New brake issue, got one more day to fix it!

The saga continues....

Finished replacing the brake booster in the 02 Jetta. Used the Motive Power bleeder (dry) to bleed all four wheel cylinders and the clutch.
For the record, I pumped the Motive up to between 10 and 13 PSI each time and never let it fall below 10 PSI.

I bled the clutch first, and accidently ran the resevoir below the minimum mark Got a lot of gurgles and tons of bubbles.....Oooops. Anyway, refilled the resevoir and re-bled the clutch twice. Disconnected everything and pumped the clutch pedal about 50 times (no kidding) good clutch pedal, so I proceeded to the brakes.

Bled in sequence LF, RF, LR, RR since the car is a later model Mk4. The fronts bled fairly easily and I got lots of clean fluid with no bubbles in my clear bleeder hose. So far so good.

On to the back. Bled both of them the same as the fronts, but they bled really slowly. Finally got clear fluid with no bubbles, so I closed everything up.

Started the car and the clutch felt good. After idling for about a minute, I got no brake or ABS indications, so I tried the brakes. The pedal was really soft but after about 2-3 pumps, it firmed up.

Now the bad part(s). Each time you hit the brakes, the pedal seems low and a tad soft, but if you tap it again, it gets firmer but never as hard as before the booster was replaced. However, if you keep pressure on the brake pedal, it now slowly sinks to the floor! If you let up on it and tap it twice, it gets semi-firm again, but with constant pressure, it slowly (about 10 seconds) sinks to the floor.

I shut the car off, and tried the standard booster check. I pumped the pedal 3-4 times and it got really firm. Holding pressure on it I started the car and it slowly sank, just like a good booster.....except it kept slowly sinking.

SO....What did I do wrong or what is the problem? I'm thinking air still in the lines somehow, but I did what I thought was a really good bleed.
The rear emergency brake was on the whole time I bled the rears, could that cause a problem?

I guess I'm looking for educated suggestions as I've done plenty of brake jobs before (just not on a VW) and never got the dreaded sinking pedal.

Should I bleed the brakes again with the Motive? Should I do it the old fashioned way?? I never bled the ABS unit as I don't believe it went dry, and I only disconnected the two Master Cylinder lines when I replaced the booster. According to my Bently, and Ross-Tech, the ABS unit needs to be bled only if it goes dry.

If I need to bleed the ABS unit can I do it with the Share version of Vag-Com, or do I need the full blown version?

Thanks for any help,

Glenn

I thought the sequence was RR, LR, RF, LF. So you bleed the one farthest away from the booster first.

I'm not sure, but I think you need the full version of VAGcom to run the output tests and cycle the ABS pump.

I did too, but according to Bently, for 2001.5 and up models you go Clutch, LF, RF, LR, RR.

By the way, I forgot to mention in my earlier post that the brake light switch was not installed when I tested the brakes (New switch on order) but I don't see that having any effect....

Glenn

For the Mk60 brakes, you begin with the front and work further away. It does not matter when you bleed the clutch.

It sounds like you need to bleed the ABS pump using a VAG-COM or similar system.

--Andy

Bump for any more ideas........

Tried my share version of Vag-Com tonight....OF course accessing the basic settings for the ABS controller is something you can only do with the registered version.

Anyway, I was able to pull a couple of codes. One stored in both the engine and the ABS controller saying the brake switch signal is implausible (makes sense as I don't have the new switch installed yet) and one P18057 saying the ABS control signal was intermittant. I cleared the code, re-seated the ABS unit plug, and read it again. This time no code.

Tried the brakes again, Still got a sinking pedal, but if I pump them up several times and then slam them on, the pedal is firm and takes about 10-15 seconds before it slowly starts to sink. If I apply them lightly they slowly sink right away. Once they start sinking, if I pump the pedal rapidly a few times, the pedal is firm and takes about 15 seconds before it again starts to sink.

I'm going to try an old fashioned manual bleed tomorrw and see what happens. It was 115 today so I could only work on it a little bit at a time!

Still open to ideas,

Glenn

Ok,

I'm starting to wonder if I got a bad replacement booster! As posted earlier, the slowly sinking brake pedal symptoms are still there. HEre is what I have done so far.

1. Bled with the Motive Power booster. Result with car off.... Low brake pedal at first, then successively harder pedal as you pump it and deplete the vacuum. Pedal stays hard no matter the pressure. Result with car started. Pedal stays hard, but as you apply brakes it slowly sinks to the floor (takes about 10 seconds). If you pump the pedal 3 or 4 times, it gets firm again, but will slowly sink to the floor if moderate pressure applied.

2. Bled the old fashioned way with a helper, and got a few bubbles out but nothing major. I changed from the blue back to amber brake fluid (I alternate between blue and amber DOT 4 each time I change...makes it easier to tell when the old fluid is gone) Anyway, the fluid out of each caliper is clear amber with no bubbles which tells me I should have all the air out of the lines and the ABS unit....Correct?? Anyway, after doing this, the results are the same. Firm pedal with the car off. Start the car and the pedal slowly sinks like it should, but then with the car running each time you press the brake pedal with moderate pressure, it slowly sinks to the floor.

I'm stumped!!! Should I do a VAG-COM ABS bleed to see if that helps? I'll have to buy the registered version but if that is what it takes, then I will do it.

I doubt is is the master cylinder as the brakes were fine before changing the booster except for random pedal dropping to the floor and a loud hiss of air (which is why I changed the booster).

Like I said, I'm stumped. Any suggestions? I'm putting in the new brake light switch tonight, but I'll be damned if I can see how that would cause this problem.

Glenn

YES! If you get air into the system by draining the reservoir, you NEED to bleed the ABS pump - and so far, you haven't done that. It's not really an option in this case, it's a requirement.

Maybe there's someone around where you live that can help. Do this and then come back and post the results.

--Andy

I had this same problem using the motive bleeder on my '04 even without running the master resevoir below minimum. I could never get the fluid to flow freely...just trickle out. After three complete bleed in as many weeks I finally paid the dealer $100 for the fluid change. Now brakes are hard normal, safe and don't bleed down. For me the motive bleeder is one of the most useless tools I own.

Ordering VAG-COM today......

Ok, I got the VAG-COM, and did the ABS bleed procedure. Got very few bubbles out each time, but I did the complete procedure. Guess what.... NO FREAKIN' CHANGE! Thinking I might have done something wrong, I did the ABS bleed and a four wheel power bleed again for a second time. I even did the ABS output tests twice. Still no change!!! I even checked the vaccuum elbow going into the brake booster and the one way vacuum valve off the vacuum pump and they are fine. Additionally there are no leaks anywhere in the system.

Pedal feels firm the first two times you press on it, but if you hold steady pressure on it, it slowly sinks to about 1.5 inches from the floor. I haven't road tested yet...I'm reluctant to.

So far I have replaced the brake booster for the original problem $164

Several liters of Brake fluid (IMPEX loves me) ~ $50

VAG-COM registration $99

New brake light switch $7

So far the car has been up on jack stands for over two weeks (waiting for parts and such) and I am out $320 in parts and I still have the same issue! My wife is starting to tell me I should have taken it to the dealer in the first place

I would really like to get the car fixed before the homeowners association starts griping at me for having a non-mobile car in the driveway for so long.

Please let me know if you have any ideas. I don't think it is the Master Cylinder as it did not have a sinking pedal before I changed the booster.

Glenn

Unfortunately, the bleeding procedure (if you stroke the pedal the whole way to the floor) can destroy the master cylinder. If the fluid is not changed on a regular basis, rust can form on the innards of the m/c and when you push the pedal down farther than normal, you can destroy or invert the seals...

I have to say, a pedal that goes farther than you'd expect is likely to mean one of two things. Either a hydraulic problem as above (flaky m/c), or the plunger setting between servo and m/c is incorrect.

HTH.

There is no need to bleed the ABS pump, it only opens when under use. Even if you sucked air into the system for 5 mins while bleeding, the ABS pump will still be fine...

As far as the bleeding order, its all personal preference, there is no right or wrong way. I usually start furthest from the booster and work my way back, but it really doesn't matter.

If your pedal is sinking to the floor slowly, your MC more then likely need replacing. The seals are probably gone, allowing fluid to leak by (which results in the pedal going to the floor). Also make sure the line from the MC to the booster isn't cracked, its notorious for cracking, you'll then have major vaccuum issue's.

bleeding brakes

Stop pi55ing around and install 4 SPEED BLEEDERS and have it over with, one man job and gets air out first time, extra couple bucks for the stainless and last a lifetime.

*sigh*

I was afraid it was probably going to be the master cylinder. I really don't want to throw anymore parts at it unless necessary, but now that the emotions have settled down a bit, at least the new booster solved the dropping pedal and whooshing sound problem. I can always use VAG-COM for other things, and the "E" model brake light switch should be good to go.

I checked the vacuum hose that goes from the Power booster to the vacuum pump on the cylinder head. It seems fine and I did not see any cracks. Any sure fire way I can test it and the one way vacuum fitting. I don't seem to have vacuum issues as if you pump the brake pedal with the car off, you get a very firm pedal, that slowly drops after you start the car (telling me the booster is good and I've got decent vacuum)

I'm going to carefully road test it this afternoon after I get off work. Until then, please kep the suggestions coming.

Problem is fixed (I hope)

Apparently the Master Cylinder Resevoir was not fully seated into the two grommets atop the Master Cylinder. Weird thing is I did not separate the resevoir from the MC when I pulled it to do the brake booster.

Anyway, long story short is that the brakes now work GREAT! In fact, they are almost too touchy. They stop a lot better with much less pedal effort now.

Thanks to all for helping me through this saga. I have done lots of brake jobs before, but this one had me going in circles for awhile.

Again, thanks to all,

Glenn