Brake Fluid

[Jemjem]

Hi

 

thought dot 3,4 and 5.1 are interchangeable and only dot 5 is special?? Now using 5.1 needs special hose?

 

jemjem

[Smhomie]

No, you do not need special hoses per se. DOT 3/4/5.1 are glycol based, DOT 5/6 are silicone based. DO NOT MIX Mixing will cause the seals at your master cylinder to break and leak over time (into your booster)... brakelines will swell due to corrosion... Pls throughoutly flush out ALL 3/4/5.1 before replacing with 5/6 and vice-versa

 

Silicone based fluids are not hygroscopic ie. do not absorb ambient moisture. However, trapped moisture (water) will degrade brake effectiveness by corroding the lines and caliper seals.

 

Glycol based fluids are hygroscopic, they absorb moisture from the atmosphere. This degrades the fluid and may cause boiling due to lowered temp tolerances.

 

How to tell? You start off your DOT 3/4/5.1 as a clear liquid. As moisture contaminates due to glycol nature, it 1st turns from clear to light gold... then honey gold... then brown.... then dark brown/black (this is the worst). This is the easiest visual indicator of moisture absorption taking place.

[Yuan]

How true this is.

 

Mine turned from transparent to light gold already and that is just in a couple of months only.

[Jemjem]

Icic.. cos one of the bros here replied that using dot 5.1 hose needs to be upgraded....

 

Thanks man for the clear explaination...

 

jemjem

[Eyke]

no need but it's good to change to steel-braided hoses nevertheless.

[Garlic]

Great clarification.

 

What is the right way to replace brake fluid?

 

Recently changed mine this is what I observed,

 

Mech A: started engine and sat in car

Mech B: went round all 4 corners with a vacuum bleeder

 

B told A to depress brake pedal as vacuum bleeder was activated, pedal pressure was eased off just before deactivating bleeder, the procedure was repeated four times and brake fluid reservoir was constantly filled.

 

The job was then completed by filling reservoir again.

[Jemjem]

Me concern with workshop doing tis brake fluid change too. Any recommendations of a workshop that will do a proper job? But of cos not one tat "chops carrot"

 

jemjem

[Smhomie]

What you have described as bleeding procedure is correct

 

However point to note : Don't stinge on the brake fluid just because its being bled out and wasted. Use more than 4 full pumps to the brake pedal to flush out the old fluid. Use a cleaned out Coke 1.5 PET bottle to contain the outgoing fluid and observe the colour. Same for all 3 other bleed nipples.

 

Whole procedure if done properly should use about 2 liters worth of new fluid. Don't listen to the mechanic who uses 500ml and says that it is enough... Sometimes people err on the context that they want to save costs

 

Remember you still have a master cylinder reservoir which holds a fair bit of fluid just before the booster pump + ABS block valves

 

Hope this helps

[Mercuri]

i read somewhere that you can use multimeter to check the moisture content of the fluid. i wonder if this method can work as most would recommend using refractometer or some litmus paper kind of strip.

 

if this multimeter method can work then would be good. But wonder how to test? any idea?

[Yuan]

I can affirm that this is the correct method to bleed. Recently I change my brake hose and the mechanic did the same for my ride.

[Karie]

just read the label for wet boiling point and get the brand with the highest.

 

Specifications: Minimum Boiling Point 260

[Darkblue]

Where to buy ? How much ?

 

Don't have this brand of brake fluid ma...

[Jemjem]

Can get from carefour or giant.. not sure if the price went up. was $9.90 i think...

 

jemjem

[Yeobh]

Yes , this method is used very much earlier before the introduction of analsyer to test moisture content. Moisture content can be determined either by boiling ( highly recommended by SAE & ISO )or measuring the amount of DC volt allowed to pass through the brake fluid. The lastest method is using a refractometer but the instrutment has limitation. Litmus paper testing is simple but expensive overtime and the test result is very subjective.

 

You will need a digital voltmeter, set to the lowest possible reading available. Place the positive probe into the brake fluid reserviour and the the negative probe to a good ground ( chassis )The reading is is milivolt ( forgetten the voltage rule of thumb reading guid line for good, fair and bad)

 

Hope this helps

[Speddevil]

Bro any workshop to recommend to do the bleeding procedure for brake fluid?

[Mercuri]

Hi Yeo,

Thanks for your reply!

 

I wanted to get the refractometer but it is too expensive an instrument to purchase. i guess i just have to try out using a newly opened bottle of brake fluid and try to get a baseline from there.

Edited September 2, 2008 by Mercuri

[Yeobh]

Yes depending on your level of testing.

[Askyway]

how abt manuel transmission