C3 brake O Ring(s)??
Ok, So I'm rebuilding the rear calipers for the first time on my 69 L68. Drivers side was leaking pretty bad. Several things, FIRST, found a significant amount of crap in them even though the car has been rarely driven and in climate controlled storage for MANY years which I guess is pretty normal for the original style brakes (anyone try bleeding the brakes more regularly as a preventative for this problem?). That's OK because the plan is to just put some seal kits in for now and probably spring for some rebuilt trailing arm assemblies here sometime in the near future (any experiences with Vtech?). SECOND, as I was putting them back together, I was looking up the torque for the caliper bolts (not the mounting bolts) and saw a photo that shows TWO o rings in the caliper and mine clearly only has ONE. Anyone have any experience as to why? Freaked me out and I took the caliper apart again just to make sure. lol. 20220129_185912.jpg
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Re: C3 brake O Ring(s)??
What you are seeing in that picture is the inner seal (which actually seals it) and the outer "mount" seal that holds everything in (I didn't look up the actual terms for those components). This is totally normal and what should have came in your rebuild kit, 4 inner seals, 4 outer seals, and 2 O-rings that seal the halves together. Yes, I bleed all my old cars brakes every year. Don H. -
Re: C3 brake O Ring(s)??
Thank you. So if I understand correctly, BOTH orings reside in the same hole between the two halves of the calipers? ...one inside the other?Comment
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Re: C3 brake O Ring(s)??
No, there are 2 grooves in the piston. The inner groove (of the piston) takes the "Flap" seal and the outer most groove takes the rubber & steel seal. Try looking up the drawing if you have the service manual. Good luck, Don H.Comment
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Re: C3 brake O Ring(s)??
I got that part just fine. I was asking about the 2 small o rings that came with the kit that goes between the 2 caliper halves. Mine only has one passageway so I was trying to ask why the kit came with 2 small o rings when only one is required. I'm wondering if there is an earlier or later casting for the caliper that requires both o rings while mine only requires one. Thanks!Comment
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Re: C3 brake O Ring(s)??
I am only familiar with mid-year calipers that have 2 passages & 2 O-rings between the caliper halves. I am sorry for the confusion. Don H.Comment
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Re: C3 brake O Ring(s)??
Brake fluid itself is hygroscopic (attracts moisture). Once introduced to the system, water reduces boiling points and compromises performance. It corrodes brake parts, lines and seals, leading to eventual failure. That's why the manufacturers tell you not to leave your cap off the bottle too long and having your master cylinder cover off very long as well.
It will absorb the moisture out of the air. During usage your BF gets hot and cold and that creates moisture inside the system too.
So it is very wise you change your brake fluid yearly even though almost nobody does it. Especially on their daily driver vehicles.
Now be careful of the Dot 5 silicone based fluid that everyone switches to thinking they solved that moisture problem. Although dot 5 is nice moisture still creates inside the system and since water and silicone doesn't mix you will have little moisture pockets laying on the bottom of your calipers creating rust.
So it's wise to flush dot 5 too.Comment
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Re: C3 brake O Ring(s)??
Rear calipers take only one (1) o-ring. They have bleeders atop each half section to remove air from each half.
Front calipers take two (2) o-rings. They have only a single bleeder at the top, so the halves need to be joined and o-ring sealed at the top to remove all the air.
LarryComment
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Re: C3 brake O Ring(s)??
I have never understood this line of reasoning. How is moisture getting into the DOT 5 system? Silicone is hydrophobic so atmospheric moisture is not going to get past the fluid in the master cylinder, the same with the piston seals at the calipers; the rest is a sealed system (or should be). Are there documented examples of lines rusted through where DOT 5 was properly used?Comment
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Re: C3 brake O Ring(s)??
I have been waiting for many years for someone to explain the water entrapment with DOT 5.
The one downside of DOT5 is its ability to trap air, but careful filling of the system and a good bleed can overcome that.
I have posted previously about my 1970 that has had DOT 5 in it for about 40 years now. No issues. I am aware more current installations are not so trouble free. Something has changed -- either the seals or the fluid, or perhaps both. To date I am aware of no one posting an identification of the root cause. There are a lot of intelligent people on the internet (in spite of what it sometimes seems
) and I would have expected someone to have the resources to seek out the cause(s) by now.
TerryComment
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Re: C3 brake O Ring(s)??
Terry
No answer, but speculation: DOT 5 is NOT recommended for use with ABS systems. ABS pump action aerates DOT 5, bubbles resulting in a "spongy" brake pedal. I expect a "daily driver" car with excessive brake rotor runout would also introduce air (and moisture) into a brake system.
Cars basically in storage would be like a sealed bottle of brake fluid - indefinite shelf life. Drive it, and you've opened that bottle, inducing air bubbles and moisture into your system.
Given usage most of these cars get, I expect it would be a LONG time before enough moisture gets introduced to rust out anything. [Then there is the rubber seal thing I will leave alone.]
Speculation.
DaveJudging Chairman Mid-Way USA (Kansas) ChapterComment
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