[mblum]

I'm struggling to fix my soft brake pedal problem. After my first track day I had a soft pedal and I flushed with Motul 600, which didn't seem to help much with the soft pedal issue. I did the flush with my motive power bleeder which I have had great luck with on my other vehicles. I figured I must have gotten some air in the system so I did the old fashioned 2 person brake bleed procedure. This also did not help my soft pedal.

So at this point I'm thinking the ABS might have air trapped, I found someone local that had a Snap On scanner that said they could do the ABS bleed. I was there for the procedure and I don't think it was done properly so I would like to do this again. Can anyone recommend an affordable scan tool that can preform this function? I really dont' need a 2K diagnostic tool. I'm avoiding the dealer and want to do this myself. Reason is in our area there are no trustworthy dealers to work on these types of car. I've already had poor service done on my ZL1 and don't want to give them a chance again.

My last thought was if a proper ABS bleed does not fix the soft pedal it may be the master cylinder, which has never gone dry. Does the mastery cylinder need to be removed to be bled?

Thanks for any help.

[Alpha1BC]

I'm not aware of any scan tool that can cycle ABS other than the Tech2 or that Snap-on tool, but maybe someone else has.

And maybe a stupid question, but did you get both the inner and outer bleed screws on both calipers? I'm assuming that since the pedal got soft after the first track day that you boiled fluid on the track, and if that's the case the air should have primarily been in the caliper and I've seen people miss the inboard bleed screw before.

If that's not it, they I agree that the next step is to try the ABS bleed in case some air worked its way back up to the ABS module. I highly doubt air made it all the way up to the master cylinder, but if it did you might be able to bleed it without removing it from the car. Service manual says to remove it, but biggest reason for that I can see is to make sure you get enough piston travel to evacuate bubbles. It might mean unhooking the pedal and moving the plunger manually if the pedal is limiting the plunger travel.

[mblum]

Both inner and outer bleeders were done each time I bled the system. I'm going to see if I can do another ABS bleed procedure.

I've bench bled may master cylinders in the past with good luck but nothing on the 6th gen. I've got LS1 F-Body brakes in my 72 Chevelle and my 97 Trans Am and have had no issue getting a good pedal on those cars, but neither one of those has ABS, which changes things.

Is the process the same to bleed the master cylinder on the 6th gen? It's a last resort but I wan to keep it in mind.

[Alpha1BC]

Ok, just wanted to check haha.

Bench bleed on these cars isn't impacted by ABS. Should still be the same process as other cars: hook hose up to the MC outports and route back to the reservoir. ABS only impacts the system bleed after that because air can get caught up in the ABS system as it gets pumped through to the calipers. That's where the scan tool come in handy because it pushes the air out of the ABS system and into the lines towards the calipers. When I've used one of those tools the ABS system bleed typically moves enough fluid through the system to clear all air that's past the master cylinder, so your approach sounds good to me. Just have to get lucky finding someone to let you borrow or rent a scan tool

[mblum]

I have a guy that has one that I think I can rent. I had him do the process before but he rushed through it and I don't think it was properly done. I was inside the car pushing the brake pedal when he needed and I could hear/feel the ABS pump cycling.

If the ABS followed by a caliper bleed does not fix the issue I will have to do a Master Cylinder bench bleed, followed by another ABS bleed and then a caliper bleed to get all air out.

Is there a way to access the GM service manual? Just curious to the recommended bench bleed process.

[Bow Tie Fanatic]

I feel like I have the same issue you describe. While bleeding helps some the pedal travel is way more than I feel it should be and always seems “soft”. The brakes have been bled the correct way multiple times and each time the brakes are bled we get lots of bubbles. Very frustrating.

[mblum]

Originally Posted by Bow Tie Fanatic

I feel like I have the same issue you describe. While bleeding helps some the pedal travel is way more than I feel it should be and always seems “soft”. The brakes have been bled the correct way multiple times and each time the brakes are bled we get lots of bubbles. Very frustrating.

Bow Tie, did your car feel this way from day one? When I first got my car the pedal felt great, very firm and responsive. It would only take slight pedal movement to feel initial bite and then had a great progressive feel and stopped incredibly well. Right now when I start the car with my foot on the brake pedal it will go halfway to the floor once the engine starts, so I know I have air in the system. I'm trying to get the pedal back to the way it felt when new, just with better brake fluid in the system. It's going to be a few weeks before I have a chance to work on the car but I will post what I find

[Bow Tie Fanatic]

Originally Posted by mblum

Bow Tie, did your car feel this way from day one? When I first got my car the pedal felt great, very firm and responsive. It would only take slight pedal movement to feel initial bite and then had a great progressive feel and stopped incredibly well. Right now when I start the car with my foot on the brake pedal it will go halfway to the floor once the engine starts, so I know I have air in the system. I'm trying to get the pedal back to the way it felt when new, just with better brake fluid in the system. It's going to be a few weeks before I have a chance to work on the car but I will post what I find

A performance shop replaced my DOT3 to Motul 600 and they didn’t bleed the brakes correctly, actually overfilled the Motul and brake fluid got all over the inside of my hood and even though I had the Motul replaced at the track and have had it bled several times, it has felt soft since that incident.

[mblum]

Originally Posted by Bow Tie Fanatic

A performance shop replaced my DOT3 to Motul 600 and they didn’t bleed the brakes correctly, actually overfilled the Motul and brake fluid got all over the inside of my hood and even though I had the Motul replaced at the track and have had it bled several times, it has felt soft since that incident.

That is frustrating to hear, how little shops care sometimes. I know there are some great shops out there that care about their work but there are so many more than just want to make some quick money and treat their customers as if they are ignorant. I envy the guys who have a trustworthy dealership to work with, I would take mine there in a heartbeat if I had one locally. All of ours and pushy liars with a tech crew that is turned over every 6 months because of buy-outs, and management changes. I have given them a few chances and each time was a mess. My only choice is to do the work myself.

Back on topic.....

[Alpha1BC]

Originally Posted by mblum

I have a guy that has one that I think I can rent. I had him do the process before but he rushed through it and I don't think it was properly done. I was inside the car pushing the brake pedal when he needed and I could hear/feel the ABS pump cycling.

If the ABS followed by a caliper bleed does not fix the issue I will have to do a Master Cylinder bench bleed, followed by another ABS bleed and then a caliper bleed to get all air out.

Is there a way to access the GM service manual? Just curious to the recommended bench bleed process.

There's a couple places to get the manual online, unfortunately not for free that I've seen though.

Recommended bench bleed process is to take the MC off the car and clamp the flange in a bench vice. Hook clear hoses up to the outports of the MC that route back into the reservoir. Fill the reservoir with fluid, then slowly push the plunger until you can't anymore (about 1"). Keep pumping fluid through like that until there are no more bubbles coming out. Then, remove the hoses and put the reservoir cap back on and re-install in the car. Also suggested to use a rag or something to wrap around the MC while installing to keep fluid from dribbling out of the ports and onto the car.

[mblum]

Thank you, that is the same procedure I've used in the past on other vehicles and have had good luck. Usually the hardest part is getting the master out, I will have to look how accessible the bolts are on the 6th gen.

[Alpha1BC]

Not a problem, good luck!

[tecmec]

I'm curious if this solves your issue. I had the same soft pedal issue after installing my GM big brake kit on my SS. I actually have the GM MDI interface, and so I have done a million ABS bleed cycles on the car. I was able to get a few small bubbles out, but have never been able to get the pedal feel to what I think it should be.

I didn't let the master run dry, so I'm not sure why it would have air in it. The brake line plumbing in these cars is funny though. The ABS module is above the passenger side wheel well, and we have lines running between there and the master, over the engine at the back of the firewall (if I'm remembering correctly). Those lines are a high point, and I imagine they would be a great place for air to collect, and would probably be almost impossible to evacuate. I was actually worried that if I disconnected the master, I'd just end up letting even more air into those lines, making things worse.

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[Walter_]

I have heard of cases where you get big brake kits and need a larger master to pump more fluid to the bigger brakes. Not sure if that is your problem.