Brake proportioning valve replacement (and lines leading to...)

If this doesn't scare you, I don't know what will...! Anyway, this obviously needs replacement before something bad happens. The lower hard line on the right is pretty ripe, so I'm going to need to attack that as well. Does anyone have a plumbing diagram for our braking system? I'm almost thinking about getting the manual valve and mounting it in the cab instead of replacing this expensive buggar. What lines go to where? Obviously I can see the line that goes to the rear axle, but there appear to be three others attached to the valve...
Anyone have experience with this mess?

 

Yikes! Hope your frame doesn't look half as bad as that..
As far as the lines go I would just track them back to the cab area and see from there. If the line is only bad near that fitting I would just cut it a ways back and add a union with new line and fitting running the the BPV.

 

I know that the top line going into your LSPV valve that comes from the front on the truck is the pressure line that eventually feeds down to the splitter on the back axle that then Leeds to the two rear brake drums. The bottom line that comes from the front of the truck is just a feedback line. If you get rid of it, you can but you will need to plug off that line, or where the line feeds from the front of the truck, you could feed a new line up to a Manuel valve in the engine compartment. I hope that helps!

 

Frame looks decent, thankfully. It was chemically treated by Toyota in 2008, and carries a 10-year warranty from then. At this point, I hope that it either lasts forever, or fails tomorrow...!


What does the feedback line actually go to under the hood, and what's it's purpose?

 

What this valve does is proportionally adjust the rear brakes to what you are carrying in the bed. If you want to replace it by a new on, it is quite pricey

The upper line is the inlet of the valve and the lower line is a return line that sends excess brake fluid and pressure back to the front brakes. Then the line on the top of the valve, facing the differential is the outlet, sending the fluid to a splitter on the axle, that then sends brake fluid to both wheels

You can get rid of this valve by connecting the upper line to the rubber line above the differential (that goes to the splitter) and plugging, or removing the lower line, as it is no longer needed (comes from a splitter located inside the driver's side wheel well)

Then you can leave it like that or, as you said, add a manually adjustable proportional valve. Though I think it would be better by the master cylinder, and not inside the cab, because you won't need to extend and insert brake lines into the cab. Just put it right at the master cylinder's outlet for the rear brake line

 

Just ordered a complete valve assembly used on ebay! All of the rest of the steel lines look decent at the flare fittings. Obviously I can't see inside the plastic sleeves, but I don't see any signs of damage anywhere, so I'll probably cut the lines in the middle of the frame where it's easiest to work on, and splice with a union. How do we feel about copper/nickel lines over steel?

 

Nice that you managed to get a used one through ebay, but I wouldn't have done this, if it were me.

Actually, this system is crap. Good idea on paper, but not so much when put on trucks. Mainly because it actually links both the front and rear brake circuits through this valve. So if there is a malfunction, the valve jams, or whatever, it can cause problems for the operation of both your front and rear brakes (much more common to see rear brakes failing, because of this valve, but there have been cases of front brakes being affected too.)

Also, in case of a leak (on the valve, or on any of the brake lines or components), you will lose ALL of your brake fluid, depriving you of brakes. When you bypass this valve (or go with a manual one), you actually isolate both circuits, eliminating this possibility. If you have a leak, you still have your front or your rear brakes as backup, depending on where the leak is (unless you have a leak on both circuits, which would be very bad, haha).

If you look on modern cars, like newer tacomas, you don't see these valves anymore, because it wasn't this great of a system

Anyway, you already bought it, so it's a bit too late to tell you all this, but I hope it works out good for you

About the copper lines, ever seen cars with copper brakes lines? No, because copper is a soft metal, not good for use with lines through which a pressurized fluid runs. The pressure in a brake system can actually be quite high, much more than people might think. You need steel lines, as they can withstand high pressure. If you are worried about rust, I think stainless brake lines exist

Don't forget to bleed your brakes after this. The order is:

• valve
• rear passenger
• rear driver
• front passenger
• front driver
  

Good luck

 

Cupro Nickel line (or copper nickel as its also called) is actually great for brake lines. It's really nice to work with as it bends smoothly and easier than steel, and won't rust. It's also purpose built for brake systems so I don't think pressure would be an issue. I would use it on my truck without a second thought.

 

Good luck with flaring used old steel lines most often they crack from being old and brittle .

A compression fitting is not suitable for the pressure in brake lines They seem to fail at the worse time

The Copper /Nickle line is all I use I just wish it came in 100' coils

 

Compression fittings are a no-go for inspection around here. Using flared unions. Are ALL the brake lines 3/16"? There are a few pre-made cupronickel kits available online, and I may go that route so I don't have to buy a double reverse flare tool that I'm hoping I won't need again... And are we 10mm or 3/8" thread on the fittings? I can't tell with all that rust...

 

Looks bad, but I will bet the internals are in better shape... At least I hope. My Haynes manual has the tube routing for the brake system. If you happen to have one, you may check there.

 

Anyone know what the thread is for the brake line nuts? Still procuring parts...

 

if you mean the fittings that connect the lines to the valve, it's 10mm fittings, with fine threads if i remember well

edit: M10 X 1.0

 

Looks like I have all my parts finally. Changed out the parking brake bellcranks already, so I'm now good there. Brake line surgery begins Friday evening...!

 

What a shitshow... Had to cut the center hose to get the fitting bracket out. Those 4 bolts holding the valve bracket to the frame fought me ALL the way out. And the way the pivot ears failed, the valve would have been completely closed for the rear brakes, which is why I've had no rear brakes for the last year...!!!

Just about half way there! Done for the night though. I'm spent...

 

Is there a write up on how to eliminate the BPV? I'd like to get rid of mine.

 

There is, depends if you pull things in the bed of your truck often or tow quite a bit, if so you should have the valve there or put a manual one somewhere. If you do not do any of this very much at all then yes you can get rid of it. The top brake line that comes from the front of the truck, connect that to the flex line that Leeds to a splitter that goes to the rear drums. The bottom line that goes into the valve also come from the front of the truck you can remove and look into the drivers side front wheel well and you will see where that connect there from another splitter. Take off that whole line and plug it off. Then bleed your brakes rear pass, rear driver, front pass, front driver. I hope this helps.

 

Thanks

 

You are very welcome

 

And I thought I had seen everything they ever put on a KFC menu...