Dolphinite no longer here Posted March 6, 2013 Share Posted March 6, 2013 I want to unhook the LSPV from the system and someone here said to "unhook the rod and wire it to the frame." What rod gets unhooked? The threaded one with the adjusting nut on it or the other, longer rod? John Quote Link to comment Share on other sites More sharing options...
WME Posted March 7, 2013 Share Posted March 7, 2013 The long rod. Try it for awhile. Then you can figure out a more perment fix. Quote Link to comment Share on other sites More sharing options...
zero Posted March 7, 2013 Share Posted March 7, 2013 I want to unhook the LSPV from the system and someone here said to "unhook the rod and wire it to the frame." What rod gets unhooked? The threaded one with the adjusting nut on it or the other, longer rod? John I find it hard to believe it serves any useful function on a Toyota RV. It's there to sense when a truck is empty or loaded and delay full brake pressure for a moment to prevent lockup.. In the case of a Toyota RV, it's "loaded" all the time. In my area of el-mucho road-salt, those things are always stuck and rusted fast anyway. I put a $20 proportioning valve on mine up front by the master-cylinder. It allowed me to "tweak" the system to get my braking the way I wanted it after putting a dually rear in with bigger brakes. Quote Link to comment Share on other sites More sharing options...
linda s Posted March 7, 2013 Share Posted March 7, 2013 Yes it's for a truck that can be unloaded. Detaching it and wiring it all the way up is the easiest way to get max braking on the rear wheels. It can be bypassed but way more complicated for the novice. As a sidenote, when I adjusted mine I discovered it hadn't been working anyway so I got no noticible results. Many others have though Linda S Quote Link to comment Share on other sites More sharing options...
Dolphinite no longer here Posted March 7, 2013 Author Share Posted March 7, 2013 The problem I'm having has to do with too much braking. When I'm on snow or another slippery surface and step on the brake pedal, even very lightly, the back brakes immediately lock the rear wheels up. For some reason, no matter how hard I push on the brake pedal, the front brakes don't engage at all, the rears are locked up and sliding and I'm in a real mess trying to stop. I'm hoping that relieving some of the pressure on the rear brakes will allow me to get all four wheels braking evenly. Any suggestions? John Quote Link to comment Share on other sites More sharing options...
linda s Posted March 7, 2013 Share Posted March 7, 2013 Look at the pictures here on post number 6. http://toyotamotorhome.org/forums/index.php?showtopic=4321 They will show you how to make the rear brakes back off a little. Are you sure your front brakes are engaging at all. If they are shot nothing is going to help but a front brake job. Do you know where your LSVP is set now. To lower rear brake pressure you don't want to wire it up. Just the opposite. you want to lower the bar like in the pics. Be careful and test it close to home Linda S Quote Link to comment Share on other sites More sharing options...
Maineah Posted March 7, 2013 Share Posted March 7, 2013 You may want to check your rear brakes sounds like you might have a leaking grease seal and wet linings. Getting the rears to lockup is hard to do unless some thing is wrong. Quote Link to comment Share on other sites More sharing options...
zero Posted March 7, 2013 Share Posted March 7, 2013 The problem I'm having has to do with too much braking. When I'm on snow or another slippery surface and step on the brake pedal, even very lightly, the back brakes immediately lock the rear wheels up. For some reason, no matter how hard I push on the brake pedal, the front brakes don't engage at all, the rears are locked up and sliding and I'm in a real mess trying to stop. I'm hoping that relieving some of the pressure on the rear brakes will allow me to get all four wheels braking evenly. Any suggestions? John In regard to the rear "locking" I agree with MaineAH. A little bit of grease/oil on the rear shoes can make them lock. The proportioning valve - when working correctly only lowers pressure to the rear for a moment and then they get full pressure anyway. It's a "delay" valve, not a "PSI lowering" valve. Seems you need to ascertain why the front is not working instead of worrying about the back. I assume your brake pedal height is OK and you've ruled out the master cylinder?? I ask because it's a unit with two separate hydraulic pumps - one for the front and one for the back. One half can go bad while the other still works. One rare thing that can happen is a bad rubber brake hose. I've only seen this happen twice in my life but - they can rupture internally and a piece of rubber shuts off the flow of brake fluid. It is easy to add a new proportioning valve under the hood next to the master cylinder. it's hooks in series to the brake line to the rear and has a thumb-wheel on it. You just dial it to the point where it works best for your. $20 for the last one I bought. Took 15 minutes to install. Quote Link to comment Share on other sites More sharing options...
Derek up North Posted March 7, 2013 Share Posted March 7, 2013 I'd agree with the others. I've never heard that a properly operating brake system has the rear locking up before the front. This is particularly dangerous (as you've found out) because when the rear locks 1st, there's a strong tendency for it to want to become the 'front'! I wouldn't do anything to try and reduce the braking done by the rear brakes because that might be the only braking you've got at the moment! I'd suggest you start by having the front brakes checked completely first, since they're the ones that are supposed to be doing the majority of the braking and they're also easiest to check. If you've never done so, by all means check the condition of the rear brakes too, and while you're in there clean, inspect and repack the rear wheel bearings. Quote Link to comment Share on other sites More sharing options...
zero Posted March 7, 2013 Share Posted March 7, 2013 I'd agree with the others. I've never heard that a properly operating brake system has the rear locking up before the front. All my GM SUVs and trucks from the 80s do the opposite. Front locks up easy when on ice, snow, or mud. GM uses a unitized proportioning valve that hooks to all four wheels. Works fine on dry roads but kind of a death trap on ice. The GM unitzied proportional valve has no "brain" to speak of. No mechanical load sensing valve. Once they started putting in ABS, they worked fine. My bigger trucks have ABS in the rear only. Quote Link to comment Share on other sites More sharing options...
DanAatTheCape Posted May 6, 2013 Share Posted May 6, 2013 suggest you read the pinned thread at the top of this forum... Quote Link to comment Share on other sites More sharing options...
Vanman Posted May 6, 2013 Share Posted May 6, 2013 Ours did that after parking for a while due to leakage of the rear wheel cyclinders, is ok after the brake job. Quote Link to comment Share on other sites More sharing options...
WME Posted May 6, 2013 Share Posted May 6, 2013 Thats the whole problem the Braking system is perfect for a 1/2 ton pickup. But its installed on a 3 ton motorhome. The mechanical device is easily confused and will do all the wrong things. WME I'd agree with the others. I've never heard that a properly operating brake system has the rear locking up before the front. Quote Link to comment Share on other sites More sharing options...
zero Posted May 7, 2013 Share Posted May 7, 2013 Thats the whole problem the Braking system is perfect for a 1/2 ton pickup. But its installed on a 3 ton motorhome. The mechanical device is easily confused and will do all the wrong things. WME That load sensing valve cannot get "confused" enough to make the rear brakes lock up on a heavily loaded truck like an RV. All it does when working is delay the high-pressure fluid charge for a moment to the rear and has no effect on the front. If this guy is locking up the rear, he likely has barely no front brakes working. I'd suspect that half his master-cylinder isn't working, or someother malady preventing the front caliper pistons from coming out. Quote Link to comment Share on other sites More sharing options...
WME Posted May 7, 2013 Share Posted May 7, 2013 The LSPV IS a pressure reducing device!! The factory book says at @ 700 psi on the front brakes there should be 500 psi on the rear, in harder stop with 1400 psi on the front there should be 800 psi on the rear. AND that adjusting the threaded shackle the psi on the rear will change about 8.5 psi per 1 turn of the adjuster. I agree with the posts that John has a mechanical problem. I adjusted my valve and all the way up and the breaking was much improved. On a dirt/gravel I could lock all 6 wheels, but never the rears alone Quote Link to comment Share on other sites More sharing options...
zero Posted May 7, 2013 Share Posted May 7, 2013 The LSPV IS a pressure reducing device!! Technically, it is a "momentary" pressure reducing device. It only delays the full pressure from reaching the wheel cylinders and does not reduce the pressure for the entire time when braking is taking place. In my opinion, it serves no useful purpose on a Toyota RV. They device is used for trucks that are sometimes empty and sometimes loaded. Quote Link to comment Share on other sites More sharing options...
WME Posted May 8, 2013 Share Posted May 8, 2013 The book pressure checks are done after 2 seconds Quote Link to comment Share on other sites More sharing options...
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