[Brakes] Rear brake issues

[bobalobmitchell]

Long story short, i put on a new refurbished axle, new flexis and all new copper brake lines. Only thing not changed was the brake compensator valve. I did put on a new spring (ebay) and set that just touching the lever. Bled, away for mot.

It failed on rear brakes imbalance and I overheard the tester complaining about not being able to lock up back brakes and that the arm was just "flapping about"

Took it back, bought a brake pressure test kit.

I have rigged the kit up last week and read the citroen docbox i have on my computer (ahem)

It says to set the front to 1450psi and read the rear pressure. As far as i understand, lever right out should only just be over 20bar. It wasnt, and i have a left/right imbalance, so i have changed the valve.

Now this is where the fun begins..

Setting the front to 1500 the back is only reading just over 100psi. Moving the lever has no effect, and front @ 3000psi has no effect.

Have i knackerd the master cylinder? I took the back gauge off, set front to 3000psi and i can still grab my rear drums and turn them if i put some effort in.

I am still to swap gauges and check for reading issues. I cant understand why i was getting too much pressure on old valve and now new valve is giving very little.

Thanks


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[bobalobmitchell]

Sorry i should add that the old valve with lever out was giving well over 1000psi. I had also put on new slack adjusters yesterday.

New valve is also giving out well over 2000psi with lever fully out so i am stumped


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[brodfather11]

The brakes are dual-circuit which means front left and right rear are on the one brake pipe circuit and front right and left rear on the other. What I cant understand how you managed to get different pressures for front and rear ? or am I reading it wrong?.  

I had problems once by stripping out the metal brake pipes prior to renewing  them all and had problems similar (I think)  to yours because of fitting  new pipes to the wrong outlets when I got back round to it a month later.

Little or no brakes at the rear and lots of grief because I had not taken notes /photos or labelled where the pipes went to and came from. 

[bobalobmitchell]

Thanks for the reply. 

Have been at it all day and have had no progress. Things have gotten worse.

 What I cant understand how you managed to get different pressures for front and rear ? or am I reading it wrong?.

The pressure gauge kit I bought has various different bleed nipple adaptors so screwed one into the front right caliper, and the other into the rear left brake expander bleed.

I am under the assumption, going by the Citroen Technical Documentation is that the Rear Load sensing valve should restrict this flow. 

They say that the method is to press the foot brake until a Front pressure of 100 bars is obtained. Then check the back and set this to X bars. X being the sticker inside the engine bay on the left side of bulkhead. [Image: e2ap01uc.jpg]

However the issue i am having is that the valve doesn't seem to be restricting the flow of fluid at all? Moving the lever, you would expect the gauge to rise and fall but it doesn't seem to move the needle. 

I had problems once by stripping out the metal brake pipes prior to renewing  them all and had problems similar (I think)  to yours because of fitting  new pipes to the wrong outlets when I got back round to it a month later. [Image: dodgy.png] 

Little or no brakes at the rear and lots of grief because I had not taken notes /photos or labelled where the pipes went to and came from.

Before I removed the old axle I took pictures of the pipe routing and put the old valve back on as per the pictures. I couldn't get the valve pressures to stay low, so I replaced the valve a few days ago thinking the internals were knackerd and letting the fluid thru regardless. But it seems that the new valve is doing the same?

I wonder if i have somehow managed to mix the pipes up?

Sorry if this is all getting confusing. 

Here is a list of what i have done.

-New Axle on
-New pipes to rear where they were rusting.
-New flexis both front and rear.
-New pads and discs front
-Used the old Rear brake valve. New spring from ebay and set per instructions. Van on ground, have the dome nut touching the lever to take up slack.
-Bled everything thru with a Gunson ez bleed @ 10psi +/- 2psi.
-Mot. Failed on rear brake imbalance and not enough rear brake effort.
-Checked and tried to set rear valve with pressure gauges, rear valve recording too much effort with lever fully out, simulating no load on axle.
-New valve on, tried to set pressures again, still the same. Pressure on rear goes to 2250psi! Potential for lockup if thats the case.
-New back brake slack adjusters.

Rear back brakes had little or no effort in mot but i think this was due to knackerd slack adjusters..

I have bled thru so much brake fluid and swapped gauges over so many times today you would not believe. 

Now i am at the stage where i have a very soft pedal with no effort. I wondered if i have somehow managed to invert the seals on the master cylinder, so i took that off earlier. Checked the seals and will look again tomorrow.

Turning into a nightmare of a job!

[bobalobmitchell]

Here are some images I took of the old valve before removing the axle.

As you can see the pipe nearest the top sort of crosses and goes into the lower of the valve. 
The lower pipe crosses again and goes into the upper. 

Would it matter if these were switched over? Maybe someone would be kind enough to check their Berlingo to see how these pipes go?

Thanks

[bobalobmitchell]

Van has now passed Mot New brake valve fitted, new slack adjusters, shoes and drums. Brake test on rear was low again so tester adjusted brake valve up. Rear brake test values increased alot.


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[gilbertotron]

Well done mate! What was the fix in the end?

[bobalobmitchell]

When I had put the new brake compensator valve and spring on I didn't set the arm very far in. The Mot tester roller brake tested the rears and it failed, i had told them it had just gotten a new valve and would just need more pressure.

Put it up on the ramps, gave the spring a bit more "pull" so the valve was open more. The brake test was almost perfect after that.

The rear brake imbalance was caused by the near side slack adjuster not working. This was throwing the handbrake adjustment to buggery aswell.


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