Front end has new wheel bearings, rotors turned, new pads and I inspected and reassembled both calipers. The pistons and seals looked fine, so I merely cleaned everything and applied fresh brake fluid to all parts before reassembly. The reason I got into the front end was because I had a sticking caliper on the driver's side. Spinning the tires with them off the ground the driver's side was real tight, while the passenger side spun freely. The driver's side had seen some heat and that's the reason for redoing everything on both sides. The master cylinder is almost new (replaced last year because of seal leaking), and today was removed, bench bled and successfully tested on the car by plugging both outlet ports and trying to move the brake pedal. Now, with the rear brakes disconnected, the outlet port plugged and only the front brakes hooked up and bled ten times I have a similar situation to what I had before. The driver's side caliper seems fine, with what seems to be proper resistance between rotor and pad. But the passenger side still turns freely, and I can see the pad and rotor separating just a tad more than they do on the driver's side when the brake pedal is released. I have heard of GM metric calipers creating vacuum inside and causing the piston to retract too far, which seems to be my case. I'm assuming that the seals are doing what they're supposed to (sealing and retracting the piston) because the piston is retracting too far. I could rebuild the passenger side caliper, buy two new '78 - '81 Malibu calipers (Before '78 they had low-drag metric calipers and '78 and after were normal.) or try and find out about a vacuum in the caliper. While I'm waiting for HAMB advice I'll check the price on new calipers.
If you crack open the bleeder on the tight side does the caliper release? If so look for a flex hose or prop valve holding pressure to that side only.
Whoops, I got it backwards... The loose side must have the seal pulling the piston back more than the other side. I don't know of anything else that could cause it. I've never heard of vacuum being created by a weird prop valve or MC. Did you replace or miss install the piston seal on that side?
I think he meant the 'tight' side?? suggesting the Driver's is actually the problem.....not retracting as fully as it should due to something holding pressure after the foot comes off the pedal....
I have heard that discs should have a 2 pound residual pressure valve -- perhaps to prevent the problem you have.... I have also heard that if the MC is on the firewall (higher than the discs) that this would create sufficient pressure (hydraulic head pressure) so that a RPV is not needed. (This is for discs only -- all drums need a RPV.)
You probably have a low drag caliper, which were installed on quite a few eighties era GM midsized cars..Those were intended to be used with a step bore master cylinder, (like a 2 stage master cylinder, the big bore takes up the slop, and the small bore makes pressure) ALL of the low drag calipers were the metric type, but not all of the metric type were low drag. The difference is in the piston seal, the standard seal is square cut, while the low drag caliper has a slight angle cut into it, which retracts the piston after a brake application.. The idea was that without the pads touching the rotors at all, they'd save gas..
I had a similar problem in my 55, considered rebuilding one till I found out NAPA sells remans for $14. (they didn't offer new). Many miles later still doing fine.
A good metric caliper to use is a 78-81 Malibu. I have found that each caliper from rebuilders needs to be checked, as many times the later calipers get put in the wrong box at the rebuilders.
Your idea has merit. Originally I cracked the bleeder on the tight side and the piston didn't retract, so I assumed it was the hardware needing cleaning and grease, which I did. The seal may not be retracting the piston like it should. Maybe my cleaning and greasing made it better, but not like it should be. It could be the seal or a collapsed rubber hose inside the stainless braid. Two new calipers can be had for less than $100.00 and they would have new seals.
http://www.hotrodders.com/forum/a-1549907-singlepost5.html http://www.hotrodders.com/forum/test-low-drag-calipers-158523.html
As you can see in those posts the piston retraction can be measured to see if you indeed do have a low drag caliper which would account for your problem.
Ran across a similar problem- someone had pulled the pickup with a chain and mashed the brake line almost closed
What's the best way to test the braided stainless hoses, run a wire through them? And what about Speedway's DOT legal brake line kit................is it any good?
I had a rubber hose that was plugged and that's how I cleaned it. After I rebuilt the caliper and mc... Hey those Malibu calipers look a lot like S10 calipers. Anyone know if they interchange?
sounds like your problem is your brake hose, they let pressure go to the caliper but when releasing the brakes,the inner rubber collapses, a s/s brake hose has 2 rubber hoses inside ,and no pushing something through will not solve the problem.
i bought a 56 from a friend, he put a speedway disc kit on it. i felt brakes draging as soon as i bought. went threw everything, i finally figured out pedal not returning all the way. i added spring on pedal for return, never have had a problem.since the spring ive driven it 10000 miles shes good.
I meant just checking the hose by pushing a wire through it. What's the best way to check the braided stainless hoses for internal collapsing?
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