Brake Fluid Flushing...how often?

project_timemachine · Tue Jul 25, 2006 11:41 pm

How often do I have to replace my brake fluid...every six months, yearly, etc? I live in the tropics so the humidity is off the scale. I noticed that the right front disc brake is beginning to get stuck, but when I drive the roadster, little by little, the brake frees itself. I'm not sure if the brake fluid is contaminated with water, but I had it replaced six months ago. Any thoughts would be greatly appreciated. Thanks

spyder · Post by **spyder** » Wed Jul 26, 2006 2:56 am

I am in San Antonio TX, (humid) and I do mine yearly and I use silicone or dot 5 juice. Dot 5 is costly but have you priced the cylinders recently!

project_timemachine · Post by **project_timemachine** » Wed Jul 26, 2006 4:57 am

Thanks for the advice! The dot 5 fluid sounds like a good decision. What do I need to do or replace in the brake system to be able to use dot 5 brake fluid? Or do I just flush the old fluid and just pour in the dot 5? Thanks!

spyder · Post by **spyder** » Wed Jul 26, 2006 11:01 am

I drained the old fluid than blew out the residue with air.

Redtail · Post by **Redtail** » Wed Jul 26, 2006 11:07 am

some good info on brake fluid:
http://www.bobbyarchermotorsports.com/pdf_2848_2.pdf

something to consider is that silicone fluid won't absorb water, so if moisture gets into your brake line it will pool somehwhere and rust the line out from the inside.

A good quality DOT 4 (I like ATE) changed once or twice a year will work for almost everyone.

project_timemachine · Post by **project_timemachine** » Wed Jul 26, 2006 7:52 pm

That link was an eye-opener Zack...thanks for the link! I think I found my problem...the reservoir cap is not sealing properly! I really appreciate the info!

spyder · Post by **spyder** » Thu Jul 27, 2006 3:58 am

Read the article. Dot5 won't absorb water and water goes to the lowest point. If a fluid will absorb moisture wouldn't that contaminate all of the brake circuit. I have been using dot5 at least 10 years and have had no problems. Water on the bottom or everywhere, It still boils down to "how often do you flush"!

Redtail · Post by **Redtail** » Thu Jul 27, 2006 11:42 am

spyder wrote:Read the article.

I did read the article. Did you?

From the link above:

Water Absorption and Corrosion
What most donÃ¢â‚¬â„¢t understand is some degree of water absorption is desirable. DOT 3-4-5.1 glycol based fluids will readily absorb water. Like many other things, this is a good thing (to a degree) as your brake system does contain water and there is nothing you can do about it. However there are corrosion inhibitors in the brake fluid formulation that handle this. Since the inhibitors are gradually depleted as they do their job, glycol brake fluid, just like antifreeze, needs to be changed periodically. The one caveat to this is the DOT 5 silicone fluids, not being water miscible, must rely on silicone (with some corrosion inhibitors) as a barrier film to control corrosion. Water is not absorbed by silicone as in the case of DOT 3-4-5.1 fluids, and will remain as a separate globule sinking to the lowest point in the brake system (typically the caliper), as water is more dense. The other issue with this is now you have water coming in contact with the metal components of the brake system. This can actually exacerbate the corrosion issue.

But i agree with you, no matter what DOT spec fluid you are using, it is most important to flush often.

spyder · Post by **spyder** » Thu Jul 27, 2006 12:08 pm

No intention of starting a flame war but who is this guy and what makes him the final authority on this subject. And once again, yes I read the article but I draw different conclusions. #1, it won't absorb water so if I am not pouring water into the master cylinder how is it going to get in there. #2, I have been using it over 10 years with no problems ... theory vs. experience.

Cheers!

P.S. When I went to silicone all brake components except the lines were new.

Redtail · Post by **Redtail** » Thu Jul 27, 2006 4:18 pm

sorry man, I just bristled at that. That's the problem with the internet, you can never tell the mood of other posters.

Anyhow if you've had good experiance with DOT 5 great. I think any of the quality fluids will work well so long as they are changed frequently.

project_timemachine · Post by **project_timemachine** » Fri Jul 28, 2006 1:52 am

Thanks for the info guys... I did learn a lot about brake fluids and their characteristics. I think I'll stick with DOT 3/4 for now since I don't have the money to overhaul the brake system. When I get the budget I guess I'll try out the DOT 5 since 10 years of experience is not to be unaccounted for. Did brake feel improve when you changed to DOT 5? Thanks!

spyder · Post by **spyder** » Fri Jul 28, 2006 3:22 am

Change the feel? Naaahhh.... I try not to use the brakes ... they just slow me down!

To be serious now. With regular fluid the cylinders were pitted and leaked. Understand I did not obtain this car new. I attempted to hone them and compensate for the increased diameter. It was hit and miss. Sometimes they would work ok than they would leak. As the car consumed more and more of my surplus cash, the brake system got replaced and I chose to use silicone specifically because it did not absorb water.