Cobra4B

Never done this and have had no ill effects. Watching Speed channel and they had a how-two on Dreamcar Garage... they said you could damage the ABS stuff by not opening the bleeder screw and pishing the fluid up stream... true? What do you all do?

Richin Chicago

Either I am very lucky or it is not true.

tigerdrvr

^ ditto. Never done it, never had a problem...yet.

MNCrystalRed2011

Never had a problem.

Cisitalia

You don't have to open the bleed screw to compress the pistons. I use very large channel locks with a brake pad across both front pistons. Don't need a pad on the single rear piston. You can use a large C clamp as well.

Essentially it is an open system. You have to be carefull with a full brake fluid reservoir and totally used pads (when changing to new pads), that you don't compress all 4 calipers and over flow the reservoir. When you compress the piston, the pressure causes fluid to flow through the system and ends up filling the brake fluid reservoir. The ABS system is just a DC motor and high pressure pump. Fluid back flows through the pump. I don't see this being a problem in a static situation. Its not like the system is being activated "on" and you have opposite pressures fighting each other.

That being said, from a technical stand point, it is probably the most conservative way to open the bleed screw and compress the pistons. That way no fluid goes up stream (or pressurization upstream) and the least path of resistance is out the bleed screw. This would be a good idea if you are changing pads and don't want to take out some fluid in the brake reservoir.

In reality it is not necessary and I (including many, many others) do not open the bleed screw when compressing caliper pistons. No detrimental effects so far, including my Z06 and many other cars.

z060ntrack

Use Speed Bleeders and this question becomes a moot issue.

VetteDrmr

I think they're referring to a situation where you might have boiled fluid and could push bubbles up into the ABS system. That would be a BAD thing.

OTOH, by opening the bleed screw, you:

a. Eliminate the risk of overflowing your master cylinder
b. Remove a good percentage of the most used fluid in the brake system.

It's not as good as a good system bleed, but it's better than not doing a bleed at all.

HTH, and have a good one,
Mike

xsiveone

The fluid in the calipers is the most contaminated and if you don't open the bleeder screw when you compress the piston, you run the risk of damaging the ABS sensor by sending this contaminated fluid to the sensor instead of out of the bleeder screw.

Whether it damages the ABS sensor is the questionionable, but I'm not willing to risk it, so I open the bleeder screw. BTW.. I also have speedbleeders, so I don't run the risk of sucking air back in the system when I do this.

X

2K3Z06

The service manual does not mention to open the bleeders when changing pads. If ABS damage was possible, it would probably be stated in the service manual.

cheers

Richin Chicago

I also don't think the fluid would be contaminated. Scorched maybe. But a good bleed would get that.

Cobra4B

Thanks for the replies, I do have speed bleeders, they're great.

larryfs

the purpose of opening the bleeder, is so your don't push all the crud and "bad" fluid up stream. and pushing the piston in becomes much easier.

I've never heard the ABS theory before, just the crud theory.

I've been doing it since I heard about it a few years ago. but for many years I never done it and never damaged an ABS componet.