All 4 brakes locked up at once

Hello, hoping someone has dealt with this before or knows what to look for in order to fix this. Today I was standing on my brake pedal trying to fight the ABS system coming to a stop on ice. Shortly after, I noticed the pedal was very stiff, then a couple minutes later extremely touchy. This happens once in a blue moon, so I didn't think it was a big deal, but when I got home a couple minutes later I noticed the truck wouldn't idle forward into the garage. I figured something was up with the brakes, so I put it up on jacks and all 4 corners are locked up. I read here that if you remove the brake booster vacuum line and the brakes go back to normal I'd need a new brake booster, but I tried that and there was no difference. Then I pulled the ABS #2 fuse incase something happened within the ABS system, and no difference. I did notice that the rear end freed up a little bit first, and then the front end freed up some about 20 minutes later. I'm letting it sit longer now to see what happens, but it seems like the brake system is holding pressure when it isn't supposed to. Also, the brake lights are staying on. I always thought they were tied to the pedal itself somehow, but are the brake lights tied to another part of the system? There aren't any lights on the dash, and the pedal feels relatively normal when I start the truck again, but if I pump the pedal a couple times, everything locks up again. Any insight as to what happened?

Edit: The rear seems to be ok now, it's just the front end staying locked up.

 

I think you will need to see some codes to start digging deeper, there are some scanners “I believe “ that read ABS codes

 

Wouldn't the check engine or ABS light be on if there was a code to read? I'll look into it.

 

You say you were standing on the brakes.
I’d crawl under the dash and see if the pedal is jammed down and pressing on the switch, and also applying pressure to the system.

The key here is probably the brake lights staying on. Something is wrong.

 

Sounds like master cylinder. Died

 

I went under the dash and only saw one plug by the pedal. Looked like all the wires were ok, and when the truck's on the pedal has full range of motion, so I don't think anything's locked up by the pedal. I just turned the truck on and ran it on jacks, and it seems like the rear end is working fine now, but the front is still locked up. When in 4wd the front end can spin, but with the tires off I can clearly see the calipers are clamping down on the rotors.

 

Is there a way to check that?

 

When your brakes are locked up crack the lines open 1 at a time starting at the master cylinder, if they free up then you have a bad master cylinder or something in the booster or linkage holding pressure on it. If they don't release when you crack the lines at the master cylinder then move to the ABS module and crack them loose there, if they release then you have a problem in the ABS module. If not then go to the bleeders and loosen them, if they release there then most likely the brake hoses are bad going to the wheels. If not then the wheel cylinders are siezing up.

 

Im not 100% on this but maybe some one else can chime in. The part i circled should look like the pic. If it shorter its compressed. Some older American vehicles had a rod from the booster to back of the master cylinder. But concept is the same. Push on brake pedal moves the rod pushes booster which pushes the master cylinder.

If its stuck that rod will be pushed in farther. Hopefully this makes sense

 

Upon further inspection, I pulled the brake pedal switch and I think it is out of adjustment. When the plug is in, the brakes lights are always on. If I give it a quarter turn and pull it out while keeping the wires plugged in, I can push the button on and off and the brake lights work as they are supposed to. This very likely isn't the culprit, but maybe it means one of the other components isn't letting the brake pedal release all the way?

 

I'll give this a try and see what happens.

 

I don't know if its the master cylinder specifically yet, but I can say it is has lost a portion of it's travel. When referencing my Hayne's manual, it says that there should be 6.22-6.62 inches of space between the floor and the brake pedal measured normal to the pedal. I currently only have about 5.25", so it's not returning all the way.

 

If I were to do this, would I need to end up bleeding the brakes after cracking every line? Sorry, my only real experience with brakes is replacing pads and rotors, and helping others bleed brakes. Normally, I should be able to crack the lines going to the wheels and be ok as long as there's fluid in the system, just like bleeding brakes because there's only one opening and fluid would be coming out of it with a reservoir on the other end to keep it full. But if I were to crack the lines coming from the master cylinder or the ABS module, then wouldn't air get in since I'm creating two openings? One at the MC or ABS module, and the other in the line? Hopefully that made some sort of sense. Is there a write up or video of this being procedure being done somewhere?

Also, would it be possible that the pistons in the caliper seized? I'm guessing not because they slowly let go some after waiting for a while.

 

You don't want to leave them open, you just want to crack them loose enough to relieve the pressure and the tighten them back up again.

 

So I'd just loosen the nuts on the MC and ABS module and supposedly, some brake fluid will blow out without air getting in there? Kind of like unscrewing a garden hose under pressure?

 

Exactly, like I said don't take them off just loosen 1/2 to 1 turn to release any pressure and then tighten them back up. That's my method to determine what part of the system is holding pressure on the brakes when they are locked up on a vehicle.

 

Well, I loosened the 2 nuts on the MC, and 6 on the ABS module by at least 1 full rotation each, and nothing came out. When loosening the bleeding valves, there was only a trickle at each corner, nothing seemed pressurized. Should I loosen the MC and ABS nuts until something comes out anyways? Is it possible I just blew out the pistons in the caliper hitting the brakes really hard? I can try removing them and squeezing the pistons back down.

 

Were the brakes locked up at the time you did that?

 

They weren't seized, but they are still difficult to turn by hand, and I can see the pads are still contacting the rotors. Should I start it up , pump the brakes to get them fully seized, then try again?

 

If you get them fully locked up and then crack lines until they release starting at the master cylinder that should tell you what's locking them up. It's possible the calipers aren't fully releasing as well but it's rare that I see all 4 wheels locked up and it not being something with the ABS or master cylinder.