Brake Proportional Valve Delete Write-Up

[coolwind57]

When I bought my truck a few years ago, it had the original front disc and rear drums.  The Height Sensing Valve (HSV) half-assed deleted by PO.  Still had 2 old crappy rusty brakes lines running to rear.  Acceptable brakes as a whole, but I chose to renovate it for since I had my truck mostly apart with other projects anyway.    

 

I chose to start things off by trying Cruiser54's front Proportional Valve (PV) trash and replace procedure, aka DELETE.  This seemed logical as a way of simplifying things and perhaps improving front brake performance..  Plus He's got real-world experience doing this and it has worked for him multiple times. 

 

I figured at least to me, that the MJ PV was designed to work a system that included the additional second brake line to the rear (to be used in cases of front brake failure) AND a system including a well-working Height Sensing Valve HSV.  Since I had neither, the MJ PV is no longer being used exactly according to its design with those two aspects missing.   

 

The MJ PV meters the front brakes down considerably after the brake line run into it from the master cylinder.  Just look up some of Cruiser54's pictures of those tiny little orifices in there.  They certainly choke the inside diameters down.

 

I removed the entire PV and then T'd-off the front calipers using an inverted flare brass T.  I can't remember where I bought the inverted flare T, but with a little searching you should find one.  You should get better braking because the small orifices of the prop valve to the front brakes are eliminated.  You're now running near-full open inside diameter of the hard brake lines that are coming off direct from the master cylinder. 

 

Pics below are from a couple different angles but it was tricky getting a good shot of the installed brass T.

 

and here's a view from side/bottomp:

 

Because I am eliminating some front and rear "bottle-necking" I used to have at the now-removed PV, I agreed with many others here that an Adjustable Proportioning Valve  (APV) may be a good idea FOR THE REAR BRAKES.  This should eliminate any rear brake lockup that I may experience if I am running a heavy payload.   

 

I sourced my APV from Speedway Motors.  I chose the Speedway APV because it is compact and appears to be simple and tough.  Another cool feature is that it allows for full shut down of fluid to the rears, which can possibly come in handy when working on your brakes.  

 

Even though TJ1 had a cool location for the APV in his rig, I ultimately sided with HOrnbrod's (God rest his soul) opinion of not having brake lines running inside my cab.  Mounting it outside of the truck near the rear of the bed would likely affect longevity and stable function due to full exposure to elements.  I installed mine under the hood, near the washer fluid reservoir. 

 

Having had removed the two original rear brake lines, I ran a new single line back there the the axle from my APV, which I installed here:

 

Speedway didn't have comprehensive flow specs on that mini APV that I show in the picture.  it shows gpm and max psi and states that it can be completely shut down whatever line it is controlling if desired.  I was curious of flow characteristics during "fully open" setting, knowing that nearly any valve in a hydraulic line would impart some level of restriction.  So I emailed them about it and this was their response:

 

Perry, I just spoke with one of my techs and he stated that it will not be fully open when the valve is fully open, there will still be some restriction there.

 

Thinking around 20% restriction, so it'll flow 80% of the fluid that a straight line will.

 

As far as I know, we do not offer a proportioning valve that will flow as if there is nothing there while fully open, however the purple proportioning valve might flow a little better as it is not a complete shutoff valve while fully closed, there will likely still be a bit of resistance there.

 

https://www.speedwaymotors.com/Speedway-Purple-Adjustable-Brake-Proportioning-Valve,23498.html

 

 

My brakes ROCK now!  Got my MJ running last night and took her for a spin.  My brakes were not so bad to begin with.  But now they are excellent!  Feels like I have 4-wheel disc brakes.   By the way, I am running the stock master cylinder.

 

Many thanks to Cruiser54 for the advice on ridding the front proportional block.  I have killer good brakes, and I now have the ability to adjust the rears (or shut them down if I choose to)"

 

Actung Baby :  If you've read much on the topic of HSV deleting/PV deleting/running a single line to your rears, keep in mind that you'll lose that safety feature that allows full braking to the rears in cases of front brake failure. 

 

Here's some additional notes: 

 

1. It took some active shopping around to find the correct sized fittings/adapters to use stock flare fittings and MC orifices with new....I didn't want to have to cut double flares on new and factory brake lines, so I had to use my brain a bit during shopping to avoid cutting/flaring.

 

2.  By design, I certainty now have isolation of from and rear brakes, for sure!  Front and rear have two different and very separate paths.  They obviously already have two different reservoirs inside your master cylinder.  My system continues from there to NOT cross paths with each other.  If I lose my front brakes, I still have rear brakes. 

 

There are advantages and disadvantages to nearly anything you do.  I'm pushing full volume to my front brake calipers now instead of dealing with a factory bottle neck.  Overall, front-and-back, I can say that I've got superior braking ability compared to what I originally had.  And at great cost and time savings.  Disadvantage is that I may lose some "fail-safe" capabilities, if you will.  I will no longer have a working brake warning light.  I weighed perceived consequences, and then decided on my course of action.  This method works for me and after nearly 3 years of use, I have no regrets.  

 

I can now shut down my rear brakes totally if I want to.  If you like to show off and do burn-outs, then this is a nice feature!  This isn't me, but I give it as an example.  Shutting down rears is also nice if you're working on your rear brakes and want to shut off fluid completely.  

 

There's several options for those out there working on their brake system.  As i had brought up above, my Proportional Valve was no longer capable of operating as designed by Jeep.  In renovating my brake system, I  chose to go a simpler route with fewer parts to go bad and which gives me far better braking capability. 

 

Do your research and weigh your options and consider risk factors.  A complete proportional valve delete like I did may be a good option for you.