Author Topic: Proportioning valve or pressure reducing valve (Read 7279 times)

clbanman · « **on:** October 20, 2008, 04:06:56 pm »

I was just looking through my Bently, and it says that only GTIs and Jettas have the pressure reducing valve at the rear axle instead of the proportioning valves on the master cylinder. My Golf has the pressure reducing valve. Would that indicate some mixing of parts or is the Bently incorrect? (91 Golf - unsure of originality as I know engine/trans was changed by PO.)

burn_your_money · « **Reply #1 on:** October 20, 2008, 07:05:09 pm »

All my MK2s have had the pressure reducing valve attached to the rear beam. They were all post 90s. Actually, I was just working on a 85 gas car, not GLI and it has the pressure reducing valve

foxracer1 · « **Reply #2 on:** October 20, 2008, 11:37:18 pm »

I just took mine off. It was froze up inside. Now all 4 lock up at will with the added rear disc and 22mm mc.

madmedix · « **Reply #3 on:** October 27, 2008, 08:02:21 pm »

My 92 Golf NA did not have it (nor the mount for it). My 90 Jetta TD has it. My 87 Golf NA does not. IMO the Jetta brakes better under duress with it. The Golfs don't wag the tail under hard braking but they sure are thinking about it.
I do know a vw stealership that used to advocate adding it when a Golf owner would complain of braking problems of some type...for a sizable chunk of change of course :roll:
I will say this, if you add it (or have it) make very sure you have closed the flange toward the body and put a stick or bolt through the eyelets BEFORE you bleed the system, or you'll blow it out/compromise it.

Cheers,
Andy

burn_your_money · « **Reply #4 on:** October 27, 2008, 09:47:56 pm »

Quote from: "madmedix"

I will say this, if you add it (or have it) make very sure you have closed the flange toward the body and put a stick or bolt through the eyelets BEFORE you bleed the system, or you'll blow it out/compromise it.

Can you explain this better for me?

madmedix · « **Reply #5 on:** October 29, 2008, 08:20:24 pm »

Sorry for the delay, really busy...but I found the picture! Could've been better, that parking brake cable is in the way... and it's too dark and cold to go out there and get another

Basically, depress the eyelet you can see towards the one hiding behind the parking cable. Stick a pin/bolt/whatever to lock it open and bleed the brakes. Then remove the pin or whatever you use to lock it open and you're good to go. It was an old time VW mech that found this problem. My Jetta was braking ok, but under avoidance braking she'd develop a lateral "warble" even after other adjustments. This mech changed it out..."too many people don't know about this..." and now she hauls down straight and narrow until ya can hear the rivets.

Cheers,
Andy

clbanman · « **Reply #6 on:** October 29, 2008, 09:23:36 pm »

Where did you get the replacement and roughly what did it cost? Mine looks like it might be seeping slightly, so I'll probably have to replace it soon.

blkboostedtruck · « **Reply #7 on:** October 29, 2008, 09:46:40 pm »

ahhh now thats the trick! thanks for the nice pic, and the explanation! see i still learn something new everyday! madmedix
Duane

jtanguay · « **Reply #8 on:** October 29, 2008, 11:15:25 pm »

Quote from: "madmedix"

Sorry for the delay, really busy...but I found the picture! Could've been better, that parking brake cable is in the way... and it's too dark and cold to go out there and get another

Basically, depress the eyelet you can see towards the one hiding behind the parking cable. Stick a pin/bolt/whatever to lock it open and bleed the brakes. Then remove the pin or whatever you use to lock it open and you're good to go. It was an old time VW mech that found this problem. My Jetta was braking ok, but under avoidance braking she'd develop a lateral "warble" even after other adjustments. This mech changed it out..."too many people don't know about this..." and now she hauls down straight and narrow until ya can hear the rivets.

Cheers,
Andy

that looks nice and new!!! mine is horrible... i'll need to do new brake lines on it in a few years

those brake proportioning valves are about $100 :cry:

i bled mine without doing that to the prop valve, and my car doesn't brake so good... the rears especially. time to downshift come winter :lol:

cyrus #1 · « **Reply #9 on:** October 29, 2008, 11:22:32 pm »

Haha! I've always wondered why my braking has been crap since I bled my brakes. Thanks a million for the heads up!

madmedix · « **Reply #10 on:** October 30, 2008, 08:40:02 pm »

I don't know where he got it; probably a jobber. I bought one for another Jetta for $92 tax in, shipped last year. Had to fab the bracket you see the two bolts in though (used a piece of old steel bed frame rail). Make sure you use something that isn't too thin.
I have since put a piece of lexan (clear plastic stuff from a bulk pack of socks) across the bottom to keep the crap out of the bellows. One winter of road salt/grime filled the area around it...probably why the bellows were trashed on the old one.

It was expensive at the time and personally I felt it had dubious value...until I needed it. The money spent was a lot cheaper than what would have been an insurance increase....

Cheers,
Andy

burn_your_money · « **Reply #11 on:** October 31, 2008, 03:15:09 pm »

Thanks for taking the time to take pictures. My new Jetta has piss poor braking, hopefully this fixes it.

clbanman · « **Reply #12 on:** November 08, 2008, 10:38:09 pm »

I put a new valve on mine this week. The two eyelets you are referring to can't line up on mine (didn't on the original one either). When you are bleeding them this way, what method are you using? I have a Mityvac hand pump, and usually bleed all my brakes using that, but I couldn't get flow at the rear brakes at all, no matter where the reducing valve lever was positioned. I had to bleed it manually with my wife pressing on the brake pedal and myself cracking the bleeders. The vacuum works fine on the front brakes, so I'm assuming it has something to do with the reducing valve.
(Everything is new from the master cylinder back.)

jtanguay · « **Reply #13 on:** November 09, 2008, 07:16:21 am »

Quote from: "clbanman"

I put a new valve on mine this week. The two eyelets you are referring to can't line up on mine (didn't on the original one either). When you are bleeding them this way, what method are you using? I have a Mityvac hand pump, and usually bleed all my brakes using that, but I couldn't get flow at the rear brakes at all, no matter where the reducing valve lever was positioned. I had to bleed it manually with my wife pressing on the brake pedal and myself cracking the bleeders. The vacuum works fine on the front brakes, so I'm assuming it has something to do with the reducing valve.
(Everything is new from the master cylinder back.)

you need to switch to the pressure bleeder

madmedix · « **Reply #14 on:** November 09, 2008, 02:29:35 pm »

It's a powerfist bleeder that unfortunately, princess no longer sells. Wish they did, it's great: it builds pressure in a cylinder about the size of a large prescription drug cannister with a pressure guage on top of it. Squeeze like crazy and then push a button and instant bleed...it can build up to 100 lbs. suction.

Any way, the eyelets do line up on the horizontal plane. There's about a 1/2" space when it is depressed all the way in, but the holes do line up. The on the Golf I used a #12 machine screw and on the Jetta the last time I used the biggest zip tie I could find to keep it in.

Also, you have the top two lines going to the wheels and the bottom two connecting to the lines from the MC right? I've seen it different on a few...