99Hawk120

I forgot no PV = no warning switch.

I would still disconnect the center brake line at the junction block. It's STILL easier than pulling the master and will isolate whether the problem is at the front or rear of the car. If it still dribbles out of there, then you've got either a plugged hard line or a bad MC.

BMmonteSS

Yep I'll give that a try this weekend. If it doesn't work i'll just get a new mc and go from there. Thanks for you help its great to have another mechanicaly inclined mind to help trouble shoot these kinds of problems.:hail:

poncho9789

The best thing you could do is put adjustiable proportioning valve in your cars to adjust the front and the back but this mod to the factory valve is basicly a cheep way to make your brakes work the way they should. I wouldn't remove the front brake valve under any condition. You most likely have a bad master cylinder or a masive fluid leak if you have a large petal travel and no brakes. I just finished fixing my dads brakes on his 97 chevy truck and the wheel cylinders were shot and leaking out fluid but the master cylinder was bad also. If you check your brake lines all the way to your calipers on the back and see a gummy dirt clod on any part of the system then you have a leak of brake fluid in the system. Check arround the seal for the caliper piston to make shure that you have not leak there. You might also look into replaceing the master cylinder again it is possiable to get a bad master cylinder from the parts house (believe me on this one I have seen them come back bad) and I haven't worked in parts very long.

ebby53

Before I start this..Does anybody who has done this mod know what the thread size is for the plug on the front of the pv??? I've been thinking that I would like to replace the original plug with a brass one and not have to thread and plug the original one. Appreciate it............

poncho9789

It isn't a pype plug so it would be best to plug your stock plug. If you notice the seal at the sholder of the bolt that is what seals it.

wuter

I read about this mod about 2 years ago, it was on a b body site.
i was going to do it but got pbr rear brakes instead. anyway they said to plug the front with a solid plug from the rear from another valve. you can read more here:
http://www.b-body.net/Technical/Brak...Mod/index.html

Ward

iTrader: (1)

Instead of modifying the plug which threads into the end of the PV, wouldnt It jsut be easier (and maybe safer) to use a thread in plug? You know, the ones with the allen head that screw into an intake to block unused vacuum ports...

sIcK pUpPy

That is the prefered method, but everyone seems to gravitate toward plugging the existing nut which works as well.

TomP

Think about using a sealant on that plug after you pull it off. You'll notice the threads have a reddish tinge of color to 'em- and I don't think it's Loctite. When I pulled my plug off (thought maybe I could put the rear brake line into it, but nope, it was a valve, oops), I used Permatex Hi-Tack sealant-in-a-can on the threads. The can said that it could withstand high temperatures, and was unaffected by brake fluid.

blowen90ta

i did the mod this afternoon as my rear brakes never get much pressure(cant stop them with both feet on the brake with the tires in the air) what a night and day difference but now i seem to have too much rear pressure.i dont beleave cutting the spring is the way to go as the more you cut the stiffer the spring gets.so the options as i see it now are
1--modify the plunger to allow some fluid to pass
2-- add an ajustible prop valve to the rear line
3--go junk yard hunting for different springs
im leaning to the ajustible prop valve but its getting crowded under the hood wonder if i could tuck it at the rear dist block?
guess first i'll go spring hunting and see what i can find
at least now i have options as before it is impossable to add pressure
pete:lala:

abcx09t

I am a new member with an '87 IROC-Z w/4 whl disc and want to improve my rear braking too. From what I have read I went and purchased a proportioning valve at the junk yard. Wuter said use the front brake plug from the rear of the PV to plug the rear brake port on the front of the PV (hard to follow I know). Anyway, the junkyard PV is still on the workbench and I will check that out tonight. Seems like a simple change. I was waiting to have the original plug welded. Having the extra PV is a real good idea so you have extra parts if you want to go back to original.

What you do with the plunger and spring after you curse it is stick it in a bag and save it. Install it with an original plug (saved or from junkyard) so you don't have a liability suit after you sell your car.

However, my real question is what do you guys do about the warning light? Do you just ignore the light, pull the fuse, or disconnect the wire at the PV? I have not read anything about the mod past plugging the hole in the modified PV plug. Some insight hear to finish the job would be great.

P J Moran

Does this modification affect the perfomance of the brake warning switch?

Also, the old links to the procedure don't seem to work any more. Can someone update them? I never saw this the first time around.

scauffiel

I'll upload some pix with a description when I get home later tonight.



Hopefully I'll remember. If I don't feel free to email me to remind me.

S.

scauffiel

Okay, I'm home now. Let's see.

Take the end cap off. Like so:

scauffiel

The spring may or may not come out with the valve - no drama, it'll come out eventually.

scauffiel

Pull out the valve inside with some needle nose pliers:

scauffiel

I threaded the hole in mine so it would take a metric screw, and added a gasket I had made out of gasket material:

scauffiel

...and made sure it was nice and tight. No leaks, a bit better braking and didn't cost jack. Thanks go to the original poster of this tip. I've got a spare prop valve and I may try the stacking washers trick to see which variant works better; but that may be a while.

Steve

Eightyninef

it seems some people are having problems with the rear PBR setup in 89-92?
mine work great, I am surprised to hear that????

what is the problem???

thx

urbman

Hmmm...
Anybody with some gauges ?

I would like to see something like before and after
line pressures...

And perhaps larrys "working" line pressures...

Sorry, I understand this is a "non-trivial" request

Larry ?

abcx09t

Scauffiel:

Thanks for the photos. However, what happens to the performance of the brake warning light. What mods do you need to make to keep the light off? This mod basically leaves the warning light useless correct?

Thanks

scauffiel

No idea. Unfortunately, before I did this mod my brake light was already on all of the time even though I didn't have any leaks or problems. I have to tear out my console and re-check the switch at the E-brake to make sure that's not the culprit before I go any further.

S.

Eightyninef

in1989 there was a mid year prop valve change. maybe they changed the internals besides changing the thread pitch.

I know I wore 75% through a set of rear street pads in 2 track events. so I know they are working. and I also jacked up the rear and I can stop the rear wheels no problem.

my car is a late 89 production, May 89.

89
J65

Breazlan

iTrader: (1)

Does this make the 82-88s stop better than the 89- PBRs?

BMmonteSS

In theory the PBR brakes should have more braking force than the oldr design for one reason they are bigger in diameter. They are about 11.75 or so compared to 10.5 for the older disk. Theory sucks in the real world. In the real world there is less surface area on the PBR brakes so the 10.5 inch brakes should create more friction and stop better. Thats my theory anyway the other problem you run into is cooling. The PBR's look to have better cooling. Even my theory sucks because in the real world this would only be true if both brake systems were operating at optimum levels. Most don't. This mod basically takes the proportioning properties out of your proportioning valve and gives full braking power to your rear wheels. This greatly improves braking but in some cases it gives you too much braking power to the rear wheels. In my case I adapted a 83 disk setup off a fireturd and put in on my 9" rearend in my Monte Carlo and had brake lockup problems in the rain. Most thirdgen guys don't have this problem. Your best bet would to chuck the stock prop valve and install an adjustable one. That way you can optimise your brakes. Thats what I did and i can dial my brakes for any tire combo and road condition. This will get you ahead of the game no matter what system you have. Sorry this is so long but i thought I would throw my two cents out there and see what everyone else had to say.