2008 Silverado Brake Bleeding Issues

SLOW3R · February 4, 2018

Long post, but please give it a read.

I recently purchased a 2008 Silverado Ex cab, 4x4 v8. Base model in really nice shape with 118k for a work truck. 2 owner truck, last owner had it 6 years. Had some issues to work out, Fuel pump supply line had a hole in it, needed tires. got that done. Now on to the brakes. When I bought it, the owner told me it needed brakes. It only had half pedal when I test drove, I assumed someone had been it it and didn't get the air out. After inspection it appears the front rotors and pads are brand new. Front bleeder screws looked to have NEVER been taken loose, EVER. I replaced the bleeders. Rear brake lines on the axle looks to have been completely replaced recently. All other lines look in great shape. So I pulled the drums off the back which was no easy task. They still had the original retainers on them, and were stuck. Went ahead and had the drums turned, new shoes and new wheel cylinders as they looked like they were on the way out.

Now on to to the bleeding. End result I have no pedal unless I pump a little then its gone shortly after, I believe I have a good booster and master cylinder. Hard pedal when truck is off. I started bleeding like I have done with many other vehicles. This one I cannot seem to get the air out. I suspect the previous owner blew a rear line and fluid ran low enough in the master cylinder to get air in the ABS pump. I ran over a quart and half of fluid through. I tried vacuum bleeding and traditional bleeding. I tried contacting to people I bought it from with no luck. I am trying to avoid going to the dealer to have them cycle the ABS pump for me. Which leads me to today. We got just a dusting of snow, with alot more on its way tomorrow. I was able to get the ABS to kick in a few times with what little pedal I could get. I am going to try again tomorrow with more snow to make sure I get it 100% activated to see if it will push some good fluid in there and the air out.

My question for you guys is, am I on the right track here? Any tips or advice? Any other tricks to cycle the ABS pump without having the proper scanner.

pickmeup · February 4, 2018

You are on the right track. GM dealership has bleeder vac which will purge ABS of air . But you got the conditions to do it by activating ABS on snow . I have done it that way myself but it may take 10 or 12 good activations.

SLOW3R · February 5, 2018

When I got the abs kicked on this afternoon, didn't quite sound or feel the same as my other trucks. I hope its just because I have such a weak pedal. Hoping I have enough of a pedal to have the pressure push the air out of that module.

What type of bleeding do you prefer? I was not very happy with the vacuum system I bought. Clear tube into clean brake fluid is what I have been doing as I don't have a helper.

GhostWriter · February 5, 2018

4 hours ago, SLOW3R said:

When I got the abs kicked on this afternoon, didn't quite sound or feel the same as my other trucks. I hope its just because I have such a weak pedal. Hoping I have enough of a pedal to have the pressure push the air out of that module.

What type of bleeding do you prefer? I was not very happy with the vacuum system I bought. Clear tube into clean brake fluid is what I have been doing as I don't have a helper.

I use Speedi Bleed, from Canada.

There are so many variables, here, that it could be anything.

Also, if you're right about the bleeder valves, then the front pads were probably replaced after the pistons were forced back into the caliper. That would mean all that nasty fluid pushed back into the ABS system.

Some random thoughts......

- Am assuming you are not losing any fluid.

- The booster is supposed to make the pedal easier to press; however,

the check valve can go bad.

- The firm pedal with engine off doesn't necessarily mean the master

cylinder is good.

- When bleeding, if the pedal is accidentally pressed to the floor, it could

ruin the MC.

- Your drum brakes might not be adjusted correctly.

- Verify that your bleeder valves are on "top" of the calipers.

- If there aren't any mom & pop brake experts in Pekin, have Dennison's

look at it.

Good luck!

SLOW3R · February 6, 2018

Well a $196 master cylinder from Napa fixed this thing. Brakes work perfect now.

This is the first time I have actually got to drive it since I bought it. Soon as it got warm for awhile, I got a check engine light, P0171 P0174 P0171P P0174P

Rough idle in gear, and high idle in park. Idle wont come down when revved. Looks like Intake gaskets are in my future. $300 fuel pump, $300 worth of brakes. Hopefully I can drive this soon.....

GhostWriter · February 7, 2018

Baby steps.

carnau · February 7, 2018

1 hour ago, SLOW3R said:

Well a $196 master cylinder from Napa fixed this thing. Brakes work perfect now.

This is the first time I have actually got to drive it since I bought it. Soon as it got warm for awhile, I got a check engine light, P0171 P0174 P0171P P0174P

Rough idle in gear, and high idle in park. Idle wont come down when revved. Looks like Intake gaskets are in my future. $300 fuel pump, $300 worth of brakes. Hopefully I can drive this soon.....

I was going to say I thought it was a master cylinder. Good job. I don't believe the Idle is because of the intake gaskets. I believe the idle is due to the ECM learned throttle position. I just went over this in a post with another guy and I will link it in here. It need to have an SPS program done to the ECM and it will get you going again. This happens alot if the vehicle has been sitting up for a while or if the throttle body has been recently cleaned.

Here is the post I was talking about.

http://www.gm-trucks.com/forums/topic/209103-throttle-body-clean/?page=2&tab=comments#comment-2078434

bgbdwlf2500 · February 9, 2018

On ‎2‎/‎6‎/‎2018 at 6:08 PM, SLOW3R said:

Well a $196 master cylinder from Napa fixed this thing. Brakes work perfect now.

This is the first time I have actually got to drive it since I bought it. Soon as it got warm for awhile, I got a check engine light, P0171 P0174 P0171P P0174P

Rough idle in gear, and high idle in park. Idle wont come down when revved. Looks like Intake gaskets are in my future. $300 fuel pump, $300 worth of brakes. Hopefully I can drive this soon.....

Mine idled perfectly in gear and in park but would not idle down when slowing down. it also would hang at 2500 rpm if I revved it in park. It did not throw any codes either so not sure if its the same issue but carnau from the post below thinks its the fix. try to find a gm mechanic that left a dealership, they usually will charge way less. on mine it was a 15 min procedure.

On ‎2‎/‎6‎/‎2018 at 7:53 PM, carnau said:

I was going to say I thought it was a master cylinder. Good job. I don't believe the Idle is because of the intake gaskets. I believe the idle is due to the ECM learned throttle position. I just went over this in a post with another guy and I will link it in here. It need to have an SPS program done to the ECM and it will get you going again. This happens alot if the vehicle has been sitting up for a while or if the throttle body has been recently cleaned.

Here is the post I was talking about.

http://www.gm-trucks.com/forums/topic/209103-throttle-body-clean/?page=2&tab=comments#comment-2078434

SLOW3R · February 15, 2018

Here's an update in case anyone is interested.

Vacuum leak was between the master and brake booster. Codes cleared and vacuum leak gone. Got 5 miles on it, and got a check engine light for an 02 sensor. Got that issue fixed.

So, I got 20 miles on it tonight after work. With a few hiccups, It was 40 degrees here today. Temp gauge went between 210 and the next mark. It was sitting at idle for about 10 minutes after a couple mile drive when this happened. I popped the hood and as soon as I got it open the fans kicked on and it went back to 210. They were only running on low speed though. I would assume they should be kicking on sooner.

Also I'm pretty sure I can hear the compressor kicking on and off, Heat was set on floor. When pushed, the AC button, and recirculating buttons do not light up when pushed, all other climate controls work. I'm working a lot hours lately trying to get this thing all ironed out as time allows. I cant find any info on this issue.

GhostWriter · February 15, 2018

5 hours ago, SLOW3R said:

Also I'm pretty sure I can hear the compressor kicking on and off, Heat was set on floor. When pushed, the AC button, and recirculating buttons do not light up when pushed, all other climate controls work. I'm working a lot hours lately trying to get this thing all ironed out as time allows. I cant find any info on this issue.

Sounds like your project is moving along.

Probably wouldn't draw any conclusions on your AC operation until it gets warmer, outside.

Read the fine print in the owners manual. It should list the exact conditions for your AC to be cycling, automatically. Usually tied to humidity control.