Bleeding ABS system separately needed?

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Hudson, NH
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Plan to bleed brakes on the Escalade for (probably) the first time. Doubt anyone bleeds brakes when changing pads and rotors. Wondering if the ABS system circulates, and new fluid will be picked up after a full brake bleed.
 
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19,528
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Lake Forest, CA
I don't know, even I bleed my car's brake system more than once each car the last 15 years or so. The brake fluid stay fairly clean on the next bleeding, so I think some if not all fluid in the ABS system had been bleed too. I didn't have brake system rebuilt for all my cars, even the 22 years old LS4000 with more than 370k miles has original brake system(except pad and rotor) when I sold it last week.
 
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8,871
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Marshfield , MA
Do your parts R+R completely before you do the bleed. Starting from a known good system, greatly simplifies the bleed. Figure on 2 qts of brake fluid. That's a pint per wheel. I got a good gravity bleed going and tended the MC level.. As long as you don't allow air into the system then there is no need to mess with the ABS. That is generic advice. Some cars' have special procedures, so you may want to research that. grin2
 
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1,701
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Michigan
GMT800 does have an automated bleed procedure in the scan tool, but it really only needs to be done if air has been introduced at an upstream hydraulic component (master cylinder or BPMV) or the BPMV has been replaced. If you're just flushing the system, do it like you'd do any other vehicle.
 
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ME
I'd bleed the brakes before you even start work. Drive around the block and make sure you have a good pedal. Then when you squeeze the calipers back you're shoving fresh fluid back into the MC/ ABS guts. The general fear is sending junk back. If you do them both at the same time and have a crummy pedal feel, you don't know which component of the job is at fault.
 
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4,432
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Connecticut
Originally Posted By: LeakySeals
So simply bleeding the brakes will also purge the ABS pump and all the tubes?
What (little) I've read on the subject says that you have to cycle the ABS system/pump to ensure you force all the old fluid out of the ABS lines. The OEM's or shops will use a computer input to dummy the system while they're bleeding brakes. If someone came up with such a maintenance PM, that suggests just bleeding the brakes at the 4 wheels will not clear out all the old ABS fluid. My previous daily driver went 230K miles without the brakes and/or ABS ever being separately flushed. So doing it once or twice now is a big improvement.
 
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NH
I decided that if I ran some brake fluid through the car every 1-2 years, then odds are the ABS pump would slowly get fluid pushed through it. Given how many cars troop onto 10+ years / 200k with no ABS pump issues, despite never having the fluid touched, makes me think it's not that critical. My understanding is that the worst fluid is in the calipers. I know brake fluid doesn't circulate; not sure how water that gets into the master cylinder (since it does have a vent) goes from there down through the system--or if it does at all. But only the calipers see the high heat, and thus run the risk of boiling fluid--so getting that fluid changed is the big one.
 
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7,671
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Hudson, NH
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So... The pump gives brake fluid somewhere to go during braking, changing the pressure based on electronic signals? The pump is in parallel to the main brake lines and master cylinder, and new fluid bleeding at the caliper will pass on by, not through the pump?
 
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The scantool ABS bleed simulates the deployment of ABS braking, something that cannot be achieved during a basic pedal press bleed?
 
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4,432
Location
Connecticut
Originally Posted By: LeakySeals
The scantool ABS bleed simulates the deployment of ABS braking, something that cannot be achieved during a basic pedal press bleed?
That's my understanding. A simulated input tells the ABS that 1 wheel is not turning under braking. I got to "simulate" that for a few weeks while one of my front wheel ABS tone rings was cracked. So when I braked while coming to a stop the pump would activate and cause a shudder. It got so annoying I finally just pulled the ABS fuse. But certainly the fluid got circulated. A few weeks later I got a new axle shaft installed. What a lousy design where a simple $10 ring "fails" an entire axle shaft.
 
I bleed my brakes yearly, on a summer day with low humidity. I've never cycled the ABS system because I do not have the scan tool (or whatever) needed to do so. However, both prior to and after bleeding the brakes, I purposely induce wheel lock on an individual wheel basis in order to cycle the ABS system. This can be done using a variety of techniques. One is to find a safe area and drive into a hard turn while stabbing the brake pedal. This will cycle the ABS for each front wheel, depending on the direction of the turn. I do this in a large parking lot, usually very early in the morning. You don't have to be going fast to do this. In that same parking lot, make a sharp turning circle until you start to get rear wheelspin. This will cycle the ABS because of the loss of traction. Do this turn in both directions. A warning, sometimes I find this rear wheel spin method induces too much driveline shock to my liking because the ABS system is rapid cycling the brakes on one side while the car is under power. But, so long as you're not giving it lots of power, these negative effects are mitigated. Understand, I'm not talking about a full out powerslide. I'm talking about wheelspin on the inside tire only. All this said, I am fortunate to have a nearly untraveled road that is under a canopy of trees. Sometimes the edges of the pavement are literally 3 inches deep in leaves. What I do here is get both tires on one side on the leaves and nail the brakes. Instant ABS action on both front and rear wheels on the leaf side. I do this several times for each side of the vehicle. If you have a mechanical limited slip rear diff, this would be the preferred method because inducing inside tire only wheelspin via the parking lot method would be difficult, if not impossible. Also too, I think "exercising" the ABS system once in a while is a good practice. This is a good way, and reason, to do it. Lastly, I use Pentosin "Super DOT 4" fluid. One last thing, I just realized I was on BITOG and not E46Fanatics (a BMW forum). Don't use my parking lot technique on a vehicle with a high center of gravity!!! FWIW, Scott
 
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6,135
Location
Illinois
Most ABS pumps are open valves normally. The solenoids will cycle the valves to cut pressure. So really there is no air that can get in.
 
Originally Posted By: SHOZ
Most ABS pumps are open valves normally. The solenoids will cycle the valves to cut pressure. So really there is no air that can get in.
^^^^ This is true. Say, for example, you had to replace your master cylinder. A "regular old" brake bleeding will, in virtually all cases, purge all the air out of the system. Only when the ABS unit itself is disassembled do you need to cycle the system. Scott
 
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