Where is there a picture of a Brake Proportioning Valve fitted to my 2005 [exact dates - April 1st 2004 to 31st Dec 2007] Where on the GV is the Brake Proportioning Valve, its not as I expected near the rear shocker. Where would I buy one other than a scrappy. Has anyone ever done a 'bias valve' on our ABS system GV's. Lotsa questions lads.

Symptoms .. .. car sailed through test, excellent hand and footbrick rear axle figures :

- heard a ping and found the OSR had 'spit out' a rusted pad, this pad had meat on it but had sheared from its backing altogether
- stripped everything but the backplate and replaced with brand new disks, pads, shoes and a small parts set
- every surface was 'finger filed' clean and copper or nickle greased depending on the surface
- bled through and both pistons go on but will not retract - at all - suspect the dot 4 / 3 is older than me and full of solids
- desperation, had to force the pistons off to free spinning wheel and clamp the brake lines with heavy duty mole grips
- I suspect those pistons have been in a stuck all the way out position fo many many years

 

not sure about the valve location. Will check later today....mine's due it's MOT at 11 this morning.

Re the pistons not retracting, we had a similar problem with Mike's GV and ended up replacing the rear pistons. His were binding quite badly.

Regards
Richard

 

HiYa Rich, I'll do a full post with pictures sometime later this week, I am embarrassed at what I found but what I did find suggests that unless we are prepared to do an apparently unnecessary complete strip of the whole calliper each GV owner might be blithely running around with seriously compromised brakes. I bled through last year to replace yonks old fluid .. .. after Mon its clear that a complete vacuum & double flush is the minimum that should have applied last year.

There used to be a EURO Chrysler parts disk that literally told you every single part that was fitted on the day it was built in the factory [VIN number] and I can't find it in the usual places. I'm embarrassed that I don't know enough about the bias valve employed in the Teves diagonally split braking ABS systems, hell I don't even know what they [2] look like or even where they are - thanks for your input mate - it is appreciated. Best of luck with your MOT mate ............

 

Omg what you wrote might as well be in greek for me Tfb and QientQare you boys professional mechanics. The depth you go into is far far more than a diyer ever does

 

I take it you's open the bleed nipple while pressing the pistons in. Its a just incase issue with me as some cars can have the master cylinder seals reversed when in reverse flow.

 

I'm not a pro [or any kind of] mechanic, heck after yesterday I wouldn't even consider myself competent at making bacon butties never mind fixing brakes.

 

HiYa goggsy, its that the piston does not retract ....... at all ....... stays locked on forever. Much like the maintenance payments to my four ex wives.

The correct. if I remember it right way to final adjust auto-hydraulic, is to apply light foot brake pedal pressure - while repeatedly [at least three times] giving the handbrake a pull.

 

The only reason I can see of piston not going back in, is due to piston coming too far out and not squaring up on going back in. Lop sided piston locks in cylinder in other words. I have had the experience of brakes binding after pushing pistons in and renewing pads. Had to replace whole calipers on that instance, but could have replaced pistons and seals if they were available. No such thing as Kits now, pistons, cylinder seals & dust rubber covers.

 

Agreed Goggsy, I'll post photo's later this week as a salutary lesson to all of us GV owners on how even the experienced can get caught out. I've already bought two whole S/H calipers from the same 2006 axle. I hate parts darts but it was calipers or proportioning valve [s] and I understand calipers and am clueless on specific bias valve types so the money is spent. The pistons on the set I took off were in an over extended position and might have been that way for soddin years as you will see from the footwear when I post the photo's.

- Over retracing the piston into can lock the adjuster. Over extending the piston can lock the adjuster.
- The screw type pistons wind the piston OUT by turning the piston anticlockwise here you are supposed to leave 1mm play.
- The manual bolt type remove the capping bolt and adjust the piston with the hex key to the same 1mm play.
- The auto [self] adjust type make the final adjustment using light brake pedal pressure and at least three good yanks on the handbrake.

 

- yeh I did that and take your point on the seals in the MC reversing on flow-back

Pad / disk self alignment on modern motors including our GV's tend to be single piston floating caliper as opposed to posh cars with fixed multiple caliper. In this case we are talking floating alignment with integrated parking brake 'top hat' hardware . Pressure on anti-lock accumulators have an old and new school opinion on 'how to', (1) old school is the usual hard on the pedal and turn the bleed screw (2) new school says clamp the hose to stop debris back flushing up to the master cylinder - I'm old school because putting a megga clamp on a hose can damage the hose, itself a cause of inner liner collapse [acting like an unwanted check valve] preventing the master cylinder from releasing the fluid pressure from within the caliper. However in my case I had to clamp because they were locked in death grip. As to O rings the square O ring on the cylinder piston is designed to do just that exact thing - to twist out of shape - that's how they allow the flow-back, they are designed to deform - flow-back - reform, its when they don't reform to their original shape correctly we get the twisted O ring issue and a failed caliper.

Older sods like me should always remind ourselves that modern motors do not like the pistons being pushed in, and particularly fushed in all the way. Modern brakes have extra delicate and expensive components in the form of ABS and expensive ABS modulators are easily damaged by the back-flush of debris caused when caliper pistons are shoved all the way in. Much better to bleed an excessive amount of fluid through the nipple to release the back-flush, additionally the new for old fluid top up replaces the efficacy of fluid whach has been 'boiled' by heat transfer from piston to fuid as well as the hydroscopic effect of the fluid itself.