namwens

Hi guys,

Im wanting to do a complete flush of my hydraulic system. I do not know what the brake fluid currently is in the car hence why i want to change it completely and leave no remains of the old fluid.

What is the best way to do this?

I was under the impression that you could just bleed the old fluid out by simply filling up the master with fresh fluid until it looks like the old fluid is all bled out. however, if the fluid mixes together (as it will) i will most likely never get all of the old fluid out of the system.

what is the best method to ensure the system is completely 100% clear of the old fluid? Vacuum bleeding? flushing with metho? a method im unfamiliar with? or just keep bleeding with the new fluid till the old stuff is gone? im open ears here so please tell me any methods or suggestions.

Smike

iTrader: (8)

You just bleed until you see the new fluid. Why do you think you have to have 100% change? The Motive bleeder is great for this job.

namwens

last track day the fluid boiled and i had no brake pedal. that is why i want to get rid of the old fluid 100%.

isn't the oild fluid simply going to fix with the new fluid?

Smike

iTrader: (8)

You will flush out most of the old fluid. Otherwise, you will introduce air into the system or waste a lot of money on good fluid.

And boiling is a result of the fluid properties and brake setup (pads/rotors/ducts). I would look into the Amsoil DOT4, never failed me.

What is your brake setup?

cfdfireman1

iTrader: (11)

You can get some sort of a vacuum device and suck as much of the old fluid out of the reservoir before you start.
+1 for the motive power bleeder.

TommiM

iTrader: (19)

You can use a power bleeder and just flush through a ton of brake fluid, then you will most certianly get all the old fluid out. You can also just open the caliper bleeders and pump until theres nothing but air, but then your gonna have to bleed it until all the air bubbles are out. Not a big deal, just need to make sure you have a enough fluid on hand.

Jeff_Jeske

iTrader: (66)

I have been using a Motive Powerbleeder to bleed brakes for a couple years now.... Last week after bleeding the brakes I decided to flush the clutch as well. BAD IDEA.

I just slightly opened the bleeder and fluid came pumping out like normal... but faster than normal. It pushed so much fluid that the motive unit could fill the master fast enough and I ended up pumping air into the system. Maybe I opened the bleeder too much... maybe I didn't have enough fluid in the MPB but I ended up having to call a buddy to do an old school bleed on that pig.

I guess what I'm saying is if you plan to use the MPB to do the clutch be careful.

TommiM

iTrader: (19)

Its easier with a MPB than my Blue Point cause at least you can see the fluid level. So long as you pump it up before you open up any bleeders and have enough fluid in the container you should be ok.

Chris_B

Maybe I'm still old school, but I highly recommend bleeding manually. Yes, it does take a few people but here it why I do it that way:

We spend extra money on high-end brake fluid that has higher boiling point, a lower moisture content and less dissolved air (unlike the cheaper fluids) since it is packaged in a nitrogen environment (no oxygen). We then want to pour this liquid gold into a canister and pressurize it with ambient air, containing oxygen and moisture (humidity)? Our clean, fresh, dry brake fluid will readily absorb the air and moisture, but we would rather force it in just to make a point? If we do, we can now take a Sharpie out and line through the boiling point rating on the bottle label as it no longer applies. Maybe this works for low-cost DOT3 and DOT4 fluids, but there is no way I will do this for the more expensive DOT4, DOT5.1 or racing fluids.

There are power bleeders that have bladders separating ambient air from the fluid, but they are expensive enough to take away from the parts budget that is earmarked for stuff I would rather bolt on the car. Instead, grab a few friends/kids/neighbors/dogs/whatever and do a flush. It's not very exciting, but if you supply a few beverages they might be willing to come help again when the next change is due in two years. I just tell my kids that brake bleeding is one of the reasons we agreed to have them and continue to occasionally feed them (OK, at least when my wife is not around!).

We all do realize that the reason vehicle manufacturers recommend a 2 year change cycle is that air and moisture that gets absorbed in the brake fluid -- being pulled in through the rubber brake lines (another argument for stainless steel lines) and M/C reservoir cap -- sufficiently reduces the integrity of the brake fluid to the point of becoming problematic, right?

Chris

TommiM

iTrader: (19)

The brake fluid is going to encounter air regardless, during the bleeding process. As you pour out your liquid gold into the brake fluid reservoir, its going through air before it lands in the reservoir. Now is the question, do you close the reservoir as you bleed the system? You just sealed the cap down, and in the process you sealed in the little bit of air that was left in.. Unless you tap in a line where you can pull a vacuum in the brake fluid reservoir, your going to trap in air every time you open the brake fluid reservoir as you go through the manual bleeding process. Point is, power bleeders are not introducing anything to the brake fluid to diminish its boiling point anything significant. If brake fluid was that sensitive we would have to flush it out every month. Yes it absorbs moisture from the air immediately upon contact with the air, but its not a very large amount where using brake bleeders are an issue.

Chris_B

I understand your reasoning, but lab tests prove otherwise. Encountering air at atmospheric pressure is substantially different than at 10-20 PSI over atmospheric. It forces the fluid to dissolve more air and moisture, for which great expense is undertaken at the chemical plant to avoid. After bleeding, the fluid is never exposed to additional pressurized air or water, only what is pulled in over time through rubber brake lines and the duck bill valve or diaphragm in the M/C cap. Since the typical moisture absorption rate in average climates is about 1.8% per year, we can get away with it for a while. But why start right off worse than what we paid for?

Yes, many people use pressure bleeders with no perceived issues -- that's fine. However, facts are facts. It makes no sense (scientifically speaking) to use a pressure bleeder without a diaphragm on the better fluids, which is one of the reasons you won't see them in the paddock at professional racing events. Another is the potential for internal cavitation (flash boiling even at room temperature) which can happen when pressurized fluid is forced through small orifices and rapidly expands on the other side, which is a separate topic that pertains more to multiple piston, fixed calipers.

Chris

fueler11

I bleed manually, but would use a power bleeder if I had one. Something to think about, but isn't a problem on well maintained cars is this. Over the lifetime of the master cylinder, it works within a given range of travel, I'm talking about the movement of the piston and seal assembly in the bore. Over time and with a collection of moisture and contamination, the end of the bore is probably a bit rusty, at least not smooth, and has goo (technical term) in there too. Now it's time to flush the system and the pedal is repeatedly pushed down to the floor. Pushed through a possibly pitted or rusty master cylinder bore. In my opinion this could reduce the life of the seals, requiring replacement of the cylinder sooner rather than later.

Of course, it's not going to last long anyway if in the shape I described above. Plus on a car like these with much better brakes than a civic, the brake systems are treated better by their owners anyway. Just something to think about.

But, if using a power bleeder, the pedal would never hit the floor, the master cylinder seals would never meet any pitted cylinder walls or goo that might be in the bottom travel of the master cylinder.

huevosrancheros

iTrader: (14)

Check out the howto section

jvb6806

iTrader: (3)

i use two different colored fluids if i am going to do a full bleed. either ATE super blue DOT4, ATE amber, or the amber motul700. that way you know it is all out.

i will use a vacuum bleeder to do most of the work and then go back to the manual bleed to double check.