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[Audi A3/S3] Audi S3 8L 210 APY Brake Vacuum Hose repair


p_gliddon
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Brake vacuum hose faults plagued the A3s of this era. A lot of A3's were recalled but the S3s were not as far as I can work out (I have the Audi repair guide for the A3 recall).

If you have an 8L S3 with an APY engine then you will most likely have this fault so worth looking, its easy to check. My 99 S3 is just over 10 yrs old and I think I have had a split vacuum hose for about 2-3 years!! Occasionally when I pulled away hard and then braked, the servo assist did not function. This problem can also cause some engine issues, erratic idle, uneven power from the turbo etc as the engine is drawing in air through the cracked hose and the MAF has not calculated and allowed for this extra air. Depending how hot the pipe/ engine/ air was affected how bad the fault showed up whilst driving probably due to expansion of parts under heat. Just wanted to post some info here as I struggled to find the details I needed to fix it. Its an easy DIY fix.

Firstly to check if you have a split hose. To the side of the brake fluid reservoir, behind the heat shield you should see a black hose onto the brake servo. Feel around this hose where it connects onto the 90 deg elbow. Mine was split underneath see pic 01.

Repair - The bit that took the time was working out which parts I needed as it is no longer a straight swop and you will need the entire hose from the servo to the inlet manifold at the front of the engine. There is a check valve on the hose that was split else i would have considered alternative non-OEM hoses. Audi have redesigned the two parts that join together to form the full length so you cannot as far as i can see just replace the faulty hose.

There are two part numbers

Closest to the brake servo is 8L6 612 041 B - now replaced by 8L6 612 041 G

Long hose to front of engine 8L9 612 041 B - now replaced by 8L9 612 041 G

There was a revision D at some point too just to confuse things.

In pic 03 the old parts are on the left and new parts on the right.

The difference is how they have joined these parts together but not really important. Both parts cost me £56 from Audi including one joining clip.

The actual replacing these parts is easy. Undo the jubilee clip at the inlet manifold and pull off. The 90 degree elbow on the brake servo just pulls out of a rubber grommet. Putting the new elbow in was a little trickier as it required a lot of force. I put a tiny tiny amount of fairy liquid on the rubber grommet just to make it slightly easier to push on.

Brakes now work great. I wonder how many people are driving round with this fault and dont realise?

Other known S3/A3 faults I've had are:

Window clips at about 5 years old.

Corrosion of roof rails - fixed under warranty at soton Harwoods age 8.

What do you think will be next part that I haven't had to fix yet (car is on 86k)?

...rear springs are looking a little rusty...!

Hope this helps someone.

Cheers

Paul

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The hose was a well known one on the TT forum

UK Audi TT Forum

Its also known to fail on the other end, at the u bend onto the inlet mainfold.

Waks Wide Web (scroll to bottom)

Rear springs are known to snap.

http://www.wak-tt.com/warnings/springs/springs.jpg

MAF

ARBS front suffer , wise to replace the rear as well

Battery

Front top mounts

Front wishbone bushes

Clutch

Waterpump changed for a metal one part of an early cambelt change

Thermostat

Coolant sensor

Ignition barrel

Battery in backup alarm sounder.

Rear pads, might as well replace the rear discs, as they are cheap enough.

Integral Door lock microswitches can play up.

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  • 1 month later...

Finally got a round to replacing the rear springs after a slight incident on a wet roundabout. Lift off oversteer took on a new meaning.

Turns out both springs had snapped, and the left spring had snapped twice and was missing almost a full 360 of the coil. The spring on the right didn't look broken, only when i removed it did it fall apart.

Handling much better needless to say, but also subtle improvements to the steering in a straight line. Before it felt like the tracking needed doing.

1999, 87k.

Photo attached for your amusement.

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  • 1 year later...

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