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Brake Fluid

Use this forum to discuss car maintenance, building track cars, and modifications

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laserman21
Posts: 5
Joined: Fri Oct 31, 2008 6:37 pm

Brake Fluid

Post by laserman21 » Thu Nov 26, 2009 9:12 pm

Anyone know why Porsche recommends changing the brake fluid every two years? I have a 2003 996 C4S with 12,150 miles and after 7 years of no brake fluid change, I got worried enough to change it myself today. It was as clear as the new fluid I put back in. I was told by a Porsche salesman that the fluid disolves the calipers and turns to a creamy consistency after three or four years and the brakes become non functioning. Doesn't make sense to me. Some cars go 50 years without new brake fluid.

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David Leong
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Location: Lafayette, CA
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Re: Brake Fluid

Post by David Leong » Fri Nov 27, 2009 9:36 pm

For street use, brake fluid can last a long time. The salesman was giving you a line, and didn't know what he was talking about.

What does happen to brake fluid after about a year, is it accumulates enough moisture to lower the boiling point. It does not lower it enough to boil in street use, because it is difficult to get brake fluid hot enough on the street, however, take it to the track, do about 3 or 4 stops from 100mph plus, within a few minutes, and it may not last 3 laps in that condition.

Bottom line, you change the fluid to get rid of the accumulated moisture, keep the fluid within spec, and prevent moisture-related wear and tear on the components. For track use, 1 year, or even every event, is common.
David Leong

laserman21
Posts: 5
Joined: Fri Oct 31, 2008 6:37 pm

Re: Brake Fluid

Post by laserman21 » Sat Nov 28, 2009 9:55 am

Thanks for the quick reply.

Zone7Rep(Larry Sharp)
Posts: 389
Joined: Thu May 12, 2005 7:49 am
Location: Livermore Ca

Re: Brake Fluid

Post by Zone7Rep(Larry Sharp) » Mon Nov 30, 2009 10:50 am

Brake fluid is Hydroscopic .. which means they absorb water over time .... which can corrode any metal bits in your brake system ..then it all sticks together .. better safe than sorry .. I never heard of a car going 50 years with out having the fluid replaced ..
1993 RS America
Grand Prix White
Car #6

1974 911 Carrera (resides in Australia)
Light Yellow

1974 914-6 GT (resides in San Luis obispo)

1987 944 turbo (location unknown)

1979 911SC(Hummers have it)

1972 911T (location unknown)

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Tom Weber
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Joined: Mon Jun 06, 2005 2:03 pm
Location: Half Moon Bay

Re: Brake Fluid

Post by Tom Weber » Sat Dec 12, 2009 12:36 pm

Old brake fluid can turn into a white creamy mess which can clog the lines. I've always wanted to get my hands on some to do a water content measurement as I think it comes from just too much water getting into the fluid. It has nothing to do with "dissolving" the calipers or anything else. The water can allow corrosion in the non-rubber or non-stainless steel parts (like inside the calipers).
Tom Weber
964 GTL/GT3 (Tom's Turtle, #54)

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