TBU, bigger rear cylinders, SS lines ABS delete. Chevy master cylinder?

C

CWccw

New member
I wrote this once last week and it never posted. Doh :frusty:

I did the Tundra brake upgrade last year, upgraded to SS braided brake lines, disabled the ABS fuse years ago and recently upgraded to the 1" rear cylinders. No matter how much I bleed the brakes, the pedal always goes soft 75% of the time. Probably could be air in the lines at the ABS side of things so I want to delete the ABS module. From what I remember reading a few years ago I need something from the non abs 4runner or Tacoma to delete the abs module. The proportion valve.

Aside from the deleting the ABS, I probably need a new master cylinder seeing as mine has 306k on it. I cannot find a clear answer on what to do as far as upgrading the MC and am looking for a clearer explanation from someone that has done it. Do I use a Chevy truck 1 1/8" MC and wallow out the holes or do I need some other one and an adapter plate? Thanks for everyones help!
 
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Proportionally 'soft' is the standard 'feel' of 3rd gen runners, as long as a full push gets it to near lockup with the ABS.

Will the brakes nearly lockup on a full push? If so they're OK/normal.
 
jgue467 said:
Proportionally 'soft' is the standard 'feel' of 3rd gen runners, as long as a full push gets it to near lockup with the ABS.

Will the brakes nearly lockup on a full push? If so they're OK/normal.
Click to expand...

Nope, sure dont. If I jam on them real hard quickly, the pedal gets hard but goes soft the longer I hold it. I dont have any fluid loss.
 
CWccw said:
I wrote this once last week and it never posted. Doh :frusty:

I did the Tundra brake upgrade last year, upgraded to SS braided brake lines, disabled the ABS fuse years ago and recently upgraded to the 1" rear cylinders. No matter how much I bleed the brakes, the pedal always goes soft 75% of the time. Probably could be air in the lines at the ABS side of things so I want to delete the ABS module. From what I remember reading a few years ago I need something from the non abs 4runner or Tacoma to delete the abs module. The proportion valve.

Aside from the deleting the ABS, I probably need a new master cylinder seeing as mine has 306k on it. I cannot find a clear answer on what to do as far as upgrading the MC and am looking for a clearer explanation from someone that has done it. Do I use a Chevy truck 1 1/8" MC and wallow out the holes or do I need some other one and an adapter plate? Thanks for everyones help!
Click to expand...

check out the following thread.

Master Cylinder upgrade options
 
CWccw said:
Nope, sure dont. If I jam on them real hard quickly, the pedal gets hard but goes soft the longer I hold it. I dont have any fluid loss.
Click to expand...
Pedal sinks with constant pressure on the pedal? You have an internal master cylinder leak.

If you let the master cylinder get anywhere close to dry and didn't follow the factory bleed procedures, you also likely still have air in the lines.

For the '96-'00 4Runners, here's the procedure:

BFS1dvk.jpg


-Charlie
 
Theres a lot of mods to consider here. Did the pedal start feeling soft directly after a mod, or did it gradually become soft over time? If it felt off after one of these mods, then its probably the cause.

The only thing that I'm aware of non-ABS 4runners having is an LSPV, which prevents lockup by compensating for the additional grip that comes when weight is added. There are other small differences scattered throughout the brake system, but its mostly things needed for the ABS.

The valve isn't necessary, in fact people sometimes delete the LSPV. The valve relies on the distance between the frame and the axle to do its job, changing the ride height will defeat the purpose of having it. And I bet its a pricey piece to get from Toyota too, I wouldn't bother if your rig is already modified
 
The 4Runner has a proportioning valve in the master cylinder so you don’t need a separate valve if you want to run new lines and bypass your abs module unless you get a new master cylinder that does not have the valve
 
It sure sounds like I just need a new master. But I want to get a bigger bore MC. I want to use a old Chevy one but Everything I find on the subject of a 1 1/8” MC isn’t too clear on adapting it. I get I need to wallow the bolt holes out but adapting my lines to the MC isn’t very clear to me.

One need to know is the push rod throw length for the MC. Looks like a 87 Chevy at the latest is the MC I need to go after since it’s a 1.125” bore. I realize I can get an adapter for the fittings, at least I hope.
 
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CWccw said:
It sure sounds like I just need a new master. But I want to get a bigger bore MC. I want to use a old Chevy one but Everything I find on the subject of a 1 1/8” MC isn’t too clear on adapting it. I get I need to wallow the bolt holes out but adapting my lines to the MC isn’t very clear to me.

One need to know is the push rod throw length for the MC. Looks like a 87 Chevy at the latest is the MC I need to go after since it’s a 1.125” bore. I realize I can get an adapter for the fittings, at least I hope.
Click to expand...

I know some will poopoo this suggestion but I will make it anyways

I did a frame off compete rebuild a couple of years ago and I used this master and I would say it's been just fine. nice firm feel, works well.

Amazon.com: Dorman M390367 Brake Master Cylinder Compatible with Select Toyota Models : Automotive

I have 2x 3rd gens

I rebuilt the master in my other truck with a the toyota kit

0449330232
CYLINDER KIT, BRAKE MASTER

but the new master is about the same price once you pay for shipping, it works equally as well without the hassle of cleaning it up to do the rebuild.

smaller bore less effort but longer pedal travel
larger bore more effort but shorter pedal travel

just depends on what your after
 
sleepydad said:
I know some will poopoo this suggestion but I will make it anyways

I did a frame off compete rebuild a couple of years ago and I used this master and I would say it's been just fine. nice firm feel, works well.

Amazon.com: Dorman M390367 Brake Master Cylinder Compatible with Select Toyota Models : Automotive

I have 2x 3rd gens

I rebuilt the master in my other truck with a the toyota kit

0449330232
CYLINDER KIT, BRAKE MASTER

but the new master is about the same price once you pay for shipping, it works equally as well without the hassle of cleaning it up to do the rebuild.

smaller bore less effort but longer pedal travel
larger bore more effort but shorter pedal travel

just depends on what your after
Click to expand...

Well now it seems I am hunting down M10x1.0 to 1/2-20 and M10x1.0 to 9/16-18 adapters that don’t exist.
 
CWccw said:
Well now it seems I am hunting down M10x1.0 to 1/2-20 and M10x1.0 to 9/16-18 adapters that don’t exist.
Click to expand...

Why even use adapters? new tube nuts of the correct size and flare. Adapters are probably just going to leak anyways. You can always drill tap n die your own adapters. I would still just snip off the m10 1.0 tube nuts and put new ones on of the correct size.
 
sleepydad said:
Why even use adapters? new tube nuts of the correct size and flare. Adapters are probably just going to leak anyways. You can always drill tap n die your own adapters. I would still just snip off the m10 1.0 tube nuts and put new ones on of the correct size.
Click to expand...

This is what I am going to end up doing. Just don’t know if the Chevy and Toyota tubes are the same diameter.
 
As said, you would just need new line ends. I bought complete brake lines at AutoZone, kept the fittings, and threw the lines away.

I attempted the Chevy Cylinder and have one modded to fit. You're welcome to buy it if you like, otherwise you'll need to adapt to the 4Runner brake booster mounting. The increased MC size made the problems worse - the braking performance was worse. I bought a new Advics (OEM) off of RockAuto and things improved.

I also removed the ABS unit entirely. In the meantime, take advantage of winter and go drive on the roads or some gravel, engage the ABS a bunch, then drive straight home and bleed the brakes. This will purge the ABS system of any air.

I am a believer that we actually need a smaller MC - this translates to more pedal travel but higher pressures (think leverage).
 
rideexileex said:
As said, you would just need new line ends. I bought complete brake lines at AutoZone, kept the fittings, and threw the lines away.

I attempted the Chevy Cylinder and have one modded to fit. You're welcome to buy it if you like, otherwise you'll need to adapt to the 4Runner brake booster mounting. The increased MC size made the problems worse - the braking performance was worse. I bought a new Advics (OEM) off of RockAuto and things improved.

I also removed the ABS unit entirely. In the meantime, take advantage of winter and go drive on the roads or some gravel, engage the ABS a bunch, then drive straight home and bleed the brakes. This will purge the ABS system of any air.

I am a believer that we actually need a smaller MC - this translates to more pedal travel but higher pressures (think leverage).
Click to expand...

What one do you have and how is it modded?
 
rideexileex said:
It's one from a Chevy Blazer. The mounting for it needs to be adapted to fit the stock 3rd gen 4Runner brake booster 2 bolt mounting width, so the mounting holes are reemed out.
Click to expand...

Tempting. Is it AC Delco? What do we do about the fluid sensor wires?
 
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