Flushing Brake Fluid

[ChaosMaster]

Hey guys, I'm looking to change my brake fluid. A few simple questions, as it's been a while since I last did this. Does the engine still need to be running while I do the flush (for ABS reasons)? What's the difference between Super Dot4 and normal Dot 4 (cbf going to Honda for it, so I'ma drop by SCA for some castrol). Is there anything else I need bar Jack, stands and an empty bottle (and a extra pair of feet)? A DIY guide would be nice.

Edit: Is 500ml enough? Would have thought that the reserve was larger than that.

[EuroGraphite]

http://m.wikihow.com/Bleed-Car-Brakes

The link above is a good guide. Personally I think steps 2 and 3 arent really required. Remember to start at the corner opposite to the driver. Ie. rear passenger corner first.

Hth

[BigBen]

Step 2 will save you alot of time as you are bleeding / pushing new fresh fluid into the lines. Step 3 is required to minimise dirt cutting seals and clogging up the master cylinders / ABS module.

Buy at least 2 or more 500ml brake fluid. Brake fluids are so cheap just make sure you are using an unopen bottle.

[1.mile]

http://www.ozhonda.com/forum/showthread.php?11867-DIY-Brake-fluid-flush&highlight=brake+clutch

[EuroGraphite]

Only if he does it properly and does not let the fluid levels get too low. I normally let the fluid drain until it goes close to emptying the reservoir. Then fill it with fresh fluid.
More likely to dislodge when u shove some cloth in there. Just an opinion.

[ChaosMaster]

I've done it before, just a while ago. I should be safe. Although that last time was about 7 years ago and with a car with no ABS. Which is why I'm asking if I should leave the car on for the ABS to be running. Also, I can't find the diff between SuperDOT4 and DOT4.

[e240]

Super dot 4 is like dot 5.1

Some companies use Super Dot 4 to avoid customers confusing dot 5.1 with dot 5

[ChaosMaster]

Ah, so it's fine to mix and match? Cos Euro got 4 in them stock. Not that I track my car, but it can't hurt to have a better fluid in it can it?

[trism]

I plan to use dot 4 to flush completely and then top up reservoir with super dot 4.

[androo]

Different boiling points...

[EuroGraphite]

I plan to use dot 4 to flush completely and then top up reservoir with super dot 4.
Thats a bit of a waste...i mean, the higher performance fluid is in the reservoir while a lower spec fluid is in the lines, doing the actual work. Brake fluid doesn't circulate.

CM: A tendency when you go higher spec brake fluid (e.g. dot 5) is that they absorb moisture more readily compared to a lower spec (dot 4). This tendency means you should change the fluid more often. Day-to-day driving, you will not notice any difference in the two fluids.

[ChaosMaster]

Thats a bit of a waste...i mean, the higher performance fluid is in the reservoir while a lower spec fluid is in the lines, doing the actual work. Brake fluid doesn't circulate.

CM: A tendency when you go higher spec brake fluid (e.g. dot 5) is that they absorb moisture more readily compared to a lower spec (dot 4). This tendency means you should change the fluid more often. Day-to-day driving, you will not notice any difference in the two fluids.

Thanks Graphite, I would rep you more if I could.
Yeah, I figured I wouldn't notice any difference. It's just that I figured that if I used Dot5.1 which has a higher boiling point, it would be able to take more water than Dot 4. If you get what I mean. E.g Dot 4 boiling point dry is 230c, but with 3.7% water it's 155c. Dot 5.1 dry is 270c and wet is 190c. Assuming we have to change brake fluid when it's boiling point drops to 120c, then Dot 4 would be able to hold 5.42% water before it reaches this point where as Dot 5.1 would need 7%.

Of course, that's not really how we should calculate it. And if higer spec absorbs moisture more, then wouldn't Dot 3 be even safer?

[EuroGraphite]

I got these following tidbits..

First of all, it's important to understand the chemical nature of brake fluid. DOT 3 brake fluids are mixtures of glycols and glycol ethers. DOT 4 contains borate esters in addition to what is contained in DOT 3. These brake fluids are somewhat similar to automotive anti-freeze (ethylene glycol) and are not, as Dr. Curve implies, a petroleum fluid. DOT 5 is silicone chemistry...
DOT 4 glycol based fluid has a higher boiling point (446F) than DOT 3 (401F), and both fluids will exhibit a reduced boiling point as water content increases. DOT 5 in its pure state offers a higher boiling point (500F) however if water got into the system, and a big globule found its way into a caliper, the water would start to boil at 212F causing a vapor lock condition [possible brake failure -ed.]. By contrast, DOT 3 fluid with 3% water content would still exhibit a boiling point of 300F. Silicone fluids also exhibit a 3 times greater propensity to dissolve air and other gasses which can lead to a "spongy pedal" and reduced braking at high altitudes. from http://forum.roadfly.com/threads/12527796-Can-someone-comment-about-Dot-3-vs-Dot-4

I think dot 4 is a happy medium. :)