I have a 2003 Jetta TDI with 40000 miles, the manual says to change the
brake fluid every two years regardless of mileage. Is this really necessary
or is there mileage amount it should be changed at? thanks

when in doubt, I suggest you follow the manufacturer's advice as I do.
I think the failure mechanism is a matter of time, not a matter of
miles driven.

I found this text on justbrakes.com (no affiliation, just did a google
search)

" Brake fluid is formulated to tolerate moisture absorption, control
rubber expansion and corrosion, and acts as a lubricant. It also must
not boil or freeze in brake systems over a wide range of operating
temperatures. The level is checked occasionally, but very seldom is
brake fluid completely replaced unless the vehicle's braking system
undergoes a major overhaul. Most technicians know that brake fluid
deteriorates with age due to moisture and contamination. DOT 3 and DOT
4 brake fluid are polyglycol based. This glycol ether blend of fluids
is "hygroscopic" which means it attracts and absorbs moisture. This
process takes place every time you take the cap off the container or
check the fluid in the master cylinder reservoir. Moisture is even
absorbed through microscopic pores in rubber seals and hoses in the
brake system. Also keep in mind when you use your brakes, heat is
generated at the friction contact points. As your vehicle sits, your
brakes cool down. Therefore, over a period of time the heating and
cooling action of your brake system will condense moisture in the
closed hydraulics system. DOT 3 and DOT 4 brake fluid will absorb that
water and keep it from effecting hydraulic components and helps prevent
or at least slow down the corrosive effect. Even though brake fluid
absorbs moisture, it cannot continue to absorb it indefinitely, which
is why it is recommended that you flush the system and refill with
fresh brake fluid once a year or every 12,000 miles"

btw, once a year is not necessary... this advice is coming from a
company that provides this service so you figure their motives.

If you do this service, make sure you remove as much old fluid as you
can get from the reservioir before you start. You do not want to push
dirty fluid into your braking system. I think you may be able to get
this done for under $40 and that would be money well spent. If you
really want to do this yourself, I suggest you purchase the Motive
brake bleeder from germanautoparts.com. (this what I did)

good luck!

Mark

Conventional wisdom: change the brake fluid every 2 years, as the fluid
tends to absorb moisture over time. This can corrode system components and
lead to premature deterioration of the braking system. The absorbed moisture
also tends to reduce boiling point of conventional brake fluids, which could
lead to fluid vaporization under severe use. Hydraulic brake systems depend
on the relative "incompressibility" of liquid brake fluid to transmit
braking forces within the system; gaseous fluid is much, much, much, more
compressible and will not transmit the loads effectively.

In my experience, this is very conservative advice, but brake fluid and an
hour or two of labor every two years is cheap. Your life, and that of your
passengers and other drivers, is priceless.

--
Kent
1987 VW GTI 8V, original owner, 222,000+ miles


"Mike Oxbig" <YrUfat (AT) slob (DOT) com> wrote

"Mike Oxbig" <YrUfat (AT) slob (DOT) com> wrote

I'd follow it. With my '91 GTI I didn't do that and ended up having to get
a new master cylinder at 110K miles. Brake fluid flushes aren't that
pricey. Ever since that M/C change I've followed that routine.

"Mike Oxbig" <YrUfat (AT) slob (DOT) com> wrote

Mileage is much less relevant than age on Brake fluid - it absorbs moisture
over time & 2 years is the limit on pretty much any fluid/car. Change it & I
think you'll find you have a much firmer pedal & better brakes afterwards.

I.

Mike Oxbig wrote:
With brake fluid it needs to be replace, not based on any wear factor,
but rather to the fact it absorbs water. That is why you should never save
brake fluid after the can is opened. Water in brake fluid can be very
dangerous and also can damage brake parts (even more so with ABS)

--
Joseph Meehan

26 + 6 = 1 It's Irish Math

It's like the rest of the VW manual... it's just there to take up space and
waste paper, ink, printing costs.

"Mike Oxbig" <YrUfat (AT) slob (DOT) com> wrote

I understand you point, I do follow the manual. Two years just seemed
kinda early. I'll have it down while they are fixing my heated seat since
the element wants to melt my leather in a spot. Thanks


"Woodchuck" <stv_euroski (AT) yahoo (DOT) com> wrote

Sarcasm's not going to do this guy any good, especially since the question
he asks is a good one, and there are many common misconceptions regarding
recommended service intervals. Are you here to educate these folks and help
them with their problems or to shame them into mindlessly dropping their
cars off at their nearest VW dealership every few weeks for unneeded service
and a wallet-ectomy?

There is no question in my mind that a little well-applied common sense and
hard-earned experience will allow one to extend the manufacturer's
recommended service intervals without affecting the car's longevity or
sacrificing safety. I wouldn't be so naive to believe that everything in
the VW manuals are based on solid technical requirements flowed down from
engineering. More often than not, fear of liability drives manufacturers to
be very conservative regarding service intervals. And when shorter service
intervals undoubtedly boost dealer profits, don't think that the strong
dealer lobby (akin to organized crime IMHO) doesn't do their best to keep
recommended service intervals as short as possible.

--
Kent
1987 VW GTI 8V, original owner, 222,000+ miles


"Woodchuck" <stv_euroski (AT) yahoo (DOT) com> wrote

Mike Oxbig wrote:


You bet it is.

Brake fluid is hygroscopic, which means it WILL absorb moisture from the
air, and the result is that
your brake system will corrode internally.

CHANGE your brake fluid, every 2 years, or save up for a rebuild of your
brake system.