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  • December 03, 2021, 05:40:14 PM

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Author Topic: Brake Caliper Guide Pins - Rusting - plug rubber part?  (Read 241 times)

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Offline Canoe

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Brake Caliper Guide Pins - Rusting - plug rubber part?
« on: November 19, 2021, 11:56:34 AM »
My new brake caliper guide pins rusted horribly, from installed last summer through our salted winter to this summer. I'd like to keep my brakes working nicely; calipers free to move for its auto adjusting. Has anyone tried to keep splashed water away from the guide pins by blocking the open end of the guide pin rubber housing? Say with a cork stopper, big dab of grease, tiny balloon over the opening, _____ ?

If grease, it would have to be one that doesn't bother the plastic (Delrin AF? newer replacements seems to be UHMW) liner that the guide pin slides on.

Offline Illeagle1984

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Re: Brake Caliper Guide Pins - Rusting - plug rubber part?
« Reply #1 on: November 19, 2021, 08:46:21 PM »
I have seen neat little caps that fit over the ends of the pins on a 2006ish Ford Escape.  I wonder if they would fit?  You might protect the outside of the pin, but what about the inside?  I am curious what kind of brake lube you're using.  I mentioned it before, my shop has used Sta-Lube SL3303 forever.
 
Your pins (from your previous pic) look like they are rusting at the edges of where rubber meets metal meets air.  I think rust built up in the bore between the rubber and caliper and is tight enough to wipe the lube away with the repeated movement of braking.  This is what causes the rings of rust like on your first two pins; even the best of lubes can be wiped away.  I used to see it a lot on Cavaliers and Bonnevilles, now Caravans and Escapes less frequently.

The solution is to take out the rubbers and hone that caliper out.  Tape some sandpaper around a drill bit and have at 'er until you get to bare metal all the way around, in and out.  If you reuse the rubbers, get all the flake rust off it first.  Oreilly sells a hardware kit for 12 bucks that's listed for my '84, H5552.  Not sure if it fits.  Coat the caliper bore completely before installing the rubber, then coat the inside of the rubber similarly before installing the pin.  The pin itself gets a light coat.  We also wire wheel the heck out of rusty pins to reduce their diameter a bit.  Sometimes we have to hone out reman calipers out of the box.  As a side note, I have seen pins that had some kind of epoxy coating on them and no lube.

Best of luck keeping our great enemy rust at bay; it never sleeps.  More regular pin maintenance may be the only way.
It's getting crowded down here:
1973 Ford Mustang "Rustang"
1984 AMC Eagle Sedan "IllEagle" 181k
1984 AMC Eagle Wagon
1996 Cadillac Eldorado 176k
1998 Oldsmobile Eighty-Eight 239k
2002 Cadillac Eldorado Doral Edition
2005 Chevrolet Silverado 1500

Offline Canoe

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Re: Brake Caliper Guide Pins - Rusting - plug rubber part?
« Reply #2 on: November 19, 2021, 09:32:24 PM »
That's all good to know.

I've been using Ate Bremszylinder-Paste (Ate BSP), a grease meant for inside the cylinder, for ~ two decades? It did a wonderful job when I rebuilt my calipers. Ended up reusing all of the original calipers, pistons & seals, which it incredibly revived. Completely derusted calipers inside and out, painted, and used the paste all inside the caliper, not just on the piston-cylinder surfaces, to prevent any rust if there was ever water/air infiltration. Super smooth and easy moving piston with that grease on it - low/no slip-stick - modulation of brakes is amazing! I used new pins, rubber-housing and bleed valves for that rebuild.

Since then, I'd completely clean the rubber and the insert sleeve, clean the pin holes, then coat the rubber with the Ate BSP (seems to restore rubber a surprisingly amount), Ate BSP coating inside the hole, insert the rubber, insert the sleeve, then position the caliper, coat all but the threads of the pin with the Ate BSP, and insert and torque. I'd get years out of a set of pins. Then with a touch of rust discovered last summer, I decided on four new pins. LPS had Cardone pins. Put in last summer, they got nuked with rust over one winter! Over the past decade, whatever car I'm getting pins for, the pin steel seems to have been getting softer and softer... I have a vague recollection that the set I put in last year had almost a zinc coated appearance. May not have been the set for the Eagle.

That Sta-Lube SL3303 looks interesting, with moly, PTFE and graphite. I would not have thought of using any of those three where the movement 'lube' is a 'dry lube' of the steel of the pins (ideally a hard steel) sliding on the inserts - but with rust, we have to do something. I was using the Ate BSP for its rust protection, and that it was what I used for the rubber-housing. Perhaps I should test the Red Line CV-2 for this with its red moly, rust protection, low absorption and low washout.

Those Ford caps look interesting too. I'll grab some from the junk hard to check for fit.

Offline Canoe

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Re: Brake Caliper Guide Pins - Rusting - plug rubber part?
« Reply #3 on: November 22, 2021, 10:03:39 AM »
... Perhaps I should test the Red Line CV-2 for this with its red moly, rust protection, low absorption and low washout. ...
Well, installing the new guide pins didn't go as expected.

For installation, on the first caliper, the grease part went fine. Even though it was just above freezing, this was the easiest ever for slipping (all coated with CV-2) the rubber housings into the caliper, the plastic sleeves into the rubber housings, and the pins into the sleeves.

Turning the guide pins into their threaded holes, not so much so. First went in smoothly. Second was going in smoothly. Working in the cold just above freezing, I was thinking about soon I'd be reaching for the torque wrench and this side would be done. Going in smoothly, suddenly the ratchet was loose. Ratchet drive bit wouldn't seat in the guide pin. Pulled it out of the rubber housing. There was a silver collar around the bit. The head of the guide pin had broken off. The remainder of the pin - with its sharp-bits end - is in the housing in the caliper, and the bit won't grip anything to move in or out. Part number Pronto H5029. The outside of the pin had been coated with CV-2 grease, but the then dry surface of the head that broke off appeared to have some dry rust inside the pin! The hex inset in the head is not centred in the guide pin head. The photos aren't the best, but they show the offset centre with its difference in distance from the inset edge to the outside of the pin.

I took the other Pronto guide pin out. No way I'm leaving that part in my brakes. Its head looks to be centred a lot better. Put the used pin that had been in it back in. I was happy to not get Cardone guide pins like the ones I put in last summer that rusted over one winter, but now Pronto is on the I-do-not-trust list.

I've attached a photo showing what I can get of the Pronto parts. Some of the red CV-2 grease can be seen on the hex surfaces. I'd wiped most of the grease off of the unbroken pin that was installed then uninstalled. The thickness of the 'silver' coating is variable in the hex inset. A touch of grease (shiny) got on the broken surface of the head. There's a 'silver' coating on part of the exposed break in the steel. The discoloured surface that looks like dry rust can just be seen. It looks like:
  • Some of the outside 'silver' coating had seeped into a crack in the steel from the outside.
    - Unknown if this crack is "just" a stress riser to the depth of the silver that seeped in, or if the crack extended beyond what part of the crack was filled with the 'silver' coating.
    - Also unknown of there are more cracks in this pin. Or in the other three of these new pins.
  • There was rusted bits throughout the steel?
  • The guide pin steel was cracked at the bottom of the hex insert in its head, and had rusted in that crack prior to receiving the silver coating?
  • _________________?

To get the broken guide pin out, it looks like I'll have to saw the guide pin off so I can get the caliper off. Hopefully leaving enough of the pin so I can grip it to turn it out; else it will be drilling and an extraction bit. Hmmm. Perhaps better to take the caliper bracket off, and get the pin out from working on the threaded end, so the broken head surface can be examined.

On the scale of things, this is a fairly small problem. But with temperatures in and around freezing, I really don't need this now. However, with the crack in the guide pin side and what looked like dry rust inside the Pronto guide pin, it's a lot better to have it now, than when under operation. 

Another takeaway: inspect guide pin surfaces for cracks before installing.
Is a visual inspection or running one's thumbnail down the outside of the pin sufficient for inspection for cracks...
« Last Edit: November 22, 2021, 10:16:54 AM by Canoe »

Offline Illeagle1984

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Re: Brake Caliper Guide Pins - Rusting - plug rubber part?
« Reply #4 on: November 22, 2021, 09:57:04 PM »
Wow, that confirms the theory of inferior metal, I'd say.  Bad new parts drive me insane.  It sounds like the cracks were put there during manufacturing and then covered up with plating?  You may be able to remove the bracket & caliper from the rotor and slide the bracket (with pins) away from the caliper to separate the two, leaving the brake hose and both pins untouched.  Haven't tried on Eagles, but always works on similar setups when the heads round off.

Your methods are sound, I was just making sure.  We don't take the time to rebuild calipers much anymore, but I've seen enough Cardones fail right out of the box to know why you would.  That cylinder paste looks legit, though I couldn't find out much about it.  It seems to be similar to Sil-Glyde, which I like a lot for its ability to rejuvenate rubber.

Maybe if you have some caliper paint leftover, you could try to coat your next set of replacements.  See how the CV-2 does you, it seems like it would work well.  At least we're not working on dripping, crusty, glaciated or snow-packed cars.  Yet.  :)
It's getting crowded down here:
1973 Ford Mustang "Rustang"
1984 AMC Eagle Sedan "IllEagle" 181k
1984 AMC Eagle Wagon
1996 Cadillac Eldorado 176k
1998 Oldsmobile Eighty-Eight 239k
2002 Cadillac Eldorado Doral Edition
2005 Chevrolet Silverado 1500

Offline Canoe

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Re: Brake Caliper Guide Pins - Rusting - plug rubber part?
« Reply #5 on: November 24, 2021, 07:19:05 PM »
Got the broken pin off. Caliper bracket came off with the attached caliper & pads rather easy. But not quite enough space to slide the pin out. But tons of space to get a set of pliers on the pin to get it threaded out. Thanks for that. Much easier than cutting the pin.

Definitely a crack, then plated. Both the broken-off head and the remaining pin show plating on their break surface.

It felt really really odd to be installing pins from the other end of the rubber housing, securing them to the bracket, and attaching all back to the car by bolting the caliper bracket back on, but it all fits back together easy. Went with the pins I took off last summer. Polished up, they're better than the new ones I put in last summer or the new sets that had this pin break.

LPS took the two sets of two guide pins back without issue. Seemed rather astounded that manufacturer's QA hadn't caught the hugely off-centre hex inset nor the crack that they plated over. They also feel that guide pins have been getting softer over the past decade.
 

 

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