The inside guts of a rear wheel brake cylinder... it was new to me

[GoToGuy]

Any moisture/ humidity in the air will be drawn to the brake fluid. Standard brake fluid is Hygroscopic, this moisture ,water in the brake fluid is attracted to itself. The moisture is heavier than brake fluid therefore it migrates to the lowest point in brake system. Yep ,that's the major reason you see the corrosion in the calipers and wheel cylinders.
And brake fluid is high temp operating fluid. Until it starts absorbing moisture, then the high temp boiling point starts dropping.
Dry boiling point and wet boiling point.
Testing has shown that a new brake system after two years in service has absorbed up to 3.7% water. The chart that follows shows the lower boiling point of that wetted brake fluid. The difference is quite a bit. This data goes hand in had with " flushing the fluid with new every TWO years. Or if your doing a brake job, then earlier, do it along with your service.
Big deal, bonus! 1. Your braking as to fluid will be great, far less chance of fading, fluid boil, brake loss. . 2. Your calipers and wheel cylinders will have a longer service life. $$$ !
I do this checklist item on the 93 and 95 every odd calendar year. The 98 Tahoe every even year. The Kiss princepl.
The chart shows how a small amount of water content screws up the fluid. Almost all fluid producers publish charts or have info on new dry fluid limits versus wet ( in-service ) fluid temp limits.
It's another preventative maintenance thing , and yeah, there are times when , hells bells is it that time already? But then I think I got trailer hooked up, my uncle's 57 nomad is on back and we got the " women who must be obeyed with us" and yep I better get started kicks in.
Information is one form of energy, use it wisely.

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[movietvet]

Any moisture/ humidity in the air will be drawn to the brake fluid. Standard brake fluid is Hygroscopic, this moisture ,water in the brake fluid is attracted to itself. The moisture is heavier than brake fluid therefore it migrates to the lowest point in brake system. Yep ,that's the major reason you see the corrosion in the calipers and wheel cylinders.
And brake fluid is high temp operating fluid. Until it starts absorbing moisture, then the high temp boiling point starts dropping.
Dry boiling point and wet boiling point.
Testing has shown that a new brake system after two years in service has absorbed up to 3.7% water. The chart that follows shows the lower boiling point of that wetted brake fluid. The difference is quite a bit. This data goes hand in had with " flushing the fluid with new every TWO years. Or if your doing a brake job, then earlier, do it along with your service.
Big deal, bonus! 1. Your braking as to fluid will be great, far less chance of fading, fluid boil, brake loss. . 2. Your calipers and wheel cylinders will have a longer service life. $$$ !
I do this checklist item on the 93 and 95 every odd calendar year. The 98 Tahoe every even year. The Kiss princepl.
The chart shows how a small amount of water content screws up the fluid. Almost all fluid producers publish charts or have info on new dry fluid limits versus wet ( in-service ) fluid temp limits.
It's another preventative maintenance thing , and yeah, there are times when , hells bells is it that time already? But then I think I got trailer hooked up, my uncle's 57 nomad is on back and we got the " women who must be obeyed with us" and yep I better get started kicks in.
Information is one form of energy, use it wisely.

You must be registered for see images attach

Absolutely. So many people do not know that the brake fluid system vents to outside air and that air has moisture in it.

 

[Cadillacmak]

I can remember rebuilding plenty of those in the early 70's and 80's. I still have the little hone tool in my toolbox. Hasn't been used in years though. I just started replacing the whole assembly when needed. But as a kid, a rebuild was the way to go as they were super cheap and I didn't have a lot of money to waste. It's cool you tore it apart to check it out.

We were still rebuilding them in the 90s up here just due to availability. It was a 2 week wait for everything or buy a rebuild kit today, and every dollar mattered. On-line shopping really changed things for us.

 

[movietvet]

We were still rebuilding them in the 90s up here just due to availability. It was a 2 week wait for everything or buy a rebuild kit today, and every dollar mattered. On-line shopping really changed things for us.

Yea, I ran a storage facility at one time. My relief lady had a membership at Costco. She would buy a list of things here for her daughter and her husband and box them up and ship them to Alaska and that was cheaper than them buying up there.

 

[Cadillacmak]

Yea, I ran a storage facility at one time. My relief lady had a membership at Costco. She would buy a list of things here for her daughter and her husband and box them up and ship them to Alaska and that was cheaper than them buying up there.

Oh man, I bet that was a life saver for them! We have a Costco now but back in the early 90s it was just "Castle Warehouse", which bought bulk food and sold it, and was the size of a typical NAPA. Different times! It was normal then for a kid in high school to be celebrating that they got electricity or running water.

 

[1998_K1500_Sub]

That means the entire brake system fluid has contamination. Prime case for a flush and may still have components too far gone to salvage. FUBAR

^^^ yup

In my case, it sorta doesn't matter; that crud is representative of the donor vehicle for my 9.5"

I have new cylinders for the 9.5" that'll replace the cruddy ones removed.

That cruddy brake cylinder I pictured... I disassembled it by putting it in a hydraulic press and it didn't give up easily.

 

[someotherguy]

We were still rebuilding them in the 90s up here just due to availability. It was a 2 week wait for everything or buy a rebuild kit today, and every dollar mattered. On-line shopping really changed things for us.

In the late 80's/early 90's I was rebuilding cylinders for the '60-66 trucks I was into at that time (GMT400's were brand new and way outta my price range, LOL) - but at that time, kits for the '60-62 combination brake/clutch master cylinder were unavailable, nevermind buying a brand new one. I salvaged a few by piecing together parts from other various NOS kits obtained from a friend that had whole shop buildings full of NOS parts. I miss Lynn; great friend and heck of a character. Disappeared into history.

Richard

 

[Schurkey]

In the late 80's/early 90's I was rebuilding cylinders for the '60-66 trucks I was into at that time...

I would just love to find a '60 2WD GMC with V-6 as a project vehicle.

As if I can keep up with the junk vehicles I already own...

 

[someotherguy]

I would just love to find a '60 2WD GMC with V-6 as a project vehicle.

As if I can keep up with the junk vehicles I already own...

That was the first generation of trucks I owned and loved, still love 'em. Did a salvage operation for them as well but on a smaller scale than my GMT400 shop. More of a backyard full of busted old trucks I'd pick up cheap, and a downstairs bedroom of the house loaded with loose parts to keep 'em out of the weather.

The '60-'61 are my absolute favorites, but I wouldn't turn down a '62-'63 either. I prefer the wraparound windshield cab on those over the '64-'66 by a mile. That combo clutch/brake master on the first few years is probably one of my less favorite features, though.

Richard