B4 Brake Pressure Regulator Adjustment Help

loganbmx4gt

Veteran Member
Joined
Apr 14, 2011
Location
Jackson, TN
TDI
97' Passat (1Z), 02' Golf
Changing out the rear calipers on my B4 and I notice it appears they haven't been working, the fronts are.. I start looking thru the Bentley manual and it tells me to tension the spring then press the pedals and read off figures and if necessary, readjust. Well I don't have a pressure gauge. Can I just make the tension on the spring and do it by feel?


 
Last edited:

RIP TDI

Top Post Dawg
Joined
Feb 16, 2000
Location
Santa Barbara, CA
TDI
'15 GSW SE 6MT, '01 Golf 5MT, '97 Passat sedan, '96 Passat variant
The adjustment isn't the problem; the valve is frozen in one position, a fairly common problem.

I've adjusted the valve with the tandem pressure gauge, not because the valve was frozen but because some numb nuts tried previously to adjust it without reading F. to R. pressure differential and brake balance was way off. I wouldn't recommend adjusting your new one by seat of the pants; get it done properly or set the new valve to the same position as the old one.
 

loganbmx4gt

Veteran Member
Joined
Apr 14, 2011
Location
Jackson, TN
TDI
97' Passat (1Z), 02' Golf
So that explains why it wasn't moving while I had it on stands and I had my dad press the pedal while I was watching underneath then correct? Here is a video.


Looks like I might order this then and take it to someone who can hook a gauge to it.
 
Last edited:

RIP TDI

Top Post Dawg
Joined
Feb 16, 2000
Location
Santa Barbara, CA
TDI
'15 GSW SE 6MT, '01 Golf 5MT, '97 Passat sedan, '96 Passat variant
So that explains why it wasn't moving while I had it on stands and I had my dad press the pedal while I was watching underneath then correct? Here is a video.
Looks like I might order this then and take it to someone who can hook a gauge to it.
If expense or time/energy are issues, you could try to simply install it and adjust it to the same setting as your old one. Drive it and see if it feels normal, with no gross premature locking of front or rear under a hard stop, both fully loaded and unloaded. Best to have the pressure differential checked, of course, but you may get close enough with the duplicated setting.
 

loganbmx4gt

Veteran Member
Joined
Apr 14, 2011
Location
Jackson, TN
TDI
97' Passat (1Z), 02' Golf
If expense or time/energy are issues, you could try to simply install it and adjust it to the same setting as your old one. Drive it and see if it feels normal, with no gross premature locking of front or rear under a hard stop, both fully loaded and unloaded. Best to have the pressure differential checked, of course, but you may get close enough with the duplicated setting.
Naaa I want it done right so I think I'll just order it and take it to the shop I go to when stuff like this that I can't do comes up.

This is probably a stupid & obvious question. If I do entertain possibly doing this, which I would like to learn and do it since I've never done this before, how exactly do you adjust the psi on the block?

Also can you clarify what the Bentley means by
Rear Disc Brakes:
50 bar at front axle - Rear should be 35-41 bar
100 bar at front axle - Rear should be 56-62 bar

So if I get 50 bar (725 psi) up front; the rears need to be between 35-41 bar (507-594 psi), and if I get 100 bar (1450 psi) up front then the rears need to read 56-62 bar (812-899 psi)? Is that what it is saying?
 
Last edited:

Steve Addy

Top Post Dawg
Joined
Aug 7, 2002
Location
Iowa
TDI
97 Mk3
The valve moves based on axle position, not on how much you press on the brake pedal.

If the car has no load it should reduce braking pressure to the rear to help prevent lockup. If the car is loaded heavy in the back it should allow for more rear braking.

I would agree though if you have no braking action at the rear then your prop valve is probably frozen in the off position.

If you do it yourself report back about how it went and how you tackled the job.

Steve
 

loganbmx4gt

Veteran Member
Joined
Apr 14, 2011
Location
Jackson, TN
TDI
97' Passat (1Z), 02' Golf
The valve moves based on axle position, not on how much you press on the brake pedal.

If the car has no load it should reduce braking pressure to the rear to help prevent lockup. If the car is loaded heavy in the back it should allow for more rear braking.

I would agree though if you have no braking action at the rear then your prop valve is probably frozen in the off position.

If you do it yourself report back about how it went and how you tackled the job.

Steve
I've been researching since I posted this and read that and then got back under to look and I now understand how it does that now with the bracket and spring being attached to the rear beam.

I may be looking into this harder than I need to be and it's possibly obvious and staring at me in the face. But how do I set the PSI exactly once installed? Is there a screw on it that adjusts the psi or ? I've found pressure gauges for about $50 and I feel comfortable enough now with the research I've done to do the removal and installation of the new one I think. I'm just not understanding how the psi is actually set once installed.
 

Steve Addy

Top Post Dawg
Joined
Aug 7, 2002
Location
Iowa
TDI
97 Mk3
I've been researching since I posted this and read that and then got back under to look and I now understand how it does that now with the bracket and spring being attached to the rear beam.

I may be looking into this harder than I need to be and it's possibly obvious and staring at me in the face. But how do I set the PSI exactly once installed? Is there a screw on it that adjusts the psi or ? I've found pressure gauges for about $50 and I feel comfortable enough now with the research I've done to do the removal and installation of the new one I think. I'm just not understanding how the psi is actually set once installed.
The only possible adjustment is at the bolt where the spring mounts to the bracket. There's a slot for moving the bolt and changing the tension on the spring / valve.

I always assumed one could attach a gauge to the bleeder port at the caliper and read pressure from there rather than fussing with removing hoses at the prop valve.

Whether or not you can get it set to spec is another matter though, the adjustment is rather crude and could have been handled better IMO.

I haven't set mine on the B3V yet but will have to in the future.

Steve
 

loganbmx4gt

Veteran Member
Joined
Apr 14, 2011
Location
Jackson, TN
TDI
97' Passat (1Z), 02' Golf
The only possible adjustment is at the bolt where the spring mounts to the bracket. There's a slot for moving the bolt and changing the tension on the spring / valve.

I always assumed one could attach a gauge to the bleeder port at the caliper and read pressure from there rather than fussing with removing hoses at the prop valve.

Whether or not you can get it set to spec is another matter though, the adjustment is rather crude and could have been handled better IMO.

I haven't set mine on the B3V yet but will have to in the future.

Steve
Aghhh ok! Makes more sense now. I was thinking there was something on the block that controlled flow. It's that bolt that I posted pictures of above that does the adjusting.

Yea the gauge hooks up to the bleeder valve on the caliper while still attached to the bracket/rotor. I'm thinking I might put marks on the bracket of where the bolt is that holds the tension of the spring so it's set to the same place as the old one like Chris Bell stated above and then checking it with the gauge.

Yea that set up is crazy compared to others I have seen. I'm sure there was a reason they did it that way is guess.
 
Last edited:

RIP TDI

Top Post Dawg
Joined
Feb 16, 2000
Location
Santa Barbara, CA
TDI
'15 GSW SE 6MT, '01 Golf 5MT, '97 Passat sedan, '96 Passat variant
You need a dedicated tandem brake pressure gauge with long hoses if you're doing this solo (Snap-On is the only one I've seen, but I would guess there are others), otherwise a helper if you have two separate gauges with typical short hoses. The tandem gauge makes the job easier even if you have a helper (which is the way I did it). The adjustment require a fair amount of trial and error.

I will say that the results can be dramatic. In my case, the valve was functional but badly mis-adjusted and caused a ridiculously hard brake pedal with very weak braking, as if the servo wasn't functional AND the pads were badly glazed. After adjusting the valve to specs., a normal, progressive pedal feel and efficient stopping returned. I never imagined line pressure variation could cause such extreme symptoms.
 
Last edited:

Steve Addy

Top Post Dawg
Joined
Aug 7, 2002
Location
Iowa
TDI
97 Mk3
You need a dedicated tandem brake pressure gauge with long hoses if you're doing this solo (Snap-On is the only one I've seen, but I would guess there are others), otherwise a helper if you have two separate gauges with typical short hoses. The tandem gauge makes the job easier even if you have a helper (which is the way I did it). The adjustment require a fair amount of trial and error.

I will say that the results can be dramatic. In my case, the valve was functional but badly mis-adjusted and caused a ridiculously hard brake pedal with very weak braking, as if the servo wasn't functional AND the pads were badly glazed. After adjusting the valve to specs., a normal, progressive pedal feel and efficient stopping returned. I never imagined line pressure variation could cause such extreme symptoms.
Interesting, are the ports in the regulator individual or is it just one mass cavity that gets regulated out to both wheels? I would think it's just one cavity in the valve block, otherwise how would you be able to set each side with just the one adjustment?

And yes, it's a ridiculously crude adjustment mechanism yet they used these are virtually all disc brake cars and a lot of drum brake models too. The only cars I can remember from VW that used MC mounted prop valves were Mk2 base Golf models, even the Jetta with rear drum got the rear brake pressure regulator.

Steve
 

RIP TDI

Top Post Dawg
Joined
Feb 16, 2000
Location
Santa Barbara, CA
TDI
'15 GSW SE 6MT, '01 Golf 5MT, '97 Passat sedan, '96 Passat variant
I should make this clear: If you're doing this yourself, with or without help, you need to be able to read both gauges simultaneously with them both in front of you in the driver's seat when they're attached front and rear. Thus the gauges need really long hoses.

You might think that, with an assistant using 2 typical short-hose gauges, you could hold the brake pedal at the point your assistant dictates based on his reading of front pressure while he runs back to read the rear gauge. That won't work well. Its very hard to maintain a set line pressure at the pedal. By the time he reaches the back gauge, the front gauge will be reading higher or lower pressure than specified.

I did this procedure in an ideal way; with an assistant and a Snap-On tandem gauge with long hoses. I was the brake pedal operator, reading the gauges from the driver's seat, and it was very tricky to hold and read front pressure long enough to read rear pressure on the gauge right next to it!

My point for Logan is: unless you can find gauges with really long hoses, since you have no problem having a shop do the job, do so! I applaud and embrace your repair philosophy: repair it yourself the correct way if you can and if you can't, take it to someone who can. That's what I did. I took mine to a one-man shop that had a tandem gauge. The owner said he had very little experience doing the adjustment. Since I was well versed in the procedure and had the specs but not the gauge, he suggested we do it together. We both learned from the experience!
 

artie b

Veteran Member
Joined
Sep 23, 2001
Location
zip code 46371
TDI
97 B4 TDI stock, have owned and repaired 4 B4 TDI's since 1996
I have been having a lot of issues trying to get any increase in rear brake pressure. My valve is free, and not leaking. I have tried to get an increase in pressure, everywhere within the valve's range. My rear caliper's and pins are free. And yet I have very limited rear brakes. I do have anti lock brakes with the Teves that was originally on the 95 VR6.
Is there anything I'm missing as why I don't have rear brake pressure?
I need to replace my brake lines, soon, and considering plumbing the valve out. Then relying on the old Teves anti lock for rear wheel skid control.
I do have varying weight in the rear, and would benefit from the valve working. Thanks, Artie
 

RIP TDI

Top Post Dawg
Joined
Feb 16, 2000
Location
Santa Barbara, CA
TDI
'15 GSW SE 6MT, '01 Golf 5MT, '97 Passat sedan, '96 Passat variant
Do you have lower than spec rear line pressure as measured or poor rear braking performance that you're trying to improve with greater than spec line pressure?
 

artie b

Veteran Member
Joined
Sep 23, 2001
Location
zip code 46371
TDI
97 B4 TDI stock, have owned and repaired 4 B4 TDI's since 1996
Thanks Chris, I want to improve my rear braking performance. With or without the valve, safely.
I have no idea what the pressure is, except when I bleed the brakes, I only get a dribble, with the brake pedal or a power bleeder, with the valve in any position. Thanks Artie
 
Last edited:

RIP TDI

Top Post Dawg
Joined
Feb 16, 2000
Location
Santa Barbara, CA
TDI
'15 GSW SE 6MT, '01 Golf 5MT, '97 Passat sedan, '96 Passat variant
Poor rear braking is either a line pressure issue, glazed pads, an incorrect master cylinder (rear circuit piston diameter too large relative to front piston) or some ABS issue.

If the pads aren't glazed and you're sure you have the correct GLX master cylinder, look at line pressure. If you don't know what actual line pressure differentials are, you're operating in a vacuum. You could have a brake hose with collapsed inner lining causing a pressure drop that the regulator can't address or a regulator that isn't regulating despite moving freely. Have it checked and adjusted to specs since you've now adjusted it blind. Don't try to compensate for a problem elsewhere by compromising an important part of the system.

You don't want to eliminate the valve unless you have the Teves 20 IE version with EBD (Electronic Brake Pressure Distribution) like Mk IVs use or you'll have premature rear lockup. I don't think the earlier Teves had EBD, otherwise you wouldn't also have the load-dependent proportioning valve.

If you've eliminated everything else, that leaves ABS.
 

gfnetadmin

Veteran Member
Joined
Jan 30, 2008
Location
Ledgedale, PA
TDI
97 Passat
Proportioning Valve Movement

Just wanted to confirm my proportioning valve is frozen or stuck,, I've just replaced all 4 lines connected to the valve, ready to bleed, noticed that there is no movement in the valve.

With no tension on the spring and no braking applied, should I be able to move the base of the valve?

Brakes have not been bled yet. No rear shocks on the car, plenty of opportunity to move the trailing arm up and down. As I move the arm up/down, I don't see any movement of the valve. At the top of the trailing arm's movement, the spring starts to stretch slightly, but no valve movement.

If corrosion is the problem, is it internal or external to the valve? The bracket where the valve is mounted is super rusty,, would soaking the areas around the valve with Kroil or something similar free up whatever is not moving?
 

vanbcguy

Veteran Member
Joined
Feb 22, 2013
Location
Vancouver, BC
TDI
'93 Passat - AHU mTDI with GTB1756VK
Yep, you should be able to move the valve by hand easily.

Just replace the thing. Say you bust it free internally, think where all the corrosion particles are going to go...
 
Top