low brake pedal...help

[Robert H]

I recently changed the front brake shoes on my 65 beetle, and in the process found that the master cylinder was leaking, so I replaced it as well (FTE, German) (Allegedly). The rear shoes are fairly new, about 3000 miles on them. I adjusted all shoes to be just touching, set the master cylinder pushrod to about a mm of free travel. I bleed at all wheels twice with a pressure bleeder. The brakes work OK, and don't feel spongy, but, the pedal is still low. Like maybe 2" off the floor. Lower than the accelerator pedal (I hit the accelerator pedal while applying the brakes) Any suggestions where to look next?? Thanks for any help!

[TDCTDI]

Adjust the shoes again, then check the pedal, then adjust the shoes again. It takes a few times for the shoes to find their center. Then, you will have to adjust them three or four times until they completely seat/wear into the the proper radius.
_________________
Everybody born before 1975 has a story, good, bad, or indifferent, about a VW.


GOFUNDYOURSELF, quit asking everyone to do it for you!


An air cooled VW will make you a hoarder.


Do something, anything, to your project every day, and you will eventually complete it.

[mukluk]

How far is the brake pedal from the firewall at rest, measured from the top of the pedal straight forward? It should be about eight inches distant. If less than that, the pedal stop bolted through the floor should be adjusted to allow for the correct at rest pedal position and the pedal pushrod length readjusted.
_________________
1960 Ragtop w/Semaphores "Inga"

[Cusser]

You may find that the recess on the new master cylinder was deeper than than on the old one, so the brake pushrod MAY need to be adjusted. But read up on this in the repair manual before doing this.

And yes, new brake shoes need to be re-adjusted several times until they wear to match the drum arc.
_________________
1970 VW (owned since 1972) and 1971 VW Convertible (owned since 1976), second owner of each. The '71 now has the 1835 engine, swapped from the '70. Second owner of each. 1988 Mazda B2200 truck, 1998 Frontier, 2014 Yukon, 2004 Frontier King Cab. All manual transmission except for the Yukon. http://www.thesamba.com/vw/forum/album_page.php?pic_id=335294 http://www.thesamba.com/vw/forum/album_page.php?pic_id=335297

[FeelthySanchez]

No mention of the drums, or their condition: were any of the linings properly arced to match drums?
_________________

[sjbartnik]

[Robert H]

Thanks for the replies. I readjusted the shoes, and that helped a lot. The pedal is about where has been in the past, and has about 3 inches of travel until brakes are applied pretty hard. I understand where the 1mm pushrod travel is supposed to be. I think I have that close. The clearance from the pedal to the firewall at rest is about 7.5 inches, and the pedal stop is adjusted away from the firewall. Not all the way to the end of its adjusting slot, but definitely off-center of the slot, so perhaps this would be a area to work on. If I moved the pedal stop closer to the firewall, that would put it closer to the center of its adjustment range, and move the pedal away from the firewall, closer to the 8 inches suggested. I will also review the section in the Bentley manual on adjusting the pushrod. All good stuff. Thanks again.

[Robert H]

Oh--I forgot to mention--the drums are original VW, and appear to have not been turned. They measure within .010 of nominal. The fronts are round (as near as I can tell) and the rears are a few thousandths out of round, but not bad.

[TDCTDI]

Do NOT start messing with the pedal stop. The moment you loosen it, the clutch pedal will drop to the floor & disengage the cable from the pedal requiring you to remove the pedal assembly to reattach it.
_________________
Everybody born before 1975 has a story, good, bad, or indifferent, about a VW.


GOFUNDYOURSELF, quit asking everyone to do it for you!


An air cooled VW will make you a hoarder.


Do something, anything, to your project every day, and you will eventually complete it.

[mukluk]

[sjbartnik]

[FeelthySanchez]

Out-of-round drums can cause pedal pulsing. Did you wish to solve the problem, or just cough-up more evidence?
True-up the drums, & arc the linings to match.

[Robert H]

The blue Bentley VW 1200 manual says to leave the push rod alone and adjust the pedal stop. The problem with that is that over the last 50 years, it is pretty likely that some folks (including me) have messed with the push rod. The book says that the pushrod length should be left alone, and that it is set at the factory, but they don't say what it is set at. But Bentley does say that the length is measured from the eye where the pin that attaches the rod to the pedal goes to the rounded end of the rod. I looked thru other books, and the only place I found that measurement is in a book called "Volkswagen Technical Manual" by Henry Elfrink, published in 1964. This book says the pushrod should be 52-53 mm. That's a touch over 2 inches. Has anyone else seen a source for this dimension? However, I guess one could back into it by setting the pedal-to-firewall at 7-7/8", and then adjusting pushrod to match. (thanks for the info mukluk) That might actually be better. I don't find the 7-7/8' dimension in the blue Bentley, but I do find it in the Bentley book for later models. Probably the same? I think that if I adjusted my pedal stop to about the center of travel, it will probably get close to the 7-7/8". The later book actually addresses the possibility that the pushrod has been altered, and what to do about it. Thanks for the tip on keeping track of the clutch pedal. Not sure I would have thought about that.

[sjbartnik]

Yeah generally speaking the push rod should not be messed with but it is possible that a different master cylinder from a different manufacturer may require a different push rod length or if you switch from single circuit to dual circuit, etc. I think the point is to not default to adjusting the push rod, but understand what it does and the circumstances in which you may need to adjust it.

The push rod needs to be long enough (and hence the specified pedal distance to firewall of 7 7/8") so that if one brake circuit fails, you still have enough pedal travel to apply brakes on the second circuit before the pedal hits the firewall. If your push rod is too short you're gonna have a problem there and you will find out about it the hard way.

If push rod is too long then you risk blocking the compensating ports inside the master cylinder in which case the brakes will slowly lock on as they warm up.
_________________
1965 Volkswagen 1500 Variant S
2000 Kawasaki W650

[Cusser]