Back Brake Servicing

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Back Brake Servicing

Post by biofos on Mon Oct 02, 2017 1:46 am

My '09 Porter MPV has developed a near side rear cylinder fluid leak so it's time for a full rear brake service. I'm putting together all the stuff I'll need to tackle the job but would welcome any pointers, tips or guidance from folks who have already done this job. I've read all the threads relating to rear brakes, shoes, bleeding, balancing valve, and examined the images posted by HighlyJetted and taken many notes.

I've got a pair of wheel cylinders and a set of rear shoes on the way. I have a set of line wrenches, a one man bleeding device non pressurised, brake cleaner and loads of DOT 4. I've already nipped up the flexi pipe that feeds the balancing valve and started spraying all the nipples and flange nuts with WD40. The nuts and nipples appear to be untouched by spanners and there's nothing in the service history that makes me think the brakes have been down before, so hopefully I'll be able to loosen them all without major incident  Smile

In the thread by HighlyJetted showing the balancing valve and how to renovate it, he advocates leaving one of the rubber O rings out of the  valve giving the appearance of a functioning balance valve but acting like a T piece and providing rear braking regardless of loading. Has anyone tried this? Is it successful? Was it spotted on MoT? As stripping down the balance valve will likely be my first job it would be good to know if others had taken up HJ's suggestion and the result.

If any of you guys has any wisdom to pass on please feel free. It's a job I'm not looking forward to as I've not got a pit or a lift.

Many thanks,

John.
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Re: Back Brake Servicing

Post by Raggy on Mon Oct 02, 2017 12:45 pm

Wisom...no...advice...yesy...dont leave the o ring out, the valve is there for a reason and should be working. Yours does not sound to be an issue just the leak so leave it alone unless it looks an issue.
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Re: Back Brake Servicing

Post by biofos on Mon Oct 02, 2017 4:39 pm

Thanks Raggy. I've been underneath again this afternoon between showers spraying WD40 on the flange nuts and nipples again. With the off-side wheel off and the axle chocked at the height it would be with the wheel mounted in its normal position I jacked the van up and down and watched the movement of the LSPV arm. It moves up and down just fine. At the top of its stroke it's hard up aginst the 'button' on the valve and at the bottom of the stroke its clear of the valve by a good inch and a half or more. I'm assuming the LSPV is working correctly as it moves well, doesn't appear to be seized nor is there any fluid leaking from it. In the circumstances I agree with you that it is best left alone. I'll concentrate on the leaking wheel cylinder and the bleeding for now. Anything else that raises its head I can deal with later. Good observation, thanks.
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Re: Back Brake Servicing

Post by biofos on Tue Oct 10, 2017 8:23 pm

A quick update for anyone interested. I decided to do only the jobs necessary as Raggy suggested. I've renewed the n/s rear wheel cylinder. Very pleased I spent time soaking the nut and nipple with WD40. Both came out fine. The brake shoes were hardly worn so I sprayed them and the backplate with brake cleaner and then tried the rebuild. Got to say a total pain in the BUTT. Took five minutes to strip and over an hour to rebuild! The bleeding went well and I pumped through a good amount of brake fluid. I checked the workshop manual to be told the rear brakes are self adjusting. Really? I followed the workshop manual but was unconvinced.

I'd already stripped, cleaned and greased the mechanical parts of the LSPV and knew the valve itself was working, so put it all back together and went for a drive. I wasn't overly impressed with the brakes so took it to my friendly garage who put it on their rolling road. The LSPV worked fine, as did the handbrake on the side I'd done but the o/s handbrake was weak. David suggested I jack the back end right up, drop off the wheels and drums, take off all the tension from the handbrake cable and then manually adjust both brakes. I had no idea how to do this as there's no mechanical adjuster (like on the wifes Qashqai) so it was trial and error. I removed the oblong rubber grommet from the back plates which allowed me to see the adjuster cams (with a mirror) and I managed to adjust the brakes with a screwdriver at each side and gently prising the shoes apart against the hub and watching the cams click as the shoes moved apart. After each small adjustment I'd refit the drum to judge if it was binding and then more adjustment until I was happy with both sides. Then I jumped on the brake pedal several times very hard before resetting the handbrake to 6-10 clicks.

Went for a test drive - what a difference! Wonderful brakes, good handbrake and a general feeling of satisfaction. If you've not done the rears before be prepared for a right chew-on rebuilding the shoes with the auto adjuster, cams, handbrake lever and those awful long brake springs all behind the large hub in the centre that gets in the way of everything. David is right, those auto-adjusters are not effective and with no easy means of manually adjusting the brakes it's a pain. Ironically I'd expected any woes would come from the LSPV as I've never dealt with these before, but no, it was the brake rebuild and adjust and I've done many over the years - but never on a Porter.
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Re: Back Brake Servicing

Post by Raggy on Tue Oct 10, 2017 8:57 pm

Excellent news, well done on getting it sorted. One more hijet kept going on the road, sweet! Keep the news coming. Photos are always handy for others to see what’s involved.
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