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  #41  
Old 11-05-2015, 11:51 AM
jfryjfry jfryjfry is offline
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I'd like to offer to solve this problem - I'll send you $50 for your powder coated aneurism that you can put towards a new set of factory assembled calipers. The only downside is you might go mental with all of the free time you'll have.

And I'm serious - pm me if you're interested!
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  #42  
Old 11-14-2015, 04:11 PM
cleantune cleantune is offline
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^Thanks I’ll keep that in mind.

A few updates to share:
Until an efficient way to remove the powdercoat from the bolt head surfaces on the caliper had been determined, I decided to work on something easier and sand off the powdercoat on the front and rear caliper mounting surfaces (grits:80, 150, 220 using a short piece of thick, straight, aluminum block to keep things level).



A closer examination of the old seals may have revealed something about the surface pitting on the rear caliper seal surfaces. There was a yellow/clear crust on both the front and rear seal centers (where brake fluid comes in contact with each seal), but only the rear seals (ones with the tiny surface pitting) had this crust on both faces of each seal too (larger ones in the pic below)- not sure if this is dried brake fluid or maybe old dried grease or sealant?:





^I know the old seals are worn, but I wanted to do a quick check to see how much they would compress since both halves are counterbored a bit (just how they are, I didn’t do it). It doesn’t compress much, but the two halves did slightly “wobble” over the seal, so I guess the new seals will compress some? hopefully?

I was reading an article about silicone-based brake greases stuff and since they only have silicone as an ingredient, its temp properties are not as good as pure silicone. Someone on another forum was looking for something to coat their brake shims on a motorcyle. They had used a silicone-based grease that claimed to not “melt” or “run” at temps +600ºF, but did melt and seeped into his brake pads. To be sure did an oven test with a little bit of silicone-based grease and some pure silicone grease in an aluminum foil cup and at just 250ºF the silicone-based product had turned into a brown puddle and then proceeded to almost completely evaporate nearing his oven’s 500ºF limit. The pure silicone grease looked “shiny” at the oven max, but did not melt. The silicone grease he used was “Dow Corning High Vacuum Grease”:


After looking at the Z32 FSM, it seems like this would be suitable to use as a substitute for both “rubber grease” (for the piston seals) and poly butyl cuprysil grease (for brakeshims; since FSM says to use PBC or silicone-based grease). Someone please correct me if I’m waaay off in my thinking, but I figured if this stuff is safe for rubber, stable at high temps, resistant to many chemicals and generally used to seal “o”-rings, so it may be a good candidate to help seal up those tiny voids on the seal surface.

.
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  #43  
Old 11-14-2015, 05:08 PM
cleantune cleantune is offline
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I had included that "over-engineered through-bolt design" picture in one of the emails I had sent out. A representative from Brembo explained that a through-bolt design would not be a good solution for calipers like this because the threaded bolt design helps to align the center seals; and supposedly this threaded bolt design does this more efficiently than a through-bolt design could.


Matt great call on the serrated flange bolt! After looking into “forstner bits”, (used to counterbore wood and about $10 per bit) I went back into Home Depot Motorsports to pick up a 2 pack of serrated bottomed M10 flange bolts. The bolts did start to take off the neon yellow top coat, but were not digging in enough to lift off anything substantial, so this was solved with a dremel cutoff wheel.


The "Destroyer bolt" haha:









A flange bolt was definitely what was needed though, because in addition to having a serrated shape to start with, the bolt head helped to keep both downward pressure and rotation needed to strip off the powdercoat. I just used a socket wrench to pin the bolt; a drill with a socket attachment probably would have been easier, but I wanted to make sure I wasn’t damaging the surface as the bolt head was being turned. Had to make some adjustments to the “blades” on the bolt to get the underside to cut more parallel to the caliper surface- the uneven surface contact at first is shown in the pic below.



The “destroyer” bolt did take a small amount of aluminum off , which can be observed from the presence of a small lip toward the edge of the cleaned metal:


I’d like to think that I leveled the surfaces some; however there was some surface irregularity afterwards:


Tried using the unmodified, serrated, flange bolt to help smooth out the surface, but not sure how much it really helped.





*edit: I recently smoothed these out- cut out eight 220 grit sand paper washers a tiny bit larger in diameter than the outer diameter of the flange on the bolt and used the regular, "unmodded", serrated flange bolt and a socket wrench to smooth everything out.

I’m thinking I may have to try to find another M10 flange bolt with a slightly larger diameter head because the OEM bridge bolts heads appear to be just slightly larger. It was rubbing some of the yellow top coat off around the outside of the bolt holes. *edit: did this too, just cut the bolt a little less aggressive than the last one and then smoothed everything out using the sand paper washers (again, like half a mm larger in diameter than the bolt head) and an OEM flange bolt.

Also started stripping the bolt heads with Aircraft Paint Stripper:





So before the “destroyer bolt”, sandpaper and paint stripper, we had tried using a fine grain glass bead using a blaster (blast-out-of-bag setup), didn’t work too well; maybe dulled the surface of the powdercoat, if that. The rougher grit glass bead did work to take off the powder coat, but was not as precise as I thought it would be- the side of the bolt head I wasn’t aiming for was damaged from glass bead ricochet.

I only tried it on one bolt head and one of the mounting locations on the caliper, then stopped. This is glass beaded bolt head on the left and stripped on right:



After hearing about the powdercoat melting thing, I was thinking rust could probably do something similar, right? -deteriorate the under side of the bolt head and leave a void?

What would you guys suggest? Should I just paint it with zinc paint? Grease it? Re zinc coat it? It is just this one bolt, but the other bolts appear to be losing some of their zinc coating as well.

.
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Last edited by cleantune; 11-16-2015 at 06:21 PM..
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Old 11-16-2015, 06:11 PM
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  #44  
Old 12-03-2015, 03:29 PM
cleantune cleantune is offline
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Here we go again, hah. Thank you guys sooo much for your help, we're making progress! Again... any opinions and/or advice from experience is welcome!

Quote:
Originally Posted by Def View Post
Yea... as an engineer who's designed hundreds of bolted joints over the years - you're thinking about this too much.

Clean all the fasteners and female threads the best you can, use a couple of drops of blue loctite on the bolts, fasten to reasonable torque value for lubricated bolt of that size.
Def, were you serious when you suggested using "Blue", medium strength loctite on the caliper bridge bolts that hold the two halves of the caliper together and keep the brake fluid passages sealed on each caliper?

The reason I ask is because I have seriously considered using "blue" loctite on these bolts. I've been looking into ways to lock fasteners down and while the "red" high temp formulas should be the obvious choice for a fastener that absolutely should not move at all...ever, the "blue" loctite is very tempting because it would be less permanent than a "red" and should still accomplish the same thing- fill up any play between threads so that the bolt will not loosen itself when subjected to vibration.

Basically I would rather not have to torch the caliper bolts to remove them, if they need to be taken apart again for any reason; especially since some bolts do not come out on the other side of the caliper. So, "blue" would technically make the calipers more servicable.

I went ahead and had the hardware re-zinc plated and yellow/ gold chromated (how I believe the original hardware was, based on some residual plating on the bolt shaft). *These also underwent a baking process after plating to help relieve any hydrogen pockets that may have been trapped in the material during the plating process (hydrogen embrittlement).
Zinc plated and yellow/gold chromated top:


Zinc plated and yellow/gold chromated threads:


Getting back to the "Blue" loctite... found some high temp "blue"
Loctite 246 Medium strength, high temp “blue”


link:
http://www.amazon.com/Loctite-196508.../dp/B00B749NJC

Since the two main metals in this joint, zinc and aluminum, will not react with most loctite thread lockers, a primer was chosen. From what I've gathered from the info they have on their products, either Primer "T" (7471 for most thread lockers if air gap is less than or equal to 0.010 inches) or Primer "N" (7649 if gap(s) exceed 0.010 inches).

Since both are supposed to work with the loctite threadlockers, I know its overkill, but just to make sure it would work....

Loctite 7649 Primer N Activator:


Link:
http://www.amazon.com/gp/product/B00...ilpage_o00_s00

My only concern with the 246 high temp blue medium strength loctite is it's heat tolerance and how well it would stand up to multiple heating cycles. Its rated from -65ºF to 450ºF.

I know with street use they probably wouldn't reach 300ºF, but with track use I could easily imagine they could meet that 450ºF mark.

.
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Last edited by cleantune; 12-03-2015 at 03:36 PM..
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  #45  
Old 04-10-2016, 10:02 AM
cleantune cleantune is offline
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Hi everyone. I finally had a chance to get back to this project and I had a question.

So silicone grease can be used to coat O rings in hydraulic systems to help form better seals. For the brake caliper seals (both o-rings between the halves and the seals around the pistons) most recommendations say to coat these in brake fluid.

My question is should just the silicone grease be used on these seals? or should these be coated in just brake fluid before install? maybe silicone on seal surfaces and coat o rings in brake fluid?

*reason for the silicone grease (mentioned earlier in the thread) was an attempt to seal up any small porosity/micro-pitting on the seal surfaces between the two halves
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  #46  
Old 04-11-2016, 07:02 AM
cleantune cleantune is offline
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...nevermind, just decided to go with the grease on O rings and seals. I could be wrong, but I don't believe brake fluid is a good lubricant or conditioner for rubber. Also, I'm almost positive that the 2 or 3 different greases the FSM specifies for these are all silicone-based.

.
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  #47  
Old 04-11-2016, 09:56 AM
Colorado S14 Colorado S14 is offline
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How I feel reading this thread:
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  #48  
Old 04-11-2016, 11:53 AM
Russell423 Russell423 is offline
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Generally orings are assembled with some kind of lubricant so that they don't twist or deform when they are squished into the seal groove. This ensures good seating of the orings and helps prevent damage to the orings during assembly. The grease itself isn't really providing any additional sealing, and usually doesnt sick around long anyway so if it is creating a seal it wont last. Its mostly just there to improve assembly. I wouldn't be too concerned with what you use as lubricant as long as it's compatible with the orings you are using.
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  #49  
Old 04-11-2016, 05:25 PM
Def Def is offline
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Quote:
Originally Posted by Russell423 View Post
Generally orings are assembled with some kind of lubricant so that they don't twist or deform when they are squished into the seal groove. This ensures good seating of the orings and helps prevent damage to the orings during assembly. The grease itself isn't really providing any additional sealing, and usually doesnt sick around long anyway so if it is creating a seal it wont last. Its mostly just there to improve assembly. I wouldn't be too concerned with what you use as lubricant as long as it's compatible with the orings you are using.
What this guy said. And yes, blue Loctite is a good idea on fasteners like caliper half bolts.

And +1 to the Banderas gif.
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