gryffinwings Posted February 18, 2014 Report Share Posted February 18, 2014 Hi, trying to diagnose my brake issue, here is what's happening. Brake power seems rather weak when I press down the pedal, when I press the pedal further, the wheels lock up. Things done: 1. Tires Replaced 2. Replaced Front Soft Brake Lines 3. Full Brake Flush including compressing front brake calipers. Anybody know what's up, I don't think I have air in my lines. Could this be the master cylinder or brake booster? Quote Link to comment
gryffinwings Posted February 18, 2014 Author Report Share Posted February 18, 2014 One more symptom, it seems that I can double pump the brakes and I get almost normal brake power. Quote Link to comment
Z-train Posted February 18, 2014 Report Share Posted February 18, 2014 Air in the line or failing MC.Don't forget to bleed the NLSV. Quote Link to comment
gryffinwings Posted February 18, 2014 Author Report Share Posted February 18, 2014 Air in the line or failing MC.Don't forget to bleed the NLSV. What and where is the NLSV exactly. I never heard of that or bled anything like that. Quote Link to comment
Z-train Posted February 18, 2014 Report Share Posted February 18, 2014 It's on the frame near the fuel tank.It's a load sensing valve that changes line pressure to the rear wheels depending on the load in the bed. Quote Link to comment
wayno Posted February 18, 2014 Report Share Posted February 18, 2014 I have a question, did you bleed the front or back brakes first? Quote Link to comment
gryffinwings Posted February 19, 2014 Author Report Share Posted February 19, 2014 I bled the back brakes first. Quote Link to comment
datzenmike Posted February 19, 2014 Report Share Posted February 19, 2014 This can also be poorly adjusted rear drums. The further the shoes have to travel to touch the drum surface the farther and softer the pedal. Quote Link to comment
gryffinwings Posted February 19, 2014 Author Report Share Posted February 19, 2014 This can also be poorly adjusted rear drums. The further the shoes have to travel to touch the drum surface the farther and softer the pedal. What about the double pump of the brake pedal that helps a bit on the brake power. Also can you point me to instructions on adjusting the rear drums. Quote Link to comment
datzenmike Posted February 19, 2014 Report Share Posted February 19, 2014 Yes a quick second pump gets to the rear cylinders before the shoes fully retract to their rest position. There is less distance to travel the second pump and it seems normal. Hmmm I see this is an '84. From half way through '81 the 720 has self adjusters on the rear. I suppose it's possible one or both have seized from dirt and water and they can't adjust??? Might be an idea to check. Quote Link to comment
gryffinwings Posted February 19, 2014 Author Report Share Posted February 19, 2014 Yes a quick second pump gets to the rear cylinders before the shoes fully retract to their rest position. There is less distance to travel the second pump and it seems normal. Hmmm I see this is an '84. From half way through '81 the 720 has self adjusters on the rear. I suppose it's possible one or both have seized from dirt and water and they can't adjust??? Might be an idea to check. Self Adjusters.... I'll look into it, it does sound like that, if they are messed up, how would I go about fixing this? All I'm seeing are Drum Brake Hardware Kits. Quote Link to comment
datzenmike Posted February 19, 2014 Report Share Posted February 19, 2014 Hardware kits are mainly return and anti rattle springs. The self adjusters are a lever and ratchet assy tied to the movement of the shoes. When the shoe movement exceeds a certain amount the ratchet turns the adjuster out one notch. They don't seize but the adjuster itself can. Quote Link to comment
gryffinwings Posted February 19, 2014 Author Report Share Posted February 19, 2014 Hardware kits are mainly return and anti rattle springs. The self adjusters are a lever and ratchet assy tied to the movement of the shoes. When the shoe movement exceeds a certain amount the ratchet turns the adjuster out one notch. They don't seize but the adjuster itself can. So is there anyway to fix the adjuster itself? If not where can I get the part? Quote Link to comment
datzenmike Posted February 19, 2014 Report Share Posted February 19, 2014 Sometimes just turn it to break it loose. It's basically a threaded rod with a start wheel that can be levered with a bladed screw driver through a slot in the backing plate. The threads get rusty. Sometimes a little heat and WD-40 to loosen then lube with lithium grease and good as new. The adjuster spreads the shoes apart to take up the slack from wear. Quote Link to comment
Z-train Posted February 19, 2014 Report Share Posted February 19, 2014 It's worth the hassle now to yank the adjusters and clean then and assemble with anti-seize. 1 Quote Link to comment
gryffinwings Posted February 20, 2014 Author Report Share Posted February 20, 2014 Would someone be able to point this out in a picture, so I know exactly what to take off. Quote Link to comment
datzenmike Posted February 20, 2014 Report Share Posted February 20, 2014 This looks pretty close to a Nissan automatic brake adjuster. The start wheel is threaded and moves outward to spread the brake shoes to adjust for lining wear. The metal plate above it is worked by brake action and levers the star wheel out. When the shoe travels too far, the lever catches one of the teeth on the star wheel and ratchets it out. Quote Link to comment
gryffinwings Posted February 20, 2014 Author Report Share Posted February 20, 2014 This looks pretty close to a Nissan automatic brake adjuster. The start wheel is threaded and moves outward to spread the brake shoes to adjust for lining wear. The metal plate above it is worked by brake action and levers the star wheel out. When the shoe travels too far, the lever catches one of the teeth on the star wheel and ratchets it out. Is it the part in between the two shoes at the bottom in this picture: Also I'm looking at getting brake shoes, what size to I need, rockauto list two different sizes on their site. Quote Link to comment
datzenmike Posted February 20, 2014 Report Share Posted February 20, 2014 That's it. Too much shoe movement at the top pulls on the cable and the adjuster will ratchet the start wheel ahead. This will limit movement and the adjuster will stop adjusting. #44060-10W25 or #44060-20W25 used after 10/'82 with Z24 motor. Not sure what the difference is... perhaps a heavier duty shoe? Quote Link to comment
gryffinwings Posted February 20, 2014 Author Report Share Posted February 20, 2014 That's it. Too much shoe movement at the top pulls on the cable and the adjuster will ratchet the start wheel ahead. This will limit movement and the adjuster will stop adjusting. #44060-10W25 or #44060-20W25 used after 10/'82 with Z24 motor. Not sure what the difference is... perhaps a heavier duty shoe? The two sizes I'm finding are these: 10" X 1 3/4" 8 21/32" X 2 23/32" That's what I found on rockauto.com Quote Link to comment
datzenmike Posted February 20, 2014 Report Share Posted February 20, 2014 Pretty sure they are 10" on all 2wd and 4x4 trucks. The 8" are for the dual tire Cab/Chassis option Quote Link to comment
gryffinwings Posted February 26, 2014 Author Report Share Posted February 26, 2014 Ok, well I was checking my truck again, I like to make sure if there are any problems with leaks, and it appears I have a leaky master cylinder I saw that the fluid levels were low, so I think I'm going to need a new one. Quote Link to comment
ggzilla Posted February 26, 2014 Report Share Posted February 26, 2014 So 10" or 8". If you had the wrong ones they wouldn't pump up. Have you manually adjusted the rear brakes? The self adjusters won't work until you do Where do you see the leak? Quote Link to comment
gryffinwings Posted February 26, 2014 Author Report Share Posted February 26, 2014 So 10" or 8". If you had the wrong ones they wouldn't pump up. Have you manually adjusted the rear brakes? The self adjusters won't work until you do Where do you see the leak? No, I haven't messed with the drums yet, haven't had the time yet. It looks like it's going right below the master cylinder and the brake booster, and there is a trail of grim on the lower portion of the booster, so I am assuming that rear of the master cylinder is leaking. Quote Link to comment
gryffinwings Posted February 28, 2014 Author Report Share Posted February 28, 2014 I got a master cylinder and new wheel cylinders on order, I figured I might as well replace those just in case they have a leak. Quote Link to comment
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