HOW-TO: 5th Gen 4Runner Brakes on an 80 (1 Viewer)

nukegoat

Should have bought a Jeep
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How's your braking with the one ton axles and the GM MCs? What about hydroboost?
It sucks. I am running 14" rotors with gigantic dodge floating calipers from a 2014 3500 or something. Still sucky.

Master cylinder / caliper piston sizes are a zero sum game, you just need them sized sufficiently to not exceed a certain workload.

Bigger rotors/swept area can make an improvement with no downsides (other than the need for more heat dissipation) so that's a win.

But at the end of the day, I believe the booster is insufficient. Hydroboost is neat but I'm a bit worried about the flow requirements of the downstream box/piston for steering. I would like to see universal electrohydraulic boosters become more mainstream. The one in the 100 is ridiculously better even with the stock master cylinder size than everything I've done to the 80.
 
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It sucks. I am running 14" rotors with gigantic dodge floating calipers from a 2014 3500 or something. Still sucky.

Master cylinder / caliper piston sizes are a zero sum game, you just need them sized sufficiently to not exceed a certain workload.

Bigger rotors/swept area can make an improvement with no downsides (other than the need for more heat dissipation) so that's a win.

But at the end of the day, I believe the booster is insufficient. Hydroboost is neat but I'm a bit worried about the flow requirements of the downstream box/piston for steering. I would like to see universal electrohydraulic boosters become more mainstream. The one in the 100 is ridiculously better even with the stock master cylinder size than everything I've done to the 80.

That's kind been my hunch all along; that the booster plays a big part in our crappy brakes, much more than people realize. I thought about hydroboost for a while but wasn't sure how it would play along with the hydro assist although @baldilocks reports that they both work well together. I'm hoping the brand new Seiken booster will at least give slightly better results than what I've experienced so far.
 

baldilocks

Battle Ground, WA
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That's kind been my hunch all along; that the booster plays a big part in our crappy brakes, much more than people realize. I thought about hydroboost for a while but wasn't sure how it would play along with the hydro assist although @baldilocks reports that they both work well together. I'm hoping the brand new Seiken booster will at least give slightly better results than what I've experienced so far.
I’ve only driven down the road a mile and back and did some stationary cycling of the steering wheel on pavement. People have different standards. With the engine off idle, I don’t foresee myself being disappointed on the trail. I made no mods to flow ports anywhere in the system and am running a 1.5” cylinder.
 

nukegoat

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I’ve only driven down the road a mile and back and did some stationary cycling of the steering wheel on pavement. People have different standards. With the engine off idle, I don’t foresee myself being disappointed on the trail. I made no mods to flow ports anywhere in the system and am running a 1.5” cylinder.
Different HBs have different flows I think. Maybe. I dunno
 
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So is there some agreement that the t100 booster alone with good functioning oem/stockish pads and rotors brake lines would be a significant improvement?
 

baldilocks

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Different HBs have different flows I think. Maybe. I dunno
Most likely. And I also believe that there exists differences in assist power as well. Honestly, I don’t know what part number booster I have. I got it in a kit deal from Power Brake Service in SoCal. They said it was a new GM unit.
 

nukegoat

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Most likely. And I also believe that there exists differences in assist power as well. Honestly, I don’t know what part number booster I have. I got it in a kit deal from Power Brake Service in SoCal. They said it was a new GM unit.
Ostensibly they select the right HB units (or port them) for our world
 
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UPDATE TIME!

Got everything wrapped up, bolted together and bled. First road test...AWFUL. Brakes were terrible, worse than before. Something was up. Did several rounds of the traditional 2-person bleed and still nothing. Went through almost a gallon of brake fluid, super mushy brakes.

I was convinced I had a bad MC even though it was a brand new Aisin unit. So I started diagnosing. No leaks anywhere. Wasn't losing any fluid after several road tests. To test the master cylinder, I used a pair of 10mm x 1.0 inverted flare steel plugs purchased from BelMetric. These are great to have on hand for testing or in case you need to plug a line on the trail. BLP10X1.0DF - Metric Brake Line Plug [BLP10X1.0DF] - $3.63 : Bel-Metric, Metric Hardware, Metric Fasteners, Metric Bolts, Metric Nuts & Time-Sert Thread Repair - https://www.belmetric.com/double-flare-c-17_564_1107_1109/blp10x10df-metric-brake-line-plug-p-13727.html?zenid=1cpo4ko183dkj4vjcdss8bqd20

I plugged both ports on the MC as shown below. Started the truck, pressed on the brake pedal. It wouldn't budget, rock solid. This told me the MC was fine. If the MC was bad, I would expect the pedal to move a bit as fluid blew past the seals and circulated back into the reservoir.

ePntF9zh.jpg


Next step, I left the front capped off and connected the rear line only then proceeded to bleed. After a few bleeds I got a NASTY stream of bubbles with the flaky residue that came out. Who knows where this rogue air pocket was and it's strange that no matter what I did, I could not purge it out doing a standard bleed with all circuits connected, even after going through almost a gallon of fluid.

Started the truck with only the rear line connected, brake pedal felt great! Super firm. Rolled it a few feet in the driveway, great pedal feel. But brakes obviously sucked because it was just the rear.

Then connected the front + rear. MUSHY. Bled again, still mushy. Disconnected the rear and did the front only. Bled bled bled, few tiny bubbles, nothing major. Started the truck, pedal was firm. Okay that's good right? Rolled it a few feet, pedal still firm.

Connected the rear again (all ports connected), bled bled bled. Mushy again. Ready to light the truck on fire. If I ask the wife to help me bleed again I'm afraid she's taking the kid and moving out.

What now? The rear and front brakes feel great when connected individually, but when I connect front and rear it gets soft. Then it occurred to me. PUSHROD! I adjusted the pushrod on the new booster, or so I thought. Apparently wasn't enough I guess? That explains why I was getting a soft pedal with both front and rear connected; the plunger in the MC wasn't being pushed in far enough to generate enough pressure, but it worked fine for one circuit. After adjusting the pushrod out a few turns, SUCCESS!

It was a nightmare but in the end it was a rogue air pocket and poorly adjusted pushrod that was giving me grief on the new setup.

I'm now happy to report the brakes are working great. Here's a video doing 2 emergency stops from 45-50mph GPS speed. Proportioning valve is fully open. I haven't driven a stock 80 to compare or not sure how this compares with other people's rigs, but it's the best braking I've had out of this truck for a long long time. Truck is about 6500~6700lbs on chunky 37" Nitto Mud Grapplers :cheers:

 
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thatcabledude

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UPDATE TIME!

Got everything wrapped up, bolted together and bled. First road test...AWFUL. Brakes were terrible, worse than before. Something was up. Did several rounds of the traditional 2-person bleed and still nothing. Went through almost a gallon of brake fluid, super mushy brakes.

I was convinced I had a bad MC even though it was a brand new Aisin unit. So I started diagnosing. No leaks anywhere. Wasn't losing any fluid after several road tests. To test the master cylinder, I used a pair of 10mm x 1.0 inverted flare steel plugs purchased from BelMetric. These are great to have on hand for testing or in case you need to plug a line on the trail. BLP10X1.0DF - Metric Brake Line Plug [BLP10X1.0DF] - $3.63 : Bel-Metric, Metric Hardware, Metric Fasteners, Metric Bolts, Metric Nuts & Time-Sert Thread Repair - https://www.belmetric.com/double-flare-c-17_564_1107_1109/blp10x10df-metric-brake-line-plug-p-13727.html?zenid=1cpo4ko183dkj4vjcdss8bqd20

I plugged both ports on the MC as shown below. Started the truck, pressed on the brake pedal. It wouldn't budget, rock solid. This told me the MC was fine. If the MC was bad, I would expect the pedal to move a bit as fluid blew past the seals and circulated back into the reservoir.

ePntF9zh.jpg


Next step, I left the front capped off and connected the rear line only then proceeded to bleed. After a few bleeds I got a NASTY stream of bubbles with the flaky residue that came out. Who knows where this rogue air pocket was and it's strange that no matter what I did, I could not purge it out doing a standard bleed with all circuits connected, even after going through almost a gallon of fluid.

Started the truck with only the rear line connected, brake pedal felt great! Super firm. Rolled it a few feet in the driveway, great pedal feel. But brakes obviously sucked because it was just the rear.

Then connected the front + rear. MUSHY. Bled again, still mushy. Disconnected the rear and did the front only. Bled bled bled, few tiny bubbles, nothing major. Started the truck, pedal was firm. Okay that's good right? Rolled it a few feet, pedal still firm.

Connected the rear again (all ports connected), bled bled bled. Mushy again. Ready to light the truck on fire. If I ask the wife to help me bleed again I'm afraid she's taking the kid and moving out.

What now? The rear and front brakes feel great when connected individually, but when I connect front and rear it gets soft. Then it occurred to me. PUSHROD! I adjusted the pushrod on the new booster, or so I thought. Apparently wasn't enough I guess? That explains why I was getting a soft pedal with both front and rear connected; the plunger in the MC wasn't being pushed in far enough to generate enough pressure, but it worked fine for one circuit. After adjusting the pushrod out a few turns, SUCCESS!

It was a nightmare but in the end it was a rogue air pocket and poorly adjusted pushrod that was giving me grief on the new setup.

I'm not happy to report the brakes are working great. Here's a video doing 2 emergency stops from 45-50mph GPS speed. Proportioning valve is fully open. I haven't driven a stock 80 to compare or not sure how this compares with other people's rigs, but it's the best braking I've had out of this truck for a long long time. Truck is about 6500~6700lbs on chunky 37" Nitto Mud Grapplers :cheers:

Sooooo... When are you going to do the engine swap?:hillbilly:
 

Road Apple

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What model Wilwood proportioning valve works with our system?

Wilwood Engineering 260-12627 Adjacent Proportioning Valve Knob Style (10mm X 1.0)?

Edit...Found the answer.
 
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So with your proportioning valve all the way open, you're happy with the bias front to rear? If so, it sounds like the proportioning valve isn't even needed with this specific setup, correct?
 
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So with your proportioning valve all the way open, you're happy with the bias front to rear? If so, it sounds like the proportioning valve isn't even needed with this specific setup, correct?

I'd say it's good to have. They're cheap and easy to install so I'd recommend installing up front vs having to cut into your lines later. With that said, I don't feel the need to close the rear down based on what I've tested so far.
 

baldilocks

Battle Ground, WA
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I'd say it's good to have. They're cheap and easy to install so I'd recommend installing up front vs having to cut into your lines later. With that said, I don't feel the need to close the rear down based on what I've tested so far.
50/50 might be ok on dry pavement but not so good otherwise.
 

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