bleeding brakes: pressure bleed req'd?

Question

(04 Cavalier) A brake line popped while driving. So, "extreme loss of fluid", though the reservoir might not have been _totally_ empty. For this case, the AllData manual says pressure bleeding is necessary, in conjunction with a high-end scan tool.

Not that anyone could know the exact particulars of this situation, but, in general, is this (above) a pretty solid rule? I guess the alternative would be, they're just trying to scare ppl, or you actually can do it manually, if you're willing to spend a lot of time.

(I expect I'll try a manual bleed anyway, to at least get enough brake to drive it somewhere.)

Thanks

micky · Accepted Answer

Can't you have a friend sit in the car and push on the brake pedal?

Scandisk isn't expensive, if you already have Windows, but Microsoft seems to think it's enough.

They also sell a variety of do-it-by-yourself kits, iirc, so you can sit inside and push the brake pedal. I've usually managed not to need bleeding. Well, I wasn't sure if the brakes were okay or not, until the one time I had spongey brakes and it was plain as day that all the other times, I hadn't. I could still drive the 4 blocks to the garage. Not sure how far I would have driven if that place were not so close.

Steve W. · Answer

The reason for that is the ABS.

If it has ABS and the reservoir did NOT get TOTALLY empty and you are sure the ABS unit didn't suck in air you should be able to do a manual/gravity bleed and be OK.

If it has ABS and the reservoir did get TOTALLY empty then you need the scan tool to do the automatic bleed to get the air out of the ABS system.

If you don't have ABS, you can just do a conventional manual bleed.

Steve W. · Answer

Forgot to answer the rule part.

Basically IF the vehicle has ABS you need a specific procedure to bleed the brakes. Some use a scan tool to cycle the valving and accumulators in the ABS while others you can manually bleed using bleeder valves on the ABS module. All depends on the vehicle and how the ABS is set up.

Oh and FYI, they do mean you need a real scan tool with bi-directional controls. That basically means $1000.00 dollars and up. The common code readers don't have the bleed function in them. The reason for the power bleeder is that the pedal must stay up and there has to be pressure on the system when it cycles the ABS unit.

The basic process is that you connect the FULL power bleeder up. Connect the scan tool and start the bleed procedure. The scan tool will tell you what order to open the bleeders.

George · Answer

Alas.  For now, just hope really hard that it didn't gulp any air. Thanks.

micky · Answer

Thanks for this post. I didnt' think about ABS, and I wouldn't have known it made such a difference.  Aha.  Good to know.

bleeding brakes: pressure bleed req'd?

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