suspension and brake confusion

Nat · Post by **Nat** » Sun Dec 18, 2011 6:11 pm

could someone with a better understanding of the hydraulics than me tell me what I've got crossed over, or just wrong...

I've taken the rear subframe off, cleaned painted etc and now just put back on with all new pipes

started it up, car goes up, no leaks yay.

drop it to the normal driving position, front drops, back stays up in the air.

further to this I went to bleed the brakes but nothing ever came out, pressed firmly on the brake pedals with rear suspension bleed screw out but nothing happened. This may be due to low LHM though (spilt lots when I was doing the rear subframe and haven't put any back in yet) or maybe due to a problem somewhere as it has enough LHM to go to full height...

Nat · Post by **Nat** » Sun Dec 18, 2011 6:34 pm

ok, little update

it only goes to ether the fully up or fully low positions.

I should probably point out that I replaced the rear height corrector as I destroyed the old one trying to get the pipes out :S

it'll move up to the top, then setting to bottom moves all the way down. setting it to either normal or high normal, the front moves up but the rear stays down until you select fully up then the rear rises.

RobC · Post by **RobC** » Sun Dec 18, 2011 7:19 pm

sounds like loads of air in the system.

not sure if you knew, but to bleed the rear brakes there has to be 'load' in the rear suspension. this entails either loads of sand/bricks/mother in law sat in the back (with at least one wheel on the ground, obviously) or, more easily, putting the suspension in the highest setting. if you do the latter make sure there's enough lhm in the tank so no more air gets sucked into the system while you're bleeding the brakes.

Nat · Post by **Nat** » Sun Dec 18, 2011 8:07 pm

in that case I'll be a couple of litres of LHM tomorrow and retest, thanks.

RobC · Post by **RobC** » Mon Dec 19, 2011 12:10 pm

If adding more LHM, beware of LHM-overflow at the tank when you put the car back in its low position. Not really a big problem though, apart from the mess!

I usually position some rags underneath the tank as a precaution against too much spillage.

Nat · Post by **Nat** » Mon Dec 19, 2011 6:59 pm

ok, topped up the LHM so the level indicator is between the marks when in the fully up position, left it run for a while and checked it was still between the marks and it is.

put the car fully up down up down a few times to make sure it was all pumped around...

still the same problem of either being fully up, or fully down.

could I have positioned the height corrector incorrectly?

could pipes be switched over? I did disconnect all and then re connect them half way down the car (the front half's of the pipes were fine and I couldn't undo the coupling) but I though I'd been careful to connect them the right way... although now I'm having problems I'm doubting myself...

any other ideas?

JayW · Post by **JayW** » Mon Dec 19, 2011 7:19 pm

I would suggest standing the rear wheels on something like breezeblocks or timber (remembering they move back and forth as the suspension height changes) so you can get underneath it in the low position then manually adjust the height corrector on the ARB to see if it will move in increments. If not i'd also suggest the height corrector may be at fault?

You don't need a load to bleed the brakes as the weight of the car itself is load enough but increasing the load increases the pressure of fluid to the brakes and therefor speeds up the process.

The fact that the adjustment up and down does actually work (albeit insufficiently) suggests it's plumbed up correctly as you obviously have supply in and out the correct way round.

Nat wrote:

put the car fully up down up down a few times to make sure it was all pumped around...

Bear in mind that with the work you've done it can take an INCREDIBLY long time to bleed the suspension, also bear in mind the brakes are a dead end in the system so it might be worth trying to bleed the brakes first with the suspension on high as it could be the brake lines feeding air back into the system, then give them a final bleed after all the faffing around.

ken newbold · Post by **ken newbold** » Mon Dec 19, 2011 7:28 pm

When bleeding the rear brakes, I'd suggest you remove the bleed nipples completely and ensure the hole is clear to allow fluid out. Often these are blocked solid with crud and rust.
The suspension should be at full height or at least the rear wheels have load on them otherwise they won't bleed.

As for the height corrector, ensure you have the linkage all positioned in the right place, adjustment of the ride height is a very fine adjustment and can so easily be just a tiny bit out which would mean you're up to top or down to bottom.

Nat · Post by **Nat** » Mon Dec 19, 2011 10:45 pm

we put it up on block and took the linkage to the cabin off.

pulling on the leaver to the height adjuster is then very stiff, you really have to push on it to get the car to move and then it feels as though its binding, moving in steps and it travels all the way to the far extreme of the suspension travel.

to stop it at a position between top or bottom you have to really pull back on the leaver in the opposite direction to stop the travel.

the height corrector is a "new" reconditioned unit, not that that means its working.

also, looking at the haynes manual it suggests that there should be some teeth on the linkage arm that allows selecting of positions but on mine its just smooth through out the box that holds link, this means huge amounts of hysteresis on the travel, but this would have been the case before and it was working fine to my knowledge.

I still haven't bleed the brakes so that could be having an effect some where along the lines

ken newbold · Post by **ken newbold** » Mon Dec 19, 2011 10:52 pm

The lever should move quite freely, even when connected.

I would take a look at all the points where it's housed and lubricate them.

Nat · Post by **Nat** » Tue Dec 20, 2011 1:17 am

well, sorted out the height correct, seems that it was positioned a little wrong causing the linkages to aply a little sideways pressure on it so it was sticking.

can't bleed the brakes though, there is only me so its a bit challenging to be in two places at the same time but:

took the wheel off and then choked the disc on some wood so I could get pressure in the rear suspension. lifted the suspension height so there was lots of weight on the rear suspension and then opened the bleed valve, pressed hard on the break pedal for quite some time, then went back to see if any fluid had dribbled out and nothing, nipple was still completly dry, pressed on break pedal a few more times but nothing.

am I doing something wrong or... have a I got a blockage in one of the pipes somewhere? maybe from the suspension back to the font of the car? ABS actuator to rear subframe...

and on an unrelated note, the oil you put in the rear diff really stinks, can't get the smell off my hands urrrggggg

citronut · Post by **citronut** » Tue Dec 20, 2011 8:24 am

you dont need two people to bleed hydraulic citroen brakes asit does not require the open kniple press pedel close kniple routine,

and if you have the suspension on high you dont need weight on the wheels as well,

sounds like you have some pipes mixed up to me,

regards malcolm

Nat · Post by **Nat** » Tue Dec 20, 2011 9:26 am

having slept on it I've come up with a possibility,

getting the pipe into the return sphere for the brakes (from the haynes manual the 4x4 is quite different to the normal setup, you have to feed the pipe up and then drop it down into the top of the sphere in a very small gap, also the spheres are in completly different places as the rear axle wiould go through the normal sphere locations...) and I can imagine that I put the end of the pipe in some waxoil/underseal/dirt/etc whist doing it. So I'm going to disconnect the brake return pipe halfway along the car (made a join to save me running it to the front and also couldn't undo the union at the front of the car...) and check that it pisses out... (obviously I'll take the pressure out first etc) then if it doesn't I know I've blocked the pipe, if it does come out I know I've got some pipes crossed over (not sure which two I could have crossed as theres only 3 x 3.5mm pipes and the suspension is working...)

citronut · Post by **citronut** » Tue Dec 20, 2011 1:48 pm

you do know there is around 2,5/600psi running through the brake circuit dont you,

regards malcolm

Nat · Post by **Nat** » Tue Dec 20, 2011 3:19 pm

ok, so I've disconnected each section of pipe and checked that their flow all the way to the caliper.

seems to be the caliper is blocked? well, I tried connecting just one half of the caliper and couldn't get any to flow out the connecting hole, the piston didn't move and nothing happened, but on the other hand just befor I connected the caliper I had fluid flowing out the pipe.

when I took the brakes off I did push the pistons back in to see how easy they moved (one side of the disc was less worn than the other and I wanted to check for free movement) and the pistons moved with out much force (just my fingers not trying that hard) but now I'm wondering if by pushing all the way back I've sealed a hole some where. eitherway I can't pull them back out and the brake system can't push them back out, its only been a few weeks since I took them off, not long enough for anything to have happened...

anyone know if thats a possible explanation?