to build up Pressure is the stuff that dreams are made of

So it sounds to me like your money would be far better spent on either a pair of Service Exchange Calipers or at least some new Pistons, as if you've got a Caliper problem a New Ball could well be a waste of money at least at this stage

Alex

 

gtv2c,

Just a thought,

A fault in the electrical internals of the pressure switch could cause a lack of pressure build-up in the accumulator AND cause the warning lights to come on. If it were just an accumulator problem not holding pressure, I'm not sure you'd see ABS lights coming on.

So another thought as to why it could be the pressure switch?

Paul

 

Just tested my car 26 seconds from ignition on to pump off this is with the new Bosch accumulator and the car hasn’t been run for at least a couple of weeks.
Rob.

 

thank you robbo for the test ! i appreciate it.

Paul when i read the article made xjsbanger the guy seem that he knows them pretty well , i mean i don't know but it looks very detailed and coherent. ( some of it) and one of the step he says a faulty switch could cause light to go on and off and start the pump whenever.

Do you have any idea of how i could test the switch? is it known for getting faulty? unfortunately i don't have any other jag to cross check that thing and im not sure of the availability of that part..

thank you

 

Hi Rob. I remember your original thread about the new accumulator you'd found. Was it on Amazon? Do you, by any chance, have a link for this accumulator?

 

excuse my english, but are you saying that it sounds more like a pressure switch fault? do you know how to test this part as it looks hard to find.. NLA

 

https://www.ebay.de/itm/BOSCH-Drucks...IAAOSwoCNfaj9d


i ordered it today, it says its shipped already, will see in next couple days

 

gtv2c,

Yes, my suggestion is that the symptoms SEEM to point to the switch rather than the accumulator.

It's not easy to test if the switch is cutting in and out at appropriate pressures. But it is possible to test the contacts to confirm open / closed as appropriate at zero pressure. I'll try and dig out a wiring diagram and see if I can explain to you which terminal points to check for the correct open and closed pairs (unless anyone else here knows already which ones to check?).

Cheers

Paul

 

I'm sorry for chiming in so late, a lot has been done and discussed... But,,,

Are you saying that when you pump on the brakes with the calipers OFF the rotors,,,, that the pads and pistons were not/do not extend out to the rotor (or plywood) in your testing? Moving millimeters only and differently for each pad?
What service have you given the calipers, if any...?

It sounds like the pistons are stuck in the calipers...

 

Hi All
just found this diagnoses list for these brake systems that may be usefull
https://turbotbird.com/thread-troubl...braking-system

 

Thanks to everyone the brakes are fixed, the problem was the accumulator ! good to learn some new skills on a different brake system. Thanks to the community for the advise and their time !