Weak Braking - Tried Everything

I'm pretty sure he'd notice the problem was his tires if he was sliding uncontrollably. That doesn't sound like his issue.

 

Cooper Discoverer ST Maxx, about a year old. Definitely not worn out.

 

Agree, I'm certain it's not the tires, but like I said, I'm open to anything at this point. To me it seems like a master cylinder issue, but I've already tried that.

 

Yeah tires aren't the issue here. If that were the case (not enough traction) the wheels would lock and ABS would kick in

For what its worth @bosshog1 I run the same size MTs on my 2012. Barely noticeable difference between my winter 32's. Granted 2012 has the electronic booster which is a slightly different system, but 33s should not be your problem here.

 

Yah I always kind of figured that was the case but somehow it made me feel better because I can't seem to find the issue.

 

I have 35s and my brakes are super sensitive, my brother drove my truck and made a comment on how touchy the brakes are so I agree, larger tires likely aren't the issue here.

 

I'd kill for touchy brakes. This has been the only vehicle issue to ever get the best of me. Usually if I do enough research I can solve any mechanical issue, but this one has stumped me for years.

 

Just to make sure I understand the situation, so your pedal is firm and it takes a lot of pressure to get braking action?

Is there a difference in pedal pressure when the engine is running vs when it's off? With the engine off, you should be able to pump the brakes a few times until the pedal gets very firm, as all the vacuum pressure gets bled off of the booster. If it feels roughly the same with engine on/off, it's probably the booster. More specifically either a leaky diaphragm or leaky vacuum hose

I didn't see any mention of checking or servicing the front calipers(sorry if I missed it) aside from just the pads. If the pistons in the front calipers are siezed solid, brake pedal will feel normal/firm but won't actually squeeze the pads against the rotors. And being that the front brakes do the majority of the work, that'd explain lots of excess pressure needed for the rear brakes to pick up the slack.

I'd double check the calipers and vacuum line before jumping to replacing the booster or ABS module. Also just make sure no brake lines are kinked or pinched. I could be wrong but I don't think the ABS would be the culprit if the brakes aren't spongy(from stubborn trapped air)

 

Pedal is on the softer side, not what I would call firm. It does harden up when the engine is off, so I don't think there is any issue there. I replaced one of the front calipers because the bleeder screw broke off, so that one is pretty new. The other one is older but it does not appear to be seized, and it's definitely not leaking. I could do a full check on it to rule it out though.

 

Has anyone else driven the truck and said the same thing about the brakes? (Obviously they won't have a frame of reference, but it could eliminate the chance that you are overthinking it)

 

Yes, I had my brother-in-law who also owns a newer tacoma drive it while towing the boat and he agreed.

 

Isn’t there something about bleeding the abs or something?

 

What about WITHOUT the boat?

 

I'm going back to my initial assessment, I think it's your booster. Apparently a bad booster can, in some cases, cause a soft pedal as well.

 

Without the boat is obviously better, but still weaker than it should be. I drive my wife's 2001 4runner all the time and it's much more responsive. I know those have rear disc brakes but it's still too much of a difference.

 

I feel like a read this somewhere too, but most of the info out there says that it would cause a hard pedal. I'm not opposed to swapping it out, but seems like a long shot.

 

This is what I found with a quick search, not sure I can put the link here but this is the paragraph. Seeing how you already replaced the master cylinder twice I think it's about the last thing to look at.

Can a brake booster cause a soft pedal?
Most often, a bad brake booster will cause a stiff brake pedal, but if there is an internal problem, it could potentially cause a soft pedal. When your brake pedal is soft, however, it’s more common that a brake fluid leak or a bad master cylinder is at fault.

 

have you had the VSC bled by a proper scan tool?

 

I don't think I have VSC, but I did take it to a shop and they said they bled the abs module with their scanner tool.

 

I was never happy with the brakes on my 06 Tacoma. Now that I have a 2024 4Runner braking is like night and day.