TBU Aftermath- Looking to upgrade MC/Booster

90goldtsiawd

90goldtsiawd

New member
Been doing some research on the mushy pedal aftermath of the TBU upgrade and the only bolt-on upgrade I could find for the master cylinder was here: http://www.toyota-4runner.org/2630368-post18.html. I noted that the brake booster will need to be swapped too since it's 4 bolt vs 2 bolt on the 4Runner. Has anyone else gone this route? I'm about to start ordering parts and looking to see if anyone has the oem Toyota part numbers from the T100 1 Ton for this. In that build the OP did not retain ABS but from what I've read here: https://roundforge.com/content/arti...nder-and-brake-booster-specs-for-toyota-4x4s/ and the parts listings on autozone's site it looks possible. Can anyone confirm? Any and all help is much appreciated! Will this screw with the VSC system or does the T100 have that as well?

These are the parts I have found for it on autozone's site:
Master Cyliner: Duralast New Master Cylinder (Brake System) NM55100 - Read Reviews on Duralast New #NM55100
Brake Booster: Cardone Reman Brake Power Booster 53-6401 - Read Reviews on Cardone Reman #53-6401
 
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If you have an 01 like your signature says you don't have a brake booster, it's all electronic because of the 4 channel ABS and VSC/TRAC that was introduced in 2001.
 
Ah duh... Since posting that the truck was at the shop and found the major issue to this was a frozen left rear parking brake and some air was in one of the front lines. They're working much better now.
 
90goldtsiawd said:
Ah duh... Since posting that the truck was at the shop and found the major issue to this was a frozen left rear parking brake and some air was in one of the front lines. They're working much better now.
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Everyone mentioning mushy pedal usually has an issue not pertaining to the TBU. Does the pedal feel just like the original brakes?
 
Plunger size, the only thing that would really change with a MC upgrade, doesn't correlate to a mushy pedal. Changing the size will simply change the effort required to receive the same mount of braking force.

Mushy pedal is usually (read: always) due to air in the lines, especially post TBU. Pedal pumping must be done in a slow manner, so as to not aerate the fluid when bleeding. At least that's what worked for me after TBU.
 
90goldtsiawd said:
Ah duh... Since posting that the truck was at the shop and found the major issue to this was a frozen left rear parking brake and some air was in one of the front lines. They're working much better now.
Click to expand...

absalom said:
Plunger size, the only thing that would really change with a MC upgrade, doesn't correlate to a mushy pedal. Changing the size will simply change the effort required to receive the same mount of braking force.

Mushy pedal is usually (read: always) due to air in the lines, especially post TBU. Pedal pumping must be done in a slow manner, so as to not aerate the fluid when bleeding. At least that's what worked for me after TBU.
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Yup, mushy pedal is air in the lines. Nothing to do with the brake booster.

For 01-02's, the FSM says to bleed the brakes with the engine running and the pump on. I also do this on my 98, virtually eliminates any chance of getting air in the lines. Just have to watch the fluid levels. You don't even need a helper, just put a heavy block/brick on the pedal, open the bleeder and the fluid is forced out continuously. Super easy.
 
gamefreakgc said:
Yup, mushy pedal is air in the lines. Nothing to do with the brake booster.

For 01-02's, the FSM says to bleed the brakes with the engine running and the pump on. I also do this on my 98, virtually eliminates any chance of getting air in the lines. Just have to watch the fluid levels. You don't even need a helper, just put a heavy block/brick on the pedal, open the bleeder and the fluid is forced out continuously. Super easy.
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Iirc, doesn't this only work for the rears? Where as the front still need to be bled traditionally. I could be wrong, it's been a long time
 
absalom said:
Iirc, doesn't this only work for the rears? Where as the front still need to be bled traditionally. I could be wrong, it's been a long time
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I'm wondering myself what is meant by "engine running and pump on."

When I did the upgrade I pulled off the old calipers and swung them out of the way and healed them with bunji cord. Then did what was necessary to mount the larger calipers. I installed the new rubber line on it and opened the bleeder. I then removed the old rubber line from the hard line and connected the new line while it dripped. The open bleeder in the new caliper gave the air a place to go (besides back up into the MC) Then set the old caliper and hose aside and waited for a solid stream of fluid coming out of the bleeder. Then did the same to the other side.

I then hooked up my pressure bleeder and purged all the lines till I seen clear fluid.


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absalom said:
Iirc, doesn't this only work for the rears? Where as the front still need to be bled traditionally. I could be wrong, it's been a long time
Click to expand...

I've done it successfully with all 4 lines. The brake booster applies constant pressure when you step on the brake with the engine running, so fluid will flow out of whichever line provides the least resistance (read: bleeder is open).

I like doing it that way since it gets all air and fluid out all at once. I had an issue doing it by hand with an helper when I had air in the lines once. I must have pumped a good quart of brake fluid out and still had air, since it only purged a small amount of fluid at once, and the air would just travel back upstream before I could bleed it again. With the booster/pump on it provides a steady stream that gets it all out.
 
gamefreakgc said:
I've done it successfully with all 4 lines. The brake booster applies constant pressure when you step on the brake with the engine running, so fluid will flow out of whichever line provides the least resistance (read: bleeder is open).

I like doing it that way since it gets all air and fluid out all at once. I had an issue doing it by hand with an helper when I had air in the lines once. I must have pumped a good quart of brake fluid out and still had air, since it only purged a small amount of fluid at once, and the air would just travel back upstream before I could bleed it again. With the booster/pump on it provides a steady stream that gets it all out.
Click to expand...

Is this tried and true? I bled my brakes for the first time yesterday and I feel air in the lines still and I'd love a better technique to do it right.
 
Open bleeder and push brake to the floor-close bleeder and release pedal-open bleeder and repeat the above until no air.

Once the master cylinder spool bottoms outs at its max travel when the brake pedal hits it's max travel limit there is nothing pushing fluid out the line. It's just flowing out from gravity.


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OldManKamps said:
Is this tried and true? I bled my brakes for the first time yesterday and I feel air in the lines still and I'd love a better technique to do it right.
Click to expand...

Well, it's tried and true for me. With vehicles with the brake pump (01-02) the FSM says to do it this way. I just find it works with older models with the brake booster too.
 
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