Bad LSPV ?

[gotmud]

Hey all. I'm usually lurking around the 80's area, but have a question about an '87 4X4 P/U. Specifically the LSPV. The vehicle was bought 2nd hand and has always had brake problems. At first, it was an issue of having to pump the brakes to stop. So we replaced the m/c. Problem stayed. Noticed one of the calipers was leaking, so we replaced both. Problem stayed. Rear shoes were worn and were replaced recently. Problem stayed. While searching this topic, I noticed many have had similar problems getting the LSPV properly bled. But has anyone actually had their LSPV go bad? I know the system has been bled right, but I cant think of any other place to look other than the LSPV.

 

[KLF]

Pumping the brakes usually indicates the rear shoes are out of adjustment. Does the e-brake work? Does it get used? This is how they stay adjusted.

 

[gotmud]

KLF,

Rears have brand new shoes and are properly adjusted. The e-brake works also.

A quick note: pumping the brakes now has little effect. It appears that only the fronts are working. A visual inspection of the rears, shows the wheel cylinders are physically moving when the pedal is pushed. How much pressure they are actually receiving is unknown since I do not have a way to measure the line pressure.

 

[GRM]

I have had a few lpsvs go out before. But normally it just causes the rear brakes not to work.

Is the brake pedal soft? Hard?

if you do find it is an issue with the lpsv, I have one in perfect condition in my garage for $30.

 

[gotmud]

If your definition of not working implies they don't do jack when the vehicle is in motion, than I would say they aren't working. Technically, the wheel cylinders are working. However, the pedal has no resistence until the very end of its travel, at which point the fronts begin to stop the truck.

 

[cruiser88]

I have had them go on a 62

 

[PGH854runner]

i just ditched the LSPV and used a $30 summit manual proportioning valve and it gave the truck better brakes then ever,install it in the line to the rear only(comin out of 2 line junction in pass front wheelwell)and remove the 3 way junction(just ahead of the 2way along the framerail) use a union to reconnect the line to the pass front wheel,flare some SAE fittings on your existing 3/16 line hook up and mount the summit valve approx where the LSPV was then adjust it till front brakes lock up just b4 the rears and you got good old dual system brakes,dont know how much ive fought with those LSPV's b4 this tip i got from someone else on here. good luck

 

[ToyotaNick]

i just ditched the LSPV and used a $30 summit manual proportioning valve and it gave the truck better brakes then ever,install it in the line to the rear only(comin out of 2 line junction in pass front wheelwell)and remove the 3 way junction(just ahead of the 2way along the framerail) use a union to reconnect the line to the pass front wheel,flare some SAE fittings on your existing 3/16 line hook up and mount the summit valve approx where the LSPV was then adjust it till front brakes lock up just b4 the rears and you got good old dual system brakes,dont know how much ive fought with those LSPV's b4 this tip i got from someone else on here. good luck

could you possibly take pictures of the places that you placed the proportioning valve?

 

[GRM]

From what your describing, it sounds like there is air in the lines. You bled all 5 bleeder screws, right?

 

[PGH854runner]

ill try to get a friends camera to take pictures,i was lucky in a way i did it at the same time as a full brake line replacment but look under your truck where the rear of the gas tank is mounted ....see the tube crossing the frame and the rubber brake hose going up to it...thats where u want to mount the proportionin valveplumb in to it the dedicated rear line and out of the valve over to that rubber hose on the bracket where it goes down to axle

 

[GRM]

ill try to get a friends camera to take pictures,i was lucky in a way i did it at the same time as a full brake line replacment but look under your truck where the rear of the gas tank is mounted ....see the tube crossing the frame and the rubber brake hose going up to it...thats where u want to mount the proportionin valveplumb in to it the dedicated rear line and out of the valve over to that rubber hose on the bracket where it goes down to axle

IMHO, its better to make a bracket to bolt it to the master cyl, and put it under the hood.

 

[PGH854runner]

yeah that is a good place to put it but i had good lines going back as far as gas tank then they turned to dust and i did it at the same time as those lines either way will work just make sure you can get to the adjusting knob........

 

[gotmud]

Installed the LSPV last night and I now have much better pressure going to the fronts. The old valve seems stuck and a little rusty. Bled the lines several times per the FSM's order, yet I still have some air in there.

 

[gotmud]

Tore into the brakes again yesterday and found the culprit...loose wheel bearings. The RF wheel had about an inch of slop in it. Turns out both sides needed a complete repack anyway, plus we were planning on pulling the front end apart to get the rotors turned. So SJB55 and I spent several hours in my gravel driveway (my garage is "full" with an engine-less 80) rebuilding the front end. The result...brakes are working again.

 

[cruiser88]

Freak dude.....check everything well.

Tore into the brakes again yesterday and found the culprit...loose wheel bearings. The RF wheel had about an inch of slop in it. Turns out both sides needed a complete repack anyway, plus we were planning on pulling the front end apart to get the rotors turned. So SJB55 and I spent several hours in my gravel driveway (my garage is "full" with an engine-less 80) rebuilding the front end. The result...brakes are working again.