Brake System Pressure/Bleeding Troubles

[shiskabobnut]

Hey gang,

After working relentlessly for 5 days on my 1973 standard beetle brakes, I still have no working brakes. I have scoured the posts on here and am still reading up, but haven't exactly found a post describing my condition.

My brake pedal goes completely to the floor even after numerous bleeding trials. I can get air and fluid out of the bleeder valves and because of such, I have to refill my reservoir with fluid.

Each time I open the lid to the reservoir, it makes a hissing sound, such as pressure being relieved. Because of this, I removed the supply lines to the Master cylinder from the reservoir, and fluid will not flow. The lines are free, but it seems as though the reservoir is holding a vacuum or some sorts.

At this point I am at a loss. Any Info is greatly appreciated!

[shiskabobnut]

I've also adjusted the pedal freeplay via the adjustment rod, and adjusted my star adjusters out until the drums are tight.

[AlmostHeavenWV_VW]

[shiskabobnut]

Great thought, but absolutely not. I make sure to keep an eye on the reservoir so it doesn't run dry. I barely let it get below half full before I top it up again. Each time I remove the lid I get the dreaded hissing sound.

[vwoldbug]

What kind of lid does the reservoir have . Can you get a picture

[Cusser]

[shiskabobnut]

I haven't changed the cap, but it seriously seems like the same exact cap that comes off of the brake fluid bottle. It literally fits the bottle and the reservoir. Flat black cap.

[Q-Dog]

This is the reservoir cap you should have.
http://www.wolfsburgwest.com/cart/DetailsList.cfm?ID=113611351
In the meantime, maybe try bleeding with the cap off?
_________________
Brian

'69 Dune Buggy
'69 Beetle Convertible
'70 Beetle

[Cusser]

[shiskabobnut]

UPDATE:

After making a makeshift vent in the incorrect cap, I am now able to gain some pedal pressure. However, this is only after a couple of pedal pumps. (the first pump goes to the floor)

I have about a half pedal's worth of pressure. To obtain this, when bleeding the brakes, I have to open the bleeder then almost IMMEDIATELY tighten or else it sucks the fluid back into it. It's like the whole system has a vacuum in it.

[VW_Jimbo]

Are the brake shoes adjusted properly?

Might want to try adjusting each wheel till it is locked up by both shoes, then bleed the brakes. Afterwards, readjust to slight drag.

Did you check the master cylinder push rod adjustment. If it is sloppy, you might only be actively pushing one side of the cylinder.
_________________
Jimbo

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

[shiskabobnut]

All adjustment stars are adjusted full out. (the drums are locked)

I adjusted the pushrod travel to about 1/4 of an inch of freeplay at the top of the pedal. (it used to have over 1''!)

It is the dual-circuit system. I've tried starting the bleed process at the front and at the rear. Doesn't seem to make a difference in pedal feel. (the current status was achieved through starting at the rear)

[VW_Jimbo]

Sounds like a faulty hose (interior delamination) or a bad master cylinder, improperly installed seals. My money is on the master cylinder. As per the chart. #2!

Here is a chart straight out of the Bently manual.

I have a homemade set of threaded plugs for the master cylinder. They allow me to remove the lines and completely isolate the master cylinder. Once isolated, I bleed it. After bleeding, it either holds a perfect pedal or fails.

If it passes, I add the front brakes in, one side at a time. Bleeding each one after connecting it. Testing each time, checking for proper pedal. If that passes, onto the rear brake line.
_________________
Jimbo

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

[dirtkeeper]

The above post is good . Since you had adjusted it a lot , have you rechecked the push rod play. It may have changed after you started pumping the system up.

[shiskabobnut]

So after much messing about, I now have a leaking master cylinder on the inside behind the pedal. Initially I had replaced the MC, but am now in need of another replacement.

Once I have replaced the cylinder, I'll post another update. Thanks for the help so far!

If at first you don't succeed...

[vamram]

Get a correct cap for the reservoir while you're at it.
_________________
Eventually, "we are what we pretend to be.’”
Give peace a chance - Stop Russian-Soviet Aggression!!

'74 Super 9/16 - present, in refurb process.
'73 Super - 6/18 - Present - Daily Driver!
'75 Super Le Grande...waiting it's turn in line behind '74.
Click to view image
Save the Supers!!

[AlmostHeavenWV_VW]

If I may, I bookmarked this method VW_Jimbo uses for reference if I ever have a mysterious brake bleeding/pedal issue

[VW_Jimbo]

[shiskabobnut]

After replacing the master cylinder again, along with the main steel line running to the rear of the car, I have half a brake pedal. Halfway down, the pedal is solid as a rock. The first half is mushy, and I have to "pump" to get them up to pressure.

If I wait 10 seconds, the pedal travels back to the solid halfway point. After pumping, the first half is solid. The rear of the system has totally been replaced.

At this point, I'm not sure what else to try.

[bluebus86]