Hey guys. I braked hard in the truck (87 dak, 3.9) with it off, and blew out both ends and the center of the proportioning valve on my truck. Its located on the driver side under the rocker near the leaf. Theres 4 brake lines going into it, and a rusty spring looking thing that goes to the leafs. Am I correct in assuming that this is the height sensing brake valve? Part 4313433?

The only one I could find online was $253. I went to two junkyards, but there were only 2 1st gen daks, both 1992s, and neither of them had the valve, or did it look like it was ever there.

I don't know what to do really. Luckily the dak is at my house and I can fix another truck to drive back to school. But I'm wondering if anyone else has run into this problem. Could I just bypass the whole valve and just connect the sets of lines to each other without a problem? This is really just my beater currently, so I'm not looking for a perfect fix, just a cheap functional one that will last a few months. Thanks guys.

 

I would agree that that is the "Height Adjustment Valve." (ie, proportioning valve)
You can get replacement ones (proportioning valves) from a lot of places (Jegs.com, SummitRacing.com, etc).
It will most likely have to be adjusted (most have an adjustment ****).

As with any job involving such a critical safety item such as the braking system, before attempting a fix, make sure you know/familiarize yourself with what you are doing. And make sure it works before getting on the public roadways.
If in doubt, hire a professional.

 

So would a single in single out adjustable prop valve work then? Theres a mess of rusty brake lines, so I'm probably going to just start at the master, install the valve there, and then run new lines back to the drums.

 

A single-in, single-out would work.

The new valve needs to be installed downstream of the metering valve (which is located on the frame, aft of the front left wheel-- follow the lines from the master cylinder to it).
You can read a little about Metering Valves in the following links:
http://auto.howstuffworks.com/auto-p...ter-brake2.htm
http://www.wisegeek.com/what-is-a-metering-valve.htm

 

Hm okay. The metering valve on my truck is 1 line in and 2 out, so would I just use a T to run the 2 lines into a single, then into the prop valve?

 

I don't know.
You'd have to look at the plumbing. I'm not sure exactly how things are plumbed in those years.
From what it shows in the parts manual (but, not always an accurate representation of "reality"), you have 2 lines "IN" (from the master cylinder) and 3 lines "OUT" (1 going to the front brakes, and 2 going rearward), of the metering valve.
Although, in reality, the only thing that would actually make sense would be the 2 lines "IN" and 2 lines "OUT". Since the 2 OUT lines would go to their respective tee's (front and rear brake tees)

You want to plumb the proportioning valve in between the metering valve and the rear tee.

*ADD* What you may be looking at that has a 1-in 2-out configuration, that is near the front, is the front brake tee. You need to follow the lines from the master cylinder to the first valve they run into, which should be located under the cab, if I interpret these (crappy) parts pictures correctly.

 

No this is correct. The two going rearward from the metering valve go into the load sensing valve, which takes those 2 in and sends one out, which THEN hits the T to the 2 rears.

Thats why I'm asking if I should take the 2 rear lines from the metering valve and t them into 1 before running into the adjustable prop valve. Thanks for all the help!

 

At the metering block (up front) plug the rear most line coming out of the back of the block that goes to the HSPV (Height Sensing Proportion Valve) with a brass plug (can get at any auto store). The other line from the bottom of the metering block that also goes to the HSPV is what you run to the "T" junction for the rear brakes eliminating the HSPV from the system. Be warned that the back brakes will lock up easier without that HSPV. The line from the bottom of the metering block is the high pressure line for the rear brakes and the other line is the feedback line back to the metering block. As the *** end of the vehicle lifts during braking the HSPV is supposed to help stop rear wheel lockups by bleeding off pressure which is it's function.

 

Okay, I'll run that bottom line into the adjustable prop valve, and then just run out of that to the rear t. Lockup shouldn't be too bad once I get the adjustable dialed in right? Thanks for all the help too.

 

Yes that is correct if you are using an after market proportioning valve that is a single in and single out valve which are normally used to balance out each individual brake on racing pro stock cars with four wheel disc brakes. Dialing that kind of valve will take some trial and error with rear drum brakes though. Start at the middle setting first and try both panic stops and regular stops to see when the rear wheels lock up. If you have firm braking during regular stops but lock up on the panic stops that is where you want it set at.