ABS service - air bubbles in circuit

[SK_in_AB]

I am doing an ABS service on my 2006 RT using a couple guides I got off the internet.  This is the servo system with pump and requires bleeding of 8 different circuits. All went well with the pump driven front and back caliper bleeds using a home made funnel tool to refill the reservoirs while activating the brake levers.  And the front one for the metering , control and integral circuit was ok too.  

 

When it came to the back brake I am getting bubbles through the metering bleed, and integral circuit bleed.  The middle one (control circuit) came through with no bubbles.  Added a fresh 3/16" plastic hose to bleed into because I thought it was leaking into the hose at the nipple, but no improvement.  I have put ~1/2 L of new DOT 4 fluid through the rear reservoir and out these circuits and continue to get air.  Bubbles mostly ~ 1 mm and a few larger.  Fluid has come out lookin like new from the very first bit so contamination doesn't seem to be a problem

 

Is there a chance of a hydraulic tube connection from the pedal to control unit leaking air?  Should I just keep flushing fluid through?  Done more than 30 minutes of it so far.

 

Any advice from those who have done this service on a pre 2007 RT or GS would be helpful (later years are non servo and much easier I understand)

 

 Thanks in advance

[dirtrider]

12 hours ago, SK_in_AB said:

I am doing an ABS service on my 2006 RT using a couple guides I got off the internet.  This is the servo system with pump and requires bleeding of 8 different circuits. All went well with the pump driven front and back caliper bleeds using a home made funnel tool to refill the reservoirs while activating the brake levers.  And the front one for the metering , control and integral circuit was ok too.  

 

When it came to the back brake I am getting bubbles through the metering bleed, and integral circuit bleed.  The middle one (control circuit) came through with no bubbles.  Added a fresh 3/16" plastic hose to bleed into because I thought it was leaking into the hose at the nipple, but no improvement.  I have put ~1/2 L of new DOT 4 fluid through the rear reservoir and out these circuits and continue to get air.  Bubbles mostly ~ 1 mm and a few larger.  Fluid has come out lookin like new from the very first bit so contamination doesn't seem to be a problem

 

Is there a chance of a hydraulic tube connection from the pedal to control unit leaking air?  Should I just keep flushing fluid through?  Done more than 30 minutes of it so far.

 

Any advice from those who have done this service on a pre 2007 RT or GS would be helpful (later years are non servo and much easier I understand)

 

 Thanks in advance

Morning Stephen

 

Are the air bubbles small & very regular (not different sizes, or sporadic?)

 

If so then most likely your bleeder screw is leaking at the threads.

 

Try raising your catch container ABOVE the height of your ABS controller. If the catch container is below the controller level then it can siphon the fluid in the hose therefore pulling air in around the bleeder screw threads. 

 

Caution: do not put any Teflon thread tape on the bleed screw threads as the increased thread diameter can crack the ABS module as well as the small thread-cut pieces of Teflon tape can get into the ABS system. 

[SK_in_AB]

Thx DR.  lots of small bubbles <1mm  coming in a row, then nothing for a few inches then some more.  Also some larger ones 3mm occassionally  I will try putting the container up high.  Also maybe try not opening the bleed valve so much to see if the air is from the screw area or really coming up from the brake pedal.

 

If I conclude its a leaking screw I assume I just tighten back down and go with an assumption of no air in the system?

 

Away for the long weekend but will try again more carefully next week

 

S

 

 

[dirtrider]

10 hours ago, SK_in_AB said:

Thx DR.  lots of small bubbles <1mm  coming in a row, then nothing for a few inches then some more.  Also some larger ones 3mm occassionally  I will try putting the container up high.  Also maybe try not opening the bleed valve so much to see if the air is from the screw area or really coming up from the brake pedal.

 

If I conclude its a leaking screw I assume I just tighten back down and go with an assumption of no air in the system?

 

Away for the long weekend but will try again more carefully next week

 

S

 

 

Morning  SK_in_AB

 

Just lift the catch container above the ABS unit, that will break the syphon ability.  Then give that circuit another quick bleed. If no air comes out during or after the quick bleed then just tighten the bleed screw & call it good.

 

With the hose exit below the ABS unit some will syphon air into the hose at the open-bleed-screw threads until the hose is empty. And with those tiny air bubbles that can take a loooooooooog time. 

[SK_in_AB]

Hi D.R.   So I tried this today.  Located the drain bottle in the glove box area so it was 6" above the level of the bleed screws.  No difference in the result - still a series of bubbles coming through on each stroke of the brake pedal.  I checked the hyd tube fittings on the brake pedal outlet and at the control box and they seemed tight.  Couldn't access the fitting from the reservoir into the brake pedal, but I assume since thats low on the circuit and the reservoir is open to air any entrained bubbles there would float back up to the reservoir anyway.  At one point I saw 3  large bubbles come back up into the reservoir on the return stroke of the brake pedal, but after 2 or three strokes this stopped and I haven't seen it again.

 

At a loss here on what to try next.  When I pumped the circuit from the controller to the disc it ran clear with no bubbles.  Im thinking to bolt it all back together as it is.  I realize entrained air will reduce the effectiveness of the oil, and the rear pedal may feel spongy and not provide as much braking power.  But also the rear only does <30% of the work at braking so i'm not as concerned if its less effective.  I do want to ensure I still have ABS active.

 

Any other thoughts from the brain trust out here?

[dirtrider]

30 minutes ago, SK_in_AB said:

Hi D.R.   So I tried this today.  Located the drain bottle in the glove box area so it was 6" above the level of the bleed screws.  No difference in the result - still a series of bubbles coming through on each stroke of the brake pedal.  I checked the hyd tube fittings on the brake pedal outlet and at the control box and they seemed tight.  Couldn't access the fitting from the reservoir into the brake pedal, but I assume since thats low on the circuit and the reservoir is open to air any entrained bubbles there would float back up to the reservoir anyway.  At one point I saw 3  large bubbles come back up into the reservoir on the return stroke of the brake pedal, but after 2 or three strokes this stopped and I haven't seen it again.

 

At a loss here on what to try next.  When I pumped the circuit from the controller to the disc it ran clear with no bubbles.  Im thinking to bolt it all back together as it is.  I realize entrained air will reduce the effectiveness of the oil, and the rear pedal may feel spongy and not provide as much braking power.  But also the rear only does <30% of the work at braking so i'm not as concerned if its less effective.  I do want to ensure I still have ABS active.

 

Any other thoughts from the brain trust out here?

Afternoon  SK_in_AB

 

Was the end of the hose terminating below the top of the fluid in the catch container? If not then try adding a little more fluid to the catch container so the hose terminates below the top of the fluid level.

 

That thing can't possibly be pumping that much air through it from the master cylinder & you would think any leaks at the fittings would be leaking fluid out under pressure.

 

You might try hanging a weight on the brake pedal overnight (or find a way to use a ratchet strap to pull it down overnight). This won't actually remove any air from the system  but it can force the smaller air bubbles to combine into larger ones & those larger bubbles are a lot easier to bleed out.

 

 

 

 

 

[SK_in_AB]

yes  hose was below the waste bottle fluid level  i will try your idea of overnight pressure on the pedal