Replace rubber brake lines, yea or nay?

[02FailBlazer]

2002 TB LTZ, 4WD, 198K miles.

Overhauling my brakes soon, wondering if I should replace the rubber brake lines. Pretty sure they're all original. I don't have any reason to believe any of them have failed or are seriously deteriorated, this would be a purely preventative measure. Is it worth the extra money and effort?

This has been a California car its whole life, and an inland one at that, so there's as little rust and deterioration as you could ever reasonably expect for a 24 year old vehicle. Things are generally in good shape.

 

[flyboy2610]

Personally, I would. If you're overhauling the brakes anyway it would be worth doing the whole thing.
But that's just me.

 

[Beacon]

I second that, especially if your fluid is getting dark, might as well replace them and flush everything

 

[movietvet]

By "overhaul my brakes" are you meaning pads and rotors and all calipers and master cylinder? If you are doing all that, do the lines. Especially if you plan to keep the TB.

Your screen name makes me feel that you have had some bad times with the TB. Are you on the other side of all that and gonna keep it? If you are not keeping the TB, doing the lines will not get you more money but most certainly save you some headaches. Afterall, the wear and tear of the brake lines is usually on the inside, especially in the climate you are in.

Are you doing the steel lines and rubber hoses or stainless braided hoses?

 

[BrianF]

Its not a bad thing. Seeing as you are not in the rust belt, its likely it will be an easy job.

 

[Mooseman]

And they're not overly expensive. You could get yourself all 4 for under $100. I also vote change 'em.

 

[02FailBlazer]

By "overhaul my brakes" are you meaning pads and rotors and all calipers and master cylinder? If you are doing all that, do the lines. Especially if you plan to keep the TB.

Your screen name makes me feel that you have had some bad times with the TB. Are you on the other side of all that and gonna keep it? If you are not keeping the TB, doing the lines will not get you more money but most certainly save you some headaches. Afterall, the wear and tear of the brake lines is usually on the inside, especially in the climate you are in.

Are you doing the steel lines and rubber hoses or stainless braided hoses?

Wasn't planning on doing the master cylinder or calipers, just pads, rotors, fluid change, and slide pin boots since those are cheap and easy. It's never leaked brake fluid and I looked the steel lines over whenever I had the chance to get a close look and I haven't found any areas that looked really concerning, cars last forever out here.

I'm keeping the TB, but it's a second car now and is being relegated to severe weather/off-road/backup use, it's not a daily driver anymore. I just want it in reasonably reliable, drive-able condition, doesn't need to be perfect.

 

[movietvet]

Wasn't planning on doing the master cylinder or calipers, just pads, rotors, fluid change, and slide pin boots since those are cheap and easy. It's never leaked brake fluid and I looked the steel lines over whenever I had the chance to get a close look and I haven't found any areas that looked really concerning, cars last forever out here.

I'm keeping the TB, but it's a second car now and is being relegated to severe weather/off-road/backup use, it's not a daily driver anymore. I just want it in reasonably reliable, drive-able condition, doesn't need to be perfect.

Overhauling brakes means something different to me. But I also was in shops for 40+ years. Your overhaul is "friction materials replacement with a fluid flush added on. I have always felt that the brake system on ANY vehicle, is the single most important system. Don't care about the other systems but when you apply the brakes, it BETTER stop.

 

[02FailBlazer]

Small update - before putting in a parts order I was checking a few things and there's a hiss when pressing the brake pedal to the floor. See video. Thoughts? No codes, brakes feel the way they have for the past 10 years.

Video link here.

You can hear me depress the brake pedal near the beginning and release it at the end. Phone was held over the dash in front of the steering wheel, couldn't pinpoint a source for the sound.

 

[flyboy2610]

Sounds like the brake booster to my tired old ears.

 

[02FailBlazer]

Sounds like the brake booster to my tired old ears.

That's what I suspected after a quick search, just wanted some confirmation. Guessing it needs to be replaced? Looks like the only new one available is from SKP, hopefully it's decent. Will I need anything else to do the replacement?

 

[movietvet]

Small update - before putting in a parts order I was checking a few things and there's a hiss when pressing the brake pedal to the floor. See video. Thoughts? No codes, brakes feel the way they have for the past 10 years.

Video link here.

You can hear me depress the brake pedal near the beginning and release it at the end. Phone was held over the dash in front of the steering wheel, couldn't pinpoint a source for the sound.

Yea, brake booster. You can hear an initial "whoosh" sound when you apply brakes with a vacuum booster but continuous noise like that, IMO, indicates a vacuum leak that is leaking at the inside firewall. If you pinch off the vacuum feed to the booster, engine running, and then hold brake pedal again, the noise should not be there. When you pinch off and hit pedal, it will also feel hard, like you hit the brakes without the engine running. Want to be sure the new one does not make that noise.

In your case, the brakes likely felt normal but as it would get worse, the pedal would have gotten harder over time.

 

[Mooseman]

I remember my 02 had mushy brakes and that whoosh noise. Was told at the time this was normal despite multiple brake bleeds. Apparently the aluminum calipers allowed more movement or stretch and allowed the pedal to go down to almost the floor. Now my 07 with cast iron calipers aren't mushy and don't have that whoosh noise because I can't get the pedal down enough to do it. Could be the reason they stopped using aluminum calipers in the front.

Try gently pinching the front caliper rubber hoses with hose pinchers and see if the pedal firms up and stops the noise.

 

[movietvet]

Check out In Line Tube for the lines/hoses.

 

[02FailBlazer]

Pinched off vacuum hose to brake booster, brakes firmed up to near rock-solid feel and the hiss was gone. Guessing that confirms the booster is bad.

 

[movietvet]

Failing now/going bad and hard pedal before long when it leaks enough.

 

[02FailBlazer]

New question - Any recommendations on what brand/type of vacuum hose to buy to replace or make spares for the brake booster hose? I looked for direct replacements and there aren't any.

 

[xavierny25]

@02FailBlazer I replaced the booster years ago on my 08 because it was failing and 1 thing I did forget to order is the gasket between the firewall and booster. It was totally toast and I had to make up my own gasket.

 

[movietvet]

https://www.gmpartsdirect.com/oem-parts/gm-booster-assembly-gasket-15015355

Just get the correct I.D. vacuum hose and clamp each end if you want to. I would use a thick hose that has correct I.D.. Don't want it collapsing later.

 

[02FailBlazer]

Parts will all be here soon, want to make sure I've got the process right.

Parts being replaced - vacuum booster, master cylinder, front/rear rubber brake lines, rotors/pads, front caliper brackets (exchanging to perform EXT brake upgrade), front/rear slide pin boots

Process -

• Replace vacuum booster and gasket
• Bench bleed new master cylinder, replace old master cylinder
• Separate calipers from brake lines, replace slide pin boots
• Replace rubber brake lines
• Reinstall calipers
• Replace pads/rotors
• Bleed brakes/do brake fluid change, starting at rear right and working forward

Does this look right? Do I need to do anything special when bleeding the brakes, like engaging the ABS system to bleed it?

 

[Mooseman]

For the EXT brake upgrade

For the brake bleeding, as long as you don't have air in the system to begin with, it should be fine doing a normal brake bleed/flush. The order is RR, LR, RF, LF

Be sure to use actual brake lube for the pins. I like the ceramic type, usually purple or orange, but the regular silicone type is also good.

Be sure to clean the surface of the wheel hub down to clean metal. Brake jobs can get ruined just by having some rust under those new rotors.

 

[02FailBlazer]

For the EXT brake upgrade

For the brake bleeding, as long as you don't have air in the system to begin with, it should be fine doing a normal brake bleed/flush. The order is RR, LR, RF, LF

Be sure to use actual brake lube for the pins. I like the ceramic type, usually purple or orange, but the regular silicone type is also good.

Be sure to clean the surface of the wheel hub down to clean metal. Brake jobs can get ruined just by having some rust under those new rotors.

Inland Cali checking in, what is "rust"?

Jokes aside, sounds like I'm set. Got Sil-Glyde for brake lube, seems commonly recommended. I'll stick with the standard bleed procedure and see what happens. Going to do the one-man "bottle" method - run clear tubing from the bleeder into a bottle filled part way with fluid placed above the caliper, work the brakes with a block of wood under the pedal to flush air/old fluid out, and keep the master cylinder topped off with fresh fluid.

 

[Mooseman]

Only thing with the one man method is that I would wind up with some air in the caliper as air would get sucked in through the bleeder screw's threads when you let go of the pedal. One thing I did was remove the bleeder completely and put some teflon tape on the threads, screw it back on part way, bleed and then close the bleeder.

Another way would be to use a vacuum pump, an oil pump or what this guy used.

 

[Beacon]

I like using a glob of grease, all around the bleeder and hose to prevent air from going back into the system

 

[02FailBlazer]

https://www.gmpartsdirect.com/oem-parts/gm-booster-assembly-gasket-15015355

Just get the correct I.D. vacuum hose and clamp each end if you want to. I would use a thick hose that has correct I.D.. Don't want it collapsing later.

Minor complication - this gasket is no longer available. I tried ordering from that site and GM Parts Center, neither could get one. Guess I'm making one. Are these just a rubber sheet? 1/16" thickness probably?

 

[Mooseman]

Hopefully your old one is reusable. I think it is just a rubber piece. I think you have to be conscious of the thickness if making one as this could affect the rod to brake pedal distance.

And I also remember this thread although no resolution came from the OP regarding the rod or "pill" in the booster that pushes on the master cylinder being too long:

R

Thread '04 trailblazer, brakes dragging after new pads, calipers, master cylinder'

Mar 21, 2021

So, I took my TB to a guy who does my auto work to get the brakes improved. I had like they were a little weak and I tow my camper with it, so wanted it right for spring.

he pulled all pads off, and odd thing, he told me both front calipers froze and even with clamps he couldn’t push them out. (Made no sense to me cause he said they were not froze when he test drove)
So he did 4 sets of new pads, 2 front rotors, and a master cylinder. Not sure if it was new or rebuilt but I think it was aro7 d $160 for the MC
He also told me he had a hard time bleeding them, and he replaced all the...

• Rhizzlebop
• Replies: 43
• Forum: Brakes & Suspension

• 

This one was kinda resolved:
https://gmtnation.com/forums/threads/oreilly-reman-brake-booster-adjustment.21779/

Be sure you keep an eye on this and verify that the pill doesn't push on the MC when the pedal isn't pushed. Might have to reuse the pill from the old booster.

 

[02FailBlazer]

Minor complication - this gasket is no longer available. I tried ordering from that site and GM Parts Center, neither could get one. Guess I'm making one. Are these just a rubber sheet? 1/16" thickness probably?

RE this issue - The OE gasket is a low-resilience foam rubber. It is squished totally flat between the brake booster and the firewall. It appears to be there only to do two things - First, to keep the brake booster from squeaking against the metal firewall while the vehicle is in motion. Second, to seal out air, dirt, moisture, and fumes from the engine bay so they can't enter the passenger compartment. The second purpose is far more important than the first.

That said, it appears you could use anything that is broadly resistant to heat and moisture and which will squish down between the booster and the firewall. A 1/8" thick piece of heat and flame resistant foam rubber with low resiliency would be perfect. However, if you want to take the easy way out, it's hard to see why a good metal-to-metal gasket maker with the appropriate resistances wouldn't also work fine. Just smear it on the firewall, circling the bolt holes and the center hole for the push rod assembly, bolt up the booster, and move on with your life. If you go this route, try not to put too much around the push rod hole as you don't want it to seep into the assembly on the booster.

Fabbing one up from a sheet of gasket material is much harder, thanks in large part to GM's fascination with oddly shaped holes. The hole for the push rod is shaped like an egg which makes copying it via simple measurement AND getting its spatial relationship to the bolt holes correct a difficult and time consuming task. Ask me how I know.

So to any future readers, if you want to try fabbing a gasket from a sheet of material, here's an idea - paint the surface of the firewall with a colorful, transferable substance which is easily cleaned off. Something like thin paint with a long dry time. Then, using a flat block at least as large as the whole gasket, press your gasket material sheet to the firewall to transfer the hole pattern to it, then cut out the holes. The outer dimensions of the gasket appear to be irrelevant - it does not fit inside of anything and there is plenty of spare room in all four directions, so err on the side of caution and cut the outside of the gasket larger than necessary. You can always make it smaller.

When replacing the booster, put the gasket on the booster so it is held in place, no need to try sticking it to the firewall, though if that works better for you go ahead. Torque bolts down, then shine a light through the footwell into the engine compartment. No light? Seal is good. Light coming through? Seal is bad. Simple.

 

[02FailBlazer]

Some more notes as I sit here working on this - Clearance for the push rod assembly and the studs on the brake booster is all that matters. The sealing surface on the firewall is flat, so as long as the gasket has good coverage on the sealing surface of the vacuum booster and the proper clearances, you're good to go.

 

[02FailBlazer]

An update RE the new vacuum booster and fitment to the new master cylinder - the booster is SKP part #SK5474821, master cylinder is AC Delco part #18M986.

The fit is incorrect - the master cylinder will not mount properly due to a high degree of interference with the push rod on the booster. This was checked by applying Super Lube as a sort of gauge material. However, the application of washers between the booster and the master cylinder appears to (almost) create the correct clearance, checked using silly putty because I don't have anything else on hand. The washers are .062" thick. Nuts were torqued to 27ft lbs as stated in service manual.

As you can see, there is a thin spot on the under side of the push rod, but the putty isn't totally pushed out. The master cylinder also engages the push rod seal, as it should. This is probably as good as the fit will get without fabbing up steel shims.



I would advise others to try using a Prior Automotive brand remanufactured booster before buying a new aftermarket one, they appear to be a US based company that specializes in rebuilding brake boosters. Might get better fitment going this route.

 

[Mooseman]

The fit is incorrect - the master cylinder will not mount properly due to a high degree of interference with the push rod on the booster. This was checked by applying Super Lube as a sort of gauge material. However, the application of washers between the booster and the master cylinder appears to (almost) create the correct clearance, checked using silly putty because I don't have anything else on hand. The washers are .062" thick. Nuts were torqued to 27ft lbs as stated in service manual.

This is an issue that was previously reported as I mentioned earlier. The resolution was the insertion of washers as spacers as you did. Good you checked as others didn't and wound up with brake drag as the MC's piston was slightly pushed.

 

[02FailBlazer]

Ah welp. I messed something up.

Put everything back together, fired it up, and the brake pedal is completely limp. Goes right to the floor, totally soft, zero feedback. The brakes do engage eventually but just barely. I pumped the pedal at least a dozen times and checked for leaks, couldn't see any. No fluid on the ground. I suspect I either blew up the master cylinder somehow or there's a ton of air in the system that I failed to get out.

Parts replaced -

• Vacuum booster
• Master cylinder
• All four rubber brake hoses
• Front pads and rotors
• All slide pin boots
• Slide pins were regreased with Sil Glyde
• Front caliper mounting brackets were replaced with EXT model brackets
• Brake fluid used was Prestone brand DOT 3.

Process I followed -

• Bench bled master cylinder, keeping fluid topped up
• Installed master cylinder and burped flare nuts
• Removed and replaced front left, then front right, rotors/pads/slide pin boots/brake hoses
• Removed and replaced rear right, then rear left, brake hoses and slide pin boots
• Bled brake lines starting with rear right (passenger side rear), then rear left, then front right, then front left, as outlined in the service manual.
• I used the one man method with a bottle filled with fresh brake fluid and clear tubing leading from the caliper bleeder screw into the bottle. Bottle was placed above caliper bleeder screw. Lines were bled until fresh, clear fluid filled the tubing. I used a bar clamp to hold the brake pedal down while I loosened and then tightened the bleeder screws - the pedal was NOT allowed to come back up while a bleeder screw was loose.

Thoughts? Honestly considering throwing in the towel on this and having it towed to a shop.

 

[Mooseman]

Put the phone down! We are not from the government and we're here to help!

Probably the ABS module needs to be bled. This can be done usually using a scanner capable of activating the ABS bleed procedure. Not sure if you'll need to re-bleed all the other lines after but I would anyway just to be sure the ABS didn't push the air into the lines.

Another way, supposedly, is to drive it on a dirt road and slam the brakes to activate the ABS. Read on here that did it this way. This thread had the same problem as you and resolved it:

W

Thread '2008 Trailblazer, messed up brake bleeding'

Jun 14, 2015

Bled or attempted to bleed the brakes yesterday. I primary used a vacuum bleeder off my small compressor. So here is what I ran into and where I'm at.

Started at the right rear, no problems.
Left rear, got the bleeder partially open but ended up rounding it bad. Couldn't close it couldn't open it. Moved onto the left front.
Left front, snapped the bleeder off flush, it never budged.
Right front, no problems.
Still had breaking after that, but very soft and squeshy.

Removed the left rear caliper yesterday, replaced this morning with a remanufactured from O-Reillys. The left...

• wormwood1978
• Replies: 22
• Forum: Brakes & Suspension

Or maybe it just needs to be bled some more. I'd push more forcefully with the foot to really move the fluid and air out. The last one or two times, use the bar clamp to hold it and/or use a vacuum bleeder of some sort.

 

[02FailBlazer]

Put the phone down! We are not from the government and we're here to help!

Probably the ABS module needs to be bled. This can be done usually using a scanner capable of activating the ABS bleed procedure. Not sure if you'll need to re-bleed all the other lines after but I would anyway just to be sure the ABS didn't push the air into the lines.

Another way, supposedly, is to drive it on a dirt road and slam the brakes to activate the ABS. Read on here that did it this way. This thread had the same problem as you and resolved it:

W

Thread '2008 Trailblazer, messed up brake bleeding'

Jun 14, 2015

Bled or attempted to bleed the brakes yesterday. I primary used a vacuum bleeder off my small compressor. So here is what I ran into and where I'm at.

Started at the right rear, no problems.
Left rear, got the bleeder partially open but ended up rounding it bad. Couldn't close it couldn't open it. Moved onto the left front.
Left front, snapped the bleeder off flush, it never budged.
Right front, no problems.
Still had breaking after that, but very soft and squeshy.

Removed the left rear caliper yesterday, replaced this morning with a remanufactured from O-Reillys. The left...

• wormwood1978
• Replies: 22
• Forum: Brakes & Suspension

Or maybe it just needs to be bled some more. I'd push more forcefully with the foot to really move the fluid and air out. The last one or two times, use the bar clamp to hold it and/or use a vacuum bleeder of some sort.

I hope that's all it is.

I don't have a Tech 2 so no dice on commanding the ABS open. There is this guy on YouTube who took all the wheels off, got the truck in the air, engaged 4WD to get all axles rotating, then hit the brakes and for some reason this can activate the ABS. Don't know if it would work for me with how little engagement my brakes have but I can try it.

No way I'm going to try the old "dirt road" trick, this thing is NOT safe to drive right now.

 

[02FailBlazer]

Well. This opened a rather large can of worms.

Getting prepped to try bleeding again today and noticed small glitter flakes that had apparently been pushed up into the master cylinder from... somewhere. Something is failing, and it's not the new master cylinder.

Guessing this means something in my calipers or ABS module is eating itself alive. Great. Super.

 

[02FailBlazer]

Photo of the flakes. Craftsman 9/16" wrench for size reference.



ETA: Now that I think of it, I did notice flakes of some kind come out of the bleeder screw of my rear left caliper when I cracked it open the first time. I was hoping it was just some rust flakes but maybe it's worse than I thought.

 

[Mooseman]

Maybe copper flakes? I know that when the system is contaminated with moisture, the fluid turns green because of copper corrosion. Not sure where the copper is in a brake system.

I posed the question to AI about where metal flakes could come from:

Metal flakes in brake fluid typically come from the internal wear and degradation of the brake system's metal components. [1]

1. Internal Caliper Wear​

The pistons inside your brake calipers move every time you press the brake pedal. If the protective rubber boots tear, moisture enters, causing rust. This rust and metal debris then scrape off and enter the fluid. [2, 3, 4, 5, 6]

2. Failing Brake Master Cylinder​

The master cylinder contains metal pistons that push brake fluid through the lines. Over time, the internal walls or the pistons themselves can wear down from friction, shedding tiny metal particles into the reservoir. [7, 8, 9, 10, 11]

3. Degrading ABS Modulator​

The Anti-lock Braking System (ABS) block contains highly precise internal valves and pumps. Internal mechanical wear within these complex components can release microscopic metal flakes into the fluid stream. [12, 13, 14]

4. Severe Brake Line Corrosion​

While brake lines usually fail from the outside in, severe internal corrosion—often caused by water absorbing into old brake fluid—can cause the inside of steel lines to flake off. [15, 16, 17]

---

Why This Is Dangerous​

Metal flakes act like an abrasive sandpaper inside your braking system. They will quickly destroy rubber seals, clog the microscopic ports in your ABS module, and can ultimately lead to sudden brake failure. [18, 19]
If you want to troubleshoot this further, tell me:

• What colour are the flakes (e.g., silver, gold, rusty brown)?
• Are you experiencing a spongy pedal or poor stopping power?
• What is the make and model of the vehicle?

I can help you narrow down the exact component that is failing.

On a 2002 Chevy TrailBlazer, metal flakes in the brake fluid point to a failing Brake Master Cylinder or a degrading ABS Modulator Valve Block.
The first-generation 2002 TrailBlazer uses an aluminum master cylinder and a specific Kelsey-Hayes ABS system that are highly susceptible to internal wear if the fluid has not been regularly flushed.

1. Failing Brake Master Cylinder (Most Likely)​

• The Culprit: The internal bore of the master cylinder is made of aluminum.
• The Cause: When brake fluid gets old, it absorbs moisture and becomes highly acidic. This moisture destroys the protective coating inside the cylinder, causing the metal pistons to scrape directly against the aluminum walls, shedding silver/grey metallic flakes into the reservoir.

2. Failing ABS Modulator Pump​

• The Culprit: The ABS block located down on the frame rail beneath the driver's seat.
• The Cause: This unit contains precise internal metal valves and electric pumps. If moisture enters the system, these internal valves corrode and flake apart, contaminating the fluid.

3. Disintegrated Caliper Pistons​

• The Culprit: Front or rear brake calipers.
• The Cause: Factory 2002 TrailBlazer calipers use phenolic (plastic/resin) or steel pistons. If yours has steel replacements, moisture will rust them, causing rusty metallic flakes to back-feed into the fluid lines during a brake pad change.

---

Required Next Steps​

1. Test the Master Cylinder: Open the fluid reservoir. If you see silver swirls or dark metallic glitter directly under the cap, the master cylinder is dying and must be replaced.
2. Do Not Just Flush It: Pushing fluid through a system filled with metal flakes will force those abrasives directly into the tiny, expensive valves of your ABS module, destroying it completely.
3. Replace and Flush: Replace the failed component (usually the master cylinder first), then perform a complete, deep system flush until the fluid runs 100% clear at all four wheels.

To help narrow this down further, let me know:

• Is your brake pedal spongy/sinking to the floor, or is the ABS warning light on?
• What colour are the metal flakes you are seeing?

I did call out AI on the pistons since they are phenolic/plastic.

Yes, you are 100% correct. The factory original front calipers on a 2002 Chevy TrailBlazer use dual phenolic (plastic/resin) pistons, and the rear calipers utilize a single phenolic piston. [1, 2]
Because phenolic pistons are made of a hardened non-metallic composite, they cannot rust or flake metal into your fluid. [3, 4]
If you are finding metallic glitter or flakes in your 2002 TrailBlazer's brake fluid, you can confidently cross factory-spec pistons off your list. This narrows the source down to three specific metal components:

1. The Aluminum Master Cylinder Bore (Most Likely)​

Since your pistons are plastic, the grey or silver metallic "sheen" or flakes you are seeing almost always point directly to the brake master cylinder. Over time, moisture gets trapped in the fluid and corrodes the internal walls of the master cylinder. Every time you press the pedal, the internal metal pistons scrape against the degraded aluminum bore, shedding microscopic aluminum shavings back into the reservoir.

2. The Kelsey-Hayes ABS Modulator Valve Block​

The ABS pump and valve block located down on the frame rail contains tiny steel check valves and internal pump pistons. If moisture settles into this block, those metal components corrode and shed metallic flakes directly into the fluid channels.

3. Aftermarket Steel Piston Replacements​

If the calipers were replaced at some point in the vehicle's 20+ year lifespan, the previous owner or mechanic may have installed aftermarket calipers built with steel pistons instead of phenolic ones. If water gets past the rubber dust boots on a steel aftermarket piston, it will rust, flake, and back-feed into the lines.

How to Verify: The Magnet Test​

To figure out exactly what is failing, grab a small sample of the contaminated fluid from the reservoir and run a magnet against the outside of the container: [3]

• If the flakes are attracted to the magnet: They are iron/steel, pointing to a corroding ABS block or an aftermarket steel caliper piston.
• If the flakes are completely non-magnetic: They are aluminum, confirming that your aluminum master cylinder is disintegrating internally.

Are you experiencing a spongy brake pedal that slowly sinks to the floor when you hold pressure on it?

 

[02FailBlazer]

Maybe copper flakes? I know that when the system is contaminated with moisture, the fluid turns green because of copper corrosion. Not sure where the copper is in a brake system.

I posed the question to AI about where metal flakes could come from:






I did call out AI on the pistons since they are phenolic/plastic.

Ah, interesting. Yeah the old fluid is green (and dark) as a pine forest.

Speaking of, I've opted to simply finish the flush for now with the knowledge that I may need to investigate this further and possibly replace the calipers or ABS module. I bought a kit with a one-way valve to make it easier to flush the fluid and wow there was still a TON of old fluid in there. I've gone through at least a gallon of fluid so far trying to get all the old stuff out.

 

[02FailBlazer]

Pedal is still floppy. I don't know what's left other than trying to bleed the ABS. I don't have air coming from any of the calipers and I bled the crap out of them.

Plug checked the master cylinder - removed the brake lines running into it, installed plastic port plugs, and pushed the brake pedal. Pedal was rock hard, and it didn't move down after ~2 minutes of holding my foot on it to see if it would sink so I don't think anything is getting past the seals. I still don't see any drips or runs of fluid anywhere. I might try bleeding the ABS but if that doesn't work I think I'm done, it'll go down the street to a shop and they can deal with it. I don't know what else I could do myself to fix this.