Brake Issues - Intermittent Soft Pedal

Hey guys,

New to Tacomas and the Forum. I recently bought an 96 4x4 and have been giving it a good tune up. The brakes had been neglected for awhile and the pedal feel was weird at times and randomly got soft. I replace the rotors, calipers, pads as well as the master. I properly bench bled the master and bled both sides until there were no bubbles and new fluid was coming out.

The brakes felt really hard and worked great for a few days, now I've been getting intermittent soft pedal issues. They will work great for awhile then go soft and the pedal will be almost at the floor before I stop, pumping helps. Also once they start feeling spongy, if the pedal is applied slowly the brakes are spongy but if I hit them hard the pedal stays up and brakes normally...when i pump up and hold I don't loose any pressure the pedal doesn't sink.

I'm going to pull apart the back drums in the next couple weeks and see what find, going to replace the cylinders, shoes, and hardware.

I kind of stumped, I've done a lot of brakes and not had this issue before. Right now I'm thinking possibly something leaking inside the drums but I'm not getting any noticeable fluid loss. The new master was bad out of the box? Or the LPV is bad, it looks like a rusted mess, from what I've read normally a bad LPV causes the rear to lock up.

Any input would help, Thanks.

 

It could be the LPV bypassing or the master is defective and bypassing.

 

Was the master a parts house reman unit?

When you say you bled both sides, not sure what you mean. But did you start at the wheel furthest from the master, then work your way up to the closest to the master?

 

Is there a way to Test the LPV? I would like to figure this out without throwing parts at it. Looks like the dealership is the only place to get a LPV and they are expensive..

Is was a new with reservoir Cardone unit (have not read good things about Cardone)

I have not bled the the back brakes yet as i will be doing them shortly. I did the passenger then the the driver side on the front.

 

I would finish the rear first, and re-bleed everything starting at the rear furtherest from the master.

Then see what happens.

 

Maybe change out the rear brake cylinders too, they're cheap and easy.

It's pretty well agreed oem parts are the best to use with these trucks, never once had an issue with a factory Toyota replacement part.

Usually spongy pedal means it's not bled fully. I recommend using a power bleeder at the reservoir to insure you don't run it dry and a piece of clear tubing into a bottle at the bleeder valve of each corner and pump til there's no bubbles to insure you aren't getting air feeding back in

 

Also consider the brake booster, it can be intermittent with boostage (and a spongy low pedal)
when starting the 'go south' dance...

 

I just reread this. Yeah, you have to bleed all four corners, starting at the furthest corner from the master cylinder, anytime you introduce air to the system. A new master definitely needs to be fully bled.

 

Didn't read all the posts, but since you've replaced all of the basic parts, I'd look into new brake lines from the hard pipe to the wheel cylinder/calipers,,, I don't know if it'll give you the mush feel, but they will cause some problems with "releasing" if the inner wall has collapsed inside; the truck is old and the hose is just as old if it hasn't been replaced.

When I did mine I bought the rebuild kit from Toyota for the calipers,, cheap and easy,, brakes are rock solid on mine.

 

Sounds like a bad brake booster. About $160.00 If it was just a spongy pedal I'd check brake hoses.
Since it's going to the floor the diaphragm or seals in the booster are probably bad.

 

Again, he didn't fully bleed all 4 corners, just the front brakes. You can't add a new master cylinder and not get air in the system. I don't care how hard you try, disconnecting the brake lines will introduce air into the system.

The air will find its way to the back where it splits to the rear, that also explains why he had good pedal for a short period of time before the air started to circulate back to the front with the cycling of the brakes.

Not being properly bled is the most obvious cause of this issue and the cheapest and easiest to try to fix.

Throwing parts at it is not the best way to fix anything.

 

Yep, completely agree with this. Just think about how you have to connect the master. There is no way you are going to pull the original and then bolt in the replacement instantly, so any air gap that was at the hard lines going into the master will be pushed all the way to each brake.

The proportion in valve also has a bleeder, but in my experience I never get air out of it if I was bleeding the rears before.

 

Keep us updated and let us know how it turns out.

 

Well i finally read all the posts,, my bad,,, yep the guys here are spot on, you have to bleed all 4 wheels, and I agree I usually start at the farthest away from the master cylinder,,, hopefully your new master is a good one.

 

Thanks for all the input guys, I'm going to do the drums this weekend. I will rebleed everything properly. I've gone over all the brake lines hard and soft and don't see any leaking. I've already replaced the soft lines at the front, I'll check out the back ones again and probably do them as well. Although the LSPV is a rusty mess..hopefully I can bleed it. It makes sense there could definitely be air in the system still, the intermittent thing threw me off. I think when i go up a steep hill it get worse, like air bubbles are moving around? Hopefully that solves the issue.. if not possibly a bad master out of the box or the booster is causing issues. We will see

 

Just an update, I replaced the rear cylinders, shoes and hardware. I bled the system and it's stopping better than ever!
Thanks for the suggestions.