Brake woes…. Seeking advice.

So since having to replace the master cylinder in my 04 Tacoma double cab v6 AT prerunner RWD a few years ago the brake pedal has never felt the same…. Yes I bench bled the master cylinder before installing. The brakes worked ok, the pedal just had a bit more travel than it used to or should have imo. Fast forward a couple years and The brakes also developed this odd catching feeling but only when bleeding them where the pedal would hang up just a bit when first depressing it and then it would go normally. I finally concluded that this was a faulty brake booster. I finally got around to replacing the booster, I also took the master off and tried to bench bleed it some more just in case it was some air trapped in there and it solved the sticking problem but it became glaringly obvious that the replacement master cylinder is leaking internally…. So I go get another replacement master and bench bleed it, and I’ve bled about 2x gallons of brake fluid using both the old buddy system and the motive power bleeder…. My pedal is now worse than before. The rear brakes are adjusted, I just redid the rear drums, shoes and hardware and adjusted them. I also use my parking brake all the time…. I’m at a loss at this point…. What am I missing?? Why does my brake pedal go almost to the floor before engaging the brakes?

 

Does the brake pedal pump up when its not running? I think theres an adjustment rod in between the brake booster and master cylinder

 

the brake pedal pumps up for the most part, but there is a good inch or two of movement in the pedal before it starts to be firm…. I tried to set the rod in the booster to the same length as the original one. It was pretty close but I did screw it in a little because it stuck out a bit further than the OEM one…. The thing is that this issue has been going on since before I swapped the booster… I had definitely considered the push rod, but I tried to set it as close as possible by just eye balling it…

 

Now that you mention it though, I might try and unscrew it back to where it was…. It does sorta feel like there is maybe an inch or so of free play where the only resistance is the spring in the booster. I will unbolt the master and try to extend it a little and report back!

 

I know some rods need adjusting when you put new booster in.

Ive used the cheapo one man bleeder kits with good results.

 

I usually bleed brakes the old fashioned way, with 2x people. I jusT got a motive bleeder and I have so far used both methods and put over 2x gallons of brake fluid through the damn truck. I have tried driving it a bit and rebleeding… it’s finally raining at my house and just now I went and did a few panic stops to get the abs to kick on a handful of times…. In hopes of purging any air from there as well, I’m going to try and bleed it one more time..

 

I know if air is in abs you have to go to shop. That might be issue too. 2 gallons? Thats a lot. Should only take a little to clear out the air.

 

yeah from what I have heard the most common method of purging the air in these trucks is to do some stops to engage the abs and then rebleed. I’ve heard of several stories of people paying the Toyota dealership to flush the fluid and they ended up not having the SST to even do it…. I was considering buying an innova 5610 because it does state that it will bleed the abs on my truck…. I even contacted innova and gave them my vin and they assured me that it will bleed the abs on my truck, but I am still skeptical…. I have heard that the abs in the first gens doesn’t communicate via the ob2 link…. So idk. That is a rather pricy option that I may try…. Will buy it on Amazon so if it don’t work I can return it. I hate returning stuff, but if they say it will work and I double check and they say it will work and it don’t work I guess I won’t feel to bad about returning it.

 

This is easy to understand… https://www.freeasestudyguides.com/brake-master-replenishing-port.html

If the pushrod is too long the pistons in the master cylinder will not return to the seated position for a new full charge of brake fluid, if the pushrod is too short you will get a clicking and low pedal. Verify that the rear shoes are adjusted by listening for the shoes to drag on the drum, if they are out of adjustment the first motion of the master cylinder is to take up the space between the shoes and the drum… you can test this 2 ways, with the engine off bleed the air out of the booster by applying the brakes until the pedal is hard and then pumping the pedal fast 2 or 3 times then hit the pedal hard and see if it is a “high and hard” pedal. Back off the pressure slightly and see if the pedal falls slowly to test the sealing in the master cylinder. The second way is to pull the parking brake until the shoes contact the drums and then hit the brake pedal, if the pedal is hard then your shoes need adjusting.

In troubleshooting these types of oddities I will buy a piece of brake line that has the correct flare for the master cylinder cut it off about 2 inches long bend it over and hammer it closed. I will then install these 2 plugs into the outlet ports of the master cylinder while someone slowly presses the pedal to bleed the air, the I test the pedal feel.

I reread your original post and I do not read where you bleed the LSPV on the rear axle… it could be that simple.

Does she have ABS ?

 

yes the truck has ABS. Bleeding sequence I have been using is RR LR LSVP FL FR. Following hydraulic lines from longest to shortest to the master cylinder. The rear brakes are adjusted, I will double check those too once the weather clears up. I just replaced the rear drums, shoes, and hardware in the last 2 months and I had them adjusted correctly then. I also use the parking brake religiously trying to make sure they stay adjusted.

 

So it seems that my problem was potentially being caused be air in the abs…. Last night I drove around on the wet roads and did a handful of panic stops to get the abs to activate and then I bled the brakes again with the motive bleeder and got a good burp of air bubbles out…. Pedal feels much improved. Not exactly where it should be but I am thinking I may just need to rinse and repeat a few times to purge any remaining air from the system…. Idk. Still going to check the rear brakes again once the weather clears up and I’ll take a look at the booster pushrod too.

 

Excellent… traditional method is to bleed the brakes with the engine off… it is worth a try to do it while the motor is running for the extra oomphf with the booster.

A number of years ago I had a sand car that the brakes just sucked… I bleed and bleed the system by myself. I had a buddy over and we were talking about it and he said lets bleed it one more time. When I went to do the rear I heard a sucking sound when he would release the pedal… damn seal between the 2 disc brake haves would suck air… would not leak under pressure, just suck air.

 

do you know if the key is supposed to be in the on position in the ignition while bleeding?? I had read somewhere in my researching this issue that the key should be in the ignition turned to the on position, but I believe those instructions were for the hydraboost systems on the 4Runner. At this point I have tried bleeding it both ways…. The feel of the pedal has improved a great deal after getting the abs to activate a handful of times and rebleeding, but it is still not quite how I feel it should be. Waiting for the tool to measure the booster pushrod so I can properly set it…. Don’t want to cause the brake drag issue by just guessing on the push rod length. I’m going to adjust the pushrod and double check the rear brakes this weekend if the weather stays nice. I’m very determined to figure out what is causing the pedal to travel too far. The brakes are working good at this point, the pedal just has too much travel, but once you hit the spot that the brakes pressurize it brakes normally.

 

I left car running, on 4 jack stands just to be sure.

Could be worse……my calipers have bleeders on inside and outside of each front caliper
Ugh……I hate bleeding brakes