Author Topic: No rear brakes? (Read 3418 times)

punkrawler · « **on:** Mar 12, 2008, 03:07:54 PM »

After rebuilding my rear axle I went to bleed my brake system, only to find that the read drum brakes were not having it. No fluid flows out when the bleeder valve is open and the brake pedal is depressed. Both sides of the rear are having this same issue. I checked the fronts and the LSPV to see if they were the same. They seemed to have no problems. Fronts have fresh fluid flowing as well as the LSPV in the rear. Am I missing something? Or is there a bigger problem that I am missing? The brakes worked fine before the axle tear down so I'm guessing that it was something that I did.
Any one ever have this problem? Does anybody have any suggestions?
Oh by the way, the truck is an 1986 pickup with a straight front axle.

emsvitil · « **Reply #1 on:** Mar 12, 2008, 03:28:53 PM »

The LSPV has connections to the rear system and the front system.

It meters flow to the rear based on the position of the rod and the pressure in the front.

The bleed valve bleeds the fluid that runs from the front system.

So I'm thinkin it's the LSPV. Disconnect the rod, and move it up like it would get if you had a really big load in the rear and see what happens.

twistedtoy92 · « **Reply #2 on:** Mar 12, 2008, 03:30:51 PM »

mine is disconnected

RN37DD · « **Reply #3 on:** Mar 12, 2008, 04:02:52 PM »

i got rid of mine for now. when i got the truck i changed the rear shoes only to find the old ones had zero wear. blamed it on bad adjusters. then i modified the front brakes and discovered. yeah i had e brakes but no normal rear brake action. checked the lsv and it rusted beyond repair. the rear brakes have not been right for so long.. I've got them working now' but my next step is a 90's axle and new style brakes.

punkrawler · « **Reply #4 on:** Mar 12, 2008, 05:49:52 PM »

Ok, so the load rod has been cut off to a short stub and it is zip tied in the up position. I'm guessing that moving it around won't do too much. I Don't really know know. Could the LSPV be seized up in the front biased position? Time for a new LSPV?

OOPS · « **Reply #5 on:** Mar 12, 2008, 07:34:43 PM »

Take it off and take it apart and see what you find.

punkrawler · « **Reply #6 on:** Mar 13, 2008, 03:56:30 AM »

SO I pulled the LSPV off thinking that I might rebuild it and be up an running. After taking it apart I realized that there was a bunch of rusty nastiness in the LSPV its self. I cleaned the unit thoroughly and re installed it hoping that I had it all figured it out. I was completely wrong apparently. Still no luck with the rear brakes. Maybe the LSPV was too gunked up to be rebuilt. I am stumped. Anyone have any ideas?

DTB · « **Reply #7 on:** Mar 13, 2008, 05:21:48 AM »

I would recommend removing it completely and replacing with a prop valve like front range sells. Cleans up your brakes in the rear end nicely and takes about 30 minutes to install. I might have some used LPSVs laying around if you are interested

RTA · « **Reply #8 on:** Mar 13, 2008, 06:09:47 AM »

Remove and bypass or remove and install proportioning valve.
http://store.summitracing.com/partdetail.asp?autofilter=1&part=SUM%2DG3905&N=700+4294922533+4294918719+115&autoview=sku

FIREBALL · « **Reply #9 on:** Mar 13, 2008, 11:10:04 AM »

If there was that much gunk in the lspv maybe some of it was pushed into the rear brake line too. You might try back flushing the rear lines to make sure they're clean.

punkrawler · « **Reply #10 on:** Mar 13, 2008, 05:13:05 PM »

Ok, I backflowed the lines. No issues there. So I went ahead and ordered the Front range proportioning valve. That should do it....Hopefully. And I will be rid of that LSPV forever.

RN37DD · « **Reply #11 on:** Mar 14, 2008, 04:36:47 PM »

yeah sounds good. let us know how it work. i might go that route too, if my spare valve doesn't work. have you tried adjusting your rear shoes. i know the auto adjusters on my rig don't work.

Knute · « **Reply #12 on:** Mar 22, 2008, 07:59:44 AM »

ya take them apart and clean them to it they get to dirty they wont work either just fix all your possible problems so you don't come along it again later down the trail..

punkrawler · « **Reply #13 on:** Mar 22, 2008, 05:00:42 PM »

Alright well.......I got my Proportioning valve kit from Frontrange yesterday and put the kit in today. First, let me say that the kit was a breeze to install. Super easy. The kit came with all the necessary hardware and fittings to make it a "plug and play" affair. I had the valve in and all the lines re-routed in a little less than 30 minutes. Sweet! So then after cleaning up my DOT mess in the engine bay I want to bleed the brakes as I have done so many times before. To my surprise I still could not get any fluid flowing to the rear brakes. I checked my work on the install and all is as it should be. Now I am thinking that I must have something wrong with the actual brake assemblies themselves. I guess I will have to take them apart and check them out. I find this a little weird since I didn't touch them in the first place. If they check out then I guess maybe my master cylinder?

But since I was able to bleed the LSPV before and not the rear brakes that wouldn't make much sense. Well back to the drawing board...and back to work.

Steve_925 · « **Reply #14 on:** Mar 22, 2008, 09:40:57 PM »

i had the same problem after i bought my truck the first thing i did was put my detroit and gears in and after diconnecting the rear brake lines i had never had rear brakes for like 6 months. tried 3 different LSPVs (used) none worked. so finally i just plugged the rear brake port on my master and ran all 4 of my brakes off the front brake port. its been working perfect ever since. only problem is if any brake line goes out there all out

emsvitil · « **Reply #15 on:** Mar 23, 2008, 12:32:47 AM »

The bleeder on the LSPV bleeds the front system, not the rears.................

DTB · « **Reply #16 on:** Mar 23, 2008, 05:23:24 AM »

possibly a plugged port to the rear on the master itself?

punkrawler · « **Reply #17 on:** Mar 23, 2008, 01:42:12 PM »

Yeah, a muffed up master cylinder is becoming more and more possible. I took apart the rear brake assemblies and aside from really needing new shoes they seem to be working fine.

Steve_925....It seems that we have pretty much the exact same thing going on. When I got my truck the rear was already locked with a Detroit. Unfortunately, the previous owner didn't really do a very good job building the 3rd member up. He forgot to stake the 30mm pinion bolt....and that is what brings me up to this point. Drive shaft companion flange popped off and then the pinion backed into the locker. Luckily I was able to save the locker and swap it to the front. Presto! Front and rear Detroits.

Now If I can just get my brakes working I can get the last of the snow wheeling in my area!

Steve_925 · « **Reply #18 on:** Mar 23, 2008, 02:18:35 PM »

i think i may just get the fj80 master run the rear port strait to the rear brakes and front to front. possible no proportioning valve at all. with the crapy drum i dont think i would get to much presure to the rear to make them lock up before the front

punkrawler · « **Reply #19 on:** Apr 08, 2008, 09:07:26 PM »

Ok, well here is the latest update.....I went ahead and replaced the master cylinder since I have been meaning to upgrade to an fj80 unit anyway.

I figured this is a good enough excuse for me to buy some sweet parts! At the same time I also replaced the wheel cylinders, drums and shoes just for good measure. No sense in leaving questionable parts on so they can break on the trail right? Obviously the brakes should work now right? Well damn straight. If they didn't work after all that love it would have been very bad.....

So with the proportioning valve and the new fj80 master cylinder this thing now stops well enough to detach retinas if you stomp on the pedal too hard. Even with 37"s'! The pedal feel is way better than it ever was, there seems to be less fade and I can run rear discs if I desire. So the bottom line is this: If you want better brakes, you can't go wrong with the fj80 cylinder.....obviously. Also, the Front Range prop. valve is sweet. It comes with all the fittings you need so there is no guesswork or running around to find more fittings. This does add a bit to the price, but if you want that LSPV gone fast, you can't beat plug and play. Did I mention how easy the install was? Really easy. If you are looking into getting either one of these items......do it. Your rig will love you long time.

KDXSR5 · « **Reply #20 on:** Apr 08, 2008, 09:11:07 PM »

Thats awesome! I am having brake issues as well, maybe a 1 inch bore master will help mine out as well.

wflaw45 · « **Reply #21 on:** Apr 09, 2008, 04:37:26 PM »

does the frontrange prop valve bolt up in place of the factory one?

OOPS · « **Reply #22 on:** Apr 09, 2008, 07:12:45 PM »

Quote from: wflaw45 on Apr 09, 2008, 04:37:26 PM

does the frontrange prop valve bolt up in place of the factory one?

Yes, but I would put it under the hood myself.

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