Soft/spongy brake pedal

[VIKING_MECHANIC]

So I am currently experiencing some brake issues that hopefully I can get some feedback. Here's why and how:

About the end of June I went to Joplin to pick up a new project, while towing my newly acquired 18' trailer(which was a bit much for the project - a riding mower, but I sure as hel wasn't loading it in the back of my truck by hand). Anyways, once I was in Jane, I had to come to an abrupt stop because the person in front of me decided to come to a stop for a yellow light, even thought he had time to go through it.

Once I came to a stop from about ~30MPH, I noticed three things:
1 - my rear right brake drum was smokin'
2 - my brake pedal was a bit soft
3 - the parking brake light came on, which after reading some of the threads on here I learned it has two functions: to inform you the parking brake is set; and to inform you of uneven brake pressure in the system.

After I picked up some speed, my brakes cooled off and the pedal got a bit better - not much though. The brake light was still on as I was driving to Joplin - and conveniently went off once I got to my destination. Once I got my new project, the truck and trailer drove just fine back to my house - about 70 miles.

The following day I looked at my drums and noticed that the right side wheel cylinder blew apart - so I replaced both sides and bled the rear brakes.

Nothing changed. Brake pedal is still soft.

Over the next weeks, I bled all four corners and keeping an eye on fluid level. Since this has happened til now - I have bled the brakes about 4 times and the fluid is solid at all corners.

So after reading some threads about brakes I think this is may have happened - As I was coming to a abrupt, quick stop with about 2000 - 2500Lbs pushing against me up a slight incline with a truck who's brake system is working overtime with 400K on the clock. I suspect that the proportioning valve was over pressurized and damaged internally. I even tried that bled valve on the side and it doesn't help.

I suspect it's the proportioning valve/ABS module that has failed and no longer holding pressure. I got another one from pick-it-part but I haven't swapped it out yet.

Also, now my parking brake doesn't work. It will apply, but WAY to soft and won't hold the truck.

Any thoughts?

Trailer info if your curious:
18L'x8.5"W
~2500Lbs
Has a braking axle, but it's not wired into the main harness(it has been abused)

(EDIT)
This is on my 1997 C1500
5.7 with a built 4l60E for towing

 

[evilunclegrimace]

Year of truck might help

 

[SUBURBAN5]

400k on the clock... that's awesome. My opinion you need that abs module/ proportioning valve serviced or replace. Second I'm hoping you have new brake lines. If not throw in the stainless steel braided lines. 3rd I dont think the master/ brake booster would cause it but I would have that new aswell if it was me... if everything is already new then I would focus on the KH module. Btw if you look on the bottom there weep holes. Any fluid spilling???

 

[thegawd]

I just replaced a brake line for the front passanger side tire. I never actually seen it before but had been over my lines many times, this one is kinda hidden. It also sits on top of the frame and in my opinion not the best location. There is a black plastic shroud like a skid plate in the very front between either side of the frame. 2 bolts let it hang down to inspect this area and 2 more gets it out of your way.

Just have a look at this line and make sure it's not your problem.

For $100 I got 2 new tools and brake line and completely replaced this line in a few hours. Fairly easy but required a lot of brain thinking and slightly rerouting the line so it is not touching the frame anywhere but suspended and secured.

Good luck

Al

 

[VIKING_MECHANIC]

Year of truck might help

Sorry, it's a 1997

 

[VIKING_MECHANIC]

400k on the clock... that's awesome. My opinion you need that abs module/ proportioning valve serviced or replace. Second I'm hoping you have new brake lines. If not throw in the stainless steel braided lines. 3rd I dont think the master/ brake booster would cause it but I would have that new aswell if it was me... if everything is already new then I would focus on the KH module. Btw if you look on the bottom there weep holes. Any fluid spilling???

That's what I am suspecting needs to be replaced. Surprisingly for 400+ miles, the brake lines are in good shape. No signs of rust or damage. The two rubber ones for the front calibers have been replaced in the last 2 years. The booster is original and it works flawlessly and the master was replaced about 3 years ago. On your last part, weep holes, not sure about what you're talking about.

Oh and the miles, I'm pretty sure the previous owner was a first responded which I think is why it has so many miles.

 

[VIKING_MECHANIC]

I just replaced a brake line for the front passanger side tire. I never actually seen it before but had been over my lines many times, this one is kinda hidden. It also sits on top of the frame and in my opinion not the best location. There is a black plastic shroud like a skid plate in the very front between either side of the frame. 2 bolts let it hang down to inspect this area and 2 more gets it out of your way.

Just have a look at this line and make sure it's not your problem.

For $100 I got 2 new tools and brake line and completely replaced this line in a few hours. Fairly easy but required a lot of brain thinking and slightly rerouting the line so it is not touching the frame anywhere but suspended and secured.

Good luck

Al

I'll take a look at those, but since the fluid comes out solid at both calipers, I don't think that's an issue. And I don't have any fluid leaks anywhere.

 

[SUBURBAN5]

That's what I am suspecting needs to be replaced. Surprisingly for 400+ miles, the brake lines are in good shape. No signs of rust or damage. The two rubber ones fro the front calibers have been replaced in the last 2 years. The booster is original and it works flawlessly and the master was replaced about 3 years ago. On your last part, weep holes, not sure about what you're talking about.

Oh and the miles, I'm pretty sure the previous owner was a first responded which I think is why it has so many miles.

It's on the bottom of the module where it says Kelsey hayes

You must be registered for see images attach

 

[96-2D-Hoe]

If you've checked everything to be in good working order with no leaks then it must be air or your MC went bad. Proportioning valve or ABS would not normally give you a ****** pedal. To check MC start the truck and hold the pedal firmly, if the pedal keeps traveling the MC is bad.
It is also extremely difficult to get the air out of these systems. Could try bleeding with the rear of the truck as high as possible. It was suggested to me to jack the back of the truck up. Can also try setting off the ABS and bleeding again which is the only way I get a decent pedal after MC swap. Slam the brakes on some loose ground a couple times to set the ABS off and then bleed the brakes again. Might need to do that more than once. I one man bleed and I try to give the rear passenger 40 pumps of the pedal which will give you around a pint of fluid, the rear drivers only needs 10-15. Also the fronts put out twice as much fluid as the rear when you pump the pedal and about 20 pumps gives you a pint. Don't push the pedal too far as you will screw up the MC, I usually pump it around 1/2 way /to about where the brakes start to engage fully, then wait 10 secs to push it again. I normally give 10-15 pumps before I check the fluid level in the reservoir. Do not let it run dry as then you will have to start again like I managed to do a couple times recently.

 

[VIKING_MECHANIC]

It's on the bottom of the module where it says Kelsey hayes

You must be registered for see images attach

Oh, okay. I'll check it out.

471K!? Damn, are you excited that's about to roll over to half a million??