Soft brake pedal after replacing all the brake lines and the front calipers?

Tiny
JEFF HERMAN
  • MEMBER
  • 1999 PLYMOUTH VOYAGER
  • 3.3L
  • V6
  • 2WD
  • AUTOMATIC
  • 117,000 MILES
I replaced all the brake lines and the front calipers. The brakes have been bled on all four wheels. The pedal will not maintain pressure. It takes 2 or 3 pumps and then will hold steady. I can't do the ABS autobleed with my scanner. Something about a COR or something specific to Chrysler. I didn't bench bleed the master but bled it in the car and there doesn't appear to be any air coming out. Is it possible the small return port in the master could be plugged and cause this issue? BTW my scanner is a Foxwell NT630plus.
Sunday, March 10th, 2024 AT 1:55 PM

5 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,055 POSTS
Hi,

The base brake's hydraulic system must be bled anytime air enters the hydraulic system. The ABS though, particularly the ICU (HCU), should only be bled when the HCU is replaced or removed from the vehicle. The ABS must always be bled anytime it is suspected that the HCU has ingested air. Under most circumstances that require the bleeding of the brake hydraulic system, only the base brake hydraulic system needs to be bled.

You indicated the master cylinder was bled in vehicle. Did you have it connected to the brake line when you bled it?

Next, when you bled the brakes, did you follow the manufacturer's sequence? Are the rear brakes properly adjusted?

Take a look at the pics below. They are the manufacturer's bleed procedures. Let me know if they help.

Take care,

joe

See pics below.
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Sunday, March 10th, 2024 AT 8:52 PM
Tiny
JEFF HERMAN
  • MEMBER
  • 468 POSTS
All lines were removed from both the master and the ABS block. Would that in and of itself mandate bleeding of the master? Yes, the lines were connected to the master. I pressured up the pedal and placed a bar to hold it. I barely cracked each line, one at a time, on the master and didn't see any air bubbles. I was thinking of bench bleeding it with fittings and tubes back into the reservoir but while it's installed, using the pedal to compress the piston. That is also a different sequence than usual. I haven't been able to loosen the bleeders on rear but I gravity bled at the line connections. Usually, the cylinder doesn't hold much air like a caliper would. I will try the new sequence. Also, when I bleed, I attach a tube into a jar of fluid before I crack the bleeder and pump the pedal.
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Sunday, March 10th, 2024 AT 9:47 PM
Tiny
JEFF HERMAN
  • MEMBER
  • 468 POSTS
I meant would that mandate bleeding of the ABS block.
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Sunday, March 10th, 2024 AT 9:48 PM
Tiny
JEFF HERMAN
  • MEMBER
  • 468 POSTS
Update, took my time and a little heat and was able to get the rear bleeders open. Bled the brakes in the suggested sequence and pedal pressure is great. As soon as I opened the rear bleeders there was pressure even before doing all four corners. Thanks for the help.
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Monday, March 11th, 2024 AT 3:39 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,055 POSTS
Hi,

Thanks for the update. I'm glad to know it helped.

Feel free to come back anytime in the future if you have questions.

Take care,

Joe
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Monday, March 11th, 2024 AT 6:48 PM

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