Air in brake lines.
06-05-2018, 05:06 PM
#1
Air in brake lines.
2008 GMC Yukon Denali.
Issue is I just keep getting air in brake lines. Most noticeable in passenger front.
From the top, brakes worked fine no issues just pads worn and a little warp. I do new pads and rotors and then go to do a fluid flush/bleed.
Only mistake I can figure is I was having a tough time with a rear caliper and the bleeder was not backing out smoothly. I figure I probably let air in the system while working on that. I now assume I let air into ABS system.
I have bled 3 large bottles of brake fluid and I have little to no brake pedal response. Front passenger side just keeps getting air bubbles through.
My scanner has the automated brake bleed feature for the abs and I have run that twice and just keep going through the motions with the same results.
I find no leaks but there is way more air in the line then should even be possible.
Did I damage the master cylinder? Is the booster pumping air in?
Bleed procedures used. Gravity bleed, vacuum bleed, two person procedure. Repeated all 3 with ingnition off as well as on.
Im so perplexed by the amount of air I keep getting!
Issue is I just keep getting air in brake lines. Most noticeable in passenger front.
From the top, brakes worked fine no issues just pads worn and a little warp. I do new pads and rotors and then go to do a fluid flush/bleed.
Only mistake I can figure is I was having a tough time with a rear caliper and the bleeder was not backing out smoothly. I figure I probably let air in the system while working on that. I now assume I let air into ABS system.
I have bled 3 large bottles of brake fluid and I have little to no brake pedal response. Front passenger side just keeps getting air bubbles through.
My scanner has the automated brake bleed feature for the abs and I have run that twice and just keep going through the motions with the same results.
I find no leaks but there is way more air in the line then should even be possible.
Did I damage the master cylinder? Is the booster pumping air in?
Bleed procedures used. Gravity bleed, vacuum bleed, two person procedure. Repeated all 3 with ingnition off as well as on.
Im so perplexed by the amount of air I keep getting!
06-05-2018, 09:22 PM
#2
Senior Member
True Car Nut
OK, so what you are saying is the vehicle braked ok, until you did the brake job?
All you did was change pads and rotors....did you do fronts or backs? Or both?
Did you open the bleeders at each wheel?
Describe EXACTLY, the procedure you used at each wheel.....did you maintain the proper level in the reservoir while bleeding?
Did you do RR first? then LR? Then RF? Then LF?
Just for future reference, If I am going to do a fluid flush, I use a manual vacuum pump with a fluid air separator cup(these usually come as an accessory with the pump)....I open the bleeder at RR, and suck out of the bleeder until the fluid is clear(while continuing to fill the reservoir)....then go in order to the next one......
This is a closed system, so for air to get in there has to be a leak somewhere.....either at the bleeders or the pistons.......
All you did was change pads and rotors....did you do fronts or backs? Or both?
Did you open the bleeders at each wheel?
Describe EXACTLY, the procedure you used at each wheel.....did you maintain the proper level in the reservoir while bleeding?
Did you do RR first? then LR? Then RF? Then LF?
Just for future reference, If I am going to do a fluid flush, I use a manual vacuum pump with a fluid air separator cup(these usually come as an accessory with the pump)....I open the bleeder at RR, and suck out of the bleeder until the fluid is clear(while continuing to fill the reservoir)....then go in order to the next one......
This is a closed system, so for air to get in there has to be a leak somewhere.....either at the bleeders or the pistons.......
06-05-2018, 10:09 PM
#3
Thank you Tech II,
vehicle was braking just fine good pedal feel just time to do pads and rotors. I did front and rear.
Did the fronts no problem and never touched a bleeder while changing the rotors and pads. Between each corner I kept fluid level within tolerance.
When I got to the passenger rear I was struggling a bit and was ready to start changing fluid and bleeding lines. I found the bleeder was very hard to remove. Used socket so I could extract and inspect/clean.During this time that caliper was open as the socket allowed breathing.
I then used a extraction pump to remove fluid from the resevoir and place new fluid in. Gravity bleed PR, DR at PF is when I notice loss of pedal response and noticed lots of air. Continued DF and then started to repeat bleed process because I now didn’t have brakes. There was a time I’ll struggle to recall exactly as there started to be frustrations and I startled a neighbor with bad language. In this time I had started the vehicle as I felt like I got brake pedal response but once I started the car the pedal went straight to the floor and took lots of fast pumping to get any pressure. I got my wife to help me do two person pumping bleed. This is when I really got frustrated as the I had now been bleeding for hours and kept getting so much air through PF. Did notice milk shake suds out of rear but it cleared out as expected.
I went to buy a vacuum pump as Ive always done fine with gravity. Used pump in same sequence and again find lots of air bleed through and keep coming back to PF as I keep getting bubble.
Now im on YouTube and forums.... this is where I find the struggles if I’ve cycled the ABS or allowed air into the system. I assume in all my frustration I got air where I didn’t want it and the vacuum pump kept fighting me so I almost felt like I was going backwards.
Cap was off so I shouldn’t have built negative pressure....at any rate I found multiple videos suggesting I got air in ABS so I got the scanner out the cycle the bleed procedure and ABS bleed.
im now 3 bottle of fluid in, no brake pressure and still getting a lot of air through front passenger side. never sucked air through resevoir only air would go through bleeders.
vehicle was braking just fine good pedal feel just time to do pads and rotors. I did front and rear.
Did the fronts no problem and never touched a bleeder while changing the rotors and pads. Between each corner I kept fluid level within tolerance.
When I got to the passenger rear I was struggling a bit and was ready to start changing fluid and bleeding lines. I found the bleeder was very hard to remove. Used socket so I could extract and inspect/clean.During this time that caliper was open as the socket allowed breathing.
I then used a extraction pump to remove fluid from the resevoir and place new fluid in. Gravity bleed PR, DR at PF is when I notice loss of pedal response and noticed lots of air. Continued DF and then started to repeat bleed process because I now didn’t have brakes. There was a time I’ll struggle to recall exactly as there started to be frustrations and I startled a neighbor with bad language. In this time I had started the vehicle as I felt like I got brake pedal response but once I started the car the pedal went straight to the floor and took lots of fast pumping to get any pressure. I got my wife to help me do two person pumping bleed. This is when I really got frustrated as the I had now been bleeding for hours and kept getting so much air through PF. Did notice milk shake suds out of rear but it cleared out as expected.
I went to buy a vacuum pump as Ive always done fine with gravity. Used pump in same sequence and again find lots of air bleed through and keep coming back to PF as I keep getting bubble.
Now im on YouTube and forums.... this is where I find the struggles if I’ve cycled the ABS or allowed air into the system. I assume in all my frustration I got air where I didn’t want it and the vacuum pump kept fighting me so I almost felt like I was going backwards.
Cap was off so I shouldn’t have built negative pressure....at any rate I found multiple videos suggesting I got air in ABS so I got the scanner out the cycle the bleed procedure and ABS bleed.
im now 3 bottle of fluid in, no brake pressure and still getting a lot of air through front passenger side. never sucked air through resevoir only air would go through bleeders.
06-06-2018, 02:23 PM
#5
Senior Member
True Car Nut
06-06-2018, 04:22 PM
#6
Wife in car, 3 half pumps to built up pedal, I open bleeder on 4th pump and then close it as she holds.
Repeated 4-5 times each corner. I started furthest LR, RR, LF, RF. And I repeated this with ignition on after the first pass failed.
As an update today I have started at LR then RR and am now at LF and I have taken things apart, checked calipers for leaks, checked lines connections and bleeders. At each corner I have gravity bled a roughly 2-3 ounces with no air. Still working on the fronts. I’ll report back on pedal response when this is completed.
As for how far I opened bleeder I am at 1/4 to 1/2 turn and stopping once I see fluid moving.
I’ve learned now that when vacuum bleeding there will be steady air bubbles as it pulls through threads of bleeder. I’m a rookie with vacuum bleeder so there’* that. Fact remains that when I press on the brakes it has perhaps 8% brake response at the floor and hardly stops the truck from a 1-5mph brake check.
Repeated 4-5 times each corner. I started furthest LR, RR, LF, RF. And I repeated this with ignition on after the first pass failed.
As an update today I have started at LR then RR and am now at LF and I have taken things apart, checked calipers for leaks, checked lines connections and bleeders. At each corner I have gravity bled a roughly 2-3 ounces with no air. Still working on the fronts. I’ll report back on pedal response when this is completed.
As for how far I opened bleeder I am at 1/4 to 1/2 turn and stopping once I see fluid moving.
I’ve learned now that when vacuum bleeding there will be steady air bubbles as it pulls through threads of bleeder. I’m a rookie with vacuum bleeder so there’* that. Fact remains that when I press on the brakes it has perhaps 8% brake response at the floor and hardly stops the truck from a 1-5mph brake check.
06-06-2018, 05:07 PM
#7
Retired
Certified Car Nut
Last I knew, RR, was the furthest from the MC.
RR, LR, RF, LF.
RR, LR, RF, LF.
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Retired Administrator
2002 *-10 5.7 V8
2023 Jeep Rubicon Diesel
Retired Administrator
2002 *-10 5.7 V8
2023 Jeep Rubicon Diesel
06-06-2018, 06:47 PM
#8
Senior Member
True Car Nut
Wife in car, 3 half pumps to built up pedal, I open bleeder on 4th pump and then close it as she holds.
Repeated 4-5 times each corner. I started furthest LR, RR, LF, RF. And I repeated this with ignition on after the first pass failed.
As an update today I have started at LR then RR and am now at LF and I have taken things apart, checked calipers for leaks, checked lines connections and bleeders. At each corner I have gravity bled a roughly 2-3 ounces with no air. Still working on the fronts. I’ll report back on pedal response when this is completed.
Repeated 4-5 times each corner. I started furthest LR, RR, LF, RF. And I repeated this with ignition on after the first pass failed.
As an update today I have started at LR then RR and am now at LF and I have taken things apart, checked calipers for leaks, checked lines connections and bleeders. At each corner I have gravity bled a roughly 2-3 ounces with no air. Still working on the fronts. I’ll report back on pedal response when this is completed.
When the piston in the master cylinder travels far outside of its normal range of travel it will sometimes cause other problems in the master cylinder. When I'm bleeding brakes I'll stop about 3/4 of the way down to avoid that.
This is usually on well-worn master cylinders.
How many miles on this car?
Are these city miles or highway?
Yeah, I never like seeing all those bubbles with a vacuum bleeder. Feels wrong.
06-06-2018, 10:48 PM
#9
Update is I now have brakes.
Thank you for attempting to assist.
The mistake I made was stupid and cost me many hours of frustration. When I struggled with the rear bleeder due to corroding I then removed the front passenger bleeder to check for the same issue. I appearantly got some chunk of crap that then kept the bleeder from seating completely. As I bled the rear I guess I was sucking air through the system or some thing.
After going over all the steps again and doing a really long gravity bleed I started to feel some pedal. When I found the chunk of crap stuck to the front bleeder I cleaned that and the caliper hole and started the bleed all over. I finally stoped getting air and now have brakes.
I got frustrated enough that I skipped the basic step of cleaning around bleeder before removing it and replacing it.
Thank you again.
Thank you for attempting to assist.
The mistake I made was stupid and cost me many hours of frustration. When I struggled with the rear bleeder due to corroding I then removed the front passenger bleeder to check for the same issue. I appearantly got some chunk of crap that then kept the bleeder from seating completely. As I bled the rear I guess I was sucking air through the system or some thing.
After going over all the steps again and doing a really long gravity bleed I started to feel some pedal. When I found the chunk of crap stuck to the front bleeder I cleaned that and the caliper hole and started the bleed all over. I finally stoped getting air and now have brakes.
I got frustrated enough that I skipped the basic step of cleaning around bleeder before removing it and replacing it.
Thank you again.
The following 2 users liked this post by YukonBrakes:
CathedralCub (06-07-2018),
Soft Ride (06-07-2018)
06-06-2018, 11:46 PM
#10
Senior Member
True Car Nut
Sometimes it'* something real simple.......the only thing you opened were the bleeders, and the possibility(rare) of the piston leaking when retracting them....surprised the bleeder didn't leak as you were pumping the brakes......
Glad you found it, and posted the solution...
Glad you found it, and posted the solution...
The following users liked this post:
Soft Ride (06-07-2018)