2004 Tacoma Stiff Brake Pedal Issue (1st gen Tacoma)

Hi guys,

I have an issue with my 2004 Tacoma’s brakes that I have had for years at this point and I’m getting really over it.

The Issue:
If I have to STOMP on the brake pedal in an emergency, the pedal is stiff and difficult to press and the truck DOES NOT slow down as fast as it should. (Yet to have any accidents luckily).

The strange thing is that if I ease onto the brakes and then stomp the pedal, the boost is there and the truck stops much better than if I just stomp on it. I still think that as I get deeper into the pedal travel is does start to stiffen up again BUT there is a huge difference in braking power when easing into them vs stomping on them.

Now over the many years of me having this issue I have replaced the booster a few times, checked the vacuum pressure coming from the plenum with a gauge which looks good, replaced the calipers once, replaced the soft lines in the front, adjusted the proportioning valve at the rear, adjust the drums, bled the brakes a handful of times, etc.

It seems like every time I replace something, the brakes work as they should for a while, meaning when I stomp them I can lock the tires and the ABS kicks in as it should. However this stiff brake pedal issue ALWAYS seems to come back and I cannot for the life of me figure out what the issue is. I have experience working on a lot of different vehicles and I have done regular brake maintenance on many vehicles. I have never driven anything with this issue and I am over it.

The booster that’s on the truck now, I pulled from a junkyard truck with the master attached to it. The booster has no leaks and holds pressure for days, and the check valve works as it should.

I replaced the calipers because I noticed the pads were wearing unevenly as if one of the pistons was not working.

I replaced the soft lines in the front because the old ones looked bad.

The only thing I can think of at this point is that there is an issue with one or more of the hard lines. Either something that got into the lines somehow or rot on the inside of the lines restricting the flow of the fluid. So maybe when I am stomping the pedal, the fluid simply cannot flow as it should be able to in an emergency, but when braking more slowly and normally the fluid is able to flow at a rate fast enough to provide the braking power I would expect.

Im not sure if the ABS unit would have anything to do with this or the way the linkage is adjusted under the dash but if anyone has experienced this before and solved the issue I would love to hear about it.

A couple more things maybe worth mentioning is that the hard lines appear to be rust free on the outside. It’s a California truck. The truck also has a small lift, maybe 1-1.5” and slightly larger 32” tires.

I have tried to find threads with this specific issue in the past but I have yet to find anything.

Thanks for reading.