gravity brake bleeding

[moribundman]

Yes, but the best way is to not get any air into the ABS control unit in the first place. Once air gets in, which can easily happen if the brake fluid reservoir runs too low, it may become tedious. How to properly remove the air out of the ABS control unit, depends on your car's particular ABS system. Here's a bit about it:

http://www.aa1car.com/library/abs_bleeding.htm

 

[Audi Junkie]

Originally Posted By: moribundman
Originally Posted By: Audi Junkie
Let's just cease the whole "pumping" the brakes thing. Pushing the mc seals beyond the normal range of travel abrades them against the worn lip of the cylinder bore. That's an invitation to destruction.


Nowhere did I suggest to push the pedal all the way beyond the normal range! Apparently common sense isn't common any more.



Nowhere did you say to avoid doing so either. Am I not allowed to do so unless you say it's ok?

Common sense is that the "pusher" will have a natural tendency to push the pedal to the floor, or at least not know where the normal range is. That's my experience, but I'm pretty new at this car stuff.

 

[mechtech2]

ben - It is good to activate the ABS system during a bleed. It gets fluid out of internal passageways.
There are factory scan tools that do this.
At home, you can jack the car and turn a wheel with the key on [engine not running] while tapping the brake.
Also, sometimes pumping the pedal with the car off 50 times is needed.

 

[moribundman]

Originally Posted By: Audi Junkie
Originally Posted By: moribundman
Originally Posted By: Audi Junkie
Let's just cease the whole "pumping" the brakes thing. Pushing the mc seals beyond the normal range of travel abrades them against the worn lip of the cylinder bore. That's an invitation to destruction.


Nowhere did I suggest to push the pedal all the way beyond the normal range! Apparently common sense isn't common any more.



Nowhere did you say to avoid doing so either. Am I not allowed to do so unless you say it's ok?

Common sense is that the "pusher" will have a natural tendency to push the pedal to the floor, or at least not know where the normal range is. That's my experience, but I'm pretty new at this car stuff.


You are 100% right: I should always presume an absence of common sense. I won't make that mistake again.

Seems like your pusher isn't up to snuff.

 

[SHOZ]

On my '97 the ABS solenoids are normally off and the valves are normally open. So unless you activate the ABS then there is no way air can get into the individual valves. There is so little fluid in the valves it is not worth worrying about. And unless there is a lack of fluid down stream very little new fluid will get pumped into the lines.


I use the Harbor Freight vacuum hand pump and it works great. I do take out the bleed screws and wipe the treads with some liquid pipe dope. This stops any air from getting in. Absolutely the easiest way I have done it.

Racing the car on road courses a couple times a year I generally bleed them before any event. And if they get to hot during an event or afterward.

But I would bleed my brakes every two years otherwise. Good point about the pistons being pushed in. Never though about that.

 

[demarpaint]

I want to gravity bleed the brakes on my 08 Jeep as part of my maint on it. Can I open the two rear bleeders and let them gravity bleed for say half an hour, and just keep topping up the master cylinder? Then do the same for the front two wheels? I want to make it a one man operation, and not have to buy any special tools.

Is half an hour enough time? Or should I go by a certain amount of brake fluid?

Can I remove the bleeder valves and coat them with anti-seize w/o introducing air into the system?

 

[SteveSRT8]

yes. Just keep the fluid off paint or decals with a piece of hose.

Half an hour is too long. Simply watch the color of the discharged fluid.

On my car I've had all 4 calipers gravity bleeding at the same time. I can't tell you about removing the bleeder valves because I would think that would mean air intrusion.

 

[demarpaint]

When I bleed brakes as part of a caliper replacement I hook up a hose and drain them into a coffee can sitting in a drain pan for oil changes, nice and neat. I guess I can use clear glass and look for color change instead for this job.

I read people let them gravity bleed an hour, seems very, very long. I'll keep an eye on the fluid instead as you mentioned. Thanks!

If the bleeder opens easy I won't mess with it, maybe just a dab of some oil so they don't rot in place?

 

[Audi Junkie]

Just crack the bolts a hair and you'll see tiny bubbles percolate out. Take your time and do not pump the brakes. That action puts the cylinder through an unusual range of movement and wears the seals against the inside ridge of the master cylinder.

 

[demarpaint]

Thanks AudiJunkie. How much fluid do you run through the system to do a gravity bleed as part of my maint'? My Jeep will be 3 in December and probably have only 18,000 miles on it. I want to flush the brakes next tire rotation which should be around then.

 

[mechtech2]

Get a large can/bottle of brake fluid.
Then you are sure to have enough, unless you screw up.

BTW, a gravity bleed is actually a pressure bleed, just less pressure!

 

[demarpaint]

I'm looking for something that can be done with 1 person and no tools or stepping on the pedal. If I can crack the bleeders, run about 6-8 ounces out of each calpier, or a qt thru the entire system I figure I should be fine?