Moisture?

 

Interaction of the fluid and the rest of the system. Nothing to worry about.
That job should be accomplished every two years or so as moisture is an ongoing issue with brake fluid. Heat from the system will break down the chemicals as well, so if you work the truck hard consider doing the job more often. If you exchange the fluid more often the colors will be lighter.

Fairly easy and quick when you have the correct tools. I will do mine in a few weeks when I change the oil again. Regular maintenance never stops.

 

Good post subject, but it ain't the calipers.

The fluid has been in there for some time, and maybe the front calipers were replaced or bled at one time - or not.

Brake lines are made from flat stock, rolled, and then brazed to form a tube. Brake fluid contains anti-corrosion additives for iron and copper - copper from the brazing. The copper oxidizes when those additives get depleted, which takes about five or so years, along with continual moisture absorption, despite being a sealed system—the green penny.

It's a long set of tubes going to the rear brakes, so there is lots of copper to oxidize. Almost three times the length, and more, if you have four-channel ABS. So the rear fluid can have a higher degree of copper oxide contamination.

The new trend among some mechanics and many DIY'ers when replacing pads is not to open the bleeders when pushing the calipers in (debris usually does not get pushed up into the ABS) and, therefore, not bleed the brake system. Some mechanics have justified the situation by saying if the bleeder is frozen in place, not bleeding saves the customer from buying an expensive caliper. That justification gets higher points with DIY'ers.

Along with the trend of brake pads lasting longer, brake fluid takes a hit. And, therefore, so do the hard lines.

The freak out of reading what I just wrote is the question, what about the integrity of the brake lines after this, brake lines rusting from the inside? That's something no one can answer. But usually, it's the corrosion on the outside that causes brake line failure. And typically, behind areas like the fuel tank that do not dry out as fast from high moisture are retained by a line holding clip, so there is abrasion of the lines, especially without the protective polyvinyl fluoride coating.

But green is a telling sign of a problem.

 

I tend to agree mostly with TooManyToys on this, the assessment is pretty spot on. It is time for a complete fluid flush. The green is a good indicator that the fluid has not been flushed regularly like it should be. It's not an indicator of a caliper issue, just a lack of fluid flushing. So long as the bleeder screws aren't stuck, it shouldn't be a hard job with 2 people.

Now I tend to find some limited validity to opening bleeder screws when replacing brakes. Not in automotive stuff though. It's REQUIRED on particular Harley Davidson products, such as Sportsters for the rear brakes. On those, pushing fluid back upstream actually damages the master cylinder's seals and necessitates a rebuild. Something I've learned firsthand when I was a harley mechanic..... I have to pull up a brake replacement procedure through Mitchell or the like and I wouldn't be surprised if I don't see mention of bleeder screws being touched. I just know the way I've done it for years, and that the procedures sometimes change as what's "generally accepted" in the industry.

 

On motorcycles, I’ve always recommended opening the bleeder. They have short lines, so it's really easy to get particles to the masters or the ABS that are available today.

And I do with car and truck calipers. For me, I want to know if the bleeder is stuck before I do the work. And I always bleed after replacing pads, so it would be crazy to re-bolt everything up and find I need a caliper. I usually make it through two pad changes before replacing or rebuilding calipers. The second set of pads' life will not be as long, the rubber is getting aged, and the piston pullback is lessened.

Since discussing bleeders and this subject is evolving more, I coat the bleeder screw threads with caliper silicone grease and then blow out the through hole, then squirt alcohol into the bleeder hole and again blow it out before putting on the rubber cap. Leaving brake fluid in the bleeder hole promotes rusting as it is hygroscopic. I really don't want a frozen bleeder under any circumstance. You can get the caps from auto parts stores, Amazon, RockAuto, etc.

 

TooManyToys, I just realized what your experience stems from, I'm going to assume it's safe to say your experience far outweighs my own.

I'll ABSOLUTELY agree with cleaning and having a cap on a bleeder. Too many, especially on salvaged bikes I used to tear down the bleeder was clogged with crap, or rust, because someone didn't put a simple cap on there. Even more on cars, I've had them seized and snapping off because of poor care. Let me tell ya, that's a LOAD of fun to get a broken bleeder out.

And since we're on the subject of calipers. Something I do, and notice a number of people seem to not do. Slide pin maintenance. The boots are very important, especially in northern environments, for keeping moisture and rust creating elements OUT, and grease in. Next, I do like to clean a slide pin and the bore as thoroughly as possible so the pin glides on the grease like it should. That helps the brakes use both pads evenly as the caliper can slide along and apply equal pressure to both sides at once. Along with cleaning the surface the pad hardware sits on so the hardware rests evenly and isn't also pinching the pads. This can cause a pad to also stick and wear unevenly.

There's so much that can go into doing a really good brake job, vs just pad slapping and hoping for the best like some shops do. It baffles me that Mavis even offers that service. Something I outright refuse to do under any circumstances. Been burned too many times. If I'm not machining or replacing rotors depending on which is more appropriate, I'm not willing to do it. Brakes matter, in my book more than being able to get moving.

 

Maybe from an engineering standpoint, but I never discount service personnel experience. We may have flipped through five or more brake changes every week, but they were on vehicles for only 1 or 2 weeks. Working with fleet operations, taxis, buses, OTR, etc, and long-term issues was always interesting.

Some day I might actually do some videos about brakes, LOL.

As you point out, so many calipers are trashed because of poor bleeder attention. That's probably lessened with people not changing brake fluid as much, a side benefit from lack of maintenance.

In my former life on TheDieselStop, before it was TDS, I harped on slide pin maintenance quite a bit. I also wrote an extended essay about the Superduty caliper and slide pin issues for my company. But, unfortunately, it was too long for the company's public relations. I tend to be OCD, which is not bad if you work in R&D.

I check for pin freedom every oil change, while I'm under there. It's easy to do while you are waiting. Unscrew the pin bolts for about 1/4", then push and pull the bolts to move the pin to check movement. If good, tighten back up and move on. You can find a pin that is starting to be an issue before it is. I also don't use the rubber bushing on the front lower pins. That was the third modification to the pins and boots that Ford INSISTED on with the caliper manufacturer of the '99 to '04 design level, Akebono. Akebono had it right the first time; their calipers on Honda's never had the issues we have. TRW taking over caliper design in '05 has its own problems, pistons.

When I do have to deal with slide pin issues, I put the brackets in a vice after washing out the bores, use a power brush or hone to get most of the rust out, but not hone long enough to alter the bore excessively, then pour in Evapo-Rust and let it set overnight. That will chemically remove the rust without causing hydrogen embrittlement. IMO, all oxide removal is essential as any oxides left behind with a wire brush seem to propagate, even with grease.

Over the life of my original '03 and the few years of owning my '01, I've only had pins start to degrade, caught during the oil change checks. Pads developing a lack of freedom from the end of the pads rusting has been more of a challenge since my truck can sit for weeks to months.

We worked with Ford on the issue of rotor total indicated runout problems, and the incorporation of the on-car lathe, specifically Pro-Cut, who we also worked with. The partner of Pro-Cut brought his newest lathe (at the time) to us in the back of his Mercedes. You can cut a rotor to the tolerance necessary today on a bench lathe, but it won't happen by checking with a scratch cut; you have to measure and index the runout of the rotor on the vehicle hub, transfer that to the bench lathe and cut from there. It's how a machinist would do it; service people don't want to. But the on-car lathe turns the rotor installed on the hub, so the runout is minimized.

Few people know the initial Excursion rotors were cut on the vehicle using a bevy of Pro-Cut lathes in the Assembly plant parking lots because the new tolerance rotors had not been sorted out. Rotors and hubs were changed on the Pickups earlier, but even at that initial stage, the rotors were still not to the revised spec.

So in retired life, I replace rotors. I can get 100k out of them, but by then the Northeast rust clogs the cooling vanes too much. You can needle-scaler the rust out in a pinch, but rotors are not that expensive - and I buy OE. I will put a newer set of pads on older rotors as long as there is not a hint of pulsation, and the runout measures in spec (0.0015"), as long are there is no excessive grooving. It takes longer to wear in the new pads since they are a polished finish, but I'm aware of the longer "burnishing" time that occurs from that.

The inside joke within my group was that grooving improved braking due to more surface area.

 

I got none of these notifications.

Fluid is only a few months old, less than 5k miles. If you remember my thread about the soft pedal/master cylinder issues, @TooManyToys helped me with.

I found it odd it was only on the right rear. Google says it's moisture or copper. Easy day.

I still haven't got the brakes 100% what I think they should be. Stops just fine but I don't get the firm pedal evertime.

Everything that's been done to the brakes:
Front hard lines (motorcraft)
PMF hoses all the way around
Original calipers and pads
3rd master cylinder (motorcraft)
Dot3 super tech brake fluid
(Edit) slide pins have been cleaned and greased as well.
Only vehicles I've had brake issues with are powerstrokes..

 

Only vehicles I've had brake issues with are powerstrokes..

LOL!

What size tires? When my rotors and pads were new the brakes were firm. Better than the rams with stock tires. Put carli stainless lines and same good braking... after several thousand miles they're feeling a little less...

Brake longevity is highly correlated to driving style...

 

I'm pretty conservative with driving.

I have 36x13 Toyo MTs. Didn't have issues when I first got them 40k or so miles ago

 

My 2007 6.0 braked fine but it ate calipers

 

It seems the best way of dealing with the TRW '05+ caliper piston issues is fine craftsman-like massaging of the pistons and bores.

The new fluid may be releasing some of the copper corrosion off the brazing of the older rear lines. It doesn't seem to be in the new front lines fluid.