Brake fluid flush question: how much fluid should be extruded from the master cylinder reservoir? (1 Viewer)

[lx570gogogo]

I’m going to do the brake fluid flush next weekend, and I watched a few videos and posts about how to do it. I plan to do it in the tradition two-person way. The very first step is to use syringe to extrude the old fluid from the reservoir and fill with the new one. My question is how much should I extrude? Some people said only get it down the minimum line and some people said get out as much as you can. If only making it down to the minimum line, doesn’t the new fluid and old fluid will be mixed together?

 

[gasman4u]

Without having done the LC myself, I can say in other cars (assuming the car is off), I will get as much as I can out of the reservoir first and then add new. Yes, you will mix some fluid, but ideally you will bleed that stuff out and you will see the color change with bleeding. If you have techstream, this supposedly makes it MUCH easier and cleaner to do with the brake booster handling the pumping. But again, I haven't done it and don't have the link to show the inevitable mud hive-mind resource to reference. Good luck and let us know what you did/learned!

EDIT - Here's some helpful threads:

Brake Bleeding with Techstream

Thought this was something potentially useful for those of us with access to Techstream. So many ways to bleed brakes, just adding this one to the tool belt. Seems like an efficient way to push a higher volume of fluid so may be a good option for a full flush, especially when time is short.

forum.ih8mud.com

sequence:

What is the brake bleed sequence for 200?

Just picked up a 2010 LC and baselining my fluids. Can someone tell me the brake bleed sequence for a 200 series? I am assuming PS Rear, DS Rear, PS Front, DS Front. Thanks!

forum.ih8mud.com

another bleeding post bookmarked (2016+ MY in case that matters):

Brake master cylinder/bleeder valve method?

Looking at replacing the front and rear brake pads and rotors this weekend. This is going to be my first brake pad/rotor replacement job on my 200. Originally, I planned to just pull the cap off the master cylinder to push the pistons in, vs opening the bleeder valve. Am I going to cause damage...

forum.ih8mud.com

 

[TimCFJ40]

Draw as much out of the reservoir as you can. Then replace with clean fluid. Flush at each wheel until you get clean fluid at the brake. Don't let the level in the master cylinder go low enough to draw air into the master cylinder. You can go below low, but not too far...

 

[RT Cruiser]

I've changed the brake fluid twice on my 2008. I'll be doing it again this week when I change the rotors/pads. I didn't suck out the existing fluid in the reservoir because I didn't have a tool that would have helped. Not a bigge cuz the fluid will move quickly to the bleed valve as you pump the brake pedal. A tool would have saved me, perhaps, a few minutes.

There is a proper sequence:
1) Front right
2) Front left
3) Rear right
4) Rear left

I use Dot 4 instead of 3 because 4 has a higher boiling point. Do not use Dot 5 unless your system specifies Dot 5 because it has silicates in it that can damage the braking system. Dot 4 and 3 are (mostly) compatible. If your manual specifies Dot 3 and you move up to Dot 4, don't ever go back to Dot 4... keep it consistent going forward.

I use the method of putting a hose on the bleeder valve into a plastic container filled with old brake fluid or water to keep air from moving upward into the brake line. Pump the brakes and make sure the reservoir has plenty of fluid.

If your fluid is old enough, you'll see when the new fluid comes out of the bleeder valve. I get 3 of the 1 qt Prestone bottles because I usually use about 3 qts in the process.

I credit @Taco2Cruiser for some of this information and helping me in this process.

 

[marques]

I’m going to do the brake fluid flush next weekend, and I watched a few videos and posts about how to do it. I plan to do it in the tradition two-person way. The very first step is to use syringe to extrude the old fluid from the reservoir and fill with the new one. My question is how much should I extrude? Some people said only get it down the minimum line and some people said get out as much as you can. If only making it down to the minimum line, doesn’t the new fluid and old fluid will be mixed together?

These trucks have a huge brake fluid reservoir. You can easily remove at least 1/2 quart. As others have said, try to get as much out as you can. If you can see exactly where the master cylinder gets the fluid from, you can start bleeding the rears (just lightly pressing the brake pedal with the ignition on and a bleed nipple open) until the fluid drops to just above that point. Just keep in mind there may be some internal partitions that may keep the front fluid level at some higher point while the fluid for the rear brakes keeps dropping (and vice versa). You definitely don't want to empty the reservoir to the point the master cylinder draws air. After you're satisfied you got as much old fluid out as you can, dump as much new fluid as it will take (could be a whole quart) and start flushing.

And you don't really need two people: just use some clear tubing that fits tightly around the bleed nipple and position it to drain into some container. Open the nipple about 1/4 to 1/2 turn and (in the case on the rear brakes), just press the brake pedal very lightly with the ignition on. The ABS pump will push the fluid for you. In the fronts, the ABS pump won't help you, so you will need to pump the brakes repeatedly the old fashioned way (at least 10 full strokes for the 1st nipple, then at least 5 more for the 2nd nipple on the same caliper). Keeping the ignition on means you have power brakes and don't need much force, so you can just use your hand to pump the brakes while you keep an eye on things. The master cylinder is very good at pushing fluid down to the calipers, but won't suck hardly any fluid back in when you raise the pedal, so there is no need to hold the pedal down while you close the nipple, then let it come up before opening the nipple again, etc. And the small clear hose you have on the nipple will ensure that whatever little fluid the master may suck back in is actually fluid and not air.

Make sure you have at least two quarts of fresh fluid before you begin and good luck!