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(Rear Calipers rebuild). How much pitting is allowed in the brake piston seal groove?

4K views 7 replies 3 participants last post by  helpthe95 
#1 ·
Hello, I recently am finishing up my rear axle rebuild. It is out of the car freshly painted on jack stands. Long story short, it bothers me to put my dirty abused calipers back on my new axle so I’m restoring them myself.
First, because it gives me something to do.
Second, it teaches me about my car and saves me a buck possibly.
Third, I’ve thought about Autozone OEM remanufactured lifetime warranty calipers but wonder the real condition of them. My car is a California car as far as I know so weather hasn’t been too bad for rain, snow, salt and such and that may cause pitting in the seal grooves in the reman calipers more than mine have. I feel like I’ll never know how good Autozone calipers really are or any auto parts stores remanufacture calipers for that matter. I know mine have 135k on them as far as I know if they are the originals. You see what I’m saying? IDK, I just don’t want to possibly trade my cores for something that may be worse when I can restore mine. Anyway, they are aluminum where the piston seal sits. My steel piston was pit free, just a little rubber stain that came off with polish and a t shirt. I polished the groove with a plastic dremel brush and metal polish.

How much pitting, (in this case aluminum pitting oxidation or whatever) is allowed before they scrap them? Do reman companies re machine the groove and put larger seals in them or do they clean them like I am attempting to do and put stock replacements in them? I’m guessing the pits you see in my photo are not even a half a thousandths deep. They are just surface pits. I just want some feed back from experiences of those who rebuilt theirs and were maybe worse than mine and didn’t leak? am I taking a big chance here? Also one of my guide pins were stuck and it’s pitted so I’m guessing the cast iron pin guide barrel is pitted somewhat too. I plan on replacing my guide pins and tube brushing the barrels with a drill tube brush. I really want to know if remainufacture Oem calipers have pits. How can this be not possible unless my car is worse than most and ain’t find this hard to believe. Thanks here are some photos.
Alloy wheel Wheel Rim Auto part Automotive wheel system
 

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#2 ·
You can get away with a lot in the bore and seal groove, as long as the piston is basically perfect.

I would doubt you would find remans as good as yours.
They are usually calipers that someone else gave up on.
The other trouble area is the sealing surface for the hose washer and the bleeder seat.
Buy some seal kits , assembly lube and have at yours.
 
#3 ·
Thanks for the Reply 95wagon. Just for kicks, here they are ready for my next move. Used a wire wheel on a pneumatic die grinder to remove the old paint. It took some time but came out pretty good. The lower guide pin bores or “barrels” (2 on each caliper) “the lower ones” had some corrosion going on making my pads wear unevenly. I don’t know if this is common with vehicles with stock wheels? I do know my larger 5 spoke wheels get a little more water action when I’d wash my car. As of now, I’m just thinking of steel tube brushing the females and putting new male pins on, lube and boots.
 

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#4 ·
"I’m just thinking of steel tube brushing the females"

Be careful with this procedure. Females need special treatment. :giggle:

Be in all seriousness, use a brass or non metallic brush if anything at all. Aggressive here will wear off the plating and rust will result.
 
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#5 ·
Thanks for the tip grandpas wagon. I have not done it yet. I will see if I can use something that will not get under the plating (if any is left). My lower male pins were corroded (one on each side L and R) After I clean them with something (maybe plastic brushes and some metal polish?) IDK, after I can inspect with a flash light and magnifying glass to see if pits are in there too. I wonder how the remanufactured ones look? Pits or what? Lol. I’m thinking if some of the plating is left and there are some pits, the pits may help hold the grease in there maybe? IDK, they should work better than before. Thanks again.
 
#6 ·
Got my calipers done. New guide pins, pin boots, piston seals, piston dust cover, bleeder valves. Banjo bolts are on the way. I have a couple questions:

1. I used Sil Glyde on my piston seals and lubed the pistons a little bit to make assembly easier. Is this ok? Seen others doing it. Made it easier for sure. Will this contaminate my fluid?

2. Also I purchased this Prestone High Temp DOT 3 “Synthetic”. Is Synthetic ok?

Photos attached.

Thanks.
 

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#7 ·
I would not have used it on the actual piston pressure seals or area of the pistons that are fluid side of the seals, As long as you do not have blobs of that grease inside the caliper, I wouldn't lose sleep over it .
There are specific hydraulic brake assembly lubes.
I like and use Sil glyde all over, just not inside were the brake fluid is.
I don't want silicon in the hydraulic side and want any assembly lube inside to mix and flush out during bleeding.
 

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#8 · (Edited)
I would not have used it on the actual piston pressure seals or area of the pistons that are fluid side of the seals, As long as you do not have blobs of that grease inside the caliper, I wouldn't lose sleep over it .
There are specific hydraulic brake assembly lubes.
I like and use Sil glyde all over, just not inside were the brake fluid is.
I don't want silicon in the hydraulic side and want any assembly lube inside to mix and flush out during bleeding.
Thanks for the reply and info on the assembly fluid. I couldn’t find assembly fluid on the shelf and the parts store pointed me to this. I’m sure you know all about Sil Glyde. I used it sparingly and any excess probably swept any excess Sil Glyde against the idust cover groove. I guess the excess will always kind of sweep back and forth on the piston unless it stiffens up. I agree with not wanting that stuff in the hydraulic side of the system. I’m glad I didn’t put any on the inside face of the piston-I put just enough on the piston seal to make it shine and keep moisture out. That was because the tube says it’s ok for rubber seals and keeps moisture out. (did skim coat the O.D of piston too) anyway... That was my deciding point vs using brake fluid as I couldn’t find assembly fluid. I was scared brake fluid would cut into my caliper paint job and make a mess Because I had no idea how easy or difficult getting them assembled would be. I learned that these are pretty easy using the technique I found online. Not saying this video is right or wrong for anyone reading. This was just my choice. Next time when I do my front brakes, I’m going to get the assembly fluid. My question with that is how long can one let their assembled brake sit out-of-service with assembly fluid before any sticking or ripping of seals happens-if that even happens. And wondering about the caliper paint smearing. It’s just something I’m considering here as I read that About the sticking of the seals. That was specifically for using brake fluid. I don’t know all this stuff so just putting it here. I suppose rebuilding brakes and reassembly as quick as possible is always better. I was thinking about removing the pistons and wiping them out but like you said if I didn’t glob it all in there I shouldn’t lose any sleep over it. I think I’m just going to live with it as I didn’t over do it with the Sil Glyde. Again, thanks for the feedback 95wagon.

Video link>>>
 
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