Can't figure brake problem

One failure mode for wheel cylinders is for their seals to suck air. Kinda rare, but can happen.

I had a similar problem and thought it might be the line from reservoir to MC sucking air. Replaced it and the problem disappeared. If you haven't replaced yours, I would consider that. Or it's also possible that you're letting the fluid level get too low when you're bleeding.

-Chip

'56 ghia, '66 bug

Another thing, how are you bleeding the cylinders? Pressure on the brake pedal, crack the line, then close it again before you let the pedal up? If not you may be sucking air at the wheel cylinders.

-Chip

'56 ghia, '66 bug

Be sure to have adequate "free pedal". When you adjusted the rod, I assume you lengthened it. Probably a no-no. When the piston inside the MC returns, it has to return all the way - so be certain that rod is not totally tight when in the "released" position. It does not need a lot of slack to function properly, but does need some.

Since you are getting good squirts out the bleeders, it stands to reason that you do not have air bubbles back at the MC outlet ports. If that was the case, loosening the brakelight switch enough for fluid to seep out while under pressure, closing it before letting the pedal up (same procedure as for bleeding at the wheels) and doing the same at the outlet ports will usually allow any air bubbles at that point to escape - but it seems that is not a problem for you as you are getting good flow at the wheels.

When you checked all four wheel brake components, did you really get in there and INSPECT? There could be one broken piece at one wheel that is allowing that wheel cylinder to travel way beyond normal and NOT expand the brake shoes. Look for possible broken parts that effect the operation of the shoes. You said you adjusted them all, so it should be good, but check thoroughly anyway.

-BaH

Welcome boominbug,

Hmmm Are you sure that you don't have any brake fluid leaks? The brake line from the master travelling to the rear is the one that rusts the fastest, at least in the rust belt areas. ;-)

If no then are you sure you adjusted all 8 (2 per wheel) brake shoe adjusters?

Make sure the brake hoses are not swelling up when the brake pedal is applied!

Are you still using the original brake master or did you update to the tandem brake master cylinder?

TIP: Adjust all adjusters tight and test pedal travel! If it is now tight then it is an adjustment problem. If it is not tight then you have a hydraulic problem. You must rule out drums that are cracked and flex when the brake pedal is applied too! You can also bleed the brakes with the adjusters tight. Of course after you are through bleeding and all is good to go, don't forget to loosen the adjusters so the drums turn "freely"! later, dave Reminder........ Before you criticize someone, you should walk a mile in their shoes. That way, when you criticize them, you are a mile away from them, and you have their shoes. Frieda Norris

The air that you are getting out of it is likely coming from around the threads of the bleeders. I concur with another poster that adjusting the push rod was a mistake. You need to get it back to it's previous setting, since it worked well before. My guess is that your brake shoes are not adjusted properly and it takes too much pedal travel to push the shoes against the drums. Like already suggested, tighten all 8 adjusters and recheck the pedal. H

Your Flexible Brake lines are collapsed internally and will not allow things to operate properly. If you adjusted the pushrod, you shouldn;t have. Time to open the lines where the flex line meets the hard line and see if you have flow at that junction. this will determine whether or not it is a flex line issue.

I'm gonna go out on a limb here.................You haven't done a search in the RAMVA archives on google for this issue , have you?

Hope this helps.

( the opinion above is exactly one opinion of one individual and should not be taken as gospel by anyone who is more intelligent or more experienced. It is however another point of view that might be worthwhile to checkout )

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The original problem sounded like a defective master cylinder, especially since it happened all of a sudden and there were no leaks. As far as suggesting the brake hoses, I doubt it. Collapsed hoses would generally still allow pressure, but wouldn't release it. You'd still have a pedal. As long as you know the master cylinder is good, your problem description sounds like the one I had. 3 master cylinders and about 20 hours later I finally solved it by simply adjusting the brakes properly. Apparently there is very little amount of fluid moved by a VW master cylinder, and unless the brake shoes are adjusted out far enough, (as with all drum brakes), the wheel cylinders won't travel enough for the shoes to create pressure. I had to adjust the shoes snug, rotate the wheel a few times and adjust snug again. I had to repeat this up to 10 times on a couple of wheels. I would have never believed it was something that simple. I've worked on plenty of drum brakes and never had any that were so demanding for perfectly correct adjustment. Hope it's that simple for you too.

(P.S. I thought my system was sucking air too.. as I had some tiny bubbles too)