trouble with brakes, may be BRAKE CNTROL VALVE

[autumn64]

Hi All, I'm new but can't find any info about this.

VReg Xantia HDI 2000
Failed it's test, we knew it would as back brakes faulty but thought we'd see what else was wrong, and nothing is. Husband replaced the brake disks and pads on the rear. The system won't bleed and there is no brake pressure. He thinks it is the brake control valve. Any information on obtaining or repairing the valve would be good, is it a big job. He was/is a motor mechanic. We've had the car 14 years and just found this site, it is a good little runner, sound in every way, we don't want to scrap it but we seem to have hit a brick wall with this. HELP HELP HELP

[myglaren]

Did he attempt to bleed the brakes with the rear end of the car raised?
If so there will be no pressure in the rear braking system.

Either have one of the rear wheels on the ground and or select the highest suspension position. If the latter you may need to lift a wheel or suspension arm slightly to start it off - be very careful, I almost lost an arm discovering that trick by accident. The watchword with hydraulic Citroens is to NEVER go under a car that is not well supported on axle stands, ramps or a two or four post lift - even the latter can spring surprises on the unwary.

I presume he is aware of the method of bleeding Xantias but just in case - crack the bleed nipple, attach a longish piece of hose to direct the fluid into a clean receptacle - a largish one, half litre minimum, then with the engine running just press the brake pedal until the bubbles clear and the fluid runs clear and green - it will be a nasty brown colour at first.

It is unlikely to be the brake doseur - hopefully not as it isn't much fun to deal with and is relatively expensive to replace.

Welcome to the FCF, hope you have many years of Citroen motoring to come.

[autumn64]

When we bled the brakes it was in the high hydraulic position in the cab, with all wheels on the ground. He's now got the front wheel driver's side off because he wasn't sure where the brake control valve was, but he's now found it, in the engine compartment up against the bulkhead (where he thought it was so I'm not sure why the wheel is off), but he's mentioning caliper. The car is up on a jack, and maybe axle stands. He will post later, with proper info. Thanks

[citronut]

i always bleed hydraulic citroen rear brakes with the suspension fully up on its highest setting ( suspension fully up )
this opens the brake circuit fully to allow a strong flow of citroen blood out of both rear caliper bleed nipples,

using this method you do not need the cars weight on its wheels,

were are you located

also welcome

[Old-Guy]

The engine must be RUNNING to provide hydraulic pressure to bleed the brakes on a Xantia (or any other hydro-pneumatic Citroen).

[autumn64]

Actually when we bled the brakes only one wheel was on the ground, after he read your post we did it with both wheels on the ground and it bled properly. Thank you. He then put the wheel on and it wouldn't turn, so he took the wheel off, put the wheel nuts on and it still wouldn't turn. It turns out there was rust behind the caliper, so off came the caliper and he cleaned the rust off, put all together and the wheel turns. Thank you again.

[Hell Razor5543]

The calliper corrosion issue is a known problem. It is caused by dis-similar metals having an adverse reaction to each other. If you can put some thin gasket material between the calliper and the trailing arm that should prevent a re-occurrence. You might need to replace the disks and pads.

[citronut]

the obvious sign of caliper jacked out with rust/corrosion is when you take the old pads out and they are wedge shaped,

im surprised you got the new pads back in whilst the corrosion was still in there, ( lump hammer comes to mind )