99 Tacoma 2.7l non abs brakes locking up

My truck started engaging all four brakes while driving down the road and smoked the two front rotors yesterday before I could stop. Smoke was pouring out of the wheels. I had to break the fitting loose at the master cylinder and you could hear them all 4 release after bleeding off the fluid . What could be causing this ?

 

Bad rubber lines can allow fluid to push one way but not so much the other. Weird it would be all 4 though.

 

Sounds like your brake master cylinder / booster is suspect.

 

I went to the store a little bit ago it was cutting out bad idling at 1800-2000 rpm I parked at the grocery store did my deal went to leave all four brakes locked up had to bleed it off again and I can hear them release and made it home no problem . What the hell is that about?

 

@Glamisman that was my first thought and with the rough idle and high idle and cutting out when im driving I thought vacuum but one may have nothing to do with the other . I did just replace every hose , sensor , exhaust , new coils , plugs , wires , injectors, valve cover gasket etc etc so if it’s vacuum I got a faulty part or pinched/clogged hose. If it’s not vacuum I don’t know what it is? The brake issue has me at a loss now especially since they locked when it was parked and turned off for 45 min.

 

If this is your only vehicle that puts you in a tough situation... if it were me, I would get a new brake master cylinder and take my old one off and disassemble it for an inspection. Look at the end of the master cylinder where the circlip is to see if it is wet with brake fluid, if so, the rubber in the brake booster is probably shot. If you have a non ABS truck you can pry the master away from the booster enough without cracking the brake lines.

 

There have been a small number of trucks I’ve seen on here with a vacuum leak in the booster. Pinch off the hose and see if your idle issues go away (if they’re still present).

 

Yeah it sucks I sold my new trucks so I could retire early and relax a bit after being gone 25years now all I do is work on shit! I think it’s an unwritten rule at my house if I need to use it I have to wrench on it first lol. So yeah I kept this truck and have a 1945 white super power im restoring but my yoda is the only one running (somewhat) right now and I live in a rural area and can’t just walk to a store so yeah it’s a pain in the ass!

 

I’ll try the vacuum first thing then I’ll order in a booster and go from there.

 

Thanks for the advice I’ll keep you posted !!

 

one time i installed the booster's V hose on backwards(that check valve)
this caused the opposite thou......no brakes...hard as a rock....barely could stop backing out of inclined driveway

i have never heard of this b4....
but
what if the internal MC's push rod gets stuck in full position? (from wear)
would kinda explain the full 4 corner lock up

 

@MAD nachos yeah it locked them down the e brake doesn’t even brake that good lol. Then I pulled into sonic turned it off went to back out and locked up again had to bleed it to release them . Day before yesterday the drivers side smoked and yesterday the passenger side smoked so something bizarre is going on it went from all 4 to drivers side then passenger side . Just replaced all the vacuum lines and going to check the ms now.

 

So today I flushed and replaced with new brake fluid . When I start the truck now it idles low and wants to die once it warms up its back to high idle until I hit the brakes and it idles down then back to 1500-1700rpms . There is a brake proportioning valve that might be suspect also so aside from spending $3k on all new brake system I’m at a loss. The proportioning valve lines in and out had gotten so hot it burned all the chafeguard coating and it just peeled off when I touched it . Any thoughts on where to start next?

 

Did you pinch off the brake booster vacuum hose and let it idle? Was there any change?

 

The only time it changed, not pinched but when I step on the brake and hold it idling . It would idle down and almost die or would die then step on the brake and hold it and it idle 1500-1700 and stay til I killed it . I don’t know what the hell is going on with that. And I made sure there was no vacuum leak I cut up some air hoses and used them for vacuum lines they’re pretty new so they won’t leak

 

Sounds like it could be a coincidence - the engine doesn’t need to be hooked up to the booster to run correctly - the port can be capped off and hold vacuum on its own without being connected to the booster. The booster needs the engine to be connected to it to work, not the other way around.

Is it repeatable that the engine idles correctly when the brake is applied and only when it’s applied? Anything else sounds too coincidental.

It could be two issues - a vacuum leak and an issue with your proportioning valve making the brakes act up. Engine idle should be pretty easy to separate from being related to the booster like I mentioned though.

 

That’s what I thought too that it was two totally different issues just happen to be going on simultaneously and the brakes locking up may have caused an unrelated issue but one cf at a time I’ve got new soft hose for the brakes might as well replace them while we’re here they’re 30 yrs old so … then completely drain the whole brake system blow a little air through it to get the old gunk out and start anew with brand new fluid and hoses and go from there . That brake fluid was nasty shit and smelled burnt bad! If I had my 1945 white superpower finished I’d pull the cab and bed and frame off this little gem but im too far out on it to pull it off with only one vehicle so not this time but soon. And with that said I wonder if that maf sensor is acting stupid and causing the idle issues . If I remember you can unplug that sensor , disconnect the battery for 10 min and reconnect leaving the maf unhooked and it will delete it out of your system temporarily so im going to check that out tomorrow also . I just don’t see a vacuum leak being possible with the hose and clamps I used . It’s 3 core rubber air hose not plastic 500 psi non collapsible I mean it could have a vacuum leak but highly doubtful on the hoses . Round 3-4-5 —- whatever tomorrow we’ll see what happens

 

So I pinched off the booster and the brakes were very responsive and after it warned up it idled at 1100 ish down from 1700 rpm’s . On initial startup it idles up real high and on the down idle it drops to 5-600 ish and then dies if you don’t give it fuel and once it warms up its 11-1200 rpm . Now the brakes work better with the booster pinched off from the vacuum what’s that about?

 

Oh and the brake light went off also

 

I just noticed this after the power wash yesterday the mc is now leaking at the booster gasket .