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  #1 (permalink)  
Old 04-07-2011, 10:39 PM
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Default Can't get brake pedal hard

So, here's the problem at hand. Car is 2.0 Auto. Last month wife complained about spongy brakes. The brake fluid was to the max line so I figured no leaks. I replaced the brake fluid because I didn't know when it was last changed. I took it for a drive and it seemed better. Today, I went to put gas in it and same issue. Brake fluid is at max level. Thinking air maybe in the lines, I bled them again going through 2 liters of fluid. Yes, it was overkill, but I wanted to make sure no air was in the system.

Well, the pedal was still soft and traveled almost to the floor before the brakes would work. And by working, I mean coming to a gradual stop. Definately not safe because if a car stopped 20 feet ahead of me, there's a good chance I would hit it.

There are no codes, I used my Vag-Com.

I inspected the master cylinder and brake booster. I did find a split brake booster hose, but everything I've read said that this would cause a hard pedal





Does anyone have a clue as to what may be the problem or what I should be looking for or testing?

Many Thanks in Advance
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Old 04-07-2011, 11:11 PM
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sounds like an ABS issue. I am not sure how the brake fluid flows thru the ABS on the beetle, but I would be my paycheck it is in the ABS module. Do you have a Bentley manual? My understanding is they are the best tech manual for the beetles.
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Old 04-07-2011, 11:23 PM
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Yes, I own a Bentley...
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Old 04-08-2011, 12:35 AM
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This might sound ridiculously simple, but have you checked the pads to make sure they still have sufficient material? If the pads or rotor are worn down too far, the brake piston may not exert enough force on the pad/rotor to generate noticeable force until the absolute bottom of your brake-pedal travel.

Also, to check if there is still air in the line, turn the car off, and pump the brakes all the way from top to bottom in one press, then release. Repeat until the pedal gets rock-hard (you'll know when this happens). If it never gets rock-hard, or takes more than 2 or 3 stabs, you still have air in the lines.

That crack in the hose might be introducing air into the system, if I was in your shoes that would be my first suspect. It would be an easy/cheap fix since it sounds like you're more of a DIYer than most.

Other than that, it could be the brake booster, master cylinder, ABS module, you name it!

The only time that I have personally experienced something like this was on the racetrack: I stepped on the pedal, it went all the way to the floor, and nothing happened... I had to gradually downshift and slowly pull the ebrake... still ended up in the gravel. I had boiled the brake fluid because of repetitive hard braking , but I doubt that is the case here.

Good Luck!

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Old 04-08-2011, 01:15 AM
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Judee, Thank you for the reply.

The pads and rotors are all good. Plenty of meat on pads and rotors have about 1/16" wore out of them.

I did the pedal test and it took 3-4 pumps before it got hard. I don't know how air could still be hiding in there after I flushed 2 liters through it.

I'm going to see if the dealership has the hose. ETKA shows 3 different part numbers for my BGD 6-Speed model and I don't want to order the wrong one online.
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Old 04-08-2011, 05:05 AM
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Well that blows my brake pad theory.

The brake pedal DOES get completely hard after a few pumps, right? That means you don't have air in the line. If you had air, it would never get completely solid, it would alway feel spongy no matter how many times you pumped the pedal.

New Theory!
That cracked hose is what provides the vacuum assist to the brake booster to provide "power" brakes. So it would make sense that if there isn't any vacuum assist, but still has an air leak, that it takes more travel to start pushing the brake fluid through the lines. I think that might make your car run a tiny bit lean since there is unmetered air getting into your engine, but not enough to create a CEL.

I think if you fix that cracked hose, your brakes will be back to normal.

.addicted2sp33d (Judee's Chauffer)
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Old 04-08-2011, 12:49 PM
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The cracked hose IS causing your spongy brake pedal, but that has nothing to do with the brake fluid. The brake booster uses vacuum from the engine to amplify the force provided by your foot. Replace the line, problem solved.

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Old 04-08-2011, 11:09 PM
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Thank you for the replies gentlemen. I wrapped the hose w/ hi-temp silicone tape since I'm waiting for the hose to come in. Wrapping it however didn't solve the problem and there is no way that air is getting past that tape.

I'll see if I can better describe whats going on with them. With engine off, I pump brake pedal till its hard , hold foot on pedal, start the car and the pedal can be pressed all the way to the floor with slight resistance.

While driving, when the brake pedal is pressed, about the halfway point, I can feel the brakes slowly engaging. At the 3/4 point, they are grabbing a little more, when the pedal is all the way to the floor, they bring the car to a complete stop.

Once at a complete stop w/ foot still on the pedal, I'll slowly release the pedal, and the car will start to move once the pedal is almost at the top.

The pedal is never hard throughout driving nor is it snap neck braking.

On my TS and other 2.0, the brake pedal is hard and the brakes start to engage once the pedal is pressed about a 1/2" down and the pedal remains rigid and firm...not so w/ the wifes car.

I've ordered a motive power brake bleeder and plan to flush the system again.

If the new hose and brake flush don't fix the issue, it's mechanic bound
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Old 04-09-2011, 03:13 AM
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This might not be the case on a beetle but I know on the Smarts that when you bleed the brakes you have to do so with the ABS pump running or old fluid or air can stay in it. We use our diagnostics to do this, again don't know if VAG-COM can do this but I'd guess it could.

Kate
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Old 04-12-2011, 12:15 AM
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So, with the hose fixed and another flush/bleed job using the motive power brake bleeder, 4 liters of fluid, VCDS to flsuh the ABS pump 3 times the car stops a little better.

The car will come to a complete stop when the pedal is pressed a little over half way down, but I'm still able to press the pedal all the way to floor board...and the pedal still isn't firm.

I just don't get it...am I missing something here???
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Old 04-12-2011, 12:22 AM
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Quote:
Originally Posted by Palmettoguy View Post
So, with the hose fixed and another flush/bleed job using the motive power brake bleeder, 4 liters of fluid, VCDS to flsuh the ABS pump 3 times the car stops a little better.

The car will come to a complete stop when the pedal is pressed a little over half way down, but I'm still able to press the pedal all the way to floor board...and the pedal still isn't firm.

I just don't get it...am I missing something here???
Sounds like a brake booster problem... that or you need viagra.



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Old 04-12-2011, 01:32 AM
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Quote:
Originally Posted by DZLBUG View Post
Sounds like a brake booster problem... that or you need viagra.
According to Bentley, the test for the booster is sat and according to my wife Viagra is un-needed

I'm just going to throw in the effing towel...

I've searched the forum and there were posts about people having my same problem, but no one closed the thread with a fix...Guess I'll do the same and not close this thread with a fix when I do get it fixed/figured out
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Old 04-12-2011, 03:06 AM
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Sounds like a bad master cylinder to me...
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Old 04-12-2011, 04:08 AM
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Quote:
Originally Posted by Palmettoguy View Post
According to Bentley, the test for the booster is sat and according to my wife Viagra is un-needed

I'm just going to throw in the effing towel...

I've searched the forum and there were posts about people having my same problem, but no one closed the thread with a fix...Guess I'll do the same and not close this thread with a fix when I do get it fixed/figured out
Happy to hear your plumbing still works... but as titillating as that topic could-be, let's get back to the Beetle before the conversation heads for the gutter and the mods freeze this thread!

There are only a few possibilities left:
Brake Booster Diaphragm
Brake Master Cylinder
Brake Master Cylinder CAP
ABS Unit behaving bonkers
Low Vacuum pressure (this one is a little harder to diagnose)

I'm guessing since you have the Motive kit that you tested the reservoir itself... but no-one ever tests the cap itself. Easy fixes first!

Try putting a piece (or two) of plastic wrap from your kitchen over the brake fluid reservoir, and then screwing the cap on over it. Drive around and see if the brake pedal is still spongy. If your cap is not sealing properly, the air in the brake fluid reservoir may get pushed out (path of least resistance), and once the fluid hits the cap, it plugs the leak and that's when you actually start braking. Air could get through because it is far more fluid than the brake fluid, if that makes any sense. Cheesy solution, but I've seen old/brittle reservoir lids crack and cause these symptoms.

Master Cylinder would be a likely culprit since you mention that the car starts to brake about halfway through the pedal travel... but changing one of these is a mess, and I would prefer to keep the brake fluid contained for as long as possible. That stuff will eat through paint like acid rain.

After that, I would guess brake booster. If the master cylinder diaphragm has a perforation in it, it would be leaking vacuum boost. This would still jive with the brake-pedal-while-the-engine-is-off test results, since the pedal becomes solid after a few pumps. If the diaphragm in the brake booster is leaking, you would not build up sufficient vacuum boost until further down the pedal travel.

Here's an image I found that might aid your troubleshooting:


I'm sorry if I seem to find your troubles so interesting, but I'm an Engineer and now I'm REALLY interested to see what fixes this.

.addicted2sp33d (Judee's Chauffeur)
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Old 04-12-2011, 04:05 PM
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Thanks for the replies. I'm starting to lean towards a bad MC.

I'll try the cling wrap test though.

If that doesn't solve it, I'll try to replace the MC this weekend and go from there.
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Old 04-12-2011, 07:17 PM
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It has all the symptoms of a bad MC. I'm betting a dime on that.
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Old 04-12-2011, 07:33 PM
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Give it Viagra.
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Old 04-12-2011, 08:14 PM
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Quote:
Originally Posted by SMG View Post
Give it Viagra.
Beat you to this joke already.

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Old 04-12-2011, 08:23 PM
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Old 04-16-2011, 12:12 AM
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FML...

Just got done replacing the MC...problem still there

The car stops w/ pedal pressed 1/2 way to the floor, but I can still press the pedal to the floor. It just wont stay firm....

I did everything by the book. I bench bled the new MC, bled the ABS pump w/ VCDS, bled the brake lines in the correct order.

This problem is getting very tiresome very quickly.


I'M ADMITTING DEFEAT


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