Brake question

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HiHoeSilver said:

Does cycling the key really purge the air from abs effectively? There's all kinds of talk about needing a Tech II, or going to a gravel road and slamming on the brakes.... Planning on doing calipers and lines all around soon, been unsure about proper bleeding.

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iamdub said:

I've never had a problem doing it. It may not be as fast as using a Tech II to hold the valves open, but it works just fine for someone that doesn't have such equipment. I've done the slamming on brakes in gravel (or in a grassy field in my case), but then I have to park and get back under the car to bleed it again if not jack it up and pull the wheels. By that time, the air bubbles could work their way back to the module.

If the fluid is under pressure (when you just start to apply pedal pressure), then the fluid and air bubbles should move the instant the valves open. Since the valves cycle during the self-test when the key is turned on, doing this trick a few times properly should be plenty effective enough.

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Awesome, thanks for sharing. I'm going to give it a shot next weekend. It sounds like it'll be a pain in the rear, but it beats forking over a few hundred dollars for a shop to do it. Have you done yours yet?

sumtallguy said:

So I won't be able to bleed the brakes the "old fashioned" way? What I've read is that I won't need the scan tool unless I let the master cylinder run empty, is this not true?

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No tech2 needed for this. If you have 4WD you can put all four corners on jack stands and then put it in drive and hit the brakes. The ABS will activate to purge any air. You then need to bleed the brakes again. Maybe have to do this procedure 2 or three times. I had this happen when I replaced the master cylinder and didn't do a bench bleed correctly.

sumtallguy said:

Awesome, thanks for sharing. I'm going to give it a shot next weekend. It sounds like it'll be a pain in the rear, but it beats forking over a few hundred dollars for a shop to do it. Have you done yours yet?

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I haven't. I am still collecting parts to upgrade the front. I want to do them all together so I only need to bleed it once. I know that those fit tings for the lines can be pretty sticky, so I'd recommend getting in there and hitting them with PB blaster or aerokroil a couple times ahead of the job. Also, it has been said that water is good for breaking rusty ones loose.

Thanks for posting that, Nate. I was gonna try to find those posts and copy/paste them here.

Colin, If your brake pedal isn't excessively soft now, then you won't have a problem bleeding them if you don't let air in the system. Don't let the MC go empty. You can minimize introducing new air into the system by doing the following:

Place a big drip pan under the brake you're working on.

Unbolt the old calipers from the brackets but leave them still connected to the system. You can let them hang out the way since you're replacing the hoses anyway.

Attach the new hoses to the new calipers.

If the piston is already pushed all the way into the caliper, blow into the hose to slowly push it out, but block it from popping out all the way.

Hold the caliper so that the bleeder screw is the highest point and remove it.

Fill the caliper with fluid until it's at the bottom of the bleeder screw hole, then reinstall the bleeder about 1/8th turn past finger tight.

Set caliper and hose down into the drip pan so that the bleeder screw is still up. Fluid may be dripping out of the hose at this point.

Disconnect the old hose and caliper from the hard line. Fluid will begin to run out.

Quickly position the new caliper close enough to the hard line so that you can screw in the hose by hand. I like to press the piston in with my thumb using an old brake pad laid in the caliper so that a little bit of fluid squirts out of the hose just before I begin threading it to the hard line. This ensures there is no air or very minimal air in the line.

Tighten the hose to the hard line as much as you can by hand.

Slip in the pads and put the caliper into position, but don't worry about bolting it in place yet if you can get it to stay in position.

Fully tighten the hose-to-hard line connection.

Bolt in the new caliper, be sure to grease the slide pins.

Repeat for the other side.

Be sure the MC is full and bleed the system. Remember to NOT bottom out the brake pedal. You can position a 2x4 in the floorboard to act as a stop that will let the pedal have sufficient stroke to bleed but not bottom out.

Awesome, thanks for the info. I'll give it a shot this weekend and let you all know how it goes.

...@ rockola1971

is this the scanner ??

http://www.ebay.de/itm/GM-TECH2-Dia...085508?hash=item3f7c7693c4:g:BPQAAOSwPCVYBTVc

If yes...I will buy one... because we ( friends of mine and me ... ) have a few Tahoes... and they are getting older...so more problems will show up in the future

@sumtallguy excuse me for "highjacking" your thread

Greetings Juergen

Time for an update. I've been so busy with work lately I decided to just take it to Jiffy Lube and have them do it. They replaced my rear calipers, rotors, and pads. They also bled the brakes and put in new brake fluid. Now the brakes are working great and no more caliper sticking! The heat/dust shield on the back of the rotors was toast so they took that off, and they showed me where there appears to be a small brake fluid leak on the brakes, but I'll worry about that another day.

...WOW they let you drive with leaking brakes ?? That is crazy. Also the heat dust shields have a function..
so why did´t they renew those shields ??

This is really crazy, nutty. I did bleed my brakes this morning for four hours. Three times for i still had some air in lines. i activated the ignition to purge the abs module many times for each wheel manifold. and pumped for four hours. Did a test ride and I think they are worse than when i started. Thank you GMC for making our life tougher with less money.
Going to local auto repair next week. cant afford a $ 534.00 scan tool.