Brake Flare Nut Sutck on Flare

[Slurpee12]

2011 Suburban 2500 with 234k miles.  Bought used.

 

Was chasing air in my brakes no matter how many bleeds I performed.  Pedal hardness would be intermittent.  Pumping brakes would make the pedal hard.  No leaks or bulges in lines or hoses, so replaced master cylinder due to green brake fluid and black material in line.  I suspect the internal gaskets disintegrated.  No idea why the fluid is green.

 

Removed the flare nuts from the MC cylinder no problem, barely any force needed.  Both nuts spun on the steel line.  But one nut is stuck on the brake line flare.  I've tightened back and forth and it would not release from the flare.

 

I have not tried heat or vice grips; ran out of time, and wanted to properly research before continuing.  I have map pro and a small butane torch.  My one friend said my only option is to cut the line and create another flare, as the flare could be damaged from the nut and won't seat properly, which could have been the source of my air, but I would really like to avoid that if possible.  All of the flaring kits you can rent use a vise, and I cannot find any information on what size the flare should be.  Google only results in the GMT 800 series.

[txab]

Are you bleeding your ABS sytem too?

[Slurpee12]

2 minutes ago, txab said:

Are you bleeding your ABS sytem too?

Master cylinder never went dry so I did not bleed ABS.  After bleeding pedal stays hard for entire test drive.  Don't get an intermittent pedal until after it's been sitting.  But that's not the focus of this post.

[txab]

Doesn't matter, you removed the lines now, and allowed air in. Often still need to bleed the ABS system to clear the issues.

 

You can look at the flare to see if it's good or not.

 

The tube coating is the reason your nut is not back off. Try a little lube and pull the nut back away from the flare

Edited February 26, 2024 by txab

[richard wysong]

Those are plastic coated brake lines, The nut is  probably hung up on the plastic, try penetrating oil. If the flare is cracked there should be a visible fluid leak

[Slurpee12]

18 minutes ago, txab said:

Doesn't matter, you removed the lines now, and allowed air in. Often still need to bleed the ABS system to clear the issues.

 

You can look at the flare to see if it's good or not.

 

The tube coating is the reason your nut is not back off. Try a little lube and pull the nut back away from the flare

I don't have a bi-directional scanner so I will need a shop to bleed the ABS unit.  It was my understanding that you only need to bleed the ABS unit if you activate ABS and there is air in the system.  That has not occurred with me driving, but it is not something that I considered from the previous owner, which is why I did not bleed the ABS.

 

If I can't get the nut to back off for whatever reason, is it okay to screw back in to the MC assuming there are no cracks on the flare? 

[Slurpee12]

14 minutes ago, richard wysong said:

Those are plastic coated brake lines, The nut is  probably hung up on the plastic, try penetrating oil. If the flare is cracked there should be a visible fluid leak

Was going to torch it with a mini butane torch instead of MAP pro, put some vise grips on the nut and try to pull back.  If I am unable to back off the nut and the flare is not cracked, am I able to screw the line back in?  The nut rotates freely so I can screw it in and out of the MC.

[Slurpee12]

The flare does not look damaged.  Since the nut rotates freely on the line, is there a downside to just screwing it back into the MC?

[CamGTP]

No, just clean the flare with a scotch brite pad to clean and screw it back down.

 

You can always try going down a dirt road at like 20-30mph and slamming on the brakes to engage the ABS. Do that a few times and then re-bleed the system to see how it feels.

[Slurpee12]

54 minutes ago, CamGTP said:

No, just clean the flare with a scotch brite pad to clean and screw it back down.

 

You can always try going down a dirt road at like 20-30mph and slamming on the brakes to engage the ABS. Do that a few times and then re-bleed the system to see how it feels.

Excellent. 
 

I think I am just going to bleed enough to get down to the shop and pay for a flush. Fluid should be brand new after going through 4 bottles and this is what it looked like draining from the MC after bleeding the last weekend. 

[davester]

...just fyi, disconnecting any lines upstream of the abs controller, you should bleed the abs controller afterwards.

 

The specific process for bleeding the brakes varies between gmt800 and gmt900 trucks, don't recall what it is for the 900's.