Brake fluid DOT 3, 4 and 5.1 question

[1993 Legacy]

Hello to all,

I was planning on chaning the brake fluid in my car. I have no idea when it was done for the last time as I purchased the car just recently. The fluid in the reservoir looks completely clean (like new).

 

Now here is the question

 

1993-1994 legacies use either dot 3 or 4, right?

 

I have read great things about dot 5.1 (mind you that is not dot 5 as that is a completely different fluid). What would be the best way to change the entire fluid in the system?

 

Go about bleeding it untill ... when?

 

How much fluid is there in the whole system?

 

Are there any downfalls if you use dot 5.1 in the car?

 

Thoughts, ideas, suggestions, procedures are more than welcome.

 

Thanks to all.

Best regards

 

Dusan

[1993 Legacy]

Just an addition. I can get some BENDIX SUPER+5 synthetic brake fluidwhich is a DOT 5.1 FLUID. It is reasonablz priced.

 

It says it meets the requirement of the following specs:

 

FMVSS 116 DOT 5.1 DOT 4 - SAEJ 1703 - ISO 4925 - NF.R. 12640 S.

 

 

What do you say?

 

Thanks and best regards

 

Dusan

[frag]

If the fulid is clear why change it? Usually (like that on my car at least) spent fluid (fluid that has absorbed moisture) becomes a lot darker.

Moreover if you start with clean fluid, it will be more difficult to judge when to stop bleeding cause there will be no color difference between old and new.

Just mu 2 cents.

[sasquatch]

If the fulid is clear why change it? Usually (like that on my car at least) spent fluid (fluid that has absorbed moisture) becomes a lot darker.

Moreover if you start with clean fluid, it will be more difficult to judge when to stop bleeding cause there will be no color difference between old and new.

Just mu 2 cents.

brake fluid draws water, water eats metal, eaten metal fouls lines, fouled lines decrease braking, no brakes suck.

[Setright]

Stick with a good DOT 4, like "Castrol Response". You will not be dissappointed, and won't have wasted money on 5.1. The difference in performance is not discernable on the street.

Replace it every 25-30k miles or two years.

[1993 Legacy]

Hi,

The reason to go for DOT 5.1 was that it is less hidroscopic (absorbs less water) and the place where I live is pretty humid.

 

I have to do it anyhow (it has probably been done sometime in the past but I do not know when) just to be on the safe side just as I am planning on changing all the fluids in the car (to play it safe).

 

The question is - how much fluid would I need for the whole system (total) ?

 

How do I go about making sure I have drained all the old fluid?

 

Correct me if I am wrong but all DOT 3, 4 and 5.1 are compatible. It is only dot 5 that is not compatible since it is of different composition.

 

Thank you.

Best regards

 

Dusan

P.S. One leter of the above mentioned DOT 5.1 fluid costs around 12 euros (cca. 14 USD). It doesn't really seem a lot for a procedure which one does once every year or two years, right?

[edrach]

Another vote for Castrol DOT 4; I live in the Seattle area (can you get much wetter than here?) and have never had to change the brake fluid in it's entirety in any Subaru I've owned over the last 5 years. I've only changed it that way when I've replaced calipers or did the disk conversion on the rear brakes. If you plan on changing it every two years anyway, stick with the Castrol.

[frag]

If the fulid is clear why change it? Usually (like that on my car at least) spent fluid (fluid that has absorbed moisture) becomes a lot darker.

Moreover if you start with clean fluid, it will be more difficult to judge when to stop bleeding cause there will be no color difference between old and new.

brake fluid draws water, water eats metal, eaten metal fouls lines, fouled lines decrease braking, no brakes suck.

Just wondering: how is this a reply to my post?

[Legacy777]

3, 4, & 5.1 are all compatible and interchangeable. The main difference between the 3 are the wet & dry boiling points & the hygroscopic nature.

 

Check out this page, it seems to have good info

http://www.vtr.org/maintain/brake-fluids.html

 

However, I thought Dot 5.1 was more hygroscopic then 4 & 3.

 

Either way, a good dot 4 or 5.1 fluid will work fine. If you're not racing, it doesn't matter.

[Legacy777]

brake fluid draws water, water eats metal, eaten metal fouls lines, fouled lines decrease braking, no brakes suck.

Actually, since the fluid absorbs the water and it's suspended in the fluid....it's not really a problem. The added water just lowers the boiling point of the fluid. However, if you boil the brake fluid, the water will then turn into steam, and you now have air & water in the brake system....that is not good.

 

Dot 5 fluid doesn't absorb water, so pockets of water can move/sit in the brake lines and cause rust like you mentioned.

[Hondasucks]

Just make sure you DO NOT under any circumstances either mix dot 5 (Silicone) and regular propylene glycol brake fluid (they are not compatible) OR run DOT 5 Silicone in a car with ABS! AND if you run DOT5, you must flush your brake system with denatured alcohol (Good idea when changing your brake fluid anyway, to get the moisture out.) You are actually supposed to change your brake fluid every 2 years or 24,000 miles since brake fluid absorbs water, which will lower its boiling point and make your car more prone to brake fade :-)