Bleeding issues (mk4 calipers on a mk2)

Discussion in 'Mk2' started by jmsheahan, Mar 16, 2018.

  1. jmsheahan CGTI Graphics Designer

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    Hi all,

    Hoping to get some time in on my mk2 this week and top of the list is sorting the brakes out. Last time I tried I was struggling to get them bled to a decent standard I was happy with. Pedal seemed okish with no bubbles appearing through the bleed nipples with engine off but as soon as servo assisted it wasnt great.

    The beam has been off and as such all hard and Flexi lines, handbrake cables etc replaced.

    Spec as follows:

    Modified stubby Ibiza master cylinder (unknown condition to me)
    280mm G60 front calipers (known working)
    Rear Mk4 Golf calipers (new)

    This time around Ive managed to get hold of a pressure bleeder and Im going to go around and double check there are no leaks where Ive disturbed everything.

    My question is do I need to do any reset procedures on the rear callipers or more importantly the brake bias valve (its been clamped for bleeding but the spring is very loose?)?

    I think it might be the mk4 callipers that are causing the issue

    Any help appreciated.
     
  2. KeithMac Forum Junkie

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    I have Mk4 rear calipers and they bled up fine, think I chocked the bias valve fully open.

    I used a Gunson Easi-Blead.

    Possible your master cylinder isn't pushing enough fluid?, mine is stock MK2 16v mc.
     
  3. jmsheahan CGTI Graphics Designer

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    That is a possibility I guess - it's a 23mm so should be up to the job.

    I think I'm going to try bleeding the calipers off of the carriers so I can move them around a bit. Pressure bleeder should help.
     
  4. Tristan

    Tristan Paid Member Paid Member

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    This comes up regularly, possibly should be a sticky.
    Rears off one at a time, up as high as the flexi allows, and the bleed nipple at the highest point and pointing straight up. Piston wedged with something, I use a wind back tool.
    Load compensation valve tied fully open, then bleed as normal. A few dings of a spanner on the side of the caliper while they're hanging helps shake the bubbles out too.
     
  5. Finite

    Finite Paid Member Paid Member

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    Aye I think we could do with a sticky on brakes and fuel systems. If it's a 23mm M/C it will be pushing a bit too much fluid, but the line pressure will be lower for the same effort.
     
  6. jmsheahan CGTI Graphics Designer

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    Thanks guys. Had another crack with the pressure bleeder and calipers off the carriers as described and got a load more air out. Pedal solid with ignition off, not so great with servo kicking in but perhaps itll get better with use. Its been so long since Ive driven the car I cant remember what it was like before.

    Next issue - handbrake. Got brand new late spec cables but lever seems loose even on tightest cable setting?
     
  7. Tristan

    Tristan Paid Member Paid Member

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    Definitely something wrong with the cables so.
     
  8. cupracraig

    cupracraig Paid Member Paid Member

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    sounds similar to what i had the other day when i had some air in the line.

    Make sure that when you bleed the rears, you have clamped the rear bias valve so that its open. this will allow the fluid to flow.

    When my handbrake was going high up when i pulled it, it was because there was some air in the rear offside, manually pushing the handbrake lever on the caliper forced out a bit of air and now the handbrake is back to normal..
     
  9. jmsheahan CGTI Graphics Designer

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    Thanks guys, certainly proving troublesome.

    The bias valve is clamped open (although its got no resistance when up on the stands so stays open without a clamp). I've also tried winding the calipers in and out.

    Heres how the cables are looking in the car:

    [​IMG]
     
  10. jmsheahan CGTI Graphics Designer

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    If the MC was at fault I wouldn't get a decent pedal with the engine off would I?

    The fact the compensator valve doesn't appear to be doing a lot either is odd.

    Tempted to wang the 22mm one back on as I know thats good.
     
    Last edited: Mar 26, 2018
  11. rubjonny

    rubjonny Administrator Staff Member Admin

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    if the bias valve isnt returning by itself then the springs are damaged, it should operate smooth and return to closed when released (assuming the main operating spring isnt too tight of course)

    the handbrake cables seperate issue, make sure the guide tubes under the car weren't pulled out when you removed the old cables
     
  12. jmsheahan CGTI Graphics Designer

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    Guide tubes are in there :thumbup:

    The spring on the outside seems loose to be honest, valve doesn't seem to do a lot, there's no resistance at all on the clamp. The beams been off of the car but didn't touch the valve.

    New valve required?
     
  13. rubjonny

    rubjonny Administrator Staff Member Admin

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    yep new valve is required. for the big spring the correct procedure involves pressure gauges on the rear calipers so not so easy DIY. way I do it is adjust the spring so the slack is just taken out when car is on level ground

    weird how the issue is only 1 side on the cables, both should be the same length so check the long side is definitely the same part number as the good side.
     
  14. jmsheahan CGTI Graphics Designer

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    Thanks RJ.

    I was careful not to disturb the valve when the beam came off but perhaps its just old and had it. It looks pretty rotten. Perhaps the air pocket lies in that as I'm confident the rears have been bled through following advice above but if the valve is staying shut then thats going to cause issues. Odd that pedal is solid with engine off but as soon as servo assisted feels like ****!

    Yes the cables are an odd one. They are the same as what came off as I checked the lengths. I did remove the guide tubes so maybe I haven't quite seated them right or something.

    Having not had mk4 calipers before it's new territory.
     

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