A3 2.0TFSI Brakes Failed - Lumpy idle on brake press?

RustyPleco

RustyPleco

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hello all,
havent posted for awhile as car was working fine, until tuesday. i got in my car in the morning like normal, i spent a good 10 minutes warming the car up as it was -4 outside. when the car was warm and window was cleared. i drove to the bottom of my street a lil bit quick and i went to press the brake and the pedal was rock solid, wouldnt even move a few mm's. i had to powerslide round the corner which made me absolutly cr*p myself and needless to say, i wont be coming out of my street like that again.

i have a slight hill near my house that i went down trying to warm the brakes up as i thaught they might be frozen, after going up and down the hill a few times i got a tiny bit of travel in the brake, but however still extremely hard to press.

the car is still in the same situation at the moment and i have been trying to diagnose the fault, i have done some google searches ect but i am still clueless.

i have check for obviously cracks/leaks in the vacuum hoses, but i cant spot anything obvious. i have since noticed that when my car is running that it idles perfectly fine until i put my foot on the brakes the idle becomes very lumpy and i can hear air leaking from the gator near the brake pedel (i have attached a video via youtube)




i am hoping you guys can help me diagnose the fault as im not great on the diagnostic side of the work but hopefully i can carry out the work required as i am completly skint and really cant afford to put it in the garage, i am pretty mechanicly minded.

thanks in advanced guys
 
Definitely a vacuum leak letting air into the servo, therefore no assistance.
Couldn't tell you where it might be sucking it in though, sorry!
 
i hope thats the case, i dont like the idea of replacing the servo, as i have read a few threads of servos being filled with water, which i thaught could have been possible because on the day when it was -4 the brake pedal did not move at all, so the water could have been frozen? (my thaught anyway) but the day after i have a slight bit of movement in the pedal and its -8 so i guess that kinda throws my theory.

but would this make idle rough when break pressed? im guessing a vacuum leak would.

is there anyways you can test vacuum to locate a leak?

thanks
 
99% certain it is a vacuum leak at the brake servo somewhere. The "hard pedal" would be the brakes without servo assistance, the lumpy idle will be a vacuum leak affecting the running of the engine and the "hiss" you heard would also be vacuum leak related. I'm not familiar with the A3 servo as I haven't worked on mine but problem areas can be something as simple as a bit of special rubber pipework joining the unit to the engine manifold system, a non-return valve or a gasket/seal.
 
wicked, im really hoping this is the case, i guess its just locating it. im going to go outside in a min with my vaporizor and blow smoke all arround the pipework to see if i can see any being pulled in.


i forgot to mention that i added a "blow of valve adapter" to my diverter valve on the turbo about a 2 weeks ago, i have taken it off and reinstalled to originallity since the brakes have messed up, could this be the cause?
 
i have just done a test that i see online, couldnt find too much information about it though so if someone could confirm that would be brilliant.

i started my engine, let it idle for a few minutes, i then held down the brake, (the longer i held it down the futher it went down, and it sounded like air was escaping) i then turnt the engine off, and the pedal forced my leg up, returning to original position.

the place i see this test said that if the pedal comes up then the servo its knackard and cant hold pressure, is this correct?
 
Sticking my neck out slightly :redface new: I would say that modern servo units are generally fairly trouble free. If it were me, I would start by examining any rubber pipework for damage and the little non-return valve in the pipework - people usually just test this valve by blowing through both ends - it should only be possible to do it one way i.e. in the direction that would be (in it were attached) towards the servo unit.
 
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will give it a good looking over tomorrow after work, checking the pipework and the valve like you said. is the valve located closer to the airfilter intake? thanks for replys
 
hello all, today i have checked the vac pipes, no obvious damage. i also checked the check valve, and does indeed only flow one way, away from servo, im guessing this is what pulls air into the servo.

so now completly clueless :(( i really want to cry
 
i also noticed that if i hold my foot on the brake it goes down slowly, but if i accelerate when my foot is on it, it will rise slightly.
 
ok so after doing many different tests and ripping off the servo vacuum pipe and testing the check valve, im pretty sure my servo is at fault.

however i cant find anywhere to buy one from?! anyone got any ideas?

part number 1K2614105AB
 
Give Tps ago or Mike in the parts section on here
 
checked TPS and ECP they have none :( will give mike a try though if i can find out how to get hold of him
 
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