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Old 02-27-2011, 10:16 AM
Air Randy's Avatar
Air Randy Air Randy is offline
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Originally Posted by satchel View Post
After taking the truck up to steamboat and sliding all over the place because the rear tires are not locking up and just keep pushing the truck, I thought I would start looking into this again. I actually took it to a local midas place just to see what they thought and they didn't have any input as to what the problem could be.

I have yet to change out the lspv, but have changed virtually everything else previously including the master cylinder. I did take the arm from the lspv and move it all the way up and all the way down with the truck in drive and my foot on the brake pedal and the rear tires still just keep on spinning. Any thoughts as to what this could be other than the lspv? The guys at midas just said that the rear drums weren't strong enough to stop with the v8 I've got in it, but I seriously doubt that. It's not like I'm accelerating during these tests, just letting it idle and the rear drums will not lock up at all. I guess I'll order that setup from Dave's on the previous page. Seen here: http://www.davezoffroadperformance.c...c.php?f=3&t=52

One question about that setup. What do you do with the bypass line? I have a supply line in, bypass out, and line out to the rear brakes from my valve, but this only has 1 in and 1 out.
If you really want to try and diagnose it, rig up a rubber brake line with the proper fittings that will allow you to bypass the LSPV. Bleed the rear brakes and see if that makes them work right. If so, you can get another lspv from Yotajim or a new one if they're still available. Or, get the Dave's unit ,install it and the problem is solved. Of course, you won't have all of the magical properties of the lspv, 300K brake life, anti-gravity, etc.

If the bypass doesn't work, and I'm assuming your new master cylinder is good, then it almost has to be a blocked brake line. Check all of your hard lines from the MC back to the lspv to make sure none of them are crushed or bent so far as to restrict fluid flow.
Randy Rosetta KDKWX TLCA #19351 NOW 2015 Rubicon Hard Rock & (2) 1970 Boss 302 Mustang's THEN 69 FJ40 Buggy "Meanie", Mini-truck "Gecko" & 74 FJ40 "Blue Mule"
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Old 02-27-2011, 12:59 PM
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rover67 rover67 is offline
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Have you tried swapping out the master cylinder? Maybe the piston is not sealing right in there.

I feel like if it was a blocked line the pressure would come up eventually when you press on the pedal really hard. It seems like the fluid flow would just be really slow. That doesn't seem to be the case with your truck. It seems like there is just low pressure. The volume is actually fine, the pistons in the rear drums were moving nice and fast and were both kicking out way more than they needed to.
Marco Capote
85 FJ60
82 FJ40
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Old 02-27-2011, 02:00 PM
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satchel satchel is offline
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Location: Denver, Co
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Randy, good ideas. I might just go in that direction to help troubleshoot it. Not sure how I would tie into the bypass line though, maybe using a tee I guess.

Marco, I did change the master cylinder already but I can't guarantee that the problem was happening before I did it. The new one may be bad I guess.
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