Cycling ABS pump

[Bob Kontak]

Confused as to how cycling ABS pimp pistons clears air or moves fluid.

I bought a Snap-On MT 2500 a year or so ago and I can work the little ABS servo/pistons on cars through 2005.

Where does the old fluid or air go if the bleeders are closed? How do the poisons get downstream if the downstream side is full of fluid?

[Bob Kontak]

I think I need me some Vash.

[Arizona_928]

If it's anything like a mk4 vw you cycle the pump with the breeders open. I used a power bleeder at the same time. You get trapped air out of abs pump and fresh fluid in from the reservoir.
Did you replace the abs pump, or run it dry?

[cgarr]

Here is why we use it on vw's, I guess it works the pistons and fluid in that area, still need to bleed the brakes it just takes care of the abs part?

"From Ross-Tech"

This procedure details how to bleed the ABS pump when replacing brake fluid. This procedure is NOT necessary unless your ABS pump has gone completely dry. For normal brake work including fluid replacement, hose replacement, pad replacement, etc. this procedure is NOT necessary. Also, this procedure does not take the place of good ol' fashioned brake bleeding with one person operating the pedal while the other person opens the bleeder valves one by one and collects the discharged fluid.

[Bob Kontak]

Originally Posted by AZ_porschekid

If it's anything like a mk4 vw you cycle the pump with the breeders open. I used a power bleeder at the same time. You get trapped air out of abs pump and fresh fluid in from the reservoir.
Did you replace the abs pump, or run it dry?

No on either question. Customer says no on ever "dry"

This is good info, though.

It's a Dodge Caravan.

I have an 07 Wolfsburg Edition here that I am changing out a brake switch on, FWIW.

Originally Posted by cgarr

For normal brake work including fluid replacement, hose replacement, pad replacement, etc. this procedure is NOT necessary.

Cool. I am probably working this too hard.

Customers car with left rear not gravity bleeding fluid. MityVac not helping much.

Need me a big foot.

[impactbumper]

I replaced an abs pump on an 06 tdi, and my God that pump bleeding took forever using the machine and pressing pedal. With BMWs it is so much easier.

[Bob Kontak]

Originally Posted by Berk

I replaced an abs pump on an 06 tdi, and my God that pump bleeding took forever using the machine and pressing pedal. With BMWs it is so much easier.

Agree. My brother's (mentioned) Jetta is still giving us fits. New MC and after third time bleeding it's still burping small bubbles. Stops great but pedal slowly sinks to the floor.

Car mentioned in my original post boiled down to the MC. Diagonal system. One seal was blown badly enough to not build much pressure. It would squish a little out of the front right caliper connection (not the bleeder) , enough to confuse, but when I compared the squirt factor past the MC line fittings, that put it to bed. cgarr was correct. I misdiagnosed.

Thanks!!

[Bill Verburg]

The bleeds shouldn't be open open the ABS is cycled, what happens is the fluid is returned to the m/c through the pump and accumulator.

You can do this by driving the car and locking up the brakes.

The fluid path is controlled by 3 ports in the solenoid chamber, the solenoid position controls which combination of ports are used, there are 3 positions for the solenoid
1) pass thru
2) hold pressure in the caliper(the m/c is cut off and fluid is returned from the ABS to the m/s and/or accumulator) a subset of this is reduce pressure
3) increase pressure from the accumulator fluid goes from the accumulator to the caliper