Brakes Locking all 4 corners

[90Warrior]

I've ran into an issue with the winnie this past weekend taking it out on a trip. The trip was about 12mi or so down the road.

The problem I have is that when using tbe brakes, they compressed and stopped the truck, however I was getting no release. I being smart as I am pressed onwards to get it to the end of the trip and not be stuck roadside. Driving caused the brakes the heat up and compress even more....by the time I made it to park I was just about dragging front rubber on pavement.

So, I managed to get it parked and all 4 corners were screaming hot. After it all cooled down the brakes released. I now have a brake pedal that hits the floor with barely any stopping power, probably because I burned the pads out; and no more grease in the front wheel bearings.

 

I am looking for suggestions on what it could be that caused this? Other than simple things like oil changes, brakes pads, etc I am not a mechanic. Googling around doesn't bring much up on why all 4 corners would lock. I've asked a local toyota mechanic suggestions and was guided to either the master cylinder or the LSPV since they're common items to all corners.

Have any of yall ran across this with your rig? Mines a '90 v6.

[fred heath]

Sounds like seized calipers and possibly rear brake shoes dragging. How long was it sitting and did you have the emergency brake on during this time? Many times the cables do not completely release the rear brakes due to rust etc. even though you’ve released the handle inside the cab.

It’s tough to diagnose without seeing what’s actually going on. Jack the rear axle up and see if the wheels turn freely(with the e-brake off). It could be something like the LSPV but seldom do they go bad. Pull a front caliper and see if the slides are functional. With limited mechanical experience you may need a shop to do the diagnostics.

[linda s]

I had my brakes lock and it was the master cylinder.

Linda S

[90Warrior]

Before this trip it hadn't sat for but a few weeks. I haven't taken it out on trips anywhere since owning it until recently. But usually once a month or so I'll move it around the yard or block to get fluids moving. Probably not far enough to warm things up and make the brakes lock.

The parking brake on it seems fine, currently the truck rolls freely and I can use the hand brake to stop it no problem.

I don't have any fluid leaking anywhere, none seemed to be lost during the lockup as well. I'm making vac at the booster, the pedal return spring is fine as well.

I haven't lifted an axle on it or checked any corners yet as its been so wet with these pop up storms the past few days.

I would figure it be very rare I have brake hoses collapsing on all 4 corners, or faults with the calipers and drums concurrently, but definitely not ruling it out; I have no paperwork when they were last serviced unlike everything else I have record of.

One thing Im thinking of trying is lifting the front end, pumping the brakes and see if I can get the fronts to lock again, and loosening a fitting by the MC to see if pressure releases. Maybe rule out a bad MC or not. Would that be a plausible test?

[extech]

ls your master cylinder a dual unit?. if not your test is valid.  again unlikely both front and rear parts of m/c go bad at once.

  could be something is stopping the m/c piston from returning.  if your test shows pressure held in both halves, loosen the m/c mounting bolts to see if pressure relieves

[Ctgriffi]

MC is pretty cheap and not too difficult to replace if you’re reasonably handy and have some metric wrenches and sockets around. I did it last year on my 91 Warrior. Best to have a second pair of legs around to help bleed, post-repair. 

Edited July 3, 2022 by Ctgriffi