Brake line rot

[Claud]

I don't see how a brake line can rust from the inside out. Sixth grade science lessons taught me the iron need air and water to make it it rust. Enough air in a line to allow this would mean effectively no brakes in any part of the system incorporating such a line.
Replacing brake lines with copper/nickel tubing has been a mainstay of uk vehicle repairs for decades. It doesn't rust, is easily worked, and has to conform to a minimum burst pressure rating. I have seen it used to jury rig a diesels engine with a broken injector line on occasions.
I'm sure the tubing sold as replacement brake line in North America must meet a similar requirement.

Claud.

 

[supton]

Originally Posted By: Claud
I don't see how a brake line can rust from the inside out. Sixth grade science lessons taught me the iron need air and water to make it it rust. Enough air in a line to allow this would mean effectively no brakes in any part of the system incorporating such a line.
Replacing brake lines with copper/nickel tubing has been a mainstay of uk vehicle repairs for decades. It doesn't rust, is easily worked, and has to conform to a minimum burst pressure rating. I have seen it used to jury rig a diesels engine with a broken injector line on occasions.
I'm sure the tubing sold as replacement brake line in North America must meet a similar requirement.

Claud.


Dunno. What I do know is that, on my 1999 Camry, I did a brake flush. Probably the first time that car has ever had brake fluid changed. So 17 year old -ish fluid. It was green. I could easily tell when I had new fluid at the bleeder!

I forget now where the green is from; someone here on BITOG told me. From the inside of the line? Wherever it was from, and however it corroded (oxygen or otherwise), it clearly did.

 

[SHOZ]

On my '97 Taurus the rear brake lines rusted out. Tucked up on top of the gas tank and no way could they ever be washed off. So the salt ate them away even though I had tried to cover them in a spray grease. And under the drivers seat they had a plastic shield over the lines but this too just trapped the rust.

Ford in it's wisdom would encased parts of the line that were susceptible to impact damage with plastic. These parts never failed.

Green is from copper.

 

[Trav]

Originally Posted By: Claud
I don't see how a brake line can rust from the inside out. Sixth grade science lessons taught me the iron need air and water to make it it rust. Enough air in a line to allow this would mean effectively no brakes in any part of the system incorporating such a line.
Replacing brake lines with copper/nickel tubing has been a mainstay of uk vehicle repairs for decades. It doesn't rust, is easily worked, and has to conform to a minimum burst pressure rating. I have seen it used to jury rig a diesels engine with a broken injector line on occasions.
I'm sure the tubing sold as replacement brake line in North America must meet a similar requirement.

Claud.

Its called dissolved air. Glycol based fluids being hygroscopic readily absorb moisture and with it dissolved air.

Quote:
This is not a specific DOT call-out, yet it is critically important to racers and enthusiasts. It is listed in
SAE J1705, Appendix A, A.2.2.8, under the heading, "Air Solubility." Here it states, “Air Solubility – It
has been reported that dimethyl polysiloxane fluid, which is a major part of silicone-based, low
water-tolerant type brake fluids can typically contain dissolved air at a level of 16% ±3% by volume
at standard temperature and pressure. This compares with a typical level of 5% ±2% by volume of
dissolved air for glycol ether based type fluids. An increase in brake pedal travel may be
experienced under severe operating conditions, especially at higher altitudes and high temperature
conditions."
"The term “dissolved air” (air absorbed from the atmosphere) should not be confused with the term
“entrapped” or “free air” since their effects on brake system performance can be entirely different. Air
that has been absorbed from the atmosphere does not result in an increase in fluid or system
volume, whereas entrapped air or free air does occupy system volume and can be easily
compressed when force is applied to the system.