How to bleed the master cylinder and ABS unit?

[FireFox31]

Can anyone share tips about bleeding the master cylinder and ABS unit on a 2000 V70?

Brake fluid leaked out of Geronimo, emptying the reservoir, likely introducing air into the master cylinder and ABS unit. I replaced the calipers, filled and bled the system. When driving slowly, the brakes work but require the pedal to be pressed quite far. When stopped with the car off, pressing the pedal a few times still leaves it kind of soft.

The fluid I used is Pentosin Dot 4 Super, but it had been sealed on my shelf for 2.5 years. The fluid is light brown instead of clear. Could the fluid be ruined, contributing to soft braking?

This video describes bench bleeding the master cylinder by connecting its outlets to hoses leading back to the reservoir and working the piston. Could I do that with the cylinder on the car using the brake pedal. Can anyone recommend a recirculation kit? What are the thread size/pitch on the master cylinder (with and without TRACS have different sockets)? This will let me get thread-to-tube fittings.

Is there a way to bleed the ABS unit without VIDA or the dealership? I've got a faulty ABS module which triggers the ABS constantly while driving at 30 mph. Could I drive around with the ABS firing to bleed the system? Could that harm something else?

This brake bleeding thread has good info. cn90 gives a trick to push air out of the ABS unit by forcing it backward from the calipers. I thought you weren't supposed to push fluid backward in the system to not damage the ABS?

Other people mention bleeding the system with the car running. What's that procedure and is it recommended?

[wizechatmgr]

Reverse bleeding may help, but only after you are already running clear fluid out of the calipers.

You're not going to be able to tell if you're running clean due to the condition of the old fluid you just used.

Why did it drain down again, and how was it repaired?

[Oro]

I had the system completely empty on my 2000 car for a week while doing a brake rebuild recently. I just used a few pedal pumps and a vacuum unit like this, everything was fine afterwards:

https://www.ecklers.com/brake-bleeder-k ... 078-1.html

You can buy much cheaper ones off amazon or at harbor freight.

If the fluid was actually sealed, sitting on the shelf for 2.5 years has nothing to do with it. Even if it had been previously opened, sitting closed tightly for 2.5 years would have nothing to do with it; it would be usable. But either way, it should not be brown coming out of the bottle, but even if it was, that's not likely your problem. Unless you are tracking the car and boiling the fluid often, DOT 3 is better as it absorbs less water over time. DOT 4 has a (marginally) higher boil point, but absorbs more water. If it happens to rain or snow where you live (NH?), use clean DOT 3 unless you are tracking or otherwise abusing the car.

The ABS firing is not going to "bleed" the system if the caliper screws are closed (e.g. driving around). The air has to go somewhere, which is out the opened bleed screws.

If your ABS unit is faulty, all bets are off. Just go to midwest-abs and get a rebuilt unit. I got a rebuilt one (blem) from him this past summer for like $40.

[FireFox31]

I'm ordering this Thexton 804 master cylinder bleed kit because it has the threaded-to-hose adapters. I could buy the adapters from McMaster, but they have far fewer thread sizes. I think the cylinder fittings are M12 but don't know if they're 1mm or 1.5mm pitch.

Is there any way to bleed the ABS unit without VIDA? How will a dealer do it with VIDA? Maybe I'll reverse bleed after trying everything else.

The brake fluid drained because I had the front calipers removed for a month. I tried to prevent loss by leaving the brake pedal pressed pressed half way to close the valve and had caps on the hose ends. Either it still leaked or all leaked when the car was towed for two hours (because they released the brake pedal, opening the valve). I have installed all new calipers and replaced the rear fittings.

I had the system completely empty on my 2000 car for a week while doing a brake rebuild recently. I just used a few pedal pumps and a vacuum unit like this, everything was fine afterwards:

Interesting. I'm using a Motive bleeder to push air into the reservoir instead of your vacuum to draw fluid out. How much fluid did you pull from each caliper before the bubbles stopped?

The fluid in the bottle was a very light brown but not clear. I previously used Genuine Volvo fluid which was also sealed for three years and it was very light yellow. I'll probably get new fluid if the master cylinder bleeding doesn't help.

I have a Midwest ABS unit on its way to me. I'm glad they had a blemished one for $40 instead of $130, saving money for the car owner.

[Oro]

There are other units that will fire the ABS to bleed it, I have an Icarsoft one but not sure if it will bleed ABS. Some units like those will do it without going full VIDA. I don't think you'd really need that honestly as I've done many cars and the ABS has never been an issue. If you want, an old-school trick is to put the car on stands, let it idle in gear. Grab one front wheel (it will be turning slowly and not a problem). This will fire the ABS and effectively bleed the unit if it has air in it.

Another note - you may know this - is the ABS units can be slightly tricky to remove/re-install. You need to get underneath it with a small torx, or maybe it was an e-torx, socket in a tight spot. Some people replace the long bolts with hex-headed ones to make it easier to re-install and remove if needed in the future.

I used nearly a full bottle (qt) of fluid when the system was empty, and it stopped bubbling pretty quickly once I got fluid. It did take a while to get fluid; a lot of air to remove.

My situation was the same as yours, I had the calipers off for about 10 days so the whole system bled down. I had no problem. I wonder if your abs module is somehow causing a problem. Not sure if it would, just speculating because I had no issue in the same situation and that would be the only difference.

[abscate]

It’s an E5 external Torx. They get crusty and aren’t fun when they strip

We have sourced S.S. ones from McMaster Carr here in this Forum

viewtopic.php?f=1&t=60808&p=310520&hili ... er#p310520

[deano1]

This has happened to me a couple or four times where the brake system has completely drained while reworking the brake system. first time it happened i was a little nervous about the ABS being a problem but don't over think this.
If the fluid can completely drain out then it can completly fill.
Just refill reservoir and keep it filled with all four bleeders open.. Don't press the brake peddle!
Crack a favourite beverage and wait,,,soon enough gravity will do it's thing.
Close bleeders as they become active, some will start quicker that others.
You can lightly tap calipers as they're bleeding and that sometimes help release surface bubbles.

Use a couple pumps of the peddle per wheel if peddle not hard enough for ya but basically That's it.
Cheers

[abscate]

I ran Grunhilde dry a couple of weeks ago because junk had accumulated in the reservoir fill neck. Make sure that is clean. We just used slow, open bleeder strokes to fill each bleeder, rear first , then front.

Don’t worry about slight colour changes in brake fluid. Replace bleeders on calipers, and DO use antiseize on the threads in the Northeast and rust belt. Don’t overtighten them either, there is no torque spec but if you use a 6 inch ratchet handle it’s too tight. After you clean so that you can screw finger tight down to the taper, bleed, the just a slight nip , 1/8 turn max , to seal the taper

[FireFox31]

Tonight, I replaced the fourth and final brake caliper on Geronimo. I bled the brakes as normal. The pedal is working better but it's still a little soft.

I recall dealerships getting my pedal to slam on the brakes with the lightest touch. Is that how brakes should perform?

I will try the master cylinder bleed, hoping to see air bubbles being removed. Then I'll finish flushing in my old-but-sealed fluid. If it's still soft, I may take it to a dealership or the local Volvo specialist.

[abscate]

Temp lock to cull out the s70 topic