Master Cylinder Pushrod Adjustment

[abl1111]

A few weeks back, I R/R my master the cylinder on my 79 Super. Pretty straightforward. Spacers in place ( a b*itch to do alone !!!! ) - all bolted up nice. I bled the brakes both hydraulically and the pump and bleed method.

THE ISSUE

I noticed that the travel before my brake pedal touched the master cylinder 'pin' was too long. I tried to adjust it via the bolt/stop on the floor near the pedal assembly - but that adjustment is already max'd out. I have a travel of 2.5" ! as opposed to the Bentley spec of 3/16" ?!

I don't want to touch the factory-set rod length adjustment before I got some input from you guys.

What's your opinion ?[/u]

[Northof49]

If it's like mine, you first set the pedal distance to the firewall using the pedal stop on th flor, then when that is correct you look at the length of the rod.
_________________
1958 Karmann Ghia owner

[Tim Donahoe]

ab,

do not fear to adjust the master cylinder pushrod length. I've done it a number of times and it's quite easy (if you know how).

This is one of John Muir's methods that actually isn't a weird way of getting the job done.

You're already adjusted the stop plate to line up your pedals, correct? Okay.

What you're looking for is a quarter-inch "before resistance" play, measured at the top of the brake pedal. If you want to go 3/16ths, be my guest. It's actually 3/16 to 9/32 of an inch, so I go 1/4 inch. This amount of play will translate to a 1 mm amount of play between the master cylinder push rod tip and the master cylinder piston. So how on earth do you do that?

Easy.

Loosen the locknut on the mc pushrod. Turn the pushrood in until it stops. You can feel that the tip of the pushrod has made contact with the mc piston. You don't keep turning at this point because you want this contact to be just enough to be contact. In other words, don't keep turning after you feel contact. You can loosen it and do this again if you feel paranoid.

Now back out the pushrod 1/2 turn only. This should give you 1/4 inch pre-resistance freeplay (measure with a ruler--maybe twice). If the freeplay is over or under the 1/4 inch, turn the rod a teeny bit one way or the other to get the 1/4 inch. But I never have to play with it ....

Once the 1/4 inch is correct, smile and tighten the locknut--then check the freeplay one last time.

From reading Bently, you'll be afraid to do this. But the guy at the VW plant knew how to do it--and now you do.

You need this 1mm clearance inside the mc so that you don't block compensating ports, which will not allow the mc to refill when it should.

You might spray a little WD 40 on the rods threads before doing this.

Be brave and conquer!

Tim

[abl1111]

Tim,

I'll try this tomorrow. Had a bad wheel cylinder today ( at least it leaked under 10 psi pressure bleeding ). So, I spent a good part of the day tracking a non-chinese one down ( boy, the chinese ones I saw are made like SH*T ! ). Settled for italian made.

Then, the brake line connecting to that wheel cylinder failed so I had to make my own ( sigh… ).

Master Cylinder - One thing I did not realize was how that bolt that acts as an adjuster really holds the clutch pedal up ! I will re-adjust that and then go for the space between the pedal and the MC. 1/4" sounds fine to me. Thank you for the guidance and confidence boost. I try not to do anything if: a) does not make clear sense to me b) a bible type manual says not to c) we're talking about brakes !


[/u]

[Tim Donahoe]

ab,

I'm very sticky about brakes, too. When I did my front disc conversion, I bought the best German MC I could find FTE or ATE (something like that) on the box from Wolfsburg West, and new German rubber lines.

Conversely, I bought an Empi front disc conversion; but I had heard very good reviews on this kit (from people I trust at Wolfgang International), and I was very happy with the quality and fit that came with the kit. Of course, later I found out that the kit was cheaper because it didn't contain a number of new items that, say, Topline includes in their kits (which also include Empi calipers, by the way).

The adjustment should be done at the pedal stop first, then at the mc rod.

Tim

[abl1111]

All done. NICE ! Feels tight. I think that the 'new' aftermarket stuff probably is slightly different and these adjustments are necessary.

NEXT - Now onto why my emergency brake is not functioning !

It never ends !

[DeathTrap]

[Tim Donahoe]

Brake adjustments have their place (down the road), but sometimes you got to prime the pump, first. And the pump needs to be set up to spec.

Such advice also works in a good marriage ... but I digress

Tim

[abl1111]

I cannot say enough about the effect of adjusting the brake rod to spec.

I think I have been driving, and I'm sure others are too, with that adjustment way off for a long time. I always blamed it on wearing brake shoes, needing to bleed, etc. All those things must be correct, but the final adjustment is to make sure that the rod is 1mm from the master cylinder valve. Makes brake pedal travel much shorter and effective...

As for the e brakes - I entered a new post, but I've ordered new brake cables. I'm 'pretty sure' that's the issue...

[DeathTrap]

Apparently they come in various lenths

many times it would be my parkbrake height along with pedal travel indicating need of adjustment

when adjusted the shoes sit very close to the drum taking little travel, pedal or lever to make contact.

as for me, doing bug brakes for some period from the 60's on professionally
I would back off the park brake cables before adjusting the brakes as they (the pk brk cables being tight) would provide a false relationship making the shoes snug up prematurely. Meaning I just couldn't achieve full pedal height with the park cables still tight.

All brakejobs came with free adjustments for life of the shoes

[Mr.Duncan]

[Tim Donahoe]

Have you installed that MC, yet? If not, make sure you hook up the blue reservoir lines first so, you have some room to get them on well. And get a little brake fluid on the nipples. New blue hoses are really tight.

I hooked up everything, first (my daughter held the MC insdie the cabin), and put the hoses on last. What a bear that was.

Tim