Chasing mushy brakes caused by LSPV? (2 Viewers)

[jpoole]

Not sure it's helped but I bleed the individual lines on the ABS unit as my final step in the bleed process as it allows me to easily run the fluid that remains in the pressure bleeder out and get the MC reservoir to level if nothing else. Rinse before/after with copious water to keep the fluid off the paint.

New MC, Lines, Calipers, Rotors, Pads, Booster and tight bearings/etc. and my brakes were ok. Pedal feel was good but stopping power not quite what I wanted. Changed pads back to OE formulation and stopping power went up pretty dramatically. I don't recall what the pads were before but it was nice to finally have the stopping power I wanted after all of the work to get the pedal feel was done.

Not my image, etc. but there are threads on mud about abs activation while the vehicle is stationary.

 

[BILT4ME]

OK, that's very good to know. The LSPV isn't leaking on mine, so I will work from the position that it's either good or likely not the issue now. I'll replace the MC as I've got one coming and I don't know the age of the one on this truck.


So the subject of the ABS keeps coming up as I'm researching. In one post I found that a guy even had the unit rebuilt and it still sucked so he bypassed it entirely and the brakes were better than new. In another someone said their insurance WENT DOWN because the insurance co. looks at the very old ABS systems as a hindrance, which I found to be an interesting comment, to say the least. So I'm starting to think it is the ABS, or very likely, that is the issue here.

As for the test module you mention, do you have details on how to build one of these? Are there plans out on the 'net somewhere? I'd be game to build one.

Also, you need to raise the actuator arm on the LSPV all the way up during the bleeding in order to open the valving to the rear. This will assist in flow and may help remove trapped air bubbles.

 

[Camino]

I just had my pedal go to the floor and I rammed a building on my property. I bench bled a new master and replaced it. When I started bleeding, the fluid looked like mud. I had to bleed 3 large bottles thru the system to get the fluid to look fairly clear. Now the brakes work, but I still have to tackle the e brakes.

 

[SHIfTHEAD]

I just had my pedal go to the floor and I rammed a building on my property. I bench bled a new master and replaced it. When I started bleeding, the fluid looked like mud. I had to bleed 3 large bottles thru the system to get the fluid to look fairly clear. Now the brakes work, but I still have to tackle the e brakes.

I just got to work on this truck that I got from a friend about 6 months ago. One of the jobs was the e-brake, but I knew what I was in for from working on them on my 60 series. Two main things you will need; a Propane torch and a bunch of Patience. The e-brake levers (bell cranks?) are likely going to be seized in several places. First the pin to the cable, then the pin to the crank itself. But the easiest way I found to work that all out was to remove the aluminum housing/bracket from the axle and use a vise, flame wrench, vise grips, hammer, PB Blaster, cussing, etc. It will eventually break free and then you can use PB Blaster to start working it back and forth washing away the oxide residue. Once I got one totally torn apart I went at it with the wire wheel on my grinder and then hit the bell crank with some rattle can. Once assembled I coated everything with moly grease and especially inside the rubber boot. No idea if this part is available, but it took me a solid 8 hrs to restore two of them.

 

[BILT4ME]

I just got to work on this truck that I got from a friend about 6 months ago. One of the jobs was the e-brake, but I knew what I was in for from working on them on my 60 series. Two main things you will need; a Propane torch and a bunch of Patience. The e-brake levers (bell cranks?) are likely going to be seized in several places. First the pin to the cable, then the pin to the crank itself. But the easiest way I found to work that all out was to remove the aluminum housing/bracket from the axle and use a vise, flame wrench, vise grips, hammer, PB Blaster, cussing, etc. It will eventually break free and then you can use PB Blaster to start working it back and forth washing away the oxide residue. Once I got one totally torn apart I went at it with the wire wheel on my grinder and then hit the bell crank with some rattle can. Once assembled I coated everything with moly grease and especially inside the rubber boot. No idea if this part is available, but it took me a solid 8 hrs to restore two of them.

I concur. Did the same thing on my 80.

Filled the boot with white lithium grease after I was done to keep out moisture and make sure that never happens again. I also use it regularly.

 

[SHIfTHEAD]

So a little follow-up on this issue, before the trip this past weekend I had the mushy brakes that have been bugging me. I'd replaced the pads, rotors and rebuilt the front calipers, and really felt no change in the feedback from the pedal. The truck stops, but it's very vague as to how much pressure you are actually applying if that makes sense.

This past weekend my buddy and I had a camping trip planned to WV, we live just south of Charlotte NC, so a bit of highway driving. I wasn't crazy about the idea of high-speed driving with the brakes mushy like this but it was stopping, and if I applied a lot of pressure it would stop rapidly, so I went. I noticed a little improvement from just driving which I accounted for as the pads seating into the new rotors. We camped that night in a road well off the beaten path, he in his 3rd gen 4runner and me in the 80. The next morning we did some exploring in the FS roads and found a little bit of fun, but nothing too crazy. That night we went up to Canaan Valley and camped way up on Canaan Loop Road, which has a section designated as "Not Suitable for Passenger Vehicles" when it should probably say "Only suitable for billy goats" . So we got to do some pretty decent off-roading back in there, nothing really crazy, but it was my buddy's first foray into some actual off-road conditions in his truck. A few rock steps, lots of off-camber stuff with small boulders, and a few smaller water crossing, one was maybe 2-3 feet deep after the rain, so he 'got his feet wet' as it were.

The point to this whole story is that because I was doing all of this I heard the ABS activating numerous times throughout the trip, I'd guess probably more than 2 dozen times because of the slippery conditions (there was lots of ice back in there, we woke up to 18 degrees Saturday morning). And now the brakes, while not "stiff" like the 100 series are absolutely adequate. So I have to assume the workout the ABS got on the trip got some trapped out of the system. So maybe using the method from the image above would help others who are having this issue, assuming it's air in the ABS...

 

[-Spike-]

...I heard the ABS activating numerous times throughout the trip, I'd guess probably more than 2 dozen times because of the slippery conditions (there was lots of ice back in there, we woke up to 18 degrees Saturday morning). And now the brakes, while not "stiff" like the 100 series are absolutely adequate. So I have to assume the workout the ABS got on the trip got some trapped out of the system. So maybe using the method from the image above would help others who are having this issue, assuming it's air in the ABS...

Good info, thanks for the update.

 

[BILT4ME]

So a little follow-up on this issue, before the trip this past weekend I had the mushy brakes that have been bugging me. I'd replaced the pads, rotors and rebuilt the front calipers, and really felt no change in the feedback from the pedal. The truck stops, but it's very vague as to how much pressure you are actually applying if that makes sense.

This past weekend my buddy and I had a camping trip planned to WV, we live just south of Charlotte NC, so a bit of highway driving. I wasn't crazy about the idea of high-speed driving with the brakes mushy like this but it was stopping, and if I applied a lot of pressure it would stop rapidly, so I went. I noticed a little improvement from just driving which I accounted for as the pads seating into the new rotors. We camped that night in a road well off the beaten path, he in his 3rd gen 4runner and me in the 80. The next morning we did some exploring in the FS roads and found a little bit of fun, but nothing too crazy. That night we went up to Canaan Valley and camped way up on Canaan Loop Road, which has a section designated as "Not Suitable for Passenger Vehicles" when it should probably say "Only suitable for billy goats" . So we got to do some pretty decent off-roading back in there, nothing really crazy, but it was my buddy's first foray into some actual off-road conditions in his truck. A few rock steps, lots of off-camber stuff with small boulders, and a few smaller water crossing, one was maybe 2-3 feet deep after the rain, so he 'got his feet wet' as it were.

The point to this whole story is that because I was doing all of this I heard the ABS activating numerous times throughout the trip, I'd guess probably more than 2 dozen times because of the slippery conditions (there was lots of ice back in there, we woke up to 18 degrees Saturday morning). And now the brakes, while not "stiff" like the 100 series are absolutely adequate. So I have to assume the workout the ABS got on the trip got some trapped out of the system. So maybe using the method from the image above would help others who are having this issue, assuming it's air in the ABS...

If you are wheeling in low range, this typically locks the CDL and locks out the ABS. It shouldn't be activating the ABS if you're crawling.

 

[SHIfTHEAD]

If you are wheeling in low range, this typically locks the CDL and locks out the ABS. It shouldn't be activating the ABS if you're crawling.

A good bit was in low range, but lots of the not-so-crazy stuff wasn't. The ABS makes a strange whirring sound when it activates, so it's pretty easy to spot. In fact, one of the noises that's been bugging me for a bit, that being that every time I drive off I would hear this odd noise initially and have finally figured out that the ABS activates every time I initially set off. Not sure if this is normal or not.

 

[ColoradoLC]

I just wanted to add a couple of personal experiences to this thread in case anyone else has this issue. I've had it twice, both with different causes.

First issue was after bleeding my brakes when I added extended brake lines do to lifting my 80 with the ICON/Slinky lift, which ended up being right at about 4". I bled the system twice, in the proper order, and still had some much, then I read a thread saying it helps bleed the ABS system if you drive and get that system to activate, which apparently rattles the air out of the lines further. I can attest that this did indeed help, and after I bled them again, I once again had solid brakes. Very solid, in fact.

The second time I had brake issues was a more odd situation. I had just finished rebuilding my knuckles and over about a month, I would get occasional pedal to the floor action on the brake pedal. This was very strange to me since it would work great, and then sometimes it would push almost to the floor. Very disconcerting. I proceeded to take the right front wheel off and noticed a lot of play in the wheel. I quickly traced this back to the outer 54mm nut, which had spun itself loose. I followed the directions for my knuckle rebuilt and torqued it to 45 lb-ft, as directed. The lock washer had apparently bent, so I reseated the rotor assembly, replaced all of the 54 mm nuts (I did the other side as well), put new lock washers on and tightened the outer 54mm nut a tighter than the previous time. No difference in play in spinning the wheel this time. As near as I can figure, when this came loose, the play in the axle caused the brake to behave the way I described above. Drives perfect now and a lesson about double nutting. Tighten the outer one a little more than spec. The key is to make sure the wheel spins and is in the range on the torque spring.

Best of luck in your diagnosis.

Winston