A3 - Bleeding Rear Brake Lines...

[Stealth TDI]

Hi,

It's cool to have a forum just for the older cars. Certainly someone in here has bled the brakes on their '98 A3 Jetta? If so, can you address how? My RB manual states to pull the drum and peel the seal off the cylinder. But there appears to be bleeder valves just inboard the hubs under the car. Can anyone confirm that's what these little screws are? I don't want to crack them open and discover they were for something important and that I had busted them.

BTW, this car does not have ABS. It has front discs and rear drums.

Thanks,

 

[oilhammer]

Hey, Scott! (remember me? I bought your radio)

Anyways, pretty simple. If you have a good bleeder wrench, you don't even need to remove the rear wheels, but if you are doing it on the ground, it will be easier to remove them anyways. You'll need a good 7mm wrench, boxed end. Leave the drums on (never press on the brake pedal with the drum removed, you'll blow the pistons right out of the wheel cylinders!)

Find the bleeder screw, towards the inside of the car, near the top of the backing plate. It will have a little rubber cap on it which pops off (be sure to put it back on!). You'll need a helper (wives are GREAT at this!

). Have her pump the brake pedal 2 or 3 times, and hold it firmly down while you loosen the bleeder screw with your wrench. Just give it enough of a turn for the fluid to squirt out, then close it while the fluid is still coming out. The brake pedal should drop to the floor. Be sure the master cylinder reservoir is full. Do this a few times on each side, the order is not important. FWD Volkswagens use dual-diagonal brake circuits in their hydraulics. The right rear goes with the left front, left rear goes with the right front.

Flush until clean fluid is coming out, and no air spits out...just a clean stream of fresh DOT4 fluid. DO NOT GET BRAKE FLUID ON THE PAINT!!!! It will strip it away!

I flush the brake fluid in all my cars every other year. Brake fluid is hydrophillic (sp?) which means it absorbs moisture over time...that is why it needs to be changed.

 

[dzcad90]

Yep, just loosen the bleeder valve much in the same way as you would on the fronts. I put a peice of hose on the end of the bleeder and fed that into a coffee can so I had less mess.

Get a pressure bleeder. You can bleed all 4 brakes on an A3 in about 15 minutes, and probably waste less fluid this way. Well worth it.

 

[20ValveT]

Actually there is a bleed prcedure on the A3s. You have to start at the right rear and then go to the left rear than right front then left front. This is out of the manual. Remember there is a presure regulator valve on the rear brakes. Its located on the driverside rear. Air can get traped in this valve, I know it happened to me.

 

[bowlerman]

when i do the bleed the brakes on my A3 jetta should i do them a certain way? and what is the way? also what oil hammer said about the brakes being right rear goes with left front. brian its good to know this but where does it come in at? i dont use a pressure bleeder, do them the old fashioned way.

 

[oilhammer]

Originally posted by bowlerman:
when i do the bleed the brakes on my A3 jetta should i do them a certain way? and what is the way? also what oil hammer said about the brakes being right rear goes with left front. brian its good to know this but where does it come in at? i dont use a pressure bleeder, do them the old fashioned way.

<font size="2" face="Verdana, Helvetica, sans-serif">I only mentioned this because it really makes no difference which rear wheel you start with, as they are on seperate circuits, anyways. The older method was because of the older single-circuit brakes, back in the sixties.

I do both rears, then do both fronts. If you are having trouble getting good pressure out of one bleeder, try bleeding the other bleeder on that circuit (opposing corner). If you car has ABS, the earlier Bosch systems will bleed better if the key is switched "on", so that the little actuators will run and self-bleed themselves. Also, the unloader valve attached to the rear beam will limit the hydraulic pressure to both rear wheels (both circuits go through the valve) if the rear wheels are dangling, as if the car was in a hard panic stop...this is to keep rear wheels from locking up. This is rarely an issue during routine bleeding, but if you have troubles you can easily remove the little arm that attaches the valves actuator lever to the axle beam, just mark the nut before you remove it, then reinstall in the same place when you are done. These valves were cast iron on the older A2 cars and would often get rusted and gunked up if brake-fluid changes were neglected. The A3 cars have a machined aluminum unit, and probably will not be as suseptable to this. Always be sure to replace the rubber caps on the bleeders..these will keep debris and moisture out of the bleeder screw, keeping it from siezing down the road. There is a little screen in the master cylinder reservoir, if it is really gunked up, carefully pry it out and clean it, dry thoroughly and reinstall. Use only new DOT4 fluid (DOT3 will work, just a lower boiling point, I like DOT4 because I am anal, and that's what is necessary for Autobahn cruisning

)

[ December 22, 2002, 21:55: Message edited by: oilhammer ]

 

[Stealth TDI]

Thanks for the info, guys. I'll look into a pressure bleeder. But I have neighbors and co-workers who have offered to help and/or do the job for me. I want to learn by watching or do the job with "adult supervision."