strange brake issue after rebuild

[andy198712]

hi,

i have a 1973 1200 standard beetle.

i striped the chassis down and replaced all brake lines, rear brake cylinders and fitting kits and shoes and drums, all brake lines.
replaced the front drums with discs which i rebuild with new seals and braided lines.

reused my MC as it worked fine.

removed and refitted the pedal assembly.

i bled the brakes by filling the MC and putting a one way bleeder tube on the rear left brake first (RHD) then back right, then front left then front right.

i was alone so hard to test but pedal had loads of travel...

i then adjusted up the rear brakes to have slight noise of dragging.

then got my friend to be pedal man and got no real air out expect one calliper gave me a bit of foamy oil one time then clear after that.

the front brakes work as you would expect, but there is a very large amount of pedal travel then it goes firm.

the rears don't seem to engage fully though? but when you pump the pedal lots it will engage hard on some those pumps but then when done slow again after i could still move the back wheels.....

does this just sound like more air somewhere? or is it rod adjustments as i removed the pedals?

there are no leaks.

on the MC the front two ports go to the front brakes and rear port goes to the rears where it then splits at the T and goes to either rear brake....

cheers

Andy
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[TK-CS]

I think you should check the adjustment of the connecting rod between MC and pedal in any case. As you took it all apart it may be necessary to correct the adjustment there.
If the clearance is really correct then maybe there is more air in the system.
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AC:
'71 1600LE (Type 3 Notchback FI/AT) Sunroof
'75 1303 (Super Beetle) 1600DP, Sunroof
WC:
'77 Audi NSU Ro80
'88 GTI 16V
'91 Corrado G60
Daily:
'04 Passat Wagon 2.0TDI
'13 Passat Wagon 2.0TSI

[Q-Dog]

If you pump the pedal and it gets firmer/higher your brake shoes likely need to be adjusted tighter.
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Brian

'69 Dune Buggy
'69 Beetle Convertible
'70 Beetle

[beetlenut]

You should adjust your rear shoes hard against the drum before you start the bleeding process. It sounds like one of your fittings on the brake lines is not tight enough and is letting in air. On mine, it turned out to be one of the junctions on the front braided line to the hard steel line that wasn't tight enough.
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scrapyards are for quitters
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[andy198712]

cheers guys.

i'll jam the shoes up in the rear and try again, and i'll look into the push rod also. and check my unions, nothing is coming out of them though which if they were leaking air in, wouldn't they let fluid out when pressured? i'll give them a nip though and see
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[TK-CS]

[volksworld]

couple things...as far as rod adjustment goes you should be able to move the pedal an 1/8 in or so before you feel it touch the piston inside the master...too tight and it may not let the back piston retract far enough to let fluid and air release back into the resevoir....second, hopefully you realize that the 2 rear adjusters on each wheel turn in opposite directions so if you turned both of them the same way one shoe is dragging and feels good and the other is fully retracted....if all this is ok theres a possibility the rear half of the master went bad and is bypassing itself....could have gotten some crud in there out of the resevoir while bleeding it, was on its way out anyway etc....pull the boot away from the rod and see if its wet in there....my last resort option is that i have a couple of brake unions and some pre-67 front bus bleeder nipples...these are the same size as a brake line fitting and allow me to cap off and bleed the system at any point ....if you remove the main line from the master and put the bleeder in there, bleed it and get a rock hard pedal you know the masters ok...move down to the end of the main line, the hoses , lines to wheel cyls, etc till you find the spot where the problem occurs...brand new calipers and wheel cylinders can be defective and suck in air but not noticeably leak fluid as can brake lines that dont seat in distorted unions

[viiking]

I’ve commented on a number of posts re changing from drums to discs.

Disc MC’s are generally not the same as drum MC’s. No residual pressure valves on disc MC’s.

Not sure about your model but earlier standard VW disc MC’s required you to bleed front wheel circuit first then the rear. Yes this seems counterintuitive but when you understand how the internal pistons work it makes sense. Not sure if it’s the same for your model. Do you have a Bentley or any info from your MC manufacturer?

I wouldn’t fiddle with it any more until you find out the correct order of bleeding.
_________________
1968 1500 RHD Lotus White Beetle since birth. In the hospital for major surgery
1966 Lancia Flavia Pininfarina Coupe - in the waiting room
Discharged: 1983 Vanagon, 1974 1800 Microbus,1968 Low Light,1968 Type 3

[andy198712]

[andy198712]

[volksworld]

4 inches of play is a rediculous amount and should not have occured by just a pedal r&r unless you removed the pedal stop and put it in a really random spot...i think the rear half of the master is bypassing itself and your mistaking the point at which it bottoms out and hits the front piston for the point at which the rod just contacts the back of the master...i would back off on your pedal rod adjustment and hopefully now be able to feel the point of initial contact....the rod from the pedal to the master has a lock nut on it...loosen it and you can now screw the front part in or out to the proper length, then secure it in that position with the locknut (15mm)....it should have another 15mm hex molded into the rod so you can turn it....in the future , the best thing you can do with any repair is to do one thing at a time and verify that its working before you take other things apart ....its a lot easier to troubleshoot problems that way

[andy198712]

[volksworld]

at the risk of sounding like a wiseass if nothing else had been changed you'd adjust the stop till you had the right amount of freeplay....i guess for a general position the pedal pads should be vertical and not noticably leaned forwards or back....really dont have a firewall-to pedal distance in my head and dont know if your body's still on anyway....maybe someone else will chime in with a measurement....but wherever it is the pedal rod and clutch cable wingnut can be adjusted from there....i think it would be pretty noticable if they were leaning backwards an extra 4 inches though....

[andy198712]

[andy198712]

https://wolfgangint.com/news/post/pedal-stop-adjustment/

i'll do that

i may make a new stop and install a rivet on the floor if i can or weld the nut on under the floor as my stop looked pretty beat and the floor just has a bolt hole and no fixed nut.... was a pain to tighten on my own!
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