Brake problems

I had a issue with my brakes applying themselves usually on the highway or constant speed above 50mph. We found that when it happened and I pulled over and disconnected the vacuum from the booster then reconnected it would instantly free the brakes up and this would last a few days before it happened again. Before I discovered this I took it to a shop who replaced the master cylinder and brake lines and it locked up again and they said it was a bad booster. I bought a rebuilt OEM booster off Ebay and it fixed the problem and lasted five years before the same thing started happening. I replaced the booster this time with a over the counter unit and I also changed out my rotors (which were warped), calipers and pads. Now the brake pedal feels very inconsistent like sometimes it feels like I can mash it to the floor and other times its super firm but in both cases the truck stops fine. When driving on the highway I can feel the brakes apply but not enough to lock up and it only happens on the highway never city driving. It usually causes a shake in the wheel and if I stomp on the brakes or lift the pedal up with my foot I can feel them instantly release. I am now being told it could be a bad ABS module. Any ideas? 2007 Tacoma double cab auto front disc rear drums.

 

I'll try. I once had a VW TDI that I replaced the rear pads and bled the brakes. I did the wife pumped the brake pedal up and I did the bleed wrench thingy. After that, I had all kinds of problems with the left rear brake locking up. I even replaced the left rear caliper and it didn't help, it would still lock up. What I discovered and for whatever reason was the brake pedal stroke is longer than the depth of the boost and I think we damage the diaphragm in the booster. Why it only affected the left rear caliper I can't answer that. I replace the entire booster and master cylinder as a unit as recommended with an OEM unit and everything was fine. Never had an issue after that. It was spendy but worth it. I try and stay away from pumping the brake at a full stroke when bleeding them and use a brake bleeder check valve when I do brake bleeds. A one-person operation.
Also, look at the check valve between the booster and engine, you may want to change it. If it's a 2007 OEM, it could be getting dirty. I believe all vacuum-operated brake systems have one.

 

I’ll try too. If you’re having to manually lift the pedal up with your foot, something is wrong. The pedal itself I believe should have a spring to return it to the up position. Look under there with a flashlight. Look at the spring and where the pedal pivots. Push the pedal up down side to side checking for anything unusual. Check the linkage attached between the pedal and master cylinder.

 

Ok I think I described it incorrectly. The pedal does return on it's down what I meant to say is sometimes when I feel the brakes drag and steering wheel shake putting my foot under the pedal and lifting sometimes frees it up but I don't feel an obvious movement in the pedal like I can't feel it actually move but sometimes it doesn't work. I feel my next step is just to buy a OEM MC and booster do you recommend where to get them? I'm assuming go to my local dealer and just order them? Do they come as a kit or separate?

 

This second booster was from the dealership, oem? Same question with the other recently replaced brake parts.

The brake pedal sometimes mashing to the floor is a symptom of a failing mc, internally bypassing.

I once, or I should say more than once had new aftermarket rotors be warped out of the box. Once so bad they couldn’t be cut true. Warped rotors is the usual cause of shaking steering wheel during braking. If you don’t have a magnetic base dial indicator you could try the poor man method. Take the front wheels off, put a couple lug nuts back on so the rotors don’t wobble around, set a sharpie on a stable wood block or something so the sharpie tip is just barely not touching the rotor outer braking surface edge, spin the rotor. That’ll give you an idea if it’s not true.

Badly worn and out of balance tires could possibly be causing it too. Try rotating wheels and see if there’s any improvement. It won’t improve the braking problem. Then it’s really not advisable to be driving around with iffy brakes. Being able to stop is important.

 

Trucks haunted.

 

I once had a passive aggressive psychic ahole car. When I had a total of 3 cars and would think about getting rid of it because it ran crappy and looked like hell. All of a sudden it would start running really good, so I kept it. Then got rid of the other 2 cars, then it suddenly would run like crap again. So I’d look for a replacement, get it narrowed down to what I want, start looking, find some to check out, then it would suddenly run good again.

 

Are your brake calipers oem or reman. It almost sounds like you’re brake caliper is hanging up

 

This problem all started years ago. I left work had a dead battery and when I got in the truck the brake pedal was rock hard I couldn't take the vehicle out of park. I eventually wiggled the battery cables and the truck started but the brake pedal felt weird like way different than normal and super touchy and this was out of nowhere without any prior warning signs. On the way home the brakes locked up and I got towed. I took it to a shop and replaced the MC and brake lines which did not fix it and they locked up again the following day. I took it back to the shop, told the mechanic it only happens on the highway above 50mph so he took it out and sure enough they locked up. He pulled over, removed the vacuum from the booster and they instantly freed up. Their quote for a booster was way too much so I bought a rebuilt OEM one off ebay, installed it and everything went back to normal and lasted for 5 years UNTIL One day I was leaving for work and the same thing happened, battery was dead and brake pedal was hard as a rock could not get out of park. I got a jump and sure enough the pedal felt like it did that first night all wonky and super touchy and this lasted for about a week until one night on the way home they slowly started applying and just before I made it home they completely locked up so I pulled over, pulled the booster vacuum and it was fixed again. I ordered a over the counter booster, calipers, pads and rotors and replaced them all. I bled the brakes after and things didn't feel the same which I wrote off as having a smaller over the counter booster it wouldn't be the same as the larger OEM. The brakes do not lock up like before but feel like they start to drag and only above 50mph. Sometimes mashing on the brake pedal frees things up and sometimes it just frees up on its own. While they feel like they are dragging my steering wheel shakes and stops as soon as they release. On city streets everything is fine and the truck stops. The brake pedal does feel inconsistent like sometimes it's firm and other times I feel I need to press it further to stop. I have no ABS lights or warning lights on. I was told to bite the bullet and buy a OEM booster and MC I was also told it could be a bad ABS module which could go bad and not kick any codes out or cause a warning light. I find it odd that this happened after a dead battery.

 

bump

 

Since this is mc #3 for you I would suspect something else is going on. I think looking at the abs module would be a reasonable thought. Maybe look at the yaw (vcs) system too? I don’t have any knowledge with either of those systems on these trucks other than what they were designed to do. If the system senses something is wrong the brakes are automatically applied although it should also give a warning beep, and apply the abs system which would also illuminate the icon on your dash.
My first gen tundra would do it randomly and it would scare the living shit out of you. I thought I was for sure going to die one time. Full lockup going around a 55mph curve pulling me in front of an oncoming log truck. After Research I found it could be out of wack since I upgraded the front and rear suspension, altered the ride height and overall stiffness. Recalibrated the system and it never did it again.

 

See pinned post: How to reset your VSC

-J

 

Is the brake light switch jammed up and holding the pedal forward? Is the bracket bent?

I once looked at a Sienna van where the guy panic stopped on the freeway to avoid rear ending somebody. In his haste to get on the brakes he kicked the brake light switch bracket forward and it was constantly pushing the pedal arm forward. The brakes were constantly applied, 2 shops tried new master cylinders before I found the problem.

Sounds like the something in the stroke of the pedal/booster/MC is jammed up. The battery is probably draining because the brakelights are staying on.

I put a booster in an old Lexus ls400 last year and forgot the thin metal shim between the booster and firewall. The brake pedal never felt right, it was touchy yet barely stopped the car. That little shim being left out made a huge difference for some reason

 

There's also freeplay adjustments that have to be done anytime either the booster or master cylinder are replaced, if there is no freeplay in the linkage the master cylinder will not fully release and as heat builds in things fluid pressure in the lines will build up to a point where the brakes lock up.
The best method to find the culprit of locking up brakes is when it happens is to crack lines loose at each connection starting at the master cylinder and working your way out towards the wheel, if the brakes release when you crack a line you found your blockage.

 

Ok yea the aftermarket booster had a way different length size rod. We measured it to match the the factory unit as best we could but I never checked for free play. Do you know the rough amount of free play the brake pedal should have? I'm curious if it's different cause it's an aftermarket non OEM booster. How accurate does it have to be? Just asking cause I was going to adjust the rod just until the pedal moves a little.

 

I used the gasket that came on the aftermarket unit. To know knowledge these don't have shims just a gasket to keep water out of the cab but I installed the one it came with. I also saved my old boosters just incase.

 

I do not have the VCS system and no abs lights.

 

In a pinch yea that should work, I can post the procedure later I'm not at my PC right now.

 

The manual says to use a special tool. Then measure the gap a 0.0mm between the tool and rod.

See here and post #26
https://www.tacomaworld.com/threads/brake-issues.746464/page-2#post-26588883

 

Here you go.