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Nov 15, 2018 17:25:22 GMT
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Hi guys, hope someone can help. 1996 vw t4, Has been off road a number of years, Pedal was soft when purchased,
Has had:
*new flexi hoses *new bleed nipples *new pads all round *new master cylinder *new brake bias valve (load valve) *and brand new fluid purchased today.
Master was bench bled , Whole systen has now been bled multiple times , different methods including pressure bleeding, 2 man method( 1 man and a wife) , and both at same time.
No air coming out, no leaks or wet joints All calipers free and sliders freshly greased
Still the pedal is soft. Not only soft, its exatly the same as the day i bought it. Goes all the way down when van running, but not when its off, its firm when off Pedal has no adjustment on t4's
At whits end now, been trying to bleed it etc after work for last week or so now. Last thing left before first mot in years...
Any help appriciated, would be lovely to actually drive it...
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steveg
Posted a lot
Posts: 1,563
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Nov 15, 2018 17:36:17 GMT
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I guess it's got a servo, does it do the same with the vacuum disconnected and plugged ? When the pedal goes down is it actually operating the brakes. I'm thinking too much servo assistance although not sure how that wold happen.
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Nov 15, 2018 17:54:06 GMT
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Yep has a servo, has a firm pedal when engine is off (no servo assist) but as soon as its running the pedal will go right down to the stop
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Nov 15, 2018 18:55:44 GMT
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can onltly be air left in the system, are you bleeding the rears with it loaded or with the rear lifted and wheels off?
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Nov 15, 2018 20:06:44 GMT
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On the ground, have also tryed tying up the prop valve to send more fluid to rear wheels but still same.
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Nov 15, 2018 20:37:57 GMT
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Is it petrol or diesel?
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Needs a bigger hammer mate.......
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Nov 15, 2018 20:39:31 GMT
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Petrol, 2.5 5cylinder
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Nov 15, 2018 23:55:16 GMT
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Hi, Trying driving it around to bed the pads into the worn discs.
Colin
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pxr5
Part of things
Posts: 198
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Try blanking the pipe to the rear wheels and bleed, or blank each corner at a time untill you isolate the problem.
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I had this on my old Mk1 Escort. We did everything. Everything was new. We bled it and bled it and still the pedal was soft. It was the wheel bearing that was slightly too small, and as the weight of the car sat on the bearings, they would splay out and camber the brake disc in, opening the caliper. So you'd push the pedal and it felt soft because the caliper was having to pull the disc straight again before it could clamp onto it. You have no idea how long it took to discover this, and we found it purely by chance. Maybe your bearings are worn?
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1974 Skoda S100 tarmac car 1998 BMW 750 daily 1994 Mitsubishi Evo2
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Ritchie
Club Retro Rides Member
Posts: 765
Club RR Member Number: 12
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Try blanking the pipe to the rear wheels and bleed, or blank each corner at a time untill you isolate the problem. Yes, I would go round and gently pinch the flexis one by one with a pair of vice grips, or all 4x to eliminate the Master cylinder.
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Wheel bearings are fine , no play in any, i was thinking similar in regards to movement before with the caliper brackets but ruled it out.
Hadnt thought of the pads bedding in idea though. Thats a possibility.
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Try blanking the pipe to the rear wheels and bleed, or blank each corner at a time untill you isolate the problem. Yes, I would go round and gently pinch the flexis one by one with a pair of vice grips, or all 4x to eliminate the Master cylinder. Tried this yesterday evening but had same pedal, now I'm thinking either i didnt squeeze them enough or the new master is dead? . Gonna have another go tonight..
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Nov 16, 2018 11:48:44 GMT
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If it has ABS it could be you're not bleeding it in the correct manner. Tried this on a few MK4 Golfs, could never get a good pedal until I bled it the right way.
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Nov 16, 2018 12:19:17 GMT
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Is the pedal push rod coming fully back and giving a small gap to the piston with the pedal fully up?
If the piston does not fully retract then it will not draw fluid in as the inlet port remains covered.
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Nov 16, 2018 21:08:20 GMT
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Forgot to say, hasnt got ABS .
As for the pushrod returning, it seems to. If i were to grab the pedal it wont come up any further.
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froggy
Posted a lot
Posts: 1,099
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Nov 16, 2018 21:23:13 GMT
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New pads on old discs Iād go and drive it and heat cycle the pads a few times , same thing with the big sprinters / grafters after new pads all round need a quick run in to get the pedal feel back
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djefk
Part of things
Posts: 844
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Nov 17, 2018 17:47:15 GMT
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I think your new master cylinder is faulty
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I had this on a Golf 1 . Turned out to be one of the front calipers... Bizarrely, no visible external fluid leak. Found by clamping one pipe off at a time š Worn discs with new pads will also do it. If there is a big ridge on the outside of the disc,it might be worth taking it off with a grinder,as a new pad flexes on this before the pedal goes hard.
Was it a new,out of the box mastercylinder? Not recon? I do recall certain VW master cylinders have a piston that gets screwed together with a big spring and a torx bolt. There is a set distance that the screw needs to be tightened to,otherwise the seal sits in the wrong position and doesn't open the port for the brakefluid to go into the cylinder. You cannot get decent pressure or pedal feel .( This also means it won't let the air in the system to self bleed back into the reservoir when the cylinder is in the '"at rest" position)
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Last Edit: Nov 18, 2018 5:20:47 GMT by Deleted
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