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Car Forum / Driving, Maintenance, Tuning / Maintenance and Repair / September 200690 Chev 1/2 ton brake question
90 K1500 4x4 10" rear brakes. (the leading/trailing style with the adjuster at the top) replaced the rear axle seals yesterday (leaking bad bad bad) and the rear shoes. Brakes were working before - just crappily because of all the grease on them. Now... the brake light is on, and the pedal pretty much goes to the floor - not quite as soft as if there was air in there, but pretty darn soft. It would appear BOTH rear wheel cylinders are seeping. The only thing I did as far as the hydraulics was to push the pistons back into the cylinders so we could get the new shoes on. Is it possible that there was a bit of corrosion in there that caused my leak? And/or is it likely I did something wrong with the self adjusters and the leak is actually just seepage from doing that and it's not really a leak? I tried bleeding the rear brakes and they seem fine. The truck has rear wheel abs. I'm going to replace the wheel cylinders because I'm assuming they're fubared, but I'm wondering if there's some other trick/something I did wrong. Also, the park brake cable is currently not connected - the whole thing was rusted solid so we pulled it all out and I'll be getting new cables. The park brake switch was disconnected. Ray Normally there is a right and left adjuster. If you got these mixed up, the brakes might actually be adjusted the wrong way which would give you an extremely low pedal and could cause the cylinders to leak from being over extended. The cylinder pistons can actually fall out causing total failure too. This could just happen if you didn't manually adjust up the shoes when installing also. If they are out of adjustment all the way, the self adjuster won't usually grab them. They need to be manually set up close or better, exact first. Mike 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's Canadian Off Road Trips Photos: Non members can still view! Jan/06 http://www.imagestation.com/album/pictures.html?id=2115147590 (More Off Road album links at bottom of the view page) > 90 K1500 4x4 10" rear brakes. > (the leading/trailing style with the adjuster at the top) [quoted text clipped - 28 lines] > > Ray > Normally there is a right and left adjuster. If you got these mixed up, > the brakes might actually be adjusted the wrong way which would give you [quoted text clipped - 8 lines] > > Mike thanks Mike. we did one side at a time, so unless they were done wrong before... I can't have mixed up the parts. I didn't adjust them at all, I usually just do the backup/stop thing. The wheel cylinders are only like $20 so I'm going to change them as a preemptive thing (wife is picking them up today while I'm at work), and I'll be sure to adjust the brakes as per the shop manual. Ray >> Normally there is a right and left adjuster. If you got these mixed up, >> the brakes might actually be adjusted the wrong way which would give you [quoted text clipped - 21 lines] > > Ray Your gonna have to adjust the rear shoes before they will "self adjust". The self adjustment mechanism is meant to compensate for the wear of the shoes and the adjustment needs to be set after replacing the shoes. Spin the "star wheel" with a adjusting tool or a flat screwdriver until you feel a slight drag when spinning the wheel. The low pedal is probably caused by the rear shoes being so far out of adjustment. >>> Normally there is a right and left adjuster. If you got these mixed up, >>> the brakes might actually be adjusted the wrong way which would give you [quoted text clipped - 29 lines] > you feel a slight drag when spinning the wheel. The low pedal is > probably caused by the rear shoes being so far out of adjustment. thanks. I usually do the adjustment, but these were such a PITA to install and it was 11:30pm when I went for the test drive... I'll try adjusting them properly first. Ray On your truck, you are right in that when you pushed the pistons in- you probly rode over some junk. but also pushing the wheel cylinders in may have caused some air to be sucked into the cylinder. If you haven't installed the new ones yet, try bleeding each one till you get a good steady drip. And as the other guy stated, adjust your brakes up with the adjuster, backing up will never bring them up to where they should be. Extend the adjusted a few clicks and try to slide the drum on, if its still loose-adjust alittle more. once they are adjusted properly you will hear the shoes just rubbing against the drum-but will be able to turn the drum freely. If after all of this, the pedal is still low and the brake light/abs light is still on, you may have a baddump valve. the chey trucks are famous for this valve going out for the slightest reason. I've replaced many over the years, I'm a brake and front end mechanic.  Signaturessggbroot http://www.automotiveforums.com > On your truck, you are right in that when you pushed the pistons in- you > probly rode over some junk. but also pushing the wheel cylinders in may [quoted text clipped - 11 lines] > famous for this valve going out for the slightest reason. I've replaced > many over the years, I'm a brake and front end mechanic. readjusted the brakes, felt better, but still one wheel cylinder was leaking a bit, so replaced them. then had to replace the lines because they're all rusted and busted... I'm still not done - now I need the flex line because one of the hard lines snapped off flush while removing it. $10 in oil seals becomes $300 in brakes. (shoes, park brake cables, wheel cylinders, brake lines, what feels like 10 gallons of brakleen...) Whee. > On your truck, you are right in that when you pushed the pistons in- you > probly rode over some junk. but also pushing the wheel cylinders in may [quoted text clipped - 11 lines] > famous for this valve going out for the slightest reason. I've replaced > many over the years, I'm a brake and front end mechanic. ok, I replaced both wheel cylinders, both hard lines, and the flex line to the frame. bled them and bled them and still have a soft pedal that pumps up. The master cylinder went dry when I ran out of parts and it sat overnight, so we cracked the lines and bled it too. Didn't bleed the dump valve - according to the manual it should have a bleeder, but it doesn't. Do I need to have this thing pressure bled or something? There are no more leaks, and the truck was stopping fine (well at least as good as it could with grease soaked brake shoes.) Ray > > On your truck, you are right in that when you pushed the pistons in- you > > probly rode over some junk. but also pushing the wheel cylinders in may [quoted text clipped - 23 lines] > > Ray Did you manually adjust the rear brakes? You cannot get a solid high pedal with the rear brakes unadjusted. You will have to pump them up. Does the emergency brake work now? Mike 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's Canadian Off Road Trips Photos: Non members can still view! Jan/06 http://www.imagestation.com/album/pictures.html?id=2115147590 (More Off Road album links at bottom of the view page) >>> On your truck, you are right in that when you pushed the pistons in- you >>> probly rode over some junk. but also pushing the wheel cylinders in may [quoted text clipped - 35 lines] > Jan/06 http://www.imagestation.com/album/pictures.html?id=2115147590 > (More Off Road album links at bottom of the view page) I manually adjusted the rears until there's a bit of drag with the drums on. The pedal is just really soft - just resting your foot on it will cause it to sink to the floor. The ebrake doesn't work because I changed all the cables but have not yet had the time to adjust it. I haven't driven the truck either other than testing the brakes around the block - I just don't like the pedal feel. Been too busy trying to get the race car ready for the last race. (broken axle + cam swap.) Maybe I'll pull the drums again and double check the rear adjusters, it's just it feels like there's air in there or something. Ray > >>> On your truck, you are right in that when you pushed the pistons in- you > >>> probly rode over some junk. but also pushing the wheel cylinders in may [quoted text clipped - 50 lines] > > Ray I have a feeling from this description that you have a blown master cylinder now. Every time I have had a brake pedal sink under my foot with no broken brake lines or cylinders, it has been a bad master cylinder. Spongy brakes have air in them, a dropping pedal means something has failed. Mike > The ebrake doesn't work because I changed all the cables but have not > yet had the time to adjust it. I haven't driven the truck either other [quoted text clipped - 4 lines] > Maybe I'll pull the drums again and double check the rear adjusters, > it's just it feels like there's air in there or something. The way you can tell the difference between whether the pumping up is due to air or brake adjustment is how long it lasts. After pumping it up, If you let the pedal go to the top wait a second or so then push the pedal again - is it still pumped up or do you have to start pumping again to get to come up? While you have it pumped up and holding have you tried cracking the lines right at the master cylinder? It probably is air somewhere causing the problem, although, it could also be a rubber hose with an aneurysm, but that will probably break soon enough so you won't have any trouble finding it (just don't hit a tree in the discovery process). -jim jim Wrote: > The way you can tell the difference between whether the pumping up is > due to air or brake adjustment is how long it lasts. After pumping it [quoted text clipped - 9 lines] > ----= East and West-Coast Server Farms - Total Privacy via Encryption > =---- Another way is to pump the pedal quickly full stroke a dozen times or so, then hold it down, have someone observe the fluid return in the resevoir when you let off the pedal suddenly...air compresses, so on release it will create an explosive return to the master, if present in the system. Other issues don't react violently like that... Signaturejeffcoslacker http://www.automotiveforums.com > jim Wrote: >> The way you can tell the difference between whether the pumping up is [quoted text clipped - 16 lines] > release it will create an explosive return to the master, if present in > the system. Other issues don't react violently like that... thanks guys, I'll check this when I get the chance, and let you know/beg for further assistance... Ray > Another way is to pump the pedal quickly full stroke a dozen times or > so, then hold it down, have someone observe the fluid return in the > resevoir when you let off the pedal suddenly...air compresses, so on > release it will create an explosive return to the master, if present in > the system. Other issues don't react violently like that... That can be a little hard on the face of the observer and on the paint job. -jim |
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