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Old 04-16-2002, 11:49 AM   #1
cmaj7
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Default Flushing Brakes

I know this has been beaten to death but, I need a definitive answer.

I'm installing ss brake lines this weekend. I want to flush the brake fluid!

Question - Do I flush the system dry then refill it with brake fluid. OR do I empty the resevoir, leaving the lines full of the old stuff then bleed until I see the new fluid?

I've seen it posted both ways...I'd really like a qualified answer from someone

Thanks!!
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Old 04-16-2002, 01:39 PM   #2
tmat3
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When you disconnect the brake lines at the caliper, brake fluid in the line will come out. So you don't need to worry about the old fluid being stuck in the line. When I disconnected one brake line, a lot of fluid came out and the reservoir was empty. Then, I had to do a full brake bleed.
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Old 04-16-2002, 01:57 PM   #3
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Default Don't dry it out

Whatever you do you dont want to run it dry. There are seals that need the fluid in there. If you run it dry they have the possiblity of messing(tearing, etc etc) up. I would get most of the old out with a turkey baster type of thing. Then add the new, then change the lines. Bleeding after wards wouldn't hurt at all either just to ensure all of the old is out.

Just my .02

Buster
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Old 04-16-2002, 01:59 PM   #4
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Don't bleed it dry. You'll invite air bubbles to trap themselves in your brake system. You can be sure that you've replaced all the fluid by changing colors....like ATE blue to Motul 600. If you must bleed dry to change several components, then there are some good ways to cycle fluid through. One is to run fuel line from the caliper nipple to the fill resevoir of the master. Keep pumping fluid through and as it hits the resevoir, the bubbles go into the air and fluid goes in. Another is with a speedy bleed.

jack
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Old 04-16-2002, 03:03 PM   #5
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I wouldn't recommend recycling the brake fluid back through the system, invitation for problems. Bleeding or flushing the fluid is used not only to get the air out of the system but also disolved H2O / water. If you recycle the fluid u might get the air out but you will still have other nasties like water.

N.
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Old 04-16-2002, 06:39 PM   #6
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I just did the same thing this last weekend including adding the Subaru 4-pots in the front. Here's what we did.

When breaking off the lines and adding the brakes, keep the cap on the resevoir. This will keep the fluid from draining quicker. It will still do it, but not as fast and without as much worry for the internals. Once all the lines/brakes are on, and everything is tightened down again, fill the reservoir to max capacity with NEW fluid.

Start with the driver's side rear wheel and bleed the brakes, this is easier with 2 people. One to pump the brakes and another to watch the fluid and tighten the bleeder valve. When there's no more air in the system, pump the brake pedal and hold it to the floor and tighten the bleeder valve. Then start the car, and repeat that process. Next, go to the passenger side front wheel and repeat that process for that wheel. The system works this same way, and this will provide the best available performance from the brakes. Remember to keep filling the reservoir as it will easily drain when you are filling the lines up again.

Once that is done, go out and drive it and see how it is. If the pedal is really mushy, or there is no brake feel, repeat the bleeding process again.

I learned this from a guy who's entire goal in driving is to have the best brakes out there, so I feel confident in telling you this. Hope this helps.

AJ
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Old 04-16-2002, 06:50 PM   #7
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Default

thats interesting, ive never heard of starting the engine after flushing each wheel. Also the way I do it is start from the furthest point from the master cyl and work your way to the closest. I believe on our WRX that would be driverside rear, pass rear, driverside front, pass front. Last weekend at Sponaugles there was a flurry of brake flushing...but they do it the opposite way (backwards to what ive always done). Seemed to work fine for them!

Also...never let the master cyl run dry and using diff color fluid is a great idea!
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Old 04-16-2002, 07:34 PM   #8
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Well...I'm the guy that helped AJ with the bleeding, and this method works for me after much trial and error over the past couple years. Like AJ said, keep the cap on the resorvior when you replace the lines. As the fluid drains out the lines, it creates a vacuum in the master cylinder, and this holds the remaining fluid in the lines. Trust me, this works....I was bleeding the brakes with a friend once, and he started pumping the pedal until it was so stiff he couldn't even push it down anymore, and I wasn't getting anymore fluid out the line. Looked at the master cylinder and noticed I'd left the cap on. Duh. Took the cap off and the fluid came pooring out the line. We all learn from our mistakes.

Also, when it looks like the fluid is nice and consistent, with no bubbles, I like to do a couple more pumps with the car running. I learned this from a mechanic of 20 years who said something about how it "primed the ABS". Honestly, I don't really know why (I'm no mechanic and would never claim to be), but it really helps. Just make SURE you have the master cylinder full because the fluid pumps through a LOT faster with the car running.

Since the Subaru has "criss cross" brake lines, it's best to do opposite corners when bleeding. Most cars today are equipped this way because if one line fails, you still have the other line to brake on opposite sides of the car, keeping it more stable. So this is the order that I use, and would recommend: RR, LF, LR, RF.

Like I said, this method works for me, but I'm not saying it's the best way. There are all sorts of variations
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Old 04-16-2002, 07:54 PM   #9
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I'm not adding any more "systems", there isn't really any one way to do it right. One thing that is ALWAYS true never leave the TMC (master cylinder) dry. You'll never get the air bubble out again by hand. To be honest there is more than one right way and if you found something that works, why fix what's not broken.

Just FYI-

At the factory this is how it's done. They do it all one shot.

First you mount the Evac-Fill head unit to the res then all air is evacuated from the system, creating a vacuum. Then fluid is forced through the system at high pressure.

Then the car is delivered and people bitch about mushy pedal!

Just some more stuff:

I e-mailed a Tech at Ford I used to work with on the proper bleed sequence. Since techs do these all the time and engineers don't I'll take his advice.

This is it:

Doing nearest or most distant doesn't matter. What matters is if the brake system is a diagonal or front-rear system.

quick definition: diagonal means that one circuit in the master cylinder feeds the front driver's side and the rear passenger side. The other circuit the front passenger's and rear driver's. Both circuits are of equal volume. Front-Rear means that one circuit supplies the front calipers, while the other the rear calipers. The Primary circuit (front caliper circuit) is of greater volume.

All you need to do is make sure you do the circuits together. For instance, on most passenger cars it's a diagonal system. So you want to do the driver's front and passenger's rear together, which you do first is not all that important. But he does agree that the tradition is do to the rear first. Or best to get a friend and do both at the same time. And take your time (he told me to make sure I added this).

Same holds true for the Front-Rear systems. Do fronts together and rears together. Usually only trucks, SUVs and very heavy front bias cars (Ford Crown Vic) have a Front-Rear system.


Just FYI- Diagonal is used so that if one circuit fails the vehicle is still stoppable in a stable manner as at least one front and rear wheel is braking and on oppisite sides. Front-Rears are used as heavy, front-bias cars require a lot of volume up front.
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Old 04-16-2002, 08:06 PM   #10
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romanom,

You explained the "diagonal sytem" much better than I did. Great Info.
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Old 04-17-2002, 11:47 AM   #11
cmaj7
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Default Thanks..one more question

Thanks for the info everyone. I have one more question. When replacing the brake lines do I replace them all then bleed each one when I'm done...or do I replace then bleed, replace then bleed. I think it's the first but I want to be sure.

Also any tips on mess control when I pop those lines?

Once again thanks!!
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Old 04-17-2002, 12:30 PM   #12
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Replace them all, and then bleed.

Oh...something not mentioned is that you need a 1'-2' piece of clear hose to put on the bleed nipple when doing this process. This way you can see the fluid and when it's running clean, without any bubbles. You can get like 6' from Home Depot for $2.
Make sure you don't get ANY fluid on ANYTHING you want to keep the paint on. It'll eat right through.
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Old 11-10-2012, 10:40 AM   #13
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Patience is always key
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Old 11-10-2012, 10:50 AM   #14
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hmmm
Believe it or not, last time when i was putting on some SS lines on my brembos, i pretty much let the lines drain out my reservoir and left it empty the whole entire process of replacing all 4 lines, then i bleed my system with the motive power bleeder....

And my brakes still feel just as good as before... no signs of air trapped from empty reservoir...
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Old 11-10-2012, 01:45 PM   #15
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Quote:
Originally Posted by subydubydo72
Patience is always key
Last post before thread revival:

04/17/2002



Just a hunch, but I think this thread was all done...
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