Brake Fluid Color Differences Over Time

[wings&wheels]

Doing brake flushes on the fun fleet, my Fall 2-3 year ritual.

Same fluid (Castrol LMA/Advanced Performance DoT 4), same interval, roughly same mileage and use and different results; the P'cars fluid drains a very, very little bit cloudier cloudier and slightly darker than new, but the Lotus fluid looks like Pepsi... The Rovers and Triumph calipers' old fluid looks like the Porsches, but the drum brake cylinders fluid is darker as you would expect; longer stroke, exposed to more of the cylinder, etc.

My question is why the difference in results? Why is one application causing significantly more aging and/or contamination of the fluid? Thoughts from the crowd?

The Porsches and Lotus both have multi piston calipers, Porsche as Brembo calipers, the Lotus has AP, and see the same use. Only reason I can think of the the British still can't make an automotive seal

 

[Warstud]

Just change the fluid when you replace the brake pads. Siphon and Replace the brake fluid in the Master Cylinder and bleed the brake lines until the fluid looks clear after you change the brake pads and you should be good.

 

[wings&wheels]

Just change the fluid when you replace the brake pads. Siphon and Replace the brake fluid in the Master Cylinder and bleed the brake lines until the fluid looks clear after you change the brake pads and you should be good.

Thanks. I do, I do it every two to three years, but was wondering about the stark differences in the fluid condition in the two cars after the same interval and usage. I will be doing this more often in the Lotus.

Funny, IIRC the Lotus manual says to do brake fluid annually, which I thought was overkill. Maybe not...

 

[Hall]

Brake lines and hoses material

 

[Jetronic]

and clutch release if applicable. Major contributor to darkening fluid, where manuals get dark fluid and the same cars with automatic don't.

 

[supton]

Just change the fluid when you replace the brake pads. Siphon and Replace the brake fluid in the Master Cylinder and bleed the brake lines until the fluid looks clear after you change the brake pads and you should be good.

That seems like a long time, five years on fluid?

 

[Hall]

That seems like a long time, five years on fluid?

Most cars go a lot longer than that

 

[wings&wheels]

and clutch release if applicable. Major contributor to darkening fluid, where manuals get dark fluid and the same cars with automatic don't.

I would have thought the same, but the fluid bled from the slave looked almost new. Funny, the old Rovers and Triumph turn their new clutch fluid grey seemingly days from a flush...

 

[tnt_motorsports]

Most cars go a lot longer than that

^^^I agree. IMO most cars go to the scrap heap with the original fluid. The average person is not likely to change brake fluid. I’m also certain most garages don’t change fluid during a brake job. The shop I worked at ~25 years ago didn’t…

Just my $0.02

 

[Jetronic]

I would have thought the same, but the fluid bled from the slave looked almost new. Funny, the old Rovers and Triumph turn their new clutch fluid grey seemingly days from a flush...

The fluid in the reservoir always looks darker, there's just more for the light to get through, it's hard to see while bleeding though clear tubing.

And I'm sure it's not always the clutch system that darkens the fluid, but it often is. seperate circuits exist aswell, the clutch reservoir is almost always pitch black. I don't know or pretend to know why.

 

[Jetronic]

^^^I agree. IMO most cars go to the scrap heap with the original fluid. The average person is not likely to change brake fluid. I’m also certain most garages don’t change fluid during a brake job. The shop I worked at ~25 years ago didn’t…

Just my $0.02

The dealership I worked at didn't either, until shortly after I started there. Not due to me mind, but brake issues were getting more rampant. Now it's done every second service, which is typically after 2 years.

 

[supton]

Most cars go a lot longer than that

Indeed. My complaint was about doing with the brakes. My non hybrids go five years or more on brakes—yet to be seen on the hybrid, prob the same though, road salt ruins everything.

 

[Falcon_LS]

If it's DOT 4 fluid, I usually change it annually even if I don't put that many miles on it.

 

[Vercingetorix]

Lucas, The Prince of Darkness, has his fingers in more than just electrical parts.

 

[Fordiesel69]

Just change the fluid when you replace the brake pads. Siphon and Replace the brake fluid in the Master Cylinder and bleed the brake lines until the fluid looks clear after you change the brake pads and you should be good.

This does not work for all owners. Your procedure is spot on, but by the time some owners get enough miles for their brakes to wear, an entire decade or several could have passed by. I have 9 cars and I cant drive them all the same miles, so I replace brakes every 10-12 years. My '99 crown vic brakes lasted from 2005 all the way to 2017 which is a record high, and they had well over 60k on them all.

Every 3 years is best, and in some european states it is mandatory.