[mikerob]

I have a 1994 Passat GLX with ABS brakes. I just finished a complet brake job, new rotors, pads, ss lines and I got to thinking about something during the rebuild. Has anyone removed the weight copensating valve for the rear brakes??? Since the car has antilock brakes, why doesnt VW rely on the ABS allow for maximum braking on the rear wheels. Other cars I have owned - ie BMW 325i - does not use this type of a valve. Does anyone have any comments
Thanks,

 

[Penguin]

Re: Rear Brake Weight Compensating Valve (mikerob)

I've been thinking about this too on my '90 Passat. The valve is a pain in the ass (I haven't yet gotten an acceptable bleed and the only thing I can think of is brake proportioning valve). The only downside I can see is that the rear ABS had better be working really well or you're gonna have real troubles. Also need to be sure the ABS unit is up to the higher duty cycle on the rear circuit. I realize its not an answer...but I felt I needed to post as I too have been wondering this.
On a side note, how did the bleeding go? I tried to follow the Bentley to get my rears power bled, but I can totally open the bleeder valve and NOTHING will come and the system will reach pressure. However, when I tap the brake pedal it always farts out this nasty foam of air and brake fluid and the power flushes properly. Any ideas?

 

[97 Golf SC]

Re: Rear Brake Weight Compensating Valve (Penguin)

I know that on a 97 GTI with ABS there WAS NOT the rear proportioning valve. Maybe a different system. Just figured I would let ya know.

 

[spitpilot]

Re: Rear Brake Weight Compensating Valve (1997 Golf GL)

The MKIII ABS systems are supposed to be "cycled" during bleeding with the VAG tool. Could this be why you're not getting a good bleed (same ABS unit?).

 

[Evolution Sports]

Re: Rear Brake Weight Compensating Valve (mikerob)

Yes, the later VW ABS Systems do the rear brake proportioning in the ABS distribution block, like a lot of other cars.
For systems that have a seperate proportioning valve on the rear beam...
The system seems to work better if the suspension and beam are not at "full droop". So, if you have the car off the ground when bleeding, try lifting the beam with a jack to its "at rest" position, like it would be on the ground with the vehicle weight. This will allow the valve to open and should solve your difficulties.
Or you can think of it this way... when you slam on the brakes, the weight of the vehicle is shifting forward, unloading the rear. The rear rises and in such the valve starts limiting the amount of fluid to the rear brakes to try to prevent them from locking.
Also, not all Mk III need to have their ABS systems bled with the VW diagnostic tool. Only if the car is equipped with the TEVES 20GI ('97 and on in Mk III) or later systems. And only when these stystems have had air introduced into the ABS pump. Like if during bleeding you let the reservoir run dry or if replacing main ABS components.
Hope that helps.
Matt

 

[VRpoweredA2]

Re: Rear Brake Weight Compensating Valve (Evolution Sports)

here another question i was pondering for you guys.. i have an 86 golf with rear drums. My car does NOT have that rear proportioning valve on the beam. I have 2 seperate valves ON the master cylinder for each rear brake. I have a 22mm Master cylinder..front g60 brembo crossdrilled slotteds with mintex pads...i just picked up a FULL rear disk conversion...the beam and all...everyone tells me i have to swap the whole beam and all...why cant i just swap over the ebrake cables and the actualy bolt on assembly? dont the valves ON my master cylinder serve the same purpose? i mean..ive had to brake pretty hard on some occasions and ive never had the rear brakes lock up...and the car stops pretty good...i just dont want to go thorugh all the hassle of running new lines FROM the master cylinder and back to the new beam..and that beam weighs a TON...i need input on this....so can i just bolt on the disks at the stub axle and replace ebrake cables...and bleed the system?

 

[mikerob]

Re: Rear Brake Weight Compensating Valve (Evolution Sports)

So...what do ya think will happen if I disconnect mine and just install a T-fitting in it's place. The valve is rusty and I it feels like it is frozen. I don't think they are rebuildable - and I certainly don't want to buy one if the system will work without...
Thanks

 

[spitpilot]

Re: Rear Brake Weight Compensating Valve (mikerob)

I'd strongly advise against taking proportioning valve out of the system. Its there to help prevent rear wheel lock up which is the last thing you want to have happen during a panic stop...unless you like to back into an accident! Go to junkyard and pull a good valve off similar car, pull it yourself yards only charge like $10 for these, cheap when you consider the downside of not having a good one on your car!