C1500 Brake help

[alex s]

I have been working on my 92 C1500 lately and I'm having an issue with the brake pedal being way too soft. The truck will stop, but the pedal has way too much travel. I have replaced both rear wheel cylinders, rear shoes, both front calipers, front pads, master cylinder, and I have bled the brakes all the way around TWICE now. I have also removed the little "abs" block that is near the MC. I am at a loss on what to do now, this is getting very discouraging. Any ideas?

 

[wjburken]

I have been working on my 92 C1500 lately and I'm having an issue with the brake pedal being way too soft. The truck will stop, but the pedal has way too much travel. I have replaced both rear wheel cylinders, rear shoes, both front calipers, front pads, master cylinder, and I have bled the brakes all the way around TWICE now. I have also removed the little "abs" block that is near the MC. I am at a loss on what to do now, this is getting very discouraging. Any ideas?

@96-2D-Hoe went through some issues with brakes recently if I remember correctly. Might check out his posts on the matter.

 

[Bandit-66]

have you correctly bled the main brake cylinder before?

how did you bleed the brakes, pump them with the pedal or with negative pressure?

when bleeding the brakes with the pedal, the pedal should be pressed carefully and not pressed completely, as this can lead to a defect of the brake boots in the master cylinder.

 

[alex s]

have you correctly bled the main brake cylinder before?

how did you bleed the brakes, pump them with the pedal or with negative pressure?

when bleeding the brakes with the pedal, the pedal should be pressed carefully and not pressed completely, as this can lead to a defect of the brake boots in the master cylinder.

Yes I bench bled the master cylinder before installing.

The brakes were bled by me pushing the pedal, while a clear hose was on the bleeder, that hose was going into a bottle full of brake fluid. One wheel at a time.

 

[OR VietVet]

Are the rear brakes adjusted up properly? State here how you adjusted them. As @Bandit-66 asked, how did you bleed the brakes? If you had a person pumping them it should be done slowly and never let the pedal reach the floor when you open the bleeder. I always used a 2x4 on the floor to keep from bottoming out the pedal. If the pedal did go to floor then you may have damaged the master cylinder.

 

[alex s]

Are the rear brakes adjusted up properly? State here how you adjusted them. As @Bandit-66 asked, how did you bleed the brakes? If you had a person pumping them it should be done slowly and never let the pedal reach the floor when you open the bleeder. I always used a 2x4 on the floor to keep from bottoming out the pedal. If the pedal did go to floor then you may have damaged the master cylinder.

Yes the rear brakes have been adjusted and i believe are as close as they can get.

I have never heard that if the pedal touches the floor it will damage the MC. If that is true then that could be the culprit? Hopefully not, as that would be the second MC i have put on. I was thinking this problem was due to the first one being faulty.

 

[OR VietVet]

Could you please share how you did the brake shoe adjustment? I would also bet the m/c is bad if you pumped and bled to the floor. Did you also check that the caliper piston is moving properly and that has pushed out to where the pad is up against the rotor after releasing the pedal?

 

[96-2D-Hoe]

the second MC i have put on

Only two MC's? I've changed, and screwed up, mine more than I'd like to mention. I had a couple bad ones too. Was using Duralast from AZone under warranty. Recently bought a Delco from RA, I don't think it's 100% and I've not damaged it.

Yes, if you press the pedal too far it will damage the MC. Some people put a 2x4 under the pedal to stop the travel.

You can also damage the MC from plunging it too deep when you bench bleed it. No deeper than 3/4" to be safe.

You can 'bleed' the ABS some without the Tech1 by setting it off. 25mph and brake ******* loose ground 2-3x then bleed the system again. If that helps, might try it again.

I'm also pretty sure the single man bleed is not efficient enough as I spent a ridiculous amount of time and fluid on it alone. Two man is the recommended procedure.

You also need a tool for the brake proportioning valve on your 92.


PS
Should also mention the flexible brake lines that can cause a ****** pedal too. I've not changed mine out yet as they look in perfect condition, but I'm getting close to it. They are not expensive. Many people say that makes a big difference to their pedal feel.

 

[swathdiver]

Do those old trucks have a proportioning valve along the frame? I had one of those go bad once in a G-Body car.

 

[alex s]

Only two MC's? I've changed, and screwed up, mine more than I'd like to mention. I had a couple bad ones too. Was using Duralast from AZone under warranty. Recently bought a Delco from RA, I don't think it's 100% and I've not damaged it.


Yes, if you press the pedal too far it will damage the MC. Some people put a 2x4 under the pedal to stop the travel.

You can also damage the MC from plunging it too deep when you bench bleed it. No deeper than 3/4" to be safe.

You can 'bleed' the ABS some without the Tech1 by setting it off. 25mph and brake ******* loose ground 2-3x then bleed the system again. If that helps, might try it again.

I'm also pretty sure the single man bleed is not efficient enough as I spent a ridiculous amount of time and fluid on it alone. Two man is the recommended procedure.

You also need a tool for the brake proportioning valve on your 92.
View attachment 259232

PS
Should also mention the flexible brake lines that can cause a ****** pedal too. I've not changed mine out yet as they look in perfect condition, but I'm getting close to it. They are not expensive. Many people say that makes a big difference to their pedal feel.

What a mess. Maybe I will need to try another MC, as I don't know if it has been damaged now. The truck no longer has ABS, that has all been removed. I did do a 2 man bleed, with my helper holding the container with the hose in it, while controlling the bleeder as i pushed the pedal. Zero air bubbles at all 4 corners. As far as the rubber brake lines, they do look fine but I imagine new ones would help. From what I understand these trucks always had a ****** pedal, my dad's 98 does too, he complains about it often. My goal is just to get the truck to stop safely. The pedal will slow the truck to a stop, but the pedal keeps traveling slowly.

 

[alex s]

Do those old trucks have a proportioning valve along the frame? I had one of those go bad once in a G-Body car.

The proportion valve is up near the MC, with a "T" near the frame

 

[swathdiver]

The proportion valve is up near the MC, with a "T" near the frame

Is it in top form? Does yours have rear ABS? I went through six quarts of brake fluid to drain and bleed mine both manually and with the Tech-2 for the ABS system.

 

[96-2D-Hoe]

the pedal keeps traveling slowly.

You need to replace the MC again

 

[OR VietVet]

You need to replace the MC again

I would listen to @96-2D-Hoe about the master cylinder. If there is one thing he knows about, it is master cylinders.

 

[alex s]

You need to replace the MC again

I will be replacing it again tomorrow. This time I will bleed it without fully pressing and see what happens.

 

[96-2D-Hoe]

Fill it up from dry and leave it for 10 mins before you start plunging.

Tilt it forward and plunge and tilt is backward and plunge it too.

Also Bleed any air from the blanking plugs, crack one open a little, plunge the mc and close the plug before you let off the plunge

 

[kbuskill]

Put a MC off of a GMT800 truck and forget about spongy pedals. It only requires one adapter fitting to install it on your GMT400 truck.

I did this along with 1 ton rear wheel cylinders on my 1st gen Esky and it made a big difference.

Those trucks always had a soft spongy pedal.

The biggest issue I had was my rear brakes not staying in adjustment no matter what I did. I changed ALL the hardware inside the shoes several times and they still wouldn't stay adjusted without having to backup and hit the brakes, to self adjust, every couple days.

If I would have kept the truck I was going to convert the rear to disk brakes.

 

[96-2D-Hoe]

A lot of people are not happy with this swap. It seems likely the ones that are needed a new MC anyway.

 

[kbuskill]

A lot of people are not happy with this swap. It seems likely the ones that are needed a new MC anyway.

I can't imagine why they wouldn't be happy... it made a very noticeable improvement on my Esky. I swapped over just for the upgrade, my old MC was fine.

 

[96-2D-Hoe]

Because it's not designed for the 400 and the 800's have a different brake set up.

People say they get a better pedal feel but less brake force.