No, it isn't.
The reservoir on these trucks isn't designed to accept pressure. Too much pressure can blow the reservoir off the master cylinder--it's only held on with a pair of rubber seals. The reservoir itself isn't all that sturdy.
The big problem is that the reservoir is small, pressurizing it can blow the fluid out the bleeder screw so fast that the master cylinder goes empty.
ALL real pressure bleeders have a rubber diaphragm exactly for that reason. If you look in the service manual, GM specifies a pressure bleeder having a diaphragm. They specifically warn against using a "garden sprayer"-style bleeder.
Garden-sprayer bleeders are not "real" pressure bleeders.
Pressure bleeder attachment for my Trailblazer, or for GMT800-style reservoirs. The GMT400-style adapter is COMPLETELY different because the reservoir is less-sturdy. I'll get a proper photo tomorrow.
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Patent application for one style of pressure bleeder attachment for the GMT400-style reservoirs. This bleeder style puts no pressure on the top or sides of the reservoir--only on the part that's well-supported by the sealing bushings where the reservoir contacts the master cylinder.
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I have one of these, but it's in poor condition and missing one small piece.
Proper pressure bleeder having diaphragm to separate fluid from air. I pressure bleed at about 10--15 psi.
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True. But you're allowing the fluid to come into contact with MORE ambient air. More air = more humidity = more contamination.