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The abs unit is usually between the master cylinder and the caliper. I say usually because there have been a few systems out there where the abs and master are a combined unit. the actual method is still pretty much the same, the system gets pressurized, and then you open a bleeder, in the abs systems case that can be anywehere from 2 to six bleeders on the unit. And as its been a while since I did it for a living there maybe more than that on some units. Some will require specialized scan tools to cause the internal valves to cycle.

If you run the master dry then you will need to bleed the abs as well as the calipers and the wheel cylinders.

If the pedal is spongy its an indicater there is air in the system, period. You cant tell from the pedal where the air is. It might be the caliper, it might be the abs or a wheel cylinder but more than likely it will be through out the entire system.

If you work fast and know what your doing you can change a caliper with out running the master dry. But there is a cheat that works. use a stick, like a snow brush, or a piece of an old broom handle and prop it between the seat and the brake pedal, depressing the pedal about a 1/3 of its travel. this will block the ports in the master and it wont run dry. There are "clamps" for use on the rubber brake lines, but I never liked using them, especially if the vehicle has any age or mileage on it.

The most key piece of info you have left out. What bloody year, make, and model. And which ABS system, 4 wheel, rear wheel, teeves, delco, etc. Not all abs systems require scan tools to bleed, more than a few can be done the old fashioned pump and hold method. Or even as simple as gravity bleeding. I dont mean to be too awfuly down on you, but what is your level of automotive repair experiance? a vehicle that stalls or wont run is a minor problem most of the time life and death wise, one that wont stop is a whole nother ball of wax. This maybe a repair to find someone who has done a few to look over your shoulder while your working, or take it some where and have it done.

Whitelightning

Reply to
Whitelightning
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  1. What's the difference between bleeding the caliper/wheel and the ABS unit?

  1. If the master cylinder runs dry, is it necessary to bleed the ABS unit after you fill the master cylinder up again? I *know* that it's necessary to bleed the calipers. The source of my confusion is the fact that there's "2 different things to bleed (1. The caliper 2. The abs system)

*and* the ABS system cannot be bled by the weekend DIY'er.

  1. *how* can you tell if your ABS unit needs to be "bled"? I know that if you feel a "spongy" feeling, then there's air bubbles in your break line going into caliper *and* that's a good indicator to bleed the caliper. But how about ABS?

  2. *Can* you successfully remove an old caliper and install a new one without having the master cylinder run dry when you disconnect the break line from the old caliper? Can you "clamp" the line or somehow "plug" it -or- is it a necessary evil just to allow all of the fluid to come out at that time? The key is "hoping to be able to install the new caliper without having to bleed the ABS unit (but knowing the caliper/wheel should be bled after installing the line into the new caliper).

I'm asking as I'd like to do the brakes on my chevy truck and want to be prepared in case a part/bolt breaks and I have no choice but to replace a caliper.

thanks

Reply to
Anon

The one completed was a Ford Explorer 4-wheel. Another will be a 2001 Silverado and a 2000 S-10. Another a 2000 Cavalier. So my question then to you is "how" can I find out if all I need to do is the normal conventional bleeding that I'm familiar with for a particular model. Believe it or not, the Haynes manual makes no mention as to whether or not this needs to be done.

No formal training but did about 5 different pad replacements on prior cars w/o ABS. The most recent job this weekend was the first one with ABS. Everything runs perfect and the vehicle stops better now and the squeaking is gone. I just wanted to make sure *if* we had to replace the caliper (which we have the manual *and* the tools to do s) that we could do so without having to let the master cylinder run dry. Thanks for the trick about putting the block between the pedal and the floor.

Advice well taken. I plan to do this very same thing for other jobs. I "am" comfortable with pad replacement for disc brakes. What threw me off a few weeks ago (when I posted questions about it) was the addition of the ABS.

thanks for clearing this up for me.

Reply to
Anon

1) 2001 Silverado....only if you are replacing the brake pressure modulater valve (ABS unit) or if there is air in the valve, do you need to do an "automated" brake bleed procedure. If you did need that procedure done, it works basically like this....you bleed the brakes manually the way any base brake system is bled, then you perform the automated brake bleed procedure with the scan tool (it tells you what to do) and then perform "another" manual brake bleed. 2) 2000 S-10....same procedure.

3) 2000 Cavalier......much more complicated. You have to use a pressure bleeder hooked up to the system "while" you perform the automated bleed procedure with the scan tool. This will be almost an impossible procedure for most DIY'ers

And then there is the Cadillac Escalade....even more complicated then any of the above...but it's not on your list, so you won't lose any sleep over that one.

A caliper can be easily replaced before enough fluid drains out of the master cylinder. If you are really worried about it, I'd simply have a helper topping up the master cylinder while you are doing the work below. It also helps if you are organized. Do things like: loosen the banjo bolt that holds the brake hose to the old caliper, but don't remove it yet, swing the old caliper out of the way, install your new caliper, have your new brass washers ready, loosen and remove the banjo bolt from the old caliper, toss the old caliper to the side, and slide the banjo bolt with the new washers in place. Takes all of 30 seconds, if that, and you won't lose much fluid in that amount of time.

Ian

Reply to
shiden_kai

Thank you Ian. I don't know where you came from but it's a total Godsend that you're a regular answer man for this group.

I w>

Reply to
Anon

Canada, where all good things like beer, Rush, licenced technicians, toque's, The Tragically Hip....etc, all come from!

Maybe a generic one, but I doubt that you will get the Tech 2 scanner that way. You might have to do the work, and then if you think you need the bleed work done, take into a dealership, or an independent that can do this sort of thing.

Ian

Reply to
shiden_kai

Canada rocks! Same with "The Band", Neil Young, Joni Mitchell, Gordon Lightfoot, etc...

And also where good people come from as well.

Yeah. I imagine the same would be the case for replacing struts. I could change the struts but then take the car to a mechanic to have them do the alignment.

thanks again for answering the original post!!! Glad there's knowledgable and friendly people like you on this group to help us out.

Reply to
Anon

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