Brake Bleeding

New guy here again. I am going to try and bleed my brakes tomorrow it has the 4WAL brakes on it. Does anyone have any advice? I have the Haynes manual and I have a couple of Youtube videos. Some say I might need a ABS scanner to operate some module. Others have said I don't need it. Any and all inputs on thoughts and procedure would be greatly appreciated.

Jimmy

no luck doing mine, dealer visit for me.
gotta say dealer price was reasonable imo.
thinking this might help you out, gonna give it a try next time before taking to the dealer.

http://www.gmt400.com/threads/98-gmc-yukon-brakes-help-ive-done-everything.39027/

I dug up that the old Snap-on Mt2500 equipped with the black VCI module will cycle the ABS. For those who insist on staying away from dealerships.

In the past I had luck taking the truck to a large open parking lot and stopping the truck hard enough to kick off the ABS. It cycles air out of the pump, which then needs to be bled from the system.

You don't need to cycle the ABS purge if you are just flushing new fluid or changing components at the wheels. There won't be any air in the ABS unit. If you opened the lines above the ABS or removed the master, then yes.

@tinfoil_hat what if when bleeding you let the reservoir empty completely on accident and the fluid level goes below the reservoir/master cylinder? Happened to my buddy a few weeks ago, he was worried, i told him to just add more fluid and keep bleeding until the air came out. Cost him some extra fluid than he would have needed, but curious now if that would warrant a scan tool and the ABS??

It wasn't necessarily sucking wind if there was still fluid above the lines themselves. I have done the exact same thing myself. One time it was ok, another time I was not so lucky.
If he bled it a bunch more and no more air came out I would say he is golden. If a bunch more air came out after moving that fluid from the master all the way through the lines then it seems like a fair bet there is air in the ABS. He might need to just drive it to find out.

Ok. Yea i've driven it for him since and pedal seems "good enough". The only time it feels like it needs more is under hard/extreme braking. the pedal really pushes to the floor under those circumstances. new from discs and pads and fluid of course. Ill have to look more into the ABS protocol. never really learned much about it

Time to time you do need to bleed your brakes. But did you know just like your engine oil you also need to replace your brake hydraulic fluid? If you have bled the brakes starting from the Right Rear, then the Left rear, right front and lastly the left front and you still have those squishy issues with your brakes? Then you need to remove the fluid from the reservoir and replace it with fresh fluid. Then proceed to bleed your right rear brake till you feel that you have brought the fresh fluid down to it. then top off the reservoir again and do the right rear side till you think fresh fluid has come from the equalization valve that is attached to your differential. Repeat for the right front then the left front. The reason for the pattern is that the right rear is the furthest from the reservoir. This has nothing to do with ABS itself but can affect how ABS performs during times of emergencies when it is active. Your ABS may or may not sense the issues I mentioned above but it is a cheep way to rule out the major things and to point you in the right direction. Note: During a four wheel brake replacement is a good time to bleed the brakes since the reservoir is full after pushing the fluid back to the reservoir when changing them. If your not changing pads/shoes then remember where your reservoir level was when you started and only put that much back in. This is to have space for the fluid to return to when pushing fluid back for the replacement. Also, remember that any brake fluid spilled needs to immediately cleaned up toughly or it WILL remove the paint on anything in or on your vehicle.