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Discussion Starter #1
Ok, I've looked all over the internet for a solution, many forums, dealers, now here.
I have a 2002 VW Beetle 1.9l TDI that I inherited a couple of years ago. Brakes were never much good so the first thing I did was replace brakes and rotors all around. A few small issues with that but was able to work them out. I still seem to have an issue with the pedal going to the floor. I press on the pedal and the brakes activate, slowing and stopping the car. As I hold on the pedal it slowly goes to the floor. I release and re-apply and the pedal goes way down before the brakes grab and the pedal will slowly go to the floor again. I do not have local access to a dealer but I did call one in the next town over and the mechanic was perplexed. Seeing no leaks at all from the system I assumed master cylinder blow by. Replaced, twice. There is an Audi mechanic nearby and he agreed to work on a VW, as long as I park it out back. (Hey at this point I'll take anything.) He replaced vacuum lines, brake booster, master cylinder (again) and numerous other parts. I had told him what I had done and told him I thought maybe it was in the ABS, something not sealing and allowing fluid by. $500 later and still no improvement. He never touched the ABS. So after sitting I finally pursued the ABS. BTW, $2200 quote and no new in the US. Got a unit from the local pick-A-part and installed. Bleed with VCDS and still no change. Brakes work enough to stop the car when applied but then the pedal goes to the floor. No fluid leaks. Pedal is not hard to push, like a lack of vacuum assist, when car is off pedal is rock hard and does not sink.

I have had enough of this vehicle and if it wasn't my wife's mother's car, it would be down the road in a heartbeat. Can someone PLEASE come up with SOMETHING that can help me here? I've tried to give all the info I can but if I've missed something, ask. I am completely frustrated with this thing and if I snap back at a "witty" response, I apologize now.
Thanks in advance for any assistance.
 

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Sounds like a tough one; are there any brake parts, you haven't replaced? One winders, if the issue; comes down to hydraulics or vacuum assist related problems?

I recently worked on a 2005 new beetle convertible with a 09G transmission. The brakes were nit as responsive as they should have been and grabbed lower, then normal and did not respond well in a panic stop scenario. I replaced the pads, rotors and found, the vacuum pipe, from the brake booster all the way down to a connection to the 09G transmission, had a cracked pipe, (vacuum leak).

I found the vacuum pipe connection at the transmission interesting, hadn't seen that before and it had a sensor, plus a add on module that seemed to control vacuum, to and from the trans to the brake booster. That might be something to check for leaks; i could see, a vacuum leak definitely affecting brake performance, based upon this repair.

Whether your problem currently; is vacuum and/or hydraulic related, is a open question.

As always, i would start troubleshooting with a vw specific scan tool; like vcds by ross tech, see if there are any trouble codes and research, any possible output, live data testing you could possibly do.

One speculates, if there is "one more part"; you haven't replaced or tested; that could be failing, internally bleeding off vacuum or hydraulic pressure, causing the pedal, to sink to the floor?

I don't know if I've helped any but those are my thoughts, plus some recent experiences that I have had, working on this era of Volkswagens.
 

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On the end of the head (drivers side) is the vacuum pump. The nipple that the plastic hose fits on gets loose over time. Some have used jb weld to reseal that nipple or you can replace the entire pump. You can see the nipple I’m talking about in the picture, before just buying one check yours to be sure it’s loose.


The other issue is related to the pump also. The plastic hose that attaches to that nipple cracks underneath and the crack are not readily visible there is also a check valve in that same pipe.


You can see from the pic that it’s all one assembly.

If you’ve replaced all the other parts and didn’t use cheap chinese amazon or eBay parts there really isn’t much else to change and these two parts are known issues. Here is the jb weld repair thread.


If you have a mity vac hand vacuum pump and you tap it into that tiny nipple on the side of the check valve that is part of the plastic hose assembly you should get a reading of about 25lb. A mity vac is indispensable in diagnosing problems on a vw diesel.
 

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You have vcds. Are there any codes stored in the brake module? I do not think it’s your abs system, maybe a wheel sensor could be bad ($25) but that would be about it and shouldn’t cause the issues you’re describing. A bad wheel sensor would also cause the brake light and abs light to come on and stay on.
 

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Discussion Starter #6
Ok. I have VCDS and there are no codes showing. My thoughts and experience has taken me away from a vacuum issue on the theory that loss of vacuum would cause loss of assistance in applying the brakes, or harder to press the pedal. I seem to be experiencing just the opposite. I also thought the mechanic had changed a lot of these parts.
At this point I am willing to try anything and it won't be the first time I had been mistaken. I will go over the vacuum system this afternoon when I get home and report back.

Thanks!
 

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Loss of vacuum usually results in a hard pedal. However since you have tried almost everything else there's not much left. Often a soft pedal is the result of air in the brake line however you said you have bled the lines repeatedly and even with vcds. Are you sure it's been bled entirely and there is enough fluid in the reservoir?
 

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Discussion Starter #8
I bled again after replacing the ABS pump and got air out of the front right, maybe a bubble or two from the front left. Right rear flowed with no air and oddly, left rear did not seem to flow with pressure on the brake pedal when the bleeder opened. (Pedal did go to the floor when bleeder opened.) I always rechecked the reservoir after each wheel and never went below half full. I have experienced air in the line on other vehicles and it is a different feel. This is like the resistance is going away steadily. It really seems like I should be seeing a puddle of fluid on the shop floor.
 

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Leaking in the master cylinder is a possibility, however if I read your original post correctly you replaced that twice already.

Check that vacuum pump nipple and the plastic hose. Unless the master cylinder is junk (unlikely twice) there isn't much else.

If the vacuum pump is good and the hose has no cracks or splits, I would bleed the brakes again.
 

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How are you bleeding the brakes? If you aren't using one, you may want to use a pressure bleeder.
 

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Discussion Starter #11
I finally got a chance to go out and check things out. I went over the entire vacuum system and everything is either new or at least tight. I do find it odd that I have 2 check valves off of the vacuum pump and the schematic only shows one.

I re-bled the left rear since the last time it didn't seem to act right, everything good tonight. I have gone through the ABS bleed procedure and the main system procedure with both VCDS and manually. I have heard of pressure bleeders before and they give you little more than the old fashioned two person method. I have successfully removed air from the system so I am confident in my bleeding methods.

Something is allowing pressure by and it is only when the vacuum is active. The pedal is rock solid with the engine off and goes to the floor under light pressure with the engine running. I have verified piston activation when the pedal is pressed as well. If there was still air in the system the pedal would go lower than normal then activate the brakes with a "spongy" feel under the pedal. It wouldn't go to the floor unless there was a lot of air in the lines.
 

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Lets try the simple way, buy or make a couple plugs an plug the master cylinder if it goes to the floor you problem there. If it is not going down connect the master back and just bleed at the next point like abs unit. Bleed slightly right at that point before you do any pedal pushing and push that air down any further. Now check and pedal should still leak down. Plug the next outflow at the abs. I think you get the idea now. Plug and test. This should give positive isolation of this invisible problem.
 

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Discussion Starter #13
I do like your way of thinking, at this point eliminate each step all the way through the process. It just might come to it this weekend. Supposed to be cold here in the NE anyway. Might just as well spend it in a warm shop!
 
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