Tacoma soft brake behavior

I've noticed this issue getting increasingly worse over the last few weeks. I'll start with the parts. It's a 2010 Tacoma 4x4 with a 2" lift/level, new wheel bearings and front axles. I recently took apart the front brakes and cleaned out the caliper and pads at the front and sprayed (with brake cleaner) the drums at the back and then adjusted them. The fluid levels are good and there are no noticable leaks at any connections in the system.


The biggest symptom is when I push the pedal to start braking, it's almost as if there is a pause before the brakes actually kick in, and they seem to almost kick in harder than usual.

I also notice the odd time if I'm sitting at a light (stopped in drive), it feels that almost the brakes will let go a bit and my truck will crawl forward a tiny bit.

I'm not too familiar with brake diagnosis but I've read that if you pump the pedal with the truck off, the pedal should go hard. Mine goes hard after the first few pumps then loosens up completely, almost to the floor. Is this usual?

When I had the caliper off everything looked good besides the bit of rust. The pins weren't rusted (thank god) and all the rubber boots around the pistons looked good to me. I was able to move the pistons with my hands a tiny bit but it was pretty difficult

Any ideas on what to look into for a fix? I don't want to start throwing parts into it if it doesn't need them

 

A fluid flush and bleed, including the ABS modulator, is good PM if you don't know when it was done last.

 

Sounds like there is air in the system. Start with a fluid flush and go from there.

 

Yeah, I agree. Especially if you have a good firm pedal and it starts to fade that much with no apparent leaks. Could also be a problem within the master cylinder.

 

Thanks for the info everyone.

I'll give the fluid flush a try this weekend. There's no visual leaks throughout the system. I've heard the master cylinder can leak internally, is this true?

If there is no change after the fluid flush, would that mean it's most likely the master cylinder?

 

Assuming your truck has rear drum brakes, make sure the rears are adjusted properly.

 

After a proper brake bleed, that would be a likely suspect.

 

Adjust the rears.

 

You can double check the rear shoe adjustment.. but the sinking pedal is likely a bad master cylinder

Yes they can leak internally

Alot of guys will mention bleeding air out.. but the question is, how did the air get in there in the first place? You'd have to run the reservoir low or crack a line loose to introduce air

 

My guess is this is correct.

Common symptoms I’ve seen when a master cylinder is internally bypassing. If you’re idling barely moving and you gently apply pedal pressure, it’ll go to the floor. If apply normal pedal pressure as if coming to a normal non panic stop, it might grab but pedal will be low. If you slam the pedal hard as if making a panic stop it might grab higher.

Take a look at it, it might be wet.

 

When you did this step, if you disconnected the hose from the calipers, and allowed the brake fluid to drain empty, you’ve introduced air into the abs. Normal brake bleeding isn’t gonna solve it. You could try the lock the brakes up on a gravel road technique but you need to be able to slam on the brakes and have the wheels lock up. If that doesn’t work, the abs module needs to be cycled by a dealership with techstream. Or you could buy something to do it yourself. @Torspd found something that works. I think there’s limitations on which years it works with.

 

Thanks for all the feedback everyone.

Here's a few things I forgot to mention (damn ADHD).

When I said the brakes let go when stopped, the pedal doesn't go soft, it just seems like the brakes themselves let go a bit.

Also when I cleaned the front calipers and pads I never cracked the line so as long as I've had the truck the lines have been sealed from my point of view.

One big thing came to mind when you guys started mentioning adjusting the rears. In April I had an issue where when I would drive forward the rear drivers wheel would completely lock up within 5-10 feet of driving. The only way to break it was to reverse a tiny bit then I could get another 5-10 feet before locking up. I haven't used my ebrake since I bought the truck since I need to replace the cable so I don't think that caused it. I pulled the drum apart and sprayed everything down with brake clean and everything inside looked in good shape. I haven't been able to figure out why it happened but I did have to back the self adjuster thing off most of the way in order to be able to drive forward and I haven't had an issue with that since.

Could this be the culprit of my current brake issue?

 

If backing off the rear adjuster helped keep the drum from locking up you're just masking a bigger issue. Figure out why the brakes were locking up and get those adjusters back to where they should be

 

Thanks @b_r_o for the tip. I'm not really familiar with drum brakes.

Is there anything I should be looking out for when I pull them apart again?

I'll try to follow up with some pics when I get it open

 

Look for ..

Broken or missing hardware and springs

Super thin brake shoes that need replacing

Leaking wheel cylinders or axle seals contaminating the friction material

 

I had this happen when I was 16, so decade’s ago. I was driving a 70s Chevy pickup. I told the parents, they insisted I don’t know how to drive is why the brakes don’t work. After rear ending 5 people they had my mechanic uncle look, the brake reservoir was empty. I’m certain this isn’t your cause.

This symptom definitely sounds like a bypassing master cylinder.

There’s a specific procedure, something like adjust tight, then back off 15 clicks.

I recall someone recently with this same issue, they resolved it but I can’t remember what it was. You’ll have to use the search function, which we all know doesn’t work very good.

 

Thanks @Waasheem. I have noticed when the brakes start to let up when stopped that the truck idle will increase slightly. It seems to happen simultaneously. Would this be happening due to the brake issue or causing this particular symptom?

I'm about to take the drum off the rear and take a look back there

 

I've attached some pics of the rear drum to this reply.

Everything seems super coated in brake dust, is this normal?

The brake pad on the shoe towards the front of the truck is almost non-existent, it was very close in thickness to what the other shoe is now. I'll need to replace the pads but from the looks of things everything else seems to be in working shape, just dirty.

The second pic shows some sort of cable or hose running into the back of the drum coming from the front of the truck. What is this for? It looks like the part that mounts to the back of the drum has broken away but I can't see an exposed cable.

All the components seem to still "float" around how I've seen they should.

 

I had a similar issue. Rebuilt front calipers from napa fixed it.

 

Brake dust is normal and the part broken/pulled away is your emergency brake cable section for that side.