Swapping out the load sensing proportion valve on the rear brakes a DIY job?

Hi, I'm a completely amateur garage mechanic, but I'm fairly competent. The LSPV on my 97 tacoma is leaking pretty bad, and I'd like to either try rebuilding it, or swapping it out for a new one. I asked my mechanic if he's ever done manual valve bypasses on them, and he said he was never able to pull it off and get all the air out of the lines. Could be he just said that because he didn't want to do it, but I've never worked on brake lines before.

So my question-- even though I've never worked on brake lines, is swapping out that valve something I could probably do myself with a little research?

Would I need to drain the fluid before removing the valve, or can I just uncouple the lines, plug them with something, and bleed the air out after I get the new/rebuilt one in?

After I get the new one in, would I have to use the bleeder line on the valve, as well as the rear tires, to get all the air out?

Any tips from anyone who has done this would be appreciated. Thank you!

 

You should be able to replace it and bleed out the air. I would go ahead and change out all the fluid.

Change BPV, then bled the entire system on all four corners with new fluid. That way you could see a color change and know that fresh fluid has pushed all the air out.

 

Good idea, thank you. I think the previous owner of the truck had the brake fluid changed recently (new brake slave shortly before sale), and I've been adding fluid as it's been leaking. I think it was flushed about a month ago. Do you think I'd still be able to see a color change with fresh stuff with fluid that new?

Also, should I treat the bleeder valve on the LSPV like the ones on the tires, following the philosophy that you start with the farthest one away and work your way back? So, rear passenger wheel, rear drives wheel, LSPV, front passenger, front driver?

 

You may not see a change in oil if what's there is fresh. You may just use a qt. bottle then and be done. I didn't notice the BPV even had a bleed port when I fooled with mine after lifting the truck.

Remove bad valve and replace. Then flush through with a qt. to the BPV port and rear wheels. If you feel comfortable enough it's air free before a qt. is used up, do the front wheels or keep the fluid as spare.

 

I fixed my lpsv fairly easily, even though I didn't know for sure if it would work,,, mine was leaking badly also after I did a brake job and flushed the brakes,,, so I pulled the valve and disassembled it, taking my time and just cleaned everything up,,, clean,,,, inside and out, put it back together and flushed again and bled the wheels and the lpsv, no leaks, yahoo!

so far so good, been about a year and it's working fine, I also set it dimensionally according to the FSM and the truck brakes fine,, to tell you the truth, I didn't think it would work, but because it works differently than a wheel cylinder it believe is what made it work OK.

As I guess you know you can't get rebuild kits for it, I just reused all the parts and it's holding fine.

 

Looking at the section in my Haynes repair manual, after swapping it out it says to bring it to a dealer to have the valve and lever assembly 'adjusted.' Is that really necessary? I imagine there's write-ups for that around somewhere. Surprised they aren't in the manual.

 

as long as you don't change the settings on the mounts then it should be ok but it wouldn't hurt to have it checked after. the dealer puts a pressure gage to determine the back brake pressures.

if it has been leaking then the system has flushed itself of old fluid already, at least up to the LSPV but from it to the rear brakes could still have old stale fluid so make sure its clear before you stop bleeding.

when you bleed the system do the fronts first (drivers side first then passenger side) then use the bleed screw on the LSPV to clear the lines up to it, then do the rear wheels closet first then the farthest one. the LSPV can be a real PITA to purge so don't try and bleed the bake brakes until after the LSPV has been bled.

one thing to note is its hard to get fluid to the rear brakes so you will be doing some mashing on the brakes and its slow going because you only get 1/4 of the fluid movement that the front brakes get so slow and steady gets it done and don't expect it to be a 5 minute bleed job.

 

You can tie the rod up against the bed as close as it'll go and get more fluid to the rears.