New-to-240z Posted March 5, 2015 Share Posted March 5, 2015 So, I grabed some rebuilt 4x4 calipers SW12 I believe (now I can't remember, go figure). But, I'm getting a lot more clamping force from one side then the other, and the heat generated after a few really hard stops is different on each side (one by a large degree hotter). So, I thought I had a bad caliper that had stuck in its position. I took off the calipers today and pressed down on the brake pedal to see if any specific piston was not pushing out. Here's what I found . . . I thought that both sides' pistons would be pressing out of their cylinder on a fixed caliper? Am I mistaken? You can see that the side that get the fluid first is actually pressing out completely, where as the other side isn't pressing out at all?!?! Is this normal operation? I will be taking measurements of the brake pads soon to see which pistons are pulling back, or aren't pushing out (causing uneven wear). But this totally threw my off?! I did get these from AutoZone, and am guessing that might have something to do with it. But, both calipers? Quote Link to comment Share on other sites More sharing options...
Xnke Posted March 5, 2015 Share Posted March 5, 2015 They're probably fine. Just less work for the fluid to exert the force on one set of pistons that go through the caliper passage to exert force on both sets, given that there is no rotor between them to generate the minute force differential needed to force fluid through said passage. Replace your rubber lines and check for line blockages, would be my bet. Just went through this kind of thing on a 1983 ZX, the rubber lines were internally collapsed on the front brakes, could barely push fluid through them. Quote Link to comment Share on other sites More sharing options...
New-to-240z Posted March 5, 2015 Author Share Posted March 5, 2015 Replaced lines with SS Earls. I also have bled the brakes about 3 times thinking air or something else. Should I make something to hold the one side of pistons in place while I press the brakes again to see if the other side's pistons move? Quote Link to comment Share on other sites More sharing options...
jasper Posted March 5, 2015 Share Posted March 5, 2015 (edited) The brown coloration on one set of pads is characteristic of OVERHEATING. As a Toyota tech, I replace A LOT of 4 Runner front calipers for stuck/sticking inboard pistons. Always inboard pistons.........don't know why. Roughly 2000 and up vintage. If the pistons go back in easily, I would look for the L/R bias problem. Also check for problems in the Rear, leading to over loading the front brakes. Edited March 5, 2015 by jasper Quote Link to comment Share on other sites More sharing options...
New-to-240z Posted March 5, 2015 Author Share Posted March 5, 2015 These are the solid rotor S12 4x4 pickups. i believe 79 - 85 year. (Gotta look over my notes again to find out for sure.) I haven't tried pushing the pistons back in yet. Are they the push back in or turn back in kind? What do you mean by the left/right bias problem? If the fluid isn't being held up in the lines, and the pistons aren't sticking, then what would be the cause of that? Quote Link to comment Share on other sites More sharing options...
jasper Posted March 5, 2015 Share Posted March 5, 2015 (edited) Push in. Pressure difference left to right. Kinked hard line/ bad flex line/restricted line/ restricted union, contaminant, etc....... Edited March 5, 2015 by jasper Quote Link to comment Share on other sites More sharing options...
Miles Posted March 5, 2015 Share Posted March 5, 2015 (edited) I have had problems with "rebuilt" calipers new right out of the box. Especially with the Cardone and the cheap Napa house brand calipers. Problems with new out of the box calipers include: Piston would not retract into the bore. Piston seals leaked. Caliper filled with rust and debris that showed up while bleeding. Removing the bleed screw I was able to shake out rust flakes/powder. It happens. If after you have ruled out all other causes take the calipers back and buy Nugeon brand rebuilt calipers at Napa. Other stores may carry Nugeon as well. Unlike the Cardone and other cheap brands, Nugeon calipers are rebuilt in the USA (Stockton, Ca). Edited March 5, 2015 by Miles Quote Link to comment Share on other sites More sharing options...
New-to-240z Posted March 5, 2015 Author Share Posted March 5, 2015 (edited) It would seem that the amount of time required to troubleshoot bad calipers would negate the cost savings. I'll just buy some new Nugeon rebuilt calipers and test them out first before sending back the cores. Does anyone have any ideas or tests I can put the replacements through in order to verify they are working correctly before painting them and putting them on the car again? That way I can be sure that I don't run into this problem again blindly. **Update** Decided to just bite the bullet and pull everything apart and clean it out. If the pistons have any problems then I'll buy new sets, but the rebuild kits came out to only 14 total. So, will clean out cylinders and passages, and reflush everything. Side Note: Can I gravity bleed the lines to get out any particles? Or do I need to push bleed them? I'll be doing this with the calipers off to make sure that any particles don't get pushed into the calipers themselves. So, the fluid will just be coming out of the actual lines. Edited March 5, 2015 by New-to-240z Quote Link to comment Share on other sites More sharing options...
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