check valve, booster or what

[3bears]

so ever since I have owned my 4runner , I have never been real impressed with the brakes. Then I did the TBU.used Toyota pads...switched out all the hoses ( stainless)...went to synthetic fluid..used a friends pressure bleeder system.. bled the master...bled the abs....ok bit better ...not great... everything works...even the cams for the parking system and self adjust...nothing is frozen up in the drums...adjusters...cables all free and working as they should...did the old pull the emergency brake tons of times... and when I do the brakes are better...maybe....not great...not much of a noticeable difference.
no fluid loss....never had until the one cylinder started leaking and that took me a while to lock down to what was up. Checked the calipers...pulled the drums and found that issue. replaced both rear cylinders with Toyota..... bled and bled again.
I can panic stop it and feel the abs kick in...and it still stops straight

yesterday I did the rear wheel bearings and seals...shoes were tight to the drums on removal.... and today had my oldest son help bleed the brakes. yes rr, lr,rf, lf.. all clear and no bubbles. He said....hey dad ...how come the brakes are hard with the engine off and soft when its running. Guess I never paid attention to that. Took it for a drive....felt like my old 4runner....soft brakes ( compared to tons of vehicles I drive) still stops straight in a panic stop test
engine runs perfect...no codes...no difference in RPM if brake is pushed or not

maybe its just typical 3rd gen 4 runner...but I have no way to judge as this is the only 3rd gen I have driven, Ive driven a few tacos and a few 4th and 5th gen 4runners including my daughter in laws 2019, my youngest sons 2016 taco.. Ive had and driven corollas, rav4's..and owned and driven much including volvos, bmw's yadda yadda and of course tons of American stuff including big ford and cheby work trucks

thoughts ?????

 

[Hopeless Diamond]

I "think" doing the TBU has an effect on pedal feel. The calipers have a little larger piston and the volume of brake fluid coming out of the master cylinder isn't optimized to the volume of the pistons. Seems on mine to have just a little more pedal travel till they start to engage. Overall braking is better, and a lot more consistent and controlled, it's just that the pedal travels a little more.

 

[3bears]

I "think" doing the TBU has an effect on pedal feel. The calipers have a little larger piston and the volume of brake fluid coming out of the master cylinder isn't optimized to the volume of the pistons. Seems on mine to have just a little more pedal travel till they start to engage. Overall braking is better, and a lot more consistent and controlled, it's just that the pedal travels a little more.

that I expected from all that I read before doing the TBU....but it was always a bit soft BEFORE doing the TBU when the engine was running

 

[LittleCaesar]

Try bleeding the brakes with the engine running if you haven’t already.

 

[Bad Luck]

If I'm understanding you correctly OP regarding brake pedal being stiffer with engine off that is normal operation. With the engine off there is no longer vacuum being built in the brake booster. With each time you press the brake pedal you use some vacuum from the brake booster until all vacuum within is used up. At that point you have no assist when applying the brakes with the engine not running.

 

[WWRD99]

Ok so I ran out to the garage and started it up to measure pedal travel...using the top of the brake pedal as the start point it measured 4 3/4 from the floor then just using my thumb I pushed the pedal as far as I could and it went to 3 inches so I have 1 3/4 inch travel before I get resistance on the pedal. That's a very basic test that should give you an idea of where I'm at...one thing you said that you got the abs to kick in, then your brakes are working ok...not saying I like the abs but it does come on pretty easy if the brakes are working normal. I just did the tundra brakes on mine with the ss lines and I did notice a slight pedal change that they react with less travel. Also you said you used a power bleeder...is it the vacuum style that you hook to the bleeder or a pressure one hooked to the master cylinder. Hope you got the truck done!

 

[gamefreakgc]

Try bleeding the brakes with the engine running if you haven’t already.

I can't stress this enough. As soon as I started bleeding Toyotas with the engine ON, my results have been a much firmer brake pedal. Gets more air out of the system that way (and it's easier).

 

[rideexileex]

What brake pads are you using? I had similar thoughts about my brakes while using the powerstop ceramic towing brake pads - turns out they are complete garbage. I put in cheap 20 dollar auto zone semi metallic pads and it has been a night and day difference. I went a crazy route and modified in a 1 1/8 brake master to account for the TBU, but actually find myself wanting to go back to the stock 1.

 

[Desertwind16v]

Have you adjusted the rear brakes properly? Clearly the brakes have been bled to death so I highly doubt that's your issue. Rear brakes being too far out of adjustment has a huge effect on how the pedal feels so start there. I feel like you're overlooking this.

You mentioned that all the adjusters work, and that the drums were tight when you took them off. That doesn't necessarily mean it's adjusted correctly. How many clicks does the ebrake come up? It should be pretty tight after 3 clicks, so if you can pull it up much further then it's way out of adjustment.

On trucks I adjust the drums so they are in between no drag and hard to turn the drum. On cars you can get away with a lot more drag, but trucks tend to get hotter and can lock up when hot.

Hopefully this helps out.

 

[AvatarT4R]

Ok, I'll say it again. I find it extremely rude that people come here asking everyone for help, yet can't be bothered to tell us what the fix was. This is SUPPOSED to be a two way street here.

 

[calimobber]

There is no fix that I can come up with. I have the same problem since I switched over to the Tundra 210mm. Lots of travel before they engage. I have done everything even used techstream(Toyota computer app) to pump abs system. Its just an issue when you switch over to the larger setup.

If I could do all over I think I would have just kept stock. The softer peddle isnt worth the added braking for me.

 

[Jidaran]

Ok, I'll say it again. I find it extremely rude that people come here asking everyone for help, yet can't be bothered to tell us what the fix was. This is SUPPOSED to be a two way street here.

In general, yes it's good practice to follow up on your threads. Sometimes people forget though, no biggie. Not sure why you're calling out 3bears, who has over a thousand posts and provides helpful info all the time on this forum.

 

[jgue467]

Ok, I'll say it again. I find it extremely rude that people come here asking everyone for help, yet can't be bothered to tell us what the fix was. This is SUPPOSED to be a two way street here.

Yeah ought to respond...so let's respond for them...


As Calimobber said, its a standard "feature" on 3rd gens. Mine has the slightly larger brakes that come on the 16" wheels, their effective, stop on a dime yet are soft Up until they gently engage and then they're not grabby just increase grab as I increase pressure, like they should ya' know?

I think front brakes work Best when the back brakes are adjusted properly so they do their job and keeping the weight as level as possible, suspension also plays on factor here, kinda obvious yet thought I'd mention, to much 'dive' and rears can't hold much braking power and fronts get all the blame, haha.

 

[gamefreakgc]

1. Bleed with engine on
2. Make sure all pads and rotors are new or turned and pads are fresh (and not cheap garbage brands). People forget to turn the rear drums, they get very pitted over time.
3. Add stainless steel lines for a firmer brake pedal
4. Makes sure the coils and rear springs are not worn out and replace if needed

Do those four things and I personally guarantee the brakes will be better. And the rumor that the TBU makes the brakes squishy is simply not true, it means there's air in the lines and the calipers and you haven't got it all out successfully yet.

 

[Dieselchessy]

I know it’s subjective but I’ve done the Tundra upgrade to the 13WL’s on 3 rigs I’ve drove extensively and helped on others. I use Autozone rotors, pads, calipers, non-ceramic. I do nothing special, just a standard brake job. I use dot 3 or 4.
I do seat the pads and rotors, maybe that’s special?

I’ve never experienced a noticeable pedal feel change other than it takes less pressure on the pedal to get the rig to stop.

But....I’ve never worked on a 3rd gen newer than 99.
Is there perhaps some difference with the 2000+ rigs that causes these reports of squishy pedals?

Is there perhaps an issue with the newer dot4+ fluids viscosity or incompatibility that causes the issues?

The OP states “went to synthetic fluid”. What’s that mean?