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Front caliper failure

16884 Views 51 Replies 24 Participants Last post by  Fleetw00d
Yesterday I had the dreaded brake-pedal-to-the-floor experience. There was no warning. Inspection revealed a leak at the left front caliper.

Here's the interesting part: The failure wasn't in the seal. It was leaking fluid through the back of the piston. That's a new one on me!

Interior of caliper piston

Piston with all the rusted junk removed

The rusted bits—definitely ferrous—came loose
with the tiniest bit of prying force.

The back side of the piston and the cylinder's little reservoir (at least what I can see through the banjo-bolt hole) appear to be rust-free. That would seem to suggest that the piston rusted from the outside in.

One replacement caliper later, I'm back on the road. Will do the RF when time permits.
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wow - i recently changed the brakes on my '04 EX and found (not surprisingly) lots of surface rust but nothing like that! Although my passenger front caliper did have a busted seal necessitating replacement...

may i suggest filling a small pool with oil and driving through it daily whenever there's salt on the road? :D
That's interesting ! I thought those things were made from an alloy. Shows ya what I know !

Uh, Dan, when was the last time you did a brake fluid flush?
> when was the last time you did a brake fluid flush?

Flushed at 60K (2007) and 110K (2010). Now at 150K; the fluid looked pretty clean when I bled the LF today. Will do a full bleed when I change the RF caliper this spring/summer.
> when was the last time you did a brake fluid flush?

Flushed at 60K (2007) and 110K (2010). Now at 150K; the fluid looked pretty clean when I bled the LF today. Will do a full bleed when I change the RF caliper this spring/summer.
Wow! It looks like it had a ton of water in there in order to create that much rust. What brake fluid are you using?
thats new york for ya.

besides brake fluid changes. how often did you change pads?

if not often ide say salt and water got in there and in there and in there my E is only 2 years old. but every spring I disassemble the front and rear brakes. clean and lube. its a good day project and also when I remove the inner fender liners to clean out the sand and salt etc. im walking distance to the beach so its a chore ive gotten used to.

but then again. I guess thats why I never have the problems everyone always talks about.

imo these parts should all be stainless steel to prevent these rust issues.
> What brake fluid are you using?
Honda DOT3, always. Dunno if it really matters, but the price difference is so small that I figured why the heck not.

> how often did you change pads?
Fronts: 99K (2009). And I never looked inside the caliper piston. It would seem that more thorough inspections are indicated.

There's a irony in this story: I had recently ordered a set of caliper slider pins, to be installed whenever I did the next pad change. The replacement calipers come with new slider pins. While I was taking the car off the jacks, a UPS truck drove up with the pins—just as they became redundant.
Makes me want to look at them now just in case....

Makes me wonder if painting the insides would help. Or grinding a notch in the piston to let any trapped water leak out ...

Ok, I'm getting paranoid. I'll just pay closer attention next time im in there...
All my pistons also have similar rust after 179k and 10 winters in the NE, it is the quality of the metal. Never had a honda with this issue before, and that includes 20 year old hondas.
not that it would be relevant for many people.

but. can make custom stainless steel caliper pistons.

another idea may be. have you ever rebuilt your own caliper? I have...

might be a good idea to get the pistons ceramic coated. it would solve any porosity issues and make it easier to keep clean and protected. and while your at it get the slides Teflon coated.

just a thought.
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Yeah, the slides on my E were so badly pitted with rust, missing almost 50% material in places. I have the rebuild kits for the front when the seals go, but the rear slides/piston were so badly rusted, and the seal/boot were gone, so I just bought a whole new caliper.
I was able to remove the piston, and verified that the paper-thin plating is all that's left of the piston crown. The walls, despite being heavily rusted, are still pretty thick.

Back side of piston (hole has been enlarged)

Rust-free cylinder
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not sure what coating is used on the oem pistons and its purpose.

bur one can speculate it is an anti rust coating.

one can also speculate its a coating to keep the brake fluid away from the porous surface. to keep incidents like this from happening.

brake fluid on the "out" side of a coating is perfectly safe. but brake fluid on the "in" adhesion side of a coating will lead it to fail.

case in point. if you get brake fluid on a painted surface. it will not effect the paint itself. but it will effect its adhesion properties.

an un coated piece of say cast iron or even aluminum or really any un coated ferrous metal. if you get brake fluid on it it will soak in add heat and it will soak in more.

I would agree at this being a manufacturing defect. but what do they claim the lifetime of a caliper being? and what is the chance that a seal will go first?

it would seem the better care you take of said parts. the more you have to inspect them for an abnormal failure. assuming better care ie: fluid changes and lubing. will extend the life of seals and other wear parts.

perhaps a complete hydro system flush and conversion to dot5 would be in order.

On the advantage side, silicone fluid will not harm paint or plastic, and does not aggressively attract additional moisture as glycol fluid does. On the disadvantage side however, silicone fluid aerates easily.

so proper bleeding would be required.
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All 4 of mine have rust, its not a fluke, it's the metal.
I have a feeling it may be a design flaw.

or a designed in flaw

take your pick.

for me. 2 years and 13k mile shouldnt look like this. last time I did my brakes on my 01 grand caravan with 50k miles there was brake dust but no rust.

ive had pistons crack and chip

I just figured ide show. before I clean and coat them

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and whats odd is...

the rust is on the base and walls alone. the *ahem* tops of the walls and the outer walls are both shiny like new.

could it possibly be they skip any type of protective coating at all on the inside of the cup?

I had a similar condition on all 4 wheels.

the rears were not as bad. the front passenger was covered in rust and the front driver has little rust over all but one localized area on the wall. looking like it sat with about 2-3" of water over a long period of time.

which is odd since while obviously not water tight the pad shim covers the whole piston so it should be hard to get large amounts of water inside.

unless it is just as hard to get out? and any that gets in deals with the heat and just does an endless cycle of heating and cooling

well I scraped out the surface rust and used a rust neutralizer after that turned black I then used a rust preventative high heat paint.

I will keep an eye on this and update you guys as I like taking stuff apart to clean etc periodically
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> skip any type of protective coating at all on the inside of the cup?
Yeah, that seems right. Or perhaps the coating they did use was too thin or of an inadequate composition to resist rust for (in my case) eight winters.

Now I'm sorry I didn't coat the inside of the new piston before I installed the caliper.

Looks like we should all add a visual check of the piston interior to normal brake inspection and maintenance.
To the OP - You said that you had the dreaded "foot-to-the-floor" experience. Don't modern brake systems have two separate brake circuits? I've been thinking for years that there's one hydraulic system that brakes the left front and right rear wheels and another system that brakes the right front and left rear wheels - so in case something just like this happened you would still have brakes. Am I wrong?
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