Brakes not engaging

Shizzell

Veteran Member
Joined
Aug 15, 2010
Location
US
TDI
2000 Golf 1.9L GL 2dr
So the brake system has just been properly bled, using VCDS, and the brake pedal when pumped gets tight like normal. When the car is on, the brake pedal seems normal, except when stopping... you have to jump on them quite a bit for the car to stop. Now I know this indicates a vacuum leak of some sort, and I have looked at the brake booster hose and compared the entire vacuum system to another TDI. I have started the car and wiggled the hose to see if i could hear or feel any sort of leak and nothing. I don't think it is my master cylinder as it was working prior. Is there anything you guys would recommend, or what parts I should take a closer look at? Thanks
 

BobnOH

not-a-mechanic
Joined
May 29, 2004
Location
central Ohio
TDI
New Beetle 2003 manual
does the pedal feel hard or soft? if it's soft, try repeating bleed, if hard it's proly the booster
 

VeeDubTDI

Wanderluster, Traveler, TDIClub Enthusiast
Joined
Jul 2, 2000
Location
Springfield, VA
TDI
‘18 Tesla Model 3D+, ‘14 Cadillac ELR, ‘13 Fiat 500e
If it's perpetually soft or the pedal sinks as you hold it, replace the master cylinder. Beware of cheap masters at an auto parts store - sometimes they'll be bad right out of the box.
 

Shizzell

Veteran Member
Joined
Aug 15, 2010
Location
US
TDI
2000 Golf 1.9L GL 2dr
When bleeding last night, I had absolutely no air bubbles coming out at the end of the procedure. All new liquid coming out from each tube. I'm quite sure the assisted braking is not working. The pedal is not necessarily "hard" like when I had a leak from the vacuum pump to brake booster hose, but the brakes aren't engaging without significant force.

Also - the pedal does not sink, and will build up if I pump it.
 

BobnOH

not-a-mechanic
Joined
May 29, 2004
Location
central Ohio
TDI
New Beetle 2003 manual
I agree with Good Ol' Boy, it's sounds like master cylinder, but I would first repeat the bleeding procedure (don't forget the clutch cylinder) because it might still be air pockets. If the booster or the vacuum to booster is bad you would have a hard pedal
 

Shizzell

Veteran Member
Joined
Aug 15, 2010
Location
US
TDI
2000 Golf 1.9L GL 2dr
I just don't think it is the master cylinder... there would be leaks right? I have searched for vacuum leaks, and can't find any. The brake booster hose is fine. I just rebled via Motive, and no air present. How do I measure the vacuum while its running? Need a pressure gauge? Having the issues this guy is having: http://forums.tdiclub.com/showthread.php?t=262000
 

MotorCityMadman

Veteran Member
Joined
Dec 21, 2009
Location
MB
TDI
By proxy: 98 Beetle tdi, 01 Golf tdi, 03 Jetta tdi, 03Golf tdi
There doesn't need to be external leaks. Fluid inside the master cylinder can slip by the piston when the seals deteriorate or the bore is worn.
 

Shizzell

Veteran Member
Joined
Aug 15, 2010
Location
US
TDI
2000 Golf 1.9L GL 2dr
Brake master cylinder replaced. Same issue, it is definitely the brake assist system not kicking in. I replaced the vacuum pump with another one. No help. What now? Measure the vacuum? I don't want to have to wait another week to get a gauge..
 

TDIswanted

Well-known member
Joined
Jan 7, 2012
Location
Central Wisconsin
TDI
2002 Jetta 180K, 2003 Golf 335K, 2003 GMC Duramax 240K, 2006 Jetta 218K
sounds like a vacuum leak to me. Any small leak will cause the pedal to feal soft. could possibly be the vacuum pump on the end of the camshaft too I guess. I remember I had one with poor brake assist and found one small vacuum hose on the firewall was loose. hooked it back up and it worked great. If you cant find anything loose as far as vacuum lines maybe its the vacuum pump. its a pretty easy part to swap out if you have a test one you could barrow
 

TDIswanted

Well-known member
Joined
Jan 7, 2012
Location
Central Wisconsin
TDI
2002 Jetta 180K, 2003 Golf 335K, 2003 GMC Duramax 240K, 2006 Jetta 218K
Ahh... I see now you did replace the vacuum pump. I'll keep thinking on it and let you know if somthing comes to mind
 

Snizzbob

Well-known member
Joined
Feb 2, 2012
Location
Danbury CT
TDI
2015 Passat TDI DSG
Try bleeding them again, but with a LOT of force on the pedal. On some vehicles, especialy those with abs, air pockets can get trapped in odd places and wont be forced out while bleeding the system with something like a mighty vac. Ive had this type of issue with newer Ford trucks that I work on. Sometimes you really have to blast the brake fluid through the lines to dislodge the trapped air pockets.
 

40X40

Experienced
Joined
Feb 12, 2006
Location
Kansas City area, MO
TDI
2013 Passat SEL Premium
You know that vacuum hose that goes to the booster? The one that looks just fine. Replace it for giggles. It can't hurt.

Bill
 

Shizzell

Veteran Member
Joined
Aug 15, 2010
Location
US
TDI
2000 Golf 1.9L GL 2dr
You know that vacuum hose that goes to the booster? The one that looks just fine. Replace it for giggles. It can't hurt.
Replaced with the vacuum pump.
 

Shizzell

Veteran Member
Joined
Aug 15, 2010
Location
US
TDI
2000 Golf 1.9L GL 2dr
The owner wants to drive it with how the brakes are now.. it is so dangerous but all I can tell them is that I could re bleed. Anybody have any other ideas what could cause this issue?
 

Ski in NC

Top Post Dawg
Joined
Jul 7, 2008
Location
Wilmington, NC USA
TDI
2001 Jetta ALH 5sp stock
Not enough vacuum or failed booster make for hard pedal. To measure vac, tee into booster vac line and put vac gauge on the tee.

With engine off, push brake pedal a few times to bleed off vacuum. Hold pedal down. Then start engine. As vac builds, you should feel pedal move slightly down as you keep constant pressure on it. If pedal does not move, something wrong with booster or vac system.
 
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Shizzell

Veteran Member
Joined
Aug 15, 2010
Location
US
TDI
2000 Golf 1.9L GL 2dr
OK so purchased a vacuum gauge yesterday, and tee'd it between booster vac line. I got 0 to 5 in HG with the engine running. I forgot I had another vacuum hose array, and swapped it. Slowly, the pressure built up with the vacuum system replaced with a different one. It will go to around 14 in HG and sit.

The strange thing is, when I push the brakes, the vacuum immediately goes to zero, and then has to build up again. I am assuming this is great news, because now we can pinpoint what is happening.

I am going to replace all of the lines probably tonight just so I can rule that out. However, this sounds like a part that is faulty. For reference, I performed the vacuum test on another working tdi and the vacuum bounces between 10 and 15 in HG. When I hit the brakes in this car, it dips to about 9, and then is instantly bouncing between 10 and 15 again.

This issue is definitely a vacuum problem, and the results of swapping the vacuum array now result in better brakes; only once though are the brakes normal (Until you lose vacuum!)
 
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Shizzell

Veteran Member
Joined
Aug 15, 2010
Location
US
TDI
2000 Golf 1.9L GL 2dr
Anybody have any ideas? I can't seem to find any posts regarding this.
 

BobnOH

not-a-mechanic
Joined
May 29, 2004
Location
central Ohio
TDI
New Beetle 2003 manual
well it must be a leak in the can (booster). I don't know what type of failures folks are seeing with those
 

Ski in NC

Top Post Dawg
Joined
Jul 7, 2008
Location
Wilmington, NC USA
TDI
2001 Jetta ALH 5sp stock
I'm thinking booster too, but not 100% on that.

Normal booster with brakes not applied: Vacuum is on both sides of diaphragm. When pedal is pushed, it allows air into the aft portion of the can, and existing vac on fwd side pulls dia towards master cyl. I don't think it is normal for vac on fwd side to decay to zero when pedal is pushed. Vac should dip when pedal is released, as aft chamber vac is then replenished.

I'd hate to send you to swapping booster if it is not needed, but symptoms seem to fit.

Got another car around you can do the same vac test? See if vac vanishes when pedal is pushed?
 

Shizzell

Veteran Member
Joined
Aug 15, 2010
Location
US
TDI
2000 Golf 1.9L GL 2dr
Got another car around you can do the same vac test? See if vac vanishes when pedal is pushed?
For reference, I performed the vacuum test on another working tdi and the vacuum bounces between 10 and 15 in HG. When I hit the brakes in this car, it dips to about 9, and then is instantly bouncing between 10 and 15 again.
You are correct in the vacuum barely losing pressure when the brakes are applied. Zeroing is not what should happen. I was afraid it was the booster. I still need to replace the vacuum lines, and will do that before I replace it.
 
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