Soft Brakes, New Day

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nick0789

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Morning Update:
I went ahead and went through the hydroboost bleeding procedure scottydoggs outlined and did not notice an improvement. I looked into the PS reservoir and did not notice any bubbles or foaming.

I took temps of the brake rotors after driving to work this morning and the fronts were definitely cooler than the rears (like 20-25% cooler). It seems somewhat counterintuitive to me so I went ahead and ordered new pads, rotors, and guide pins as I have the torx bolts. If nothing else it allows me to break down the front brakes and clean everything up, and I will go ahead and re-bleed the master cylinder on the vehicle during this process in the event that I still have trapped air at the end of the cylinder.

I'll provide an update at some point over the weekend with what the outcome is. Thanks again for all the input!
 

rockola1971

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Morning Update:
I went ahead and went through the hydroboost bleeding procedure scottydoggs outlined and did not notice an improvement. I looked into the PS reservoir and did not notice any bubbles or foaming.

I took temps of the brake rotors after driving to work this morning and the fronts were definitely cooler than the rears (like 20-25% cooler). It seems somewhat counterintuitive to me so I went ahead and ordered new pads, rotors, and guide pins as I have the torx bolts. If nothing else it allows me to break down the front brakes and clean everything up, and I will go ahead and re-bleed the master cylinder on the vehicle during this process in the event that I still have trapped air at the end of the cylinder.

I'll provide an update at some point over the weekend with what the outcome is. Thanks again for all the input!
Front brakes provide roughly 80% of your braking power and thats "hardwired" into your brake system via the proportional valve. So I would expect the front brakes to be warmer than the rear. You dont want your rear brakes overbraking past your front brakes, that ends up being a squirrelly 2 1/2 ton with 4 wheels with you behind the steering wheel! It is NOT a fun ride. Especially on gravel, ice and wet roads.
 

Scottydoggs

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Front brakes provide roughly 80% of your braking power and thats "hardwired" into your brake system via the proportional valve. So I would expect the front brakes to be warmer than the rear. You dont want your rear brakes overbraking past your front brakes, that ends up being a squirrelly 2 1/2 ton with 4 wheels with you behind the steering wheel! It is NOT a fun ride. Especially on gravel, ice and wet roads.
newer cars and trucks use much more rear brake. all of the work trucks eat the rears way before the fronts. same goes for my 03 pick up i sold. as well as my 05 tahoe. work trucks are 3500's a 05 and a 15. even my 98 regal would use up the rears first no matter what brand pads i used.
 

Buggdave

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Just another thought, when I added hydro boost to my rig, I also changed out the flex hose to each caliper with stainless steel braided. I know that with age, the rubber ones will expand a little and take way some of the hydraulic force going to the calipers. I did not see you mention if you had changed these yet on your setup.
 
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nick0789

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Weekend Update:

I went ahead and replaced all five rubber brake lines (with rubber), gravity bled the system at each corner as I worked through the hoses, replaced the front rotors and pads, and replaced the caliper bolts / guide pins. Then I bled the system again and saw absolutely zero air at the end of it all.

I just took the tahoe for a shake down test drive and to also bed the brakes until they STANK.

I can pull part numbers if anyone ends up needing them for whatever reason but I went with NAPA hoses (AKA repackaged Sunsong hoses), NAPA ultra premium coated rotors, and Akebono ProACT (ACT785) pads.

Overall there is a noticeable improvement in braking and pedal feel once the engine warms up, though not too terribly noticeable when cold — I’m assuming this is due to the power steering and/or hydroboost needing time to warm up??

A few final notes from my “project” of the day:
1) who’s idea was it to use a soft line in the rear center of the vehicle where there is almost zero room for a wrench to rotate? I dropped the spare tire and was was able to get a stubby 9/16” wrench to remove the flare nut, though I would have really preferred to use a line wrench but oh well. It still took over 45 minutes to loosen, clean up, feed the new hose, install, and check for leaks during gravity bleeding for this one hose all while in a very uncomfortable working position.

2) who’s idea was it to use female T55 torx bolts for the front caliper guide pins? Those things are a JOKE. Im glad I looked into it before I even ordered parts so I knew what I was getting myself into but it was ridiculous: I twisted my first T55 socket when trying to remove the passenger lower bolt and had to run to the store to get a new socket … then I get back and went to town on it with my impact driver and that thing would NOT budge. I ended up pulling the caliper anyways so I took it aside and heated the bolt with a torch and it finally broke free. I clearly took the smart route during reinstall and swapped the bolts for the hex heads.

3) the driver’s front pads were STUCK to the caliper bracket. I didn’t see any evidence that the caliper wasn’t working anymore, as the old rotor was always shiny and the new rotor had the coating strip off just like the passenger side, but I still spent a solid 10-15 minutes trying to remove the stuck pads with a deadblow.


All in all, I took my time and invested over 8 hours to get it all done and tested. If I had to do it again on another tahoe tomorrow I’d likely be done in 4-5 hours
 

rockola1971

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My 05 Denali with hydroboost the brakes are firm even at cold engine start. But I bled my system with a Tech 2 using the auto feature which gets rid of the air behind and in the solenoids of the ABS manifold.
 
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nick0789

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My 05 Denali with hydroboost the brakes are firm even at cold engine start. But I bled my system with a Tech 2 using the auto feature which gets rid of the behind and in the solenoids of the ABS manifold.
Thanks for the catch. I didn’t note that I also bled the ABS module with my scan tool twice as well. I’ll go back out and bleed the module and corners one more time at some point before Monday and see if I get any improvement.
 
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nick0789

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FFDC76DB-F46C-4CE1-989A-2EE6D8E3E2F8.jpeg
Update: there was no improvement in pedal feel with additional ABS bleeding and bleeding at the corners afterwards.

I’ll be testing the power steering pump pressure as I have also been feeling some still steering wheel response when in the parking lot.

In the event that this test comes back with less-than-ideal results is this the power steering pump everyone would recommend? I’ll also be changing the two lines in the process but I have the BPH RPO code so this and the AC Delco website were slightly confusing.
If there are other recommendations for PS pumps I’ll be happy to hear them. I’d like to stay away from remanned units if possible but if there is a consensus I’ll listen to the crowd.

Thanks again!
 

iamdub

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View attachment 383014
Update: there was no improvement in pedal feel with additional ABS bleeding and bleeding at the corners afterwards.

I’ll be testing the power steering pump pressure as I have also been feeling some still steering wheel response when in the parking lot.

In the event that this test comes back with less-than-ideal results is this the power steering pump everyone would recommend? I’ll also be changing the two lines in the process but I have the BPH RPO code so this and the AC Delco website were slightly confusing.
If there are other recommendations for PS pumps I’ll be happy to hear them. I’d like to stay away from remanned units if possible but if there is a consensus I’ll listen to the crowd.

Thanks again!


Does the pedal feel change when revving the engine? Have you driven in a lower gear to get the RPM up and tested the braking?
 

B-train

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I personally stay away from reman products. Got burnt too many times years back......it sucks doing the same job twice and sometimes not able to get paid for the second time.

Find a good name company that offers new with warranty. I've used car quest and napa in the past and had decent luck. Lately though I have been going more to the OEM stuff whenever possible. Having online competition has made the OE stuff more competitive price wise.
 

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