Should my brake fluid be that dirty?

[coopns]

Just looked the brake master cylinder and the fluid was fairly dirty. I think I have read here numerous times that the brake fluid/caliper doesn't go back up to the master (please correct me). So how does that master get so dirty? I usually just turkey baster it out every six months or so. Does that sound about right, every six months just clean it up?

 

[AlienBug]

Every six months sounds excessive.

 

[tomcat27]

brake fluid is alcohol based and is hydroscopic - meaning that its molecular structure absorbs moisture from the air - which turns it caramel colored. Once every two years should be sufficient, but you need in addition to turkey basting out the master cylinder, you need to bleed all four brakes to get clean fluid thru the lines and thru the cylinders.

 

[NHGUY]

Actually its Hygroscopic.Its always confused with "hydro" because that means water/liquid,buts its actually "Hygro"

 

[Towncivilian]

Originally Posted By: tomcat27
brake fluid is alcohol based and is hydroscopic - meaning that its molecular structure absorbs moisture from the air - which turns it caramel colored. Once every two years should be sufficient, but you need in addition to turkey basting out the master cylinder, you need to bleed all four brakes to get clean fluid thru the lines and thru the cylinders.

DOT3, DOT4, and DOT5.1 brake fluid is glycol-ether based, not alcohol based. DOT5 is silicone based and does not mix with the other DOT brake fluids, but also does not absorb moisture. The correct term is "hygroscopic", not "hydroscopic".

 

[coopns]

Would it or is it even possible to 'upgrade' to Dot 4 or 5 despite it calling for Dot 3?

And, it must help a bit to clean the cyliner does it? (Maybe just making myself feel good).

 

[bdcardinal]

DOT 4 or DOT 5.1 absolutely. DOT 5 is a no-go. Read the labels carefully.

 

[Astro14]

Turkey baster method is only removing the fluid from the master...so, at least half of the fluid is still in the lines and calipers/wheel cylinders...and that fluid still has moisture, dirt, etc.

If you want to keep it clean, flush it completely, through the lines and the calipers. The fluid in all of my cars (save the Packard...which has mechanical brakes) looks very clean for at least a year after flushing...very slight change in color (They get an bi-annual or annual flush per the Mfr's recommendation).

Think of it this way: would you change your oil by siphoning and replacing 2 qts out of a 5 qt sump and leaving the rest in there?

 

[SIXSPEED]

Bleeding/flushing the brake lines is fairly easy to do and only requires about three 12oz containers of brake fluid.

 

[GMorg]

Glycols are alcohols, compounds containing a hydroxyl group at a saturated carbon.

 

[mechtech2]

The 'dirt' is rubber particles from seals, and maybe some oxidation.
Brake fluid eventually mixes all over with a turkey baster 'flush'.
Some cars faster than others.

 

[Ken2]

DOT4 & DOT5.1 have slight chemical differences from DOT3 which gives them their superior wet boiling point. That chemical difference might react poorly with the artificial rubber components in certain brake systems. I haven't had a problem upgrading the fluid, but it might happen.

 

[CLeming]

Dont waste your time with doing the turkey baster type change. Either do a complete change or nothing at all. The reason I say this is moisture will slowly seep into and mix with the brake fluid in the brake lines causing corrosion throughout the entire system over time. This is no good for ABS pumps. Trace amounts of moisture gets in to the system through the rubber brake lines, plastic reservoir (even if its sealed with a diaphragm seal), and past the seals in the calipers/wheel cylinders.

 

[ac_tc]

This is another of these it isnt perfect but better than nothing
thing...
If you do it when you service your pads it will actually remove
atleast some grime out of the system. Pressing the pistons in will force oil back to the reservoir.
Ofcourse a correct bleed and using some fancy factor tool for
cycling the abs pump is better but some one has to do it also..

 

[Hokiefyd]

I would say that a turkey baster exchange in the master cylinder, and ONLY doing that, may cause more harm than good. As pointed out, moisture is the enemy of any brake system, and the small benefit you might get via clean fluid diffusion through the system is probably outweighed by the potential of introducing moisture and/or contamination into the system by the frequent opening and closing of the master cylinder.

I would advise to do a complete fluid exchange by:

1) Turkey-basting the old fluid in the master cylinder out with fresh fluid, so you have a volume of fresh fluid to start with.
2) Bleeding each line through the bleed screw at the caliper. Bleed each line until the fluid is decidedly clear. Keep the master cylinder full as you proceed, so you don't get air into the line.
3) Bleed each line in the order prescribed in the service manual or owner's manual for your vehicle. It's often RR-LR-RF-LF, but not always. For our cars, you actually start at the LF and work clockwise around to the LR.