Bleeding Brakes after replacing steel lines

[yellowkid]

I'm original owner on a 2004 GMC Yukon w/4WD, and I'm one of those poor souls whose steel brake lines rotted out and had to be replaced. I got the "kit" from GMC, it fit fine, did the job myself. Replaced everything up front from the Master Cylinder on down to the pads including new calipers, lines rotors etc. On the rear I did the flexible lines, rotors/pads. I used a vacuum bleeder -- cheapo form Harbor Freight but worked great! All three wheels bled fine to a solid stream but I could never seem to get the air out of the LH rear. Brakes work well but they have a crunchy feel and ABS is always going off. Definitely feels like the bleeding job.

I read a while back that the problem is the ABS unit requires a special bleeding using a computer or something? Is that true? Is there no way for the layman to get this done? I hate to have done all of this on my own (after ridiculous quotes form teh dealers to do the line replacement!) and have to take it to them to do this final step. I'm sure they'll charge me a ridiculous amount. I'm almost there but not quite home!

thanks! john

 

[Scottydoggs]

if the master has some air trapped still it will fail to bleed right and leave you with a mushy pedal still.

did you bench bleed the master before putting it on?

if not, you can pump the pedal and hold it while someone cracks the rear line off the master, wrap a rag around the wrench to keep fluid from flying, if theres air, you'll hear it come out. repeat till just fluid comes out. then go and re bleed the back brakes again.

 

[Chubbs]

He only did the lines, right? What if the MC is original?

Since the ABS wasn't tampered with there would be no issue with that if it was working properly beforehand. Meaning it doesn't require the electronic pulsing with the software you were referring to.

So long as the MC reservoir wasn't allowed to go dry during the purging process it should be fine. You should be able to vac or gravity bleed that caliper until it flows straight B/F

 

[Scottydoggs]

i misread, thought he replaced the master too.

if the master drained while the lines were off its now dry and needs to be bleed first, then the calipers can be done.

short of taking it off to bench bleed it, then you need the little hoses and plastic line nuts you get with a new master, so next best thing is to use the line nuts like bleeders and bleed the master that way.

 

[Chubbs]

if the master drained while the lines were off its now dry and needs to be bleed first

With the info he orig gave, we can only assume this, I suppose.

Also to answer the OP, yes the layman can do the "dealer only" ABS purge with either the proper software (think TECH2) or jump the relay to pulse the ABS pump.

The Automated Bleed procedure is to be performed when the brake pressure modulator valve (BPMV) is replaced, which doesn't apply here.

 

[Chubbs]

@yellowkid

follow the instructions below and proper braking function will be restored.

1. If you have performed a brake master cylinder bench bleeding on this vehicle, or if you disconnected the brake pipes from the master cylinder, you must perform the following steps:
   1. Ensure that the brake master cylinder reservoir is full to the maximum-fill level. If necessary add GM approved brake fluid from a clean, sealed brake fluid container. Refer to Fluid and Lubricant Recommendations.
      
      If removal of the reservoir cap and diaphragm is necessary, clean the outside of the reservoir on and around the cap prior to removal.
      
      
   2. With the rear brake pipe installed securely to the master cylinder, loosen and separate the front brake pipe from the front port of the brake master cylinder.
      
      
   3. Allow a small amount of brake fluid to gravity bleed from the open port of the master cylinder.
      
      
   4. Reconnect the brake pipe to the master cylinder port and tighten securely.
      
      
   5. Have an assistant slowly depress the brake pedal fully and maintain steady pressure on the pedal.
      
      
   6. Loosen the same brake pipe to purge air from the open port of the master cylinder.
      
      
   7. Tighten the brake pipe, then have the assistant slowly release the brake pedal.
      
      
   8. Wait 15 seconds, then repeat steps 3.3–3.7 until all air is purged from the same port of the master cylinder.
      
      
   9. With the front brake pipe installed securely to the master cylinder, after all air has been purged from the front port of the master cylinder, loosen and separate the rear brake pipe from the master cylinder, then repeat steps 3.3–3.8.
      
      
   10. After completing the final master cylinder port bleeding procedure, ensure that both of the brake pipe-to-master cylinder fittings are properly tightened.

After this, you will then bleed the calipers starting with RR, LR, RF, LF in this order.

 

[yellowkid]

gentlemen thank you very much -- yes the MC was OK and not replaced! but of course the lines were replaced below it. I'll follow the steps above. glad to hear it is something I can do.

 

[JonnyTahoe]

gentlemen thank you very much -- yes the MC was OK and not replaced! but of course the lines were replaced below it. I'll follow the steps above. glad to hear it is something I can do.

The reason Chubbs gave that specific Bleeding sequence is because you want to start with the wheel cylinder the farthest away from the master cylinder and work your way up to the master cyl. SO the Right rear is the farthest and then Left rear then up to the Right front till you get to the Left front which is the closest. I replaced both Rear lines on a 95 last fall and like many of us had not bleed brakes in years. I had all kinds of trouble and after taking a break started all over with Gravity bleeding them one at a time and when some air bubbles came out of one of the rears I knew I found the problem.

 

[blackopsiisuks]

I'm original owner on a 2004 GMC Yukon w/4WD, and I'm one of those poor souls whose steel brake lines rotted out and had to be replaced. I got the "kit" from GMC, it fit fine, did the job myself. Replaced everything up front from the Master Cylinder on down to the pads including new calipers, lines rotors etc. On the rear I did the flexible lines, rotors/pads. I used a vacuum bleeder -- cheapo form Harbor Freight but worked great! All three wheels bled fine to a solid stream but I could never seem to get the air out of the LH rear. Brakes work well but they have a crunchy feel and ABS is always going off. Definitely feels like the bleeding job.

I read a while back that the problem is the ABS unit requires a special bleeding using a computer or something? Is that true? Is there no way for the layman to get this done? I hate to have done all of this on my own (after ridiculous quotes form teh dealers to do the line replacement!) and have to take it to them to do this final step. I'm sure they'll charge me a ridiculous amount. I'm almost there but not quite home!

thanks! john

My 04 suburban did the same.

When bleeding did your bleeding sequence go as follows:
RR, LR, RF, LF or longest distance to shortest?

I too used the napa handy bleeder. Worked great. Did have to replace a couple bleeder valves due to corrosion.

No problems since.

Oh and I used the oem 9800 psi lines instead of the stainless 5400 psi replacements. I felt the 12,000 tow capacity might be compromised by using the stainless lines.


Sent from my iPhone using Tapatalk

 

[Chubbs]

@blackopsiisuks

Great insight. In all of the brake pipes threads & discussions, this is the 1st time I've read any mention of psi rating.