2000 Limited 240,000 miles

Still having brake troubles after replacing a lot of stuff. I don't feel bad about the parts, because they were old and it's better having new on something critical as brakes. Here's what's new

Tundra rotor/caliper upgrade (5,000mi ago)

Recent stuff:

• New rear brake shoes and drums
• New front pads
• New rubber hoses on front
• New Master Cylinder
• New Booster
• Flush & bleed - two quarts DOT3 through the system

My work commute is 25mi each way. Morning traffic is mostly a breeze and I get only two to seven of the 31 traffic lights are red, so I cruise.

Home commute is a nuclear nightmare. Million cars and stop-go-stop-go-slow down-go-stop-speedup-slow down-stop-go etc etc etc (channeling Yul Brenner) for twice as long as the drive out.

Today, about 2/3 of the way in, my brake pedal has about half-an-inch of press before I have solid braking. Just shy of panic brake. Another few miles and I can't go more than 50mph with WOT, and when coasting, it feels like the brakes are engaged

A few more miles, and the truck is noticeably slowing down while I have throttle wide open. I parked for about twenty minutes and then the brakes were back to normal.

Have had this happen three times in the last couple of weeks.

Any thoughts where this is coming from?

Your input is appreciated!

—K

When this happened did you notice any excessively hot brakes or a burning smell from a specific wheel? Are your tundra caliper pistons all moving (all 8 of them) known issue on poor rebuilt calipers? How about the rear cylinders? Did you lube the rub points on the shoes backing plates?

Next place to look could possibly be a bad booster. Some type of internal failure. When the issue happens is the brake pedal lower then when it doesn't happen?

Lastly it could be a sticking master, harder to test/diagnose.

I don't think it could be the 3 rubber hoses having a internal tear preventing the pressurized fluid to return to the master. Well maybe it could be the rear one having an internal tear.

Your upgrade has clearly not helped your rig. You said it's happened 3 other times and you've had to use wide open throttle to keep going. After the first time this happened the rig should be parked till fixed. It clearly is a reoccurring thing and it's obviously in your brake system. Your caliper/ calipers are hanging. If it was just one side you'd notice more steering Input to keep the rig straight. It could be pinched brake lines after the first initial brake activation not letting the fluid bleed back. Booster could be bad. Master cylinder could be bad to. If you have the old parts I'd swap out your brake lines and try that first. With wide open throttle your brakes have to be toast and your calipers aren't fairing well either. Smoke should be pouring out of the wheels wells also. I wouldn't chance driving it again till this is fixed and certainly don't keep going down the road when you know you have a bad problem again unless you don't mind the chance of your rig catching fire and bring the stop and go traffic to a halt for miles while you get toasty from a 4Runner inferno.

Pump the brakes 5 times then keeping the foot on the brake pad start the motor the pedal should drop a little. Check the fluid. Brake pads floating on the pins. e brake good. Check valve on the booster. If you replace it also replace the grommet. I could hear a hissing air sound in the cab when parked in the garage when my brake booster went bad. Also check for diff fluid in the rear drums(rear wheel bearing leaking swelling up the shoes. Vacuum lines all good. You might stumble across the problem while doing the diagnostics. Good luck.

so with all you listed...you stopped at rear cylinders and rear hose ? I dont think it is either of those, but I have seen old hoses go bad, and swell to the inside, not be visible and blocking correct fluid flow.
When you replaced the booster , did you replace the check valve.? With those I have had them fail, but making brakes very hard to push and function, but I guess they could fail other direction too.

maybe your pressure line?