73 Super FTE master cylinder follow-up

[mascrappo]

I installed a FTE German master cylinder today, I did not bench bleed. I have spongy pedal on the top 3/4 of pedal. At the end of pedal it will lock the fronts down, skids. I hear the back drums click when I push pedal, fluid comes out when bleeding. Replaced old ATE cylinder as it was leaking badly out the pushrod. The brakes worked better than now, but leaked.

Now, I realize I need to do some brake adjusting, but why the difference in pedal travel? I have solid fluid stream from all 4 wheels. A quart of Bosch brake fluid has been run through the system today and while it stops, I have to go WAY down on the pedal, it stops straight too.

Brake lights turn on when pedal is way down and stopping, but half the pedal travel is mush and no lights.

I did not adjust the pushrod, it is a little slacky, but even this shouldn't cause what I am describing. Totally stock system. Thoughts????

[Tim Donahoe]

Loosen the push rod locknut and turn the pushrod in until it just touches the master cylinder piston. Now, turn counterclockwise one-half turn. At this point, using a ruler, check for the free play at the top of the pedal when pushing by hand. It should be 1/4inch, which provides the required 1mm freeplay between the end of the pushrod and the back of the mc piston.

If, after performing this adjustment, you don’t 1/4inch free play at the pedal, turn the rod a little one way or the other to achieve this distance. Tighten the locknut on the pushrod when done.

Bleed again if necessary.

Tim
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Let's do the Time Warp again!

Richard O'Brien

[mascrappo]

[VW_Jimbo]

It because the rod was improperly set, like Tim stated.

When the rod does not enter the Master Cylinder far enough, it will not fully depress the inner piston and move fluid in a high enough pressure to fully inact the shoes or pads. It may push the piston far enough to create some resistance but not enough.

Good luck tomorrow!
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Jimbo

There is never enough time to do it right the first time, but all the time necessary the second time!

[mascrappo]

Well I spent all day working and adjusting what needed to be done. NO IMPROVEMENT. I took it to my friend who has a pressure/vacuum bleeder this afternoon and did twice, still no pedal. Adjusted all the brakes and pushrod too.

We are in agreement that it must be a shelf-dead German unit. As there are no date codes I could find, it may be 10 years old and weak rubber for all I know.

I emailed the place I bought in from and await the reply. Thanks for the tips guys

[green1303]

I installed a master cylinder once without bench bleeding it first. After a fair amount of normal bleeding, I had no pedal and adjusted the push rod, giving me some pedal right at the bottom. There was still air in the system. We had to bleed each wheel cylinder until the fluid was clear and then keep going, because there were additional bubbles farther back. We went around the car two or three times, continually filling the reservoir and bleeding. The process took several hours, but I eventually had good brakes. It’s unlikely that the master cylinder is the cause of your problem. If you have no pedal, no leaks, and good adjustment, then you have air in the system.
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1973 green Super Beetle

[mascrappo]

I have ran almost 2 quarts of brake fluid through the system, bled it at least 6 times, plus a professional air evacuation over the past 2 days, there is no air left. It is just a weak master cylinder.

[Maddel]

[Glenn73]

Is it all drum brakes? Or do you have disc brakes on the front?
The drums need to be adjusted to full lock to bleed it proper. If not at full lock you can have similar issues. There is also a factory spec for the push rod length. You would adjust the pedal stop on the floor only. You do have to readjust the clutch though too.
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1973 Super Sat from 93-2008
https://www.thesamba.com/vw/forum/viewtopic.php?t=...highlight=
1986 Vanagon thread Sat from 2005-2017 https://www.thesamba.com/vw/forum/viewtopic.php?t=719692

VW Transporter production film https://www.youtube.com/watch?v=rceTqDtGgz8

[mascrappo]

I had great brakes before the change, only changed because old cylinder leaked badly out the pushrod. I adjusted brake shoes anyway since I have not done in several years, but they didn't really need it.

Now the new cylinder seems to be getting worse, so it tells me it's weak and losing what pressure it had. Plenty of samba posts describing the same things and new master was to blame.

Again thanks for all the tips, but I am not wasting any more time on this cylinder and will just replace it.

[Starbucket]

Take that MC apart and see what's wrong with it, if its just a torn cup put a kit in it and bench bleed it.

[mascrappo]

Alright, due to the guilt trips, I bled it again 4 more times tonight per right front, left front, right rear, left rear. Tonight I cracked and bled the fittings on the master cylinder, front then rear. Well, no air I can find and the pedal still went way down. Drove it, stops straight, and will lock up the tires--but you have to stand on it.

After the drive, however, I am able to quickly feather pump the brake pedal and pedal comes right back to the top and holds (where it was before the change). Let off the pedal and try again, almost to the floor. Quickly (not the full pedal travel) pump, brakes are hard and on top, per say.

What gives? Do I have my helper learn the fast/short pump trick to get pedal "up" then bleed again? Is the cylinder truly weak and bypassing? I have no hair to pull out, but if I did! Keep the suggestions coming folks, thanks!

[Starbucket]

OK you bleed brakes Right REAR, Left REAR, Right FRONT, and Left FRONT. You are doing it exactly wrong per your post.

[mascrappo]

[vernonc]

[green1303]

If you can pump up the brakes, and the pedal then holds firm at the top under foot pressure, then I would adjust the brake shoes out farther.
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1973 green Super Beetle

[sokyjeepster]

I had the same issue when I change the master cylinder in my 71 SB back in November. After replacement, I bled several times. I tried the push rod adjustment, but the rod came out before making contact, so I replaced it back to as original as I could. I ended up doing a Brake Pedal Travel adjustment (http://www.vw-resource.com/brake_adjust.html#travel) and then bled again. After that, all of the sponge was gone and everything ( appears ) to work great so far (just shy of 1,000 miles since).

[Starbucket]

[mukluk]

[vernonc]