Reoccurring Air in Brakes

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Ernstcr

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I have a 2016 BigHorn 2500 Cummins around 150k. Just recently did front rotors, pads, hub/bearings. When pulling the front right caliper I damaged one of the pistons and replaced the caliper with a new one from Napa. Got it all out back together bled the brakes 1,2,3 hold….. repeat. Got what I thought was all the air out of the system checked every caliper to be sure. Drove it about 15 miles and they started to get soft, checked them and had to bleed them again, 10-15 miles later again super soft brakes re-bled, did this about 3-4 more times and threw in the towel and took it to the shop and they did a flush and vacuum bleed and gave it back to me, 5 miles later again. Took it back they did abs sensor whatever(not sure what it’s called) with the expensive tool, they had it two days and told me they gave up and to take it to dealer next appointment is in 26 days! There are no leaks that me or the shop could find they were going to replace master cylinder but the boss told them to give up before that happened. Anyone have a clue what is going on?
 

markabby

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ugh....i had an '81 corvette that did that. i replaced every known part in the brake system and still got air in the lines. i finally sold it.

but, start from the beginning and work your way back...have extra fluid on hand, you'll need it. like 2020PW said...that abs module !
 

zrock

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im assuming since they changed the ABS sensor they blead the brakes using their expensive tool.. I would go back to what you changed possible you received a bad caliper i have gotten a few of those from NAPA parts, or possible your flex line is bad allowing air in, i always replace those when doing a caliper..
 

Daw14

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I had a master cylinder leak into a booster one time , it took a little to find that leak But there it was.
 

Rambeau

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I've got exactly the same issue. New master. Bled it then took it to a shop, next day soft brakes. They bled it with the factory tool. They want to replace the abs part at $1050.00 plus labor. I don't believe it's that part. Help...

Also, it seems like the brakes only have the soft pedal when it's warm. Now that the weather has cooled down the pedal is much firmer. Strange, i know. I have a brake lite on the dash all the time and a low fluid warning in my message center. I had thought that the sensor on the new master was bad, so i ohmed it yesterday. The old (working) sensor read full continuity with an empty tank. The new sensor with full fluid read open, so i believe the sensor is reading full, but still have the low fluid message.
 
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GTyankee

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i wonder if there is some kind of dye, that would show a bad fitting on a hose or steel line
 

2003F350

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i wonder if there is some kind of dye, that would show a bad fitting on a hose or steel line
Air is getting into the system somewhere, but generally if air can get in, fluid can get out. There should be a wet spot on a line somewhere.
 

Sherman Bird

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I have a 2016 BigHorn 2500 Cummins around 150k. Just recently did front rotors, pads, hub/bearings. When pulling the front right caliper I damaged one of the pistons and replaced the caliper with a new one from Napa. Got it all out back together bled the brakes 1,2,3 hold….. repeat. Got what I thought was all the air out of the system checked every caliper to be sure. Drove it about 15 miles and they started to get soft, checked them and had to bleed them again, 10-15 miles later again super soft brakes re-bled, did this about 3-4 more times and threw in the towel and took it to the shop and they did a flush and vacuum bleed and gave it back to me, 5 miles later again. Took it back they did abs sensor whatever(not sure what it’s called) with the expensive tool, they had it two days and told me they gave up and to take it to dealer next appointment is in 26 days! There are no leaks that me or the shop could find they were going to replace master cylinder but the boss told them to give up before that happened. Anyone have a clue what is going on?
What does the law of descending logic mandate? "Look at the last thing you did before having the problem"!
In reading between the lines in your message, I'd professionally start with the caliper! I do not know intimately that particular vehicles in that; will the left and right calipers fit on each others' side? Is it possible that the caliper you installed is actually one for the other side, i.e. upside down. And that would put the bleeder screw under the piston as opposed to above it. My next door neighbor recently did that on his Jeep Patriot. After he bled nearly 2 gallons of fluid through the system with a soft pedal still present, he came and knocked on my door. The caliper might just be defective as well.

I saw my neighbor's problem immediately, because I've made that mistake before. Once he "flipped" them, the problem was fixed.

One other thing you need to check is that the flex hoses flow freely. I had a customer with an F-350 that a mobile mechanic and 2 shops couldn't get a firm pedal on. I went around the truck and systematically disconnected and blocked off where each of the flex hoses attached, attempted to bleed the system to obtain a firm pedal and, VOILA! I finally found the one which, although it flowed fluid out during bleeding, had some defect internally. I replaced the hose and all was well!
 
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