Hydraulic booster issues?

I had new rotors and pads put on the front end of my TRD. 4 months later I'm having issues.
I start to drive the truck, after 15 min of driving I hear what sounds like my calipers dragging on my rotors. I took my wheels of the front and noticed the wheels don't turn easy, the calipers are still gripping the rotor with my almost new brake pads. Also my wheel nuts where very hot.

I have this hydraulic unit
https://www.tacomaworld.com/threads/master-cylinder-replacement.804930/#post-28859385

I took it to a mechanic. The machanic says it could be my master cylinder, break booster or the ABS modulator valve. Toyota said to replace all three with a new assembly, They wanted $3500 to do it.
. I don't have dead pedal
. I don't have sponge pedal
. I don't have rock hard pedal
. I don't have pinched lines
I have brakes that end up sticking after hard use. If I don't press them hard they don't stick. I can hear my actuator motor kick on and off like normal wile depressing the pedal with the key on without the engine running. Im thinking its my master cylinder not allowing the caliper pistons to return. Can I just buy the master cylinder and replace that part of the assembly?


Update 12/13/23
Had a a few mechanics look at my truck. This is where I’m at right now
Known issue's
1. I have a bad bearing that is leaving metal shavings inside the hub where the speed sensor is at.
2. The speed sensor is covered in metal shavings telling the ABS to pump the calipers at speed
3. My rotors have hot spots now and my pads are kind of glazed.
4. Had a popping sound when I turned the wheel and went backwards. All my ball joints on my control arms checked out. I did find that my sway bar links have bad rubber boots on their ball ends. Also found a hole as big as a rat in my rack and pinion boot.

The fix
1. Replace both front bearings and seals
2. Pull out axels and replace the seals that are leaking on the back side.
3. Machine the rotors and buy new pads
4. Install new sway bar links
5. Install new rack and pinion along with new bushings.
6. Debating on installing new uca from Rancho. This would help with my Bilistein lift.
7.I might go ahead and have my 5100’s adjusted to the 3rd mark instead of the 4th. This would set my stance a little closer to factory and help when I tow.

 

I can’t answer the question about the booster itself.

Nothing is for certain, but it sounds more like a caliper issue to me. It’s possible that when the brake job was done, they weren’t bled and crap that settled at the bottom of the caliper got lodged in the bore when pushing the pistons back in for the new thicker pads.

Do you know if they bled them?

It’s hard to believe that would happen to both sides though, so I can see why it’s thought to be a hydraulic booster issue.

 

Could be those things, but I'd also check the calipers. Especially if high mileage, driven in road salt, or if prior pads were worn down to the metal.

The actual hoses between the calipers and the frame can cause sticking too, especially this kind of sticking, they can wear out and sort of swell shut.

That said, suddenly having this on both wheels does support mechanic's conclusion.

This is all fairly straightforward for the home mechanic, I just replaced my calipers, hoses, pads, cylinder, and booster, upgrading to Tundra parts for the latter two. For maybe $800 in parts, including oem calipers. One exception is that you need specialty equipment to bleed the ABS, prob. best to have a shop do that. This is in addition to standard bleeding the brakes and bench-bleeding the cylinder, which you have to be able to do before the brakes will work at all, after which you can drive to the shop for the specialty ABS bleed.

Measuring the rotor temps after driving could help diagnosis. Like with a heat gun, to get a number, at the same spot on both sides, a few seconds apart. If one is dramatically hotter, this would make caliper/hose more likely. This isn't super definitive, but is easy to do and might help you decide what to do.

 

Oem pads? Check the slide pins? They should be cleaned or replaced when changing pads. California it’s not a big deal to clean or replace but if you live in the rust belt it’s a must.

 

They did bleed them, and they worked great since mid summer.
I had a second shop check the pistons and they said the worked fine.

 

East Tn brine mix during the winter. I don't have any rust or salt damage on the frame, body or engine.
Yeah the more I read about the repair work I'm finding I will need a shop to set the ABS.

 

I had that second shop check the caliper operation and they both passed.

 

Thanks y'all for the fast replies. Im taking it to one more shop on Monday to see if they can pinpoint the issue instead of a blanket remedy. They might say the same thing..

 

It would be quite uncommon for an abs module to cause this. They just don’t work that way. An exception would be if the brakes only dragged after a stop where the abs was active and that is not common during every day driving. My first guess would be sticking calipar pistons, but rare to have both sides doing it at the same time and two mechanics have confirmed they are not sticking. That leaves the master cylinder. Sorry, but have never seen one like yours before and suspect it could have a failure mode like this; just no experience to offer. If both front brakes are dragging, my first guess is an M/C with a sticking spool valve. If that valve doesn’t retract enough, the fluid does not get released from the brake circuit and the brakes drag. It has a small clearance with the mc bore and therefore they can develop situations where they don’t achieve full movement. This is where I would start. Vacuum Boosters rarely cause brake dragging and would be the last thing I checked for these symptoms. They typically fail by not producing enough boost and not by providing too much. While kinks in the lines can hold the fluid in, you really can’t have that without a noticeable decrease in braking effectiveness.

i do not understand the clicking when applying the brakes with the key on, so you clearly have a system that i do not understand. Pleas consider that as you read my reply.

suggesting you replace all three components out of the gate is lazy at best and criminal at worst.

 

When I turn the key to the on position, I have powered the truck with the battery without starting it. With the HVAC and radio off I can step on the brake twice and hear a very faint hum. I believe the is the electric booster motor on the bottom of the ABS assembly. I may be using the wrongs terms to describe all the components. when you search videos of that motor kicking on when its bad, it will sound horrible.

I am leaning towards a MC being bad. What other symptoms would slow returning spool valve present?
Also remember right now I can drive the truck and barely use the brakes and the problem will not present itself. When I smash the brakes mutable times (almost like I'm pressuring up the braking system) that's when the issue will show up. I haven't jacked up the front of the truck and tried applying the brakes and check to see if my wheel will spin freely after I let off of them. Then try it a second time after applying the brakes like Im pumping up the system, then see if I can turn my wheel. Just thinking as I'm typing this last part out, maybe that's what a bad spool valve would start to look like?

 

Check if you have a little free play at your brake pedal when things warm up.

some master cylinders have a threaded/adjustable rod that you have to adjust before installing or once things warm up the brakes drag.

An easy way to see if thats it is to unbolt the master from the booster while the wheels are locked and then see if the wheels spin freely.

there are various ways to set them up from plastigauge, to a depth micrometer or measuring the depth of the pocket/rod and doing the math to make them the same. I don't know how much play there should be but I think it's around 5mm or so

 

When they start dragging crack the lines at the master cylinder and see if they release, if they do then you have a problem in the master cylinder. If they don't then crack the bleeder at the wheel and see if they release, if they do then you most likely have a bad brake hose. If not then the caliper has a problem or the pads are binding on the slides.

 

This sounded weird to me, like maybe an ABS issue after all. But then I actually clicked the link in your first post.

You have the electronic assist, rather than vacuum assisted brakes, as I had assumed with my prior comment. Both are hydraulic, and both also have ABS, but the assist system is totally different, and the ABS modules are different as well.

Electronic brake assist is relatively modern, and in Tacomas, reportedly delivers much better braking. Mine has the decades-old vacuum boost technology, and it really sucked. I upgraded to a two-stage vacuum booster from a Tundra recently, brakes are probably better but I haven't fully bled them yet.

Anyway, to cut to the point, I don't know anything about your electronic brake booster, or how much it costs. In light of this, I'm definitely more inclined to agree with your mechanic, but hoping you find a cheaper way to fix it!

 

I believe since I have the down hill assist with my TRD package I have this monster instead of the big mushroom booster.

 

I added this update to my first post.

Update 12/13/23
Had a a few mechanics look at my truck. This is where I’m at right now
Known issue's
1. I have a bad bearing that is leaving metal shavings inside the hub where the speed sensor is at.
2. The speed sensor is covered in metal shavings telling the ABS to pump the calipers at speed
3. My rotors have hot spots now and my pads are kind of glazed.
4. Had a popping sound when I turned the wheel and went backwards. All my ball joints on my control arms checked out. I did find that my sway bar links have bad rubber boots on their ball ends. Also found a hole as big as a rat in my rack and pinion boot.

The fix
1. Replace both front bearings and seals
2. Pull out axels and replace the seals that are leaking on the back side.
3. Machine the rotors and buy new pads
4. Install new sway bar links
5. Install new rack and pinion along with new bushings.
6. Debating on installing new uca from Rancho. This would help with my Bilistein lift.
7.I might go ahead and have my 5100’s adjusted to the 3rd mark instead of the 4th. This would set my stance a little closer to factory and help when I tow
.

doing the work myself.

 

Wow, glad you figured it out! I believe those vertical things are sway bar links.

 

Yeah I got lazy on my typing

 

Quick question. The control arm going into my rack in pinion I believe is popping. The boot has a hole it and I can see the joint inside. Is there a way to fix that end? The top end of the control arm? Without replacing the entire rack and pinion?

 

That would be your inner tie rod end, if you're fine with aftermarket parts then yes you can get a new inner tie rod. Use a reputable brand though, maybe add a little extra grease to the joint before you install in and get an alignment after. Measure the length of the tie rod before replacement and afterwards to get it close for the drive to the alignment shop

 

Dude that’s going to save me about $300! Thank you