I had brake problems, so I have been replacing pads and discs/rotors and then bled the system correctly and directly after that, the pedal felt fine, but after a short test drive, the pedal feels "mushy".

The display alternates between "PAD" and "FAIL", although the pads are new.
I have reset the VCM, to no avail.

Any suggestions where to look?

 

Hi Roland,

The PAD warning probably indicates a problem with a brake pad wear indicator - either it is disconnected, open (broken wire) or shorted to ground.

The FAIL warning may indicate a problem with the hydraulic brake power boost system. My first suspicion would be air in the system.

Is it possible that when you bled the system the fluid in the reservoir got too low and air entered the system?

On left-hand-drive cars, the proper order for bleeding the calipers is:

Rear right
Rear left
Front right
Front left

The idea is to start at the caliper farthest from the fluid reservoir and work your way to the caliper closest to the reservoir. Is that the method you followed?

Please keep us informed.

Cheers,

Don

 

Many thanks for your input!!!
The previous owner has damaged the front wear connector and doesn't have a wear indicator... I'll try to loop the circuit...

I noticed, the first time I bled the system, that after starting the engine, the brakefluid level dropped too low, so I had to bleed it again, this time very observant of the level. It did drop, but this time I don't think it dropped too low.

I did bleed the brakes in just that order.

Please tell me more about the brake power boost system... It seems I've got the Teves system. Can that cause the pedal become mushy/spungy after a short test drive?

The SLS is said to be renovated, not so long ago, but I'm thinking of converting to regular suspension, since I'm not so impressed with the rear suspension... The car is sometimes a bit bouncy in the rear... Could that contribute to the brake problems I'm having?

 

Now I have bled the brakes a third time. Still no noticable air bubbles, but the pedal is more to my liking now, I've looped the wear sensor wires left front, but the brake warning light still comes on or flickers some times, but goes off again after a short time... Now I can even brake without the warning light coming on. So, all in all, I'm almost happy with the result...

 

Again the brakes are sometimes acting up...

What could possibly cause the brakes to sometimes work fine, although it usually takes a minute or so for the brake warning light to flicker and come to rest and with the brake pedal feeling ok and sometimes staying lit or lighting up after some time, with the brake pedal being somewhat mushy and indicating "FAIL" on the display...

Whenever the brakes are ok, there are no codes showing on the display...

 

Hi Roland,

Sorry to hear you are still having brake trouble. Please remind us of the model year of your car. It's a good idea to add this information to your signature line so others don't have to ask.

Some of the potential problem areas are the master cylinder, the accumulator sphere, the combined low pressure/warning switch, the electric pump motor and the wiring. Just thinking off the top of my head, the intermittent nature of your problem and the fact that you get warning lamps makes me suspect something in the hydraulic boost system, but it's possible that your master cylinder is also worn and not performing well.

Please remind us of your model year so we don't give you incorrect suggestions.

Cheers,

Don

 

Many thanks!
I've tried to edit my signature, but it won't show in my threads...

What am I doing wrong?

 

OK, now it shows... :-)

 

I can hear the electric booster pump and I can feel the sphere coming to life when I fire up the engine. The rear end is going up and down half a minute later...

Could the conversion help remedy the brake problems?

 

There is quite a bit of info about the vacuum boost brake conversion at the Jag-Lovers forum, and a few active members who have done the conversion on their own cars, so it would be worth inquiring there.

I can't recall if you've done the basic test for the accumulator. If not, I think the following test will work on your '91:

Start the engine and listenin for the electric brake system hydraulic pump to run. When the pump motor shuts off, shut off the engine. If you can't hear the electric pump run, just let the engine run for at least 2 minutes to charge the hydraulic system.

Turn off the engine, then turn the key back to Position II without starting the engine. Wait for the warning lamps on the instrument cluster to extinguish. One or two of the warning lamps may not go out, such as the Battery symbol. Now press the brake pedal as far as you can and release. Repeat and count the number of times you press the pedal before the BRAKE warning lamp illuminates. A reasonably healthy accumulator should provide boost for at least 6 pedal presses before the BRAKE light illuminates.

See the attached document for more information on the hydraulic system and various tests you can conduct. There may be a later document available online, but this is the only one I have in pdf form.

Please keep us informed.

Cheers,

Don

 

Many thanks for your suggestions and link. I'll do the test ASAP.

I'm assuming the intermittent bouncyness could have something to do with the system giving priority to the brakes...

I do have a small dripping from the right front end of the engine, from what I think is the pump. I've tried to tighten the screws, but tey are tight enough... perhaps the gasket needs replacing... or worse...

Does the valve block require any bleeding? I did have problem before, with the pressure hose to the steering rack and replaced it and did the usual turning of the steering wheel from left to right three times... Perhaps this system needs something else?

I'll also check the suspension relay in the boot...

 

I wish I could answer all your questions, but your setup is different from the system on our '93 so I don't have personal experience to draw upon. If your steering rack uses the same fluid source as the brake boost, ABS and rear suspension, then I don't think the standard steering rack bleeding procedure will be adequate. Check the hydraulics manual to see if it gives a bleeding procedure.

I'm hopeful that one of our members with a similar system will be able to offer you some suggestions.

Cheers,

Don

 

Many thanks again!!! Your input is always much appreciated!!!

Yes I seem to have the second Teves system out of the three systems available on the XJ40, which is sharing the MSHO/LHM fluid with the power steering.

I'll try to read up on the hydraulics... but not sure if I can get my head around it, if its to technical...

 

Sorry about the late reply...

I've done the test, but it seems the warning light has a life of its own and seems to have some difficulty on deciding whether to stay off or on...

I did start the engine and I could hear the servopump working and also become a bit warm, before coming to rest after a minute or so. Then I turned the engine off and turned the key to position ll. I then waited a while to see if the warning light would stay off after some flickering, which it did...
Then after pressing the pedal twice, the pump came on, as did the warning light.
(Brake pedal mushy the first 1/3 down, then rock solid)
I then waited for the servo pump to fill up the pressure again and then I could press twice again before the pump started and the warning light coming on.

I did this several times with the same result.

Any chance of this problem going away when converting the rear suspension???

It feels as if the brake/SLS problems could somehow be linked to each other... or is it just wishful thinking?!

 

It definitely sounds as though your accumulator is not holding sufficient pressure, and I suspect that is unlikely to improve even if you convert the rear SLS to convential shocks.

I don't know if it's possible, but perhaps you could block the hydraulics for the rear suspension to test the brake behavior on its own?

 

Many thanks Don!!!
Does that mean I need to get a new sphere, or can it be refilled?
I read somewhere last year that the Citroën sphere is identical at a much lower price... and that the Citroën club has some kind of exchange thing going on...

Any one know anything about the details?

Just a thought... could it be, that a new sphere could solve both (mushy) brake and (bouncy) suspension problems???

 

Hello Roland M ,

Two things need clarifying before you delve into the " Booster " area of your brakes

1 , " Mushy brake pedal after o/haul " , was the brake pedal not mushy before the o/haul

2 , " I had brake problems " , was that just general maintenance or ? .

Sid .

 

Thanks for helping out!

"I had problems" meant that I had problem with the warning light, becoming more and more of a problem and twice the ABS light wouldn't go off, right away.

My first thought was the rear pads, but that didn't solve the problems and it wasn't until after we bled the brakes that I noticed the spunginess of the pedal... It could have been there before, but I'm not sure about that.

However I have noticed that the bounciness of the rear end has been present and more or less obvious the whole time that I've owned the car. (one year now)

And because the brakeproblems seem to be more or less simultaneously present the whole time, it occured to me, that they might be connected, a suspicion somewhat confirmed by others in various threads...

And since the discs/rotors were in such a poor state, I decided to replace them all and at the same time clean the ABS rings and replacing wheelbearings.

 

As far as I know, you will need a new accumulator. I have also read about Citroën accumulators being rebuilt and found these videos:


However, as far as I have been able to determine, the accumulators being rebuilt are not the same as those used on Jaguars, but it might be worth contacting the companies who are doing rebuilds to confirm. Perhaps they are able to rebuild our accumulators also.

I am not certain that your failed accumulator is the only cause of your mushy brake pedal. The master cylinders are known to wear, a leaking caliper could contribute to the problem, or, more likely in your case, leaking rear shock absorbers. Have you noticed any fluid on the rear shocks?

Don

 

Thank you so much!!!

I'm not sure if the master cylinder is ok, but the rear struts are dry and not so old. There is no leakidge besides the occasional drop from the steering pump on the front/right side of the engine.
So I'm hoping that if I get a new sphere, the problem will go away...

Now looking for the best deal on one of those spheres...