Rear brake issue, the main brake power lower than handbrake?

Tiny
B767_400
  • MEMBER
  • 1997 PONTIAC GRAND AM
  • 3.1L
  • V6
  • 2WD
  • AUTOMATIC
  • 140,000 MILES
Hi,

I have a big issue with the Rear Main Brakes.
I have replaced both rear RH and LH Drums, Main Cylinders, all Springs.
So more or less complete new brakes for the rear.

Today I had the brakes checked and completely shocked that the left rear brake had only 0.7kn and the right one 0.9kn.
The Handbrake had about ~1.9kn for Left as well for right side.

So something is wrong. The Main Rear Brakes cannot have less braking power than the handbrake.

I followed the bleeding procedure from Haynes Repair Manual.
The only thing I did not follow was that they state to 5x Turn Ignition on, wait 10sec (that the piston is in the right position). Just did it once.

No air bubbles came out (ABS Module as well as at the RH/LH rear Brake) after the procedure done.

Front Brakes are fine ~2.8kn.

Any hints for that strange behavior?
Tuesday, August 19th, 2025 AT 5:30 AM

10 Replies

Tiny
B767_400
  • MEMBER
  • 36 POSTS
Forgot to ask before, do I maybe need a Scan Tool to operate the ABS Module or is there a way to bleed the air without a Scan Tool?
Was this
answer
helpful?
Yes
No
Tuesday, August 19th, 2025 AT 3:13 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 54,137 POSTS
There is no way to get the air out of the ABS unit unless you use the scanner to open the valves. Also, if you mix up the rear brake shoe self adjusters from side to side the brake will adjust inward instead of outward which will give you the low brake pedal. Here is a video to help you bleed the system.

https://www.youtube.com/watch?v=nQRnKyVyMuQ

Please upload pictures or videos in your response
Was this
answer
helpful?
Yes
No
+1
Wednesday, August 20th, 2025 AT 10:32 AM
Tiny
B767_400
  • MEMBER
  • 36 POSTS
Thanks very much for the feedback.
Is there maybe a picture/walk thru about correctly setting the self adjuster?
Was this
answer
helpful?
Yes
No
Wednesday, August 20th, 2025 AT 11:30 AM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 54,137 POSTS
The self adjuster on the right side should have the reverse threads. I would confirm that first. Here is an exploded view of the brake show assembly so you can make sure there are installed correctly. Here is a video that will help as well.

https://www.youtube.com/watch?v=-Ts8SRUxRc8

Check out the images (below). Please upload pictures or videos in your response
Image (Click to make bigger)
Thumb
Was this
answer
helpful?
Yes
No
+1
Wednesday, August 20th, 2025 AT 11:46 AM
Tiny
B767_400
  • MEMBER
  • 36 POSTS
Need additional help.
Cheched the Self Adjuster and everything is installed correctly.

We then had a TECH2 Scan Tool and looked for the ABS Bleeding finction, but it does not show it. Looked everywhere, also within the Special Function area.
So either, the 1997 Model does not support to activate the ABS Module via Scan Tool or the tool does not have the function.
Does someone know if the Tech 2 should support the function on a 1997 Grand Am?

So we did the procedure if a Scan Tool is not present:
Start the engine. Allow the engine to run for at least 10 seconds while observing the amber ABS warning indicator.
Should Turn off after 3sec -> Yes
If the amber ABS warning indicator turns on and stays on after 10 seconds, stop the bleeding procedure. Use a scan tool in order to diagnose the ABS malfunction.
If the amber ABS warning indicator turns on for approximately 3 seconds, then turns off and stays off, turn the ignition off.
Repeat the previous 4 steps again.

No Air Bubbles were observed (Bleeding first rearward bleeder valve, then forward bleeder valve and then bleeding air starting at the Rear Right caliper followed by the other three calipers.

Still no change. Handbrake has about 2kn or more. Main Rear Brake via pedal just has 1-1.2kn so much less. Normally it is maybe the opposite.

Drims, springs, and the Drum is completely new. I installed the CENTRIC KIT324D Drum Kit which includes everything needed.

Have no clue what else could be the culprit.
Was this
answer
helpful?
Yes
No
Thursday, August 21st, 2025 AT 10:30 AM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 54,137 POSTS
I would go over this guide which will help see everything that can cause a low brake pedal and what to do to fix it.

https://www.2carpros.com/articles/brake-pedal-goes-to-the-floor

Please go over this guide and get back to us.
Was this
answer
helpful?
Yes
No
Thursday, August 21st, 2025 AT 10:34 AM
Tiny
B767_400
  • MEMBER
  • 36 POSTS
The strange thing is that I do not have a low brake pedal.
Everything is fine, also the ABS light is off (as it should be) and brake pedal feels as it should.
Car also breaks as expected, but as said, on a Brake Tester at the Mechanics Shop it shows a low brake power at the rear.

Do you know if the TECH 2 should be able to activate the ABS Bleeding procedure?
Was this
answer
helpful?
Yes
No
Thursday, August 21st, 2025 AT 11:08 AM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 54,137 POSTS
That is good that the brake pedal is now okay, I bet if you did the full system bleed with the tech 2 the warning should go away.
Was this
answer
helpful?
Yes
No
Thursday, August 21st, 2025 AT 6:59 PM
Tiny
B767_400
  • MEMBER
  • 36 POSTS
I was not able to find the full system bleed function within the Tech 2.
May you tell me where I can find it?
Was this
answer
helpful?
Yes
No
Friday, August 22nd, 2025 AT 4:06 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 54,137 POSTS
Select the Chassis menu - ABS - Automated Bleed (wording may vary by year/model) and follow on-screen prompts
Was this
answer
helpful?
Yes
No
Saturday, August 23rd, 2025 AT 11:48 AM

Please login or register to post a reply.

Related Crankshaft Rear Crankshaft Seal Replace/Remove Content

Crankshaft Seal Replacement - Rear
GUIDE
Crankshaft Seal Replacement - Rear
The rear crankshaft seal, also known as the rear main seal, prevents engine oil from leaking where the crankshaft exits the engine block. Over time, this seal can wear out...
VIEW MORE