brake fluid flush :: is a power/vacuum bleeder needed - what about the ABS pump?

[ducatipaso]

so I'm preparing to do all 4 corners this weekend. I want to flush the system as the fluid that's in there is *gasp* 10 years old or more.

questions:

1) do I need a power/vacuum bleeder to do this or can I do it the old fashioned pump, release method?
2) on modern VWs, you need to cycle the ABS pump to finalise the task. is there anything odd like this on the E30?

also, there is an ATE tool for 'degreeing' the caliper piston. my father was telling me to not forget this step, but I can't find much info on it.

thanks guys. pix of the job after the weekend.

[whiltebeitel]

1. No.
2. Nope, just pump 15 times between releases.

[ducatipaso]

wow. that was quick. thanks. 15 pumps, release. obviously should do longest to shortest line per protocol.

[jlevie]

A pressure bleeder isn't essential, but it does make the task much easier and also makes it a on-person job. You can achieve the same results by the pedal method, but it will take longer and require a helper. And since brake fluid should be changed no less often that every other year, a pressure bleeder is a worthwhile investment.

Start with the right rear(passenger side), next the left rear, then right front, and finally left front. For a full flush you should drain a measured 200cc from each rear caliper and 125cc from each front caliper. That leaves 350cc left from a liter of fluid, which is sufficient to fill the reservoir.

Cycling the ABS is a good thing to do when changing the fluid, but not absolutely necessary. Taking the car out to a wet, empty, parking lot and getting into ABS will suffice to clear old fluid from the ABS pump.

Nothing special needs to be done to the calipers (i.e., no "'degreeing' the caliper piston").

[ducatipaso]

thanks for the additional info. i have a helper, and have done the old pump pump pump method so many times over the years that it's no big deal. the car's not my daily, so the time it takes to do the job is irrelevant.

[StereoInstaller1]

Don't pump between releases.

The cavitation of the piston makes air bubbles.

[ducatipaso]

you pump several times to build pressure in the system, then release. close the bleeder, top off the MC and repeat until clean fluid appears at each wheel, in the order described above by jlevie. I'm quite familiar with brake bleeding procedures, I was more or less enquiring if there were any special procedures due to the ABS. From what I'm gathering, no. Thanks for the input guys.

[AlarmedBread]

I highly recommend a set of these, and one for the clutch too. Just put your tube and bottle on the bleeder, go pump and you're done in 1/5 the time as the helper method. I had seen them on hydraulic systems, but it never dawned on me to get a set for the brakes until a friend mentioned it.

http://www.speedbleeder.com/

[ducatipaso]

thats a mighty fine idea there, too

[StereoInstaller1]

you pump several times to build pressure in the system, then release.

NO! Do NOT do this, that is what causes air bubbles in the system!

One pump, hold, release, repeat.

[ducatipaso]

OK so I'm getting conflicting information here. Why would multiple presses on a closed system introduce air? That'd defeat the purpose of how the hydraulic system should function.

[StereoInstaller1]

OK so I'm getting conflicting information here. Why would multiple presses on a closed system introduce air? That'd defeat the purpose of how the hydraulic system should function.

Yeah, I thought the same thing too...but after trying it this way (after YEARS of pumping) I have found that the brakes feel better and the overall process is quicker.

I am gonna do the "modified bug spray pump" deal soon, as I have 4 or 5 E30s I work on regularly. Being able to pressurize the system makes it so easy to get a solid flush/bleed.

Oh yeah, I got that info from Baer brakes, BTW. They have excellent tech pages.

[Kingb]

Ok so I also want to do this and put on SS lines ( only front for now until SB rebuild) at the same time.
Do I change the lines then bleed them in order until I get clean fluid and no bubbles at each corner?
How much fluid should I get for the flush?

[jlevie]

Ok so I also want to do this and put on SS lines ( only front for now until SB rebuild) at the same time. Do I change the lines then bleed them in order until I get clean fluid and no bubbles at each corner?

Yes

How much fluid should I get for the flush?

1 liter is plenty for a full flush, see my post above.

[Bimmerman325i]

Just a word on the pressure bleeder- I used one this past weekend and while it makes the job go much quicker and easier, make sure not to go past 15psi on a Motive type bleeder. I used 15psi and managed to bleed the fluid and leak a good half liter all over my garage-- I found out that the rubber grommets and seals between the master and the reservoir do not like 15psi once they're old and weak.