Brake Bleeding

FG1732 · Samba Member Joined: March 03, 2004 Posts: 354

Like Wayne, I too have been bleeding for several hours without luck. (New Ate German, single circuit MC). I eventually noticed that when pressed down, my brake pedal was slow to return to its resting position. So I yanked my pedal floor board out to watch the brake rod enter the piston on the master cylinder. Sure enough the master cylinder piston was returning back slower than the rod (about a 3 second delay behind the tip of the rod). So I pulled out the master cylinder thinking it was bad. After yanking it out, placing it on my garage floor and putting a screw driver inside the piston and pushing in(where the rod would normally go), it squirted brake fluid out of all three holes and shot back my screwdriver as it should. So I put it back in the car and started to bleed. The piston in the MC shot back the pedal as it should for about the first 20-30 pumps, but then eventually started to slow down as it had previously done.

As it stands, the brake pedal is still soft to the floor board. I did get the pedal to harden up a little at the beginning of the bleeding process, but it has since softened up. Im guessing that there is either still substantially more air in my lines or the master cylinder is bad.

My question is it normal for this piston in the master cylinder to slow down on the return during the bleeding process? Will it eventually gain more "return spring" once completely bled?

If the above symptom is the sign of a bad MC, I'd rather just buy another rather than deal with several more hours of bleeding.

wayne collett · Posted: Mon Oct 19, 2009 10:24 am Post subject:

hi , i dont know as ive not done any more vwork on the car , its been in the garage ever since. let me know how you get on as ive still got the same problem

hemifalcon · Posted: Mon Oct 19, 2009 7:52 pm Post subject:

wayne collett · Posted: Tue Oct 20, 2009 3:54 am Post subject:

i changed all my pipes and hoses and the mc, i even had the lines pressured up with a compressor pumping fluid directlyinto the circuit it was constantly running around the system. so when i cracked the nipples fluid was constantly coming outunder pressure. still got no pedal though.

Eric&Barb · Posted: Tue Oct 20, 2009 7:19 am Post subject:

Then it sounds like a bad MC. So either replace or take the MC apart for inspection/fix.
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wayne collett · Posted: Tue Oct 20, 2009 12:50 pm Post subject:

would it make any difference if i lock all the wheels up with the adjusting stars

Eric&Barb · Posted: Tue Oct 20, 2009 8:21 pm Post subject:

Hmm, look up our earlier post.....
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wayne collett · Posted: Wed Oct 21, 2009 2:00 am Post subject:

I HAVE READ YOUR EARLIER POST AND I DID DO THAT , I ALSO RELEASED THEM RIGHT OF AND TRIED THAT . IM NOW GOING TO TAKE THE MC APART IF I CAN GET AT IT, THANKYOU ANYWAY.SEND ME AN EMAIL AND I WILL SHOW WAT CAR IM MESSING [email protected]

wayne collett · Posted: Wed Oct 21, 2009 11:01 am Post subject:

done all that today, now where should the adjustment rod be from the pedal to the mc, ican get the pedaL to go half way down or can adjust the rod so the pedal goes all the way. locked up all wheels and bled no leaks but no pedal! have you got to bleed the mc seperate. to the brakes.

Eric&Barb · Posted: Wed Oct 21, 2009 6:52 pm Post subject:

There is good info on adjusting the brake pedal AND THEN the brake pedal pushrod.

http://www.thesamba.com/vw/forum/viewtopic.php?t=378070&highlight=brake+pedal+adjustment

There are times that one does need to bench bleed the MC, and have had to do that.
You can do the same in the VW by having a helper push the brake pedal down, while you have one of the bleeder valves open.

When pedal is all the way down, you need to close the bleeder valve, and then have the helper let up on the brake pedal.

Repeat till you get a good flow of brake fluid per push for single circuit, and dual circuit you need to do this one bleeder on each axle.
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wayne collett · Posted: Sun Oct 25, 2009 10:54 am Post subject:

done my brakes today and they finally work ,put a new mc on then bled them, still the same as before . so i took the front drums of a bled them without the wheels on . centred up the brake shoes , put the drums back on and bled them again, big air bubble appeared and then there was brakes , now ive got a good solid pedal, cheers everyone for you help. ive also got a spare mc now as well as there was nothing wrong with it.

thats that headache gone. now all ive got to do is work out all the electrics

rm56 · Posted: Mon Oct 26, 2009 1:28 pm Post subject: Brakes

I have been reading alot here regarding bleeding brakes and have discovered some differences to doing VWs brakes. First off I have a 64 Type 1 Beetle with a single circuit M/C. Over the weekend I replaced my front shoes and left front wheel cylinder which a local shop had told me was leaking. Upon removing that drum it did appear to have been leaking. I replaced the rear shoes awhile back. I was having the same trouble as others not being able to get more than 1 inch of pedal. One of the things I did not do was to adjust out the star wheels to lock up my brakes. Now here is one of my questions on that? Some say to adjust the star wheels so the shoes just drag a little, others say to adjust them so the drums are locked up tight. Which is it? Also I had my wife pump the braked 3 times and hold while I opened the bleeder then closed then had her release the brake. One member on Samba said to open the bleeder, push brake down slowly, close bleeder, then let brake pedal up slowly. Now should I do that before I do the pump 3 time hold method? Or is that just to clear air out of the lines if you have changed an M/C? All I have changed is the front shoes and left front wheel cylinder. Thanks and sorry for asking a question that may have been covered already.

Eric&Barb · Posted: Mon Oct 26, 2009 5:38 pm Post subject:

For single circuit you can just go with the drag method.

For dual circuit you really need to lock them up.

As for the bleeding itself, just like there are many ways to skin a cat......

Personally we do ten pumps and then open the bleeder.

Try not to slam the brake pedal down. That can cause a large bubbles in the lines to turn into lots of little ones!
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wayne collett · Posted: Tue Oct 27, 2009 7:31 am Post subject: Re: Brakes

rm56 · Posted: Tue Oct 27, 2009 12:00 pm Post subject: Thanks

Eric thanks, as soon as I can I'll give it a go. I got a little pedal the other day, bet its just the fact that I adjusted the shoes to just drag and then backed them off the linings. Setting them to drag will allow the cylinders to open apart just a tiny bit more. Anyone care to explain why this is a benefit to doing VW brakes? Curious I've never seen this on any other car. Thanks as always

Rick

Eric&Barb · Posted: Tue Oct 27, 2009 1:41 pm Post subject:

With single circuit MC you have the entire length and volumn of the MC to push all the brake fluid though each brake line to and out each wheel cylinder.

In dual cylinder MC you have HALF the length and volumn of the MC to push the brake fluid to that axle. So you do not have as much to push with!! So any slop will take away your already reduced ability to push the fluid with the compressable air bubbles in it.

As for removing the drums and centering the brake shoes.
Can do the same by rechecking that the brake stars are still ALL locked up when you do not get it to bleed the first time soon. With the earlier VWs this means loosening on each wheel the last brake star. Rotating the drum till you can check the first brake star you tightened that it is still tight, and then go back to the second brake star to retighten. Then try bleeding again.
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rm56 · Posted: Thu Oct 29, 2009 7:18 am Post subject: Brakes

Yesterday I re-bled my brakes with the star adjusters set so the drums were dragging but not locked up. I have a 64 with the single circuit master cylinder system. Following Eric's advice I had my wife/assistant slowly pump the pedal 10 times. Starting at the right rear I saw a small bubble come out. We did this until nothing but solid fluid came out of the bleeder valves on all four wheels. I had a decent pedal, not super hard but enough to tell me air was purged and I could continue. Once the wheels were bled I went back and looseded the star adjusters until each shoe no longer rubbed. Yey! I now have decent brakes and the icing on the cake is I did not have to readjust my parking brake. Thanks again for your help. Very Happy

Rick M
Lincoln, CA

Eric&Barb · Posted: Thu Oct 29, 2009 7:32 am Post subject:

Glad to help.
Just make sure your E-brake is only clicking up five clicks now.
If you are driving the VW daily readjust the brake stars in two or three weeks. After the shoes have worn into the diameter of the drums better.
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rm56 · Posted: Thu Oct 29, 2009 7:45 am Post subject: Check

Thanks, I will check that.


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