Weak to almost no brakes

2001 golf tdi iv spent about 4 days already trying to get to the vottom of this but so far no luck..
Symptoms 1st time pressing the brakes i almost get perfect respond releas and try again very hard pedal and bo brake..
Thisgs that iv already done
Changed the vacuum pump tested there about 25 psi sucking pressure.
Changed the hard plastic hose that goes to the booster.
Changed the booster itself 2 times ? 1st change it was leaking so o went and got 3d one which seems to hold pressure
Changed master cylinder
Flush all brake linesand abs i even unscrewed the lines from abs..and blow them with air to make aure therea nothing left
Still same thing no brakes...what do i do next ....im dying with this thing ?

Sounds like you already addressed the main suspects. Maybe a valve in the ABS unit is faulty?

turbobrick240 said:

Sounds like you already addressed the main suspects. Maybe a valve in the ABS unit is faulty?

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I got no lights on on abs .and when bleeding via vag.. it activates..how can i test this..i do have a spare on my shed maybe i just go ahead and change it.

Did you bleed the abs with vcds?
Maybe install a vacuum gauge in the system and see what happens to the vacuum when you loose braking.

maxmoo said:

Did you bleed the abs with vcds?
Maybe install a vacuum gauge in the system and see what happens to the vacuum when you loose braking.

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I did use the vcds just not sure if i used it properly

My 04 Jetta TDI is doing something similar, where the brakes work great the first time I push the pedal, but seems to lose vacuum when I have to brake off and on in traffic or going down a long hill. The pedal gets hard as a rock and I have to push it super hard to get it to stop.
I can tell it's not a fluid related issue, and the pads look new, although the round yellow light for the pad wear indicator is always on. Could my vacuum pump be going bad? I want to try replacing the vacuum check valve before anything else, but what else would you guys look at? I can't find any obvious vacuum leaks.

I think blowing air into the lines was a big mistake. We had one vehicle that the owner screwed up the right rear brake and let the fluid completely drained out from the reservoir, out the open line on the RR brake and getting the ABS to completely resolve it's air issues was a peck of trouble.

If I remember right, it took power bleeding the brakes two times and using VCDS three times to flush all the air... and it probably took a gallon of brake fluid.

Also, 25 inches is marginal. it might be your gauge, but I'd check to be sure you actually get 27+ inches. Make sure your one-way valve; the black and white separation between the turbo/ reservoir section and the brake booster is 1)working and 2) aimed the right direction. It should allow vacuum into the reservoir/ actuator side, but not out.

Also check vacuum pump to make sure the nipple is not loose and bleeding off vacuum. With the engine idling, run the vacuum gauge onto any full vacuum point and wiggle the outlet of the vacuum pump. If the gauge bounces around, you outlet flange is loose. Although you can simply replace the unit, but a 'quick and dirty' fix is to wash the flange out with brake cleaner and cram JB Weld into the crevice around the nipple. We've had them last for years by doing that. I've tried to fix the swedge, but it just breaks off.

Thanks, I'll check the nipple on the vacuum pump, and remove the check valve to check its function. I'll have to get a vacuum gauge since we no longer have one at work.

Another thing came into my mind when i was bleeding the brakes i was using the break bleeding pump i had it all hooked up and pumped 10 psi i wasnt getting much fluid coming out of any wheels.something somewhere was stoping .. when i took the pump off and did the push and hold pedal i was getting more fluid out... maybe so.ething wrong with abs system..but still 0 faulty code on it

Do you have vacuum when the brakes go hard? If not, then you have a vacuum problem. If you do, you have a hydraulic problem.

Get that part figured out first so you can stop chasing your tail.

Also where are you getting these parts you keep installing? Is it new aftermarket, new OEM, or used?

It could also be caused by a bad brake proportioning valve- much cheaper than an ABS module. I've had one fail before on a Toyota truck, but it was a different failure mode. The rear brakes would lock up on that vehicle.

If you flushed your breaks properly and have no air in them, including the ABS, and you have this issue, its a brake booster or master issue. what brand did you get as a replacement, if its not a OEM or you personally rebuild it, its garbage and your autobox store parts are defective as they usually are in 75% of the time. You need to measure your vacuum in inches of mercury, not -PSI. I recommend taking the master apart and cleaning it making sure no "aftermarket reman sand blasting crap" is left behind. Upgrade to the brake booster and master from a Audi too.
Portioning valve would not cause this issue at all and neither would the ABS. Air in the system would be spongey/soft feel and little braking force. 99% sure your master and or booster is messed up some how.

I know for a fact mine is not a hydraulic issue. I just have no power assist after using my brakes a few times, indicating that the vacuum system can't keep up with the demand. I just need to determine whether my problem is the vacuum pump, check valve, or booster, or simply a leak somewhere.
Since it's not a N/A gas engine, I can't find a vacuum leak simply by squirting ether around the intake while idling.

Chief, it gets confusing when people are trying to help two people at once.

Mongler98 said:

If you flushed your breaks properly and have no air in them, including the ABS, and you have this issue, its a brake booster or master issue. what brand did you get as a replacement, if its not a OEM or you personally rebuild it, its garbage and your autobox store parts are defective as they usually are in 75% of the time. You need to measure your vacuum in inches of mercury, not -PSI. I recommend taking the master apart and cleaning it making sure no "aftermarket reman sand blasting crap" is left behind. Upgrade to the brake booster and master from a Audi too.
Portioning valve would not cause this issue at all and neither would the ABS. Air in the system would be spongey/soft feel and little braking force. 99% sure your master and or booster is messed up some how.

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All junk yard parts ? this is my working horse i dont like puting new parts on it

Did the problem come on suddenly, was the car sitting for a long time right before, did it happen right after some brake work or bleeding? Brake fluid look nasty?

whitedog said:

Chief, it gets confusing when people are trying to help two people at once.

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You are right. I'll butt out. I have mine narrowed down and can find it from here. Thanks.

Thechief86 said:

You are right. I'll butt out. I have mine narrowed down and can find it from here. Thanks.

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Adding in your resolution is helpful.

maxmoo said:

Did you bleed the abs with vcds?
Maybe install a vacuum gauge in the system and see what happens to the vacuum when you loose braking.

Click to expand...

whitedog;5391304 [B said:

Do you have vacuum when the brakes go hard? If not, then you have a vacuum problem. If you do, you have a hydraulic problem.

Get that part figured out first so you can stop chasing your tail.[/B]

Also where are you getting these parts you keep installing? Is it new aftermarket, new OEM, or used?

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......bump

turbobrick240 said:

Did the problem come on suddenly, was the car sitting for a long time right before, did it happen right after some brake work or bleeding? Brake fluid look nasty?

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Yes the car was sitting for some 4 or 5 months i just git it as a replacement for the same car wgich had 860.000 kms.and i ddid a big mistake let that one go right away due to no room on my driveway it had good working parts. Yes the fuid was dirty blue

to.tdi said:

All junk yard parts ? this is my working horse i dont like puting new parts on it

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thats the problem. you can easily rebuild the master with new orings and some 320 grit and some parts cleaner.

buy a NEW booster.

When it comes to tires, brakes, and other safety issues or items, dont cheep out on them, just dont. these parts are not costly to start with. The time its taken you to fix this, i guess you have lots of time.

Mongler98 said:

thats the problem. you can easily rebuild the master with new orings and some 320 grit and some parts cleaner.
buy a NEW booster.
When it comes to tires, brakes, and other safety issues or items, dont cheep out on them, just dont. these parts are not costly to start with. The time its taken you to fix this, i guess you have lots of time.

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7 days already ....

So i think today i already blew the master cylinder after repitedly bleeding. Now pedal goes very soft right to the floor. But before this wgile i was bleeding the rear left stop pushing oil out it was like something jamed .all other 3 were acting notmal.now i have to change the master..i got 2 more of those to play with

You can definitely damage an old master by pumping it all the way to the floor. I like to put a block of wood behind the pedal when manually bleeding to keep the piston from going too far in the bore. You should also try the two man bleed technique- where a buddy pumps the brake while you open and close the bleeder. You could have a collapsed hose, proportioning valve issue, or just a clogged bleeder screw.

Still no mention of what happens with vacuum when the pedal goes hard. Not taking advice to stop using used parts.

Yeah. I'm out.

(And I'm not even mentioning the complete lack of proofreading. OOPS!)

yep, used parts form junk yard, not putting a block under brake peddle to keep crud from destroying seals.
Buddy, you need to rebuild the master. there is not other reason you have issues other than buying crap parts from cars sitting around for years and years.

TDLR, i got busted parts and things still aint working right!

Im with WD.

If you think it needs put together with SCRAP,
What you end up with is CRAP.

There was a day that you could buy brake cylinders and master cylinder rebuild kits. But the risk is killing either yourself or some innocent person. Do it right or don't do it.

Franko6 said:

Im with WD.

If you think it needs put together with SCRAP,
What you end up with is CRAP.

There was a day that you could buy brake cylinders and master cylinder rebuild kits. But the risk is killing either yourself or some innocent person. Do it right or don't do it.

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you are right this car is my daily use 120 km a day and i dont keep it that good in the other hand i got q7 sits on garage and i dont mind spending money on it and i wont buy any parts for it anywhere else but audi.. i dont treat my baby rabit good.

whitedog said:

Still no mention of what happens with vacuum when the pedal goes hard. Not taking advice to stop using used parts.

Yeah. I'm out.

(And I'm not even mentioning the complete lack of proofreading. OOPS!)

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Im sorry it got carried away and forgot to get back at your question ..couldnt tell u what is happening because i cant realy tell..

Mongler98 said:

yep, used parts form junk yard, not putting a block under brake peddle to keep crud from destroying seals.
Buddy, you need to rebuild the master. there is not other reason you have issues other than buying crap parts from cars sitting around for years and years.

TDLR, i got busted parts and things still aint working right!

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I get very dirty sometimes at work ..i keep this car stricly work home and therefore i dont treat it as i should

Anyhow brakea got way better almost where they should be i have no idea what was the real provlem but i went thru 7 littres of fluid and i think 99% air free now.im getting ned discs and pads this weekend and see how much better it will get