LSPV question

[60wag]

I wanted to replace the LSPV on my 96 80 because the old one appears to be stuck. I've pushed on the valve pin and it won't move at all. I ordered a brand new one, just received it and pushed on the pin to see what a new valve feels like. This one doesn't move either. Huh? What am I missing here? the pin is actuated by the lever arm and should move right? I expected the pin-piston to slide in the valve body with a spring return. I put a wrench on the valve body to take it apart but it is really tight. Should I take it apart, or send it back? How is this thing supposed to work?

 

[LandLocked93]

Curious what triggers the interest in the LSVP as the cause of what issue?
I've seen mine from time to time, but what you describe sounds steam-age. lol

 

[60wag]

I had an event recently where I lost my brakes coming down I70 into Georgetown while towing a 4000 lb trailer. I was able to the the rig stopped safely but it scared the crap out of me. I had been downshifting and using the brakes very cautiously. The trailer has electric brakes that maybe could have had a higher boost setting. Since then I have been trying to get the entire braking system dialed in as best as possible.

I had already replaced the the rotors, brake pads, soft lines and fully flushed the system. I had noticed lots of brake dust on the front wheels and none on the rear, figured that was normal. I had put an OME lift on the truck 14 years ago and never thought about properly adjusting the LSPV. Once I looked into it, it was clear the the lever arm wasn't contacting the valve actuator at all. This should reduce the rear fluid pressure to the minimum that the valve can put out. Seems like a good thing to have functioning properly.

I wondered if this contributes to the endless threads discussing the poor braking on 80s since most of our 80 are lifted, and it appears that the LSPV is usually ignored or thrown with the trash.

 

[Malleus]

Yes, you can open the LSBPV. It should actuate easily, however you might have to put a long lever arm on it to see it. I would be surprised if you could move the piston by hand on a bench, the spring is pretty stiff.

The plethora of complaints about braking have little to do with the valve, IMO. Of the three I have, only one has brakes that feel like they did when the truck was new (my newest 80 was four years old when I bought it, so I have a pretty good idea of what they should feel like), the other two range from what I would consider OK to poor. They'll stop, but they won't put your face on the dash like mine or my LX470 will.

 

[Rusty Marlin]

I recently replaced mine because it was leaking. I have a 3" lift on 33" A/T tires. Coincidentally, I also replaced both rear calipers and the master cylinder around the same time.
With the new LSVP (properly adjusted) and other new parts, the truck will STOP and I mean Right F'ing Now when needed. Its quite impressive actually.

 

[landtank]

The arm actually limits the valve’s travel. You you apply the brakes pressure from the front brakes pushes the needle out and against the rod setting the pressure applied to the rear brakes. So the start position of the valve is all the way in.

 

[60wag]

Ok, got the new valve apart and my question is answered. The spring pushes the actuator in, does not push it out. Pushing on the pin should be rock hard, so maybe my old valve that is still on the truck is ok. Applying pressure to the brakes must move the pin out until it hits the lever arm. (I was typing this when Landtank's reply came up, thanks.)

For those that adjusted the LSPV, how did you do it? Did you use the pressure gauges shown in the manual? I don't have the gauges - yet. I did measure my lift using the Delta panhard technique and found the rear end to be up 3.63". Based on the length of the lever, I should move the valve down 0.21" to get it close to the stock adjustment. I want to see if this changes how the brakes feel. Maybe I will continue on to measuring the actual fluid pressure.

 

[landtank]

I offer a kit to address this and some guidance installing it using the valve in the factory stock position.