Brake caliper - does this diagnosis make sense? (And any recommendations?)

[madpogue]

1985 (early) F250 RCLB - been having front brake issues. Initially, pulsing / noise, and the LF wheel would get HOT. I found that I had the caliper "flipped", so the flex hose was oriented the wrong way:

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I've read on other sites that this can restrict fluid flow. So I flipped it back the right way:

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Problem solved, or so it seemed. Took it out for a high speed run, felt normal, wheel at normal temperature, case closed.

NOT! Took it out again the other night, and started feeling pulsing again. Once again, hot wheel. Now I'm thinking caliper. So I thought of two tests - how hard would it be to retract the pistons, and would one piston be harder to retract than the other? Tore into it tonight. Almost new pads, so the pistons are barely extended. So I took off the outer pad, then put it back together, and GENTLY pushed the pedal, the idea being to extend both pistons enough to test the retract resistance. When I did this, the bottom piston barely moved. Top piston extended fairly nicely. So I pulled the caliper again and pushed back each piston with a c-clamp. Sure enough, the bottom piston took a LOT more force to retract than the top piston.

So.... diagnosis - bottom piston op fault -> brake drag -> heat. Does that sound like a reasonable conclusion?

I'm thinking, since I'll have the hydraulics open and will have to bleed the fronts anyway, I'll do both calipers for good measure.

Leads to the next question - any recommendations wrt. brand? I'm guessing all the FLAPS "house" brands are pretty-much the same; their prices are almost in lock-step. Unfortunately, no one stocks it, so it's special order time. Are any of the "premium-ish" offerings on RockAuto (Raybestos, etc.) really better?

 

[Waystro]

Sounds reasonable to me. Are you going to get new Calipers?
I would get new Rotors and do them too while I had the front brakes torn apart

 

[chris142]

Those calipers were used for decades. I can't believe nobody has them in stock.I walked into auto zone and out with rebuilt ones 5 minutes later.

 

[madpogue]

Sounds reasonable to me. Are you going to get new Calipers?
I would get new Rotors and do them too while I had the front brakes torn apart

DEF new calipers. My question is about what brand of calipers to get.

Rotors are pretty fresh. I've literally driven this truck maybe 500 miles since I've owned it, and the PO did rotors and pads before he sold it. He obviously didn't do the calipers; probably didn't want to mess with the hydraulics. 'Sokay, I'd rather not mess with the bearings.

Those calipers were used for decades. I can't believe nobody has them in stock.I walked into auto zone and out with rebuilt ones 5 minutes later.

Hmm, according to RockAuto, they were only used from 1980 to 1985. Looks like the '86-up calipers have two tap-in pins on each caliper, on top and bottom; the '85 has just one pin on each, on the bottom. My '95 PSDs have the threaded-pin calipers, completely different.

 

[Waystro]

DEF new calipers. My question is about what brand of calipers to get.

Rotors are pretty fresh. I've literally driven this truck maybe 500 miles since I've owned it, and the PO did rotors and pads before he sold it. He obviously didn't do the calipers; probably didn't want to mess with the hydraulics. 'Sokay, I'd rather not mess with the bearings.

Hmm, according to RockAuto, they were only used from 1980 to 1985. Looks like the '86-up calipers have two tap-in pins on each caliper, on top and bottom; the '85 has just one pin on each, on the bottom. My '95 PSDs have the threaded-pin calipers, completely different.

I'm using AutoZone Calipers. But if I do it again I'll use Napa.

Yep I got the new style(slider pins) and I need to take them back and get the old style.

 

[ironworker40]

http://www.amazon.com/Raybestos-FRC10277-Professional-Remanufactured-Semi-Loaded/dp/B001OBH7PU
Here what I used for my 93 last year. I'm sure they have the ones for your truck. Best part about it they didn't charge a core charge so I got to keep mine and I rebuilt them and have them for spares.

 

[BDCarrillo]

Have you taken off the boot around the piston? Sometimes a bit of moisture sneaks in and causes light surface rust, hindering operation. It's worth a shot to open it up and see if there's any gunk.

I had one like that on a different vehicle and it cleaned up with some 600 grit and worked great.

 

[madpogue]

Have you taken off the boot around the piston? Sometimes a bit of moisture sneaks in and causes light surface rust, hindering operation. It's worth a shot to open it up and see if there's any gunk.

I had one like that on a different vehicle and it cleaned up with some 600 grit and worked great.

Hmm, that's a thought. The boots looked pretty dry and undamaged, but you never know.

 

[madpogue]

Well I tried your suggestion BD; I wasn't able to get the boot off from the caliper body, but I was able to slip it off the groove on the piston. When I extended the piston and slipped back the boot, sure 'nuff, the piston had more than light surface rust. It required a file to get it even marginally smooth. Odd thing was, the top piston was not much better. Anyway, I got both of them smoothed out as best I could, and the bottom one is definitely a LOT easier to retract with the c-clamp. And then when I did a similar test to see how well they extended, now the bottom one extends better than the top. I'm **guessing** that's not a big deal, with the pads in place, it's not like one is going to be way "ahead" of the other. I figure if they're both retracting with minimal effort, then I should be out of the woods wrt. it dragging. Only test drove it once, did some moderate to hard braking, got it up to 60 MPH, no wheel shake, no pulse in the pedal with any range of braking effort, and the wheel was NOT hot when we parked it.

So maybe I dodged a bullet, for a while at least. Maybe with as pitted as the pistons are, the calipers aren't long for this world anyway. And I looked a little closer at the caliper this time, and noticed the bleeder is broken off. Not leaking, but just another "nudge" that if I have to do anything else on that corner, she's getting two new calipers.

So thanks for the idea. Bought me some time, anyway.

 

[BDCarrillo]

Glad to hear it worked!

 

[Shadetreemechanic]

Sounds like you may have gotten it licked.
FYI you don't need to replace calipers in pairs, rotors and pads yes, calipers can be done singly.

 

[madpogue]

FYI you don't need to replace calipers in pairs, rotors and pads yes, calipers can be done singly.

Oh I'd be lying if I said I wasn't tempted to do just the one side. And there's a new OEM one on eBay right now, driver side only, for cheap. But I'm guessing the flex hose on the other side is as old as the driver side, and I wonder about the bleeder on that side. And once I open up the hydraulics and have to mess with fluid replacement and bleeding and all, I'd rather do the major "replaceables" at once.