73-87chevytrucks.com
73-87 Chevy _ GMC Trucks => Wheels & Tires => Topic started by: wkeithwilson@gmail.com on April 15, 2014, 12:52:37 pm
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I've searched the forum and can't find exactly what I'm experiencing, so my apologies if this has been asked before.
I replaced the calipers on my 85 Silverado. I chose remanufactured calipers. I also replaced the shoes. Prior to replacing, about 3 weeks ago, the left front (drivers side) caliper would lock up and cause my truck to pull horribly to the left. After a minute or so, they would release.
I've never done a brake job before, and although dirty, it was fairly simple (at least the front brakes were). Passenger side works great. Driver side works, but the caliper still locks momentarily. I bled the brakes several times in case that was the issue. Also, if I take a screwdriver and check the piston, it engages and releases fine. But, if I press the brake pedal, it will stick, eventually letting go.
With the tires and rims off, I can rotate the wheel easily, have someone press the brake then release. For about 20 seconds, I can't budge the wheel. On the passengers side, if I do the same, as soon as the brake pedal is released, I can immediately rotate the wheel again. Driving, I can't notice it like I did before replacing. But, I can press the brakes with my hands off the steering wheel, and it will pull a split second to the left then straighten up. If I keep my hands on the steering wheel, I don't notice it....unlike before, where I would have to fight it and practically stop the vehicle until they released.
What else can I check that might be the problem? Other than that momentarily pull if I let go of the steering wheel, the brakes work fine.
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We can rule out a couple of things first. Since you said it only happens to the front drivers side, we can eliminate anything to do with the master cylinder/booster since both sides (front) would be effected. So that leaves us to the drivers front brake parts.
From what you described I can think of 2 things off the top of my head and possible 1 more. #1: your caliber on that side is sticky, or #2: your rubber hose that supplied fluid to the caliber is collapsed inside. There has been other threads where it wound up being the supply rubber hose.
We do not have a 85 manual in our tech section, so I borrowed from the 86, since 85 was the first year of the hydro-boost brake system. If you look at the brake troubleshooting (http://www.73-87chevytrucks.com/techinfo/7387CKMans//Service/X8632_1986_GMC_Light_Duty_Truck_CK_G_P_10_to_30_Service_Manual.pdf) guide in the 86 manual, section 5-6 (page 426), you will see the problem of dragging brakes description, the possible cause, and the correction.
At the top of the manual in the index you can see the systems and corresponding sections (pages) to look up for repairs.
Now in the troubleshooting guide I referenced above, it states "Malfunctioning proportioning valve", but for the life of me I can not find the section on the proportioning valve, only the combination valve. Here is a thread (http://forum.73-87chevytrucks.com/smforum/index.php/topic,22940.30.html) where BD tell the difference between a combination valve and proportioning valve.
Also in the same link above for the 86 manual, you will find the disk brake service section service starting in section 5-37 (page 457).
Good reading and let us know if we can help out with any thing else. Sorry for the long write up, just wanted to give you the info you needed.
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9 times out of 10 this is the caliper hose especially if it is old or original.
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Thanks for the replies and manual links! When I was doing the calipers, I was considering changing the hoses but decided against fooling with it. I know when doing shoes/pads you do both sides. Do I need to do both sides of the hoses, or can I leave the passenger side as is since it works.....and I've already put the wheel back on..
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I would replace it while you have the brake system open...