I've always done mine, engine running.

 

To answer your question...Engine off
What is the year/model you are working on?

Does your car have ABS? If so you need to perform "automated bleed" of ABS unit after repairs are made and then bleed system again. You may have to take it to the dealer for this as I am not sure of the capabilities of aftermarket scanners.

How are you planning to do the bleeding? There are several "tricks of the trade" that may make it easier on you. Tell me how you are planning to do it and I'll share with you some ideas to keep in mind.

 

You don't need the engine running to bleed brakes. What you're saying about the brake pedal is only true if you have the all the bleeders closed and your engine off.

As long as you have a bleeder screw open, the pedal will go easily all the way to the floor. Once the pedal is down, someone else should close the bleeder. Then the pedal should be slowly let up (which draws new fluid into the lines from the master cylinder). Then the pedal person puts gentle pressure on the brake while the other person slowly opens the bleeder. Etc. And of course the guy operating the bleeders needs to check the fluid level in the master cylinder every 3 pedal cycles or so.

How to bleed brakes right has been covered before. I've done the "one man brake bleeding" bottle from the parts store with no apparent problems. But after a lot of research and examining the various "one man" products out there, it seems the best way is to use two people, one to operate the pedal and one to open and close the bleeders and maintain the fluid level.

Two reasons for that:

1. Some folks believe that the two man way is the only way to get residual air pockets out of the system, because other methods don't provide that initial "shock" to the fluid in the system that happens when you have pressure on the pedal and then open a bleeder. Some people say this shock dislodges residual air bubbles.

2. Some folks say, when using one man bleeding methods (which generally leaves the bleeder screw in the open position), that air gets pulled in past the threads when the brake pedal is let up.

This doesn't have a chance of happening when doing the bleeding with two people, because the bleeder screw guy closes the bleeder before the pedal person lets the pedal back up. So basically, the two man way is the most certain way to do it. I guess that wasn't quite your question, but I just wanted to be thorough.

 

Whoops! After reading GM Tech's post, I should probably disqualify myself on the subject of ABS brakes. I've never bled an ABS system, and don't know the ins and out of that. My post still holds true for non-ABS brake cars and trucks, though.

 

While what GM Tech says here is "technically" right with concerns to ABS, in real world application you don't need to worry about it UNLESS you got air into the ABS system.

Fortunately, that is somewhat tough to do if you're careful about it

.

Bleed 'em with the motor off, and use the 2-man method (one person pumping the pedal, other cracking the bleed screw ONLY when there is downward force on the pedal).

 

BTW corycat28, have you signed up yet for your local club the Region Of Doom? If not, you should. We also have an e-mail list that you can subscribe to at

Regionofdoom-subscribe@yahoogroups.com

Our monthly "South Bay" meeting is the last Wed of the month (i.e. March 31 this month) at the Bennigans on Great America Pkwy (just north/east of Hwy 101) in Santa Clara. We usually gather around 5:30-6PM, and head inside to eat around 7PM. After dinner, hang out in the parking lot a while....

 

I am worried a little bit about air in the abs pump; I am about to put a line lock in. My plan is to hook up the line to the m/c in a quick like fashion, and then use my maxxvac or whatever it is called, and suck the fluid through the line lock. Then, disconnect the fitting at the abs pump, and hook up quickly. Hopefully air injestion will be attenuated, and any in the abs pump will bleed thru when I bleed conventionaly.

Peter

 

GM Tech,

Sorry missing some detail about the car.

1996 Chevy Caprice, LT1, 9C1, 4-wheel ABS/disc brake, 130K miles, ex-NYSP un-marked hi-way curiser, sever rust on brake system, the metal brake line rusted like Hirsh Chocolate sticker, the rotor was peeling off metal chips.

The bleeding will be 2 people's job, padel pressing guy and bleeder opening guy.

For the ABS, bleeding, I am trying to follow FSM ABS bleeding procdure.

I am looking forward to share your experience and idea about the brake system major over-hauling.

Jesse
NY

Originally posted by GM Tech:
To answer your question...Engine off
What is the year/model you are working on?

Does your car have ABS? If so you need to perform "automated bleed" of ABS unit after repairs are made and then bleed system again. You may have to take it to the dealer for this as I am not sure of the capabilities of aftermarket scanners.

How are you planning to do the bleeding? There are several "tricks of the trade" that may make it easier on you. Tell me how you are planning to do it and I'll share with you some ideas to keep in mind.

 

Peter : you should be OK here. It's OK if you get some air into the "entry" of the ABS, as you'll bleed that air right back out (without getting it into the small passages in the ABS) with the conventional bleeding.

What is more the concern here would be getting air into that ABS entry and then cycling the ABS valves BEFORE you get that air bled out. In other words, after you add the linelock be sure you bleed the brakes BEFORE you drive the car and potentially cycle those ABS valves....which I am 100% sure you were gonna be doing anyways .

 

I guess I'll be leaving engine OFF, and saving a little gas.

 

I've never considered this one.

Personally, I'd do it KO, and lightly pump the pedal.

There is NO need for high pressure to bleed brakes. You're only moving fluid and psi has zip to do with that. I'd also encourage everyone to NOTlet the reservoir run dry, this may well cause headaches I don't want to work on!

 

I had the same question, being new to the brake bleeding procedure: engine on or off? I got the answer 'off' also. That raises some additional questions. The pedal is rock hard. You should pump the brake several times to release the power brake boost reservoir. Next item. If you are using a one man tool such as the Phoenix Systems, you can pressure bleed by forcing new fluid from the brake fluid reservoir to the individual calipers.In order to do this, you must first hold the brake pedal down at least one inch and keep it down for the duration of the procedure. Since this is a 'one man' operation, you need to create a board device to wedge between the brake pedal and the seat cushion to push the pedal down. This means your brake lights are on and may run down your battery. Pull the associated fuse. Now you can bleed the individual brakes.

 

Jim, for the amount of time you'd be bleeding, if Battery runs down, that probably indicates you need a new Battery. Yes, No?

 

Larry, my battery is pretty good. I'm just slow.

 

Ive always been a fan of the let 'er run method...

basically 2 man but the pumper pumps 2x then holds, bleeder opens and pumper pumps untill no more air bubbles appear

while always checking the fluid level every now and then...

when no more bubbles show up, pump a few times then hold, crack and close... do this about 5x per corner...

I dont know if you need to pump on a b-body, the only brakes I have worked on are my Acuras, pumping builds a little system pressure