Brake Pressure Loss, Many Parts Replaced, No FIX...

Happy Friday TW... Here's a story for you, maybe some can provide insight:

4 hr drive from DC to WV, about 3/4 of the way there I lose some pressure in the brake pedal requiring me to press halfway through the pedals travel to get any stopping power in the system. This issue arose suddenly, and is consistent. The fix while driving was to pump the pedal to build pressure back up in the system, which works temporarily (until the next time you go to slow/stop, at which point the pressure is gone again). In order to stop more quickly/fully, the pedal needs to be pressed almost to the floor. Same issue present on the entire drive back to DC a few days later (did not drive it at all while I was there).
I recently replaced the suspension on the truck, adding the correct brake line spacer and checking for any leaks when the job was completed (~3 weeks prior to having this issue, and driving every day commuting to work) leading me to believe that the two are not related.

The truck is still under bumper-to-bumper warranty, so I took it to my local dealer (where I bought the truck) and they have had it/been working on various things for the past 2 1/2 WEEKS. They have had to open a case with Toyota, and go on Toyota's suggestions for a fix based on the symptoms. So far they have:
- Replaced the ABS Actuator
- Replaced the brake master cylinder sub-assembly
- Replaced the brake booster assembly
I just got a call from the service manager saying that he and the master tech are not satisfied that the issue is gone, and that they still feel a lack of pressure in the pedal. He told me they are going to replace the pads and rotors today to see if it makes any difference... Which it won't, because they have bled and re-bled the brake system multiple times through this process, and the fluid level should account for any pad wear present.
At the same time I first made them aware of the issue, I brought it in for the 35K service (not really much in it, but why not for $35) AND they replaced the PCV valve under warranty since they said it was clogged/needed replacing.

What the HELL else could be going on here? Has anyone else had/heard of this problem? I couldn't find much on it.
My initial thoughts were: air/moisture in the lines somewhere (should be fixed by bleeding), leak (none found), kink in a brake line (none present), booster malfunction or bad seal (now replaced)... Seems toyota is stumped.

I hope there isn't a much bigger vaccuum issue going on here... Help?

 

That really sounds like a master cylinder issue to me, as it seems to be allowing the pressure to bleed off. It is not unheard of to have a new replacement bad as well. Good luck, sounds very frustrating.

 

^^^^ What he said.It's not unheard of to put a new but bad part on something. I am in the Aviation industry and you would be surprised how many new parts fail out of the box, expensive shit that cost a quarter of a million dollars. These techs could have replaced a component that was the failed part and think its good. They are probably standing around your truck scratching their heads going, "Well bob, we put this new part in and this one in and its not fixed." In reality, the new part is broke dick.

 

There have been a few others on this board with the same issues on third gens. I'd look for those threads and see what resolution was. I'd be very concerned that this could occur again in the future and at a time of need. I'd also support that a replacement part could have been bad.

I'd also start looking at lemon law in your state... if they cannot figure it out in a month (30 days in shop) you may choose, based on your situation, to have Toyota to buy the truck back.

 

While not on the same level as say a FADEC Module, I had a bad brake light in my old truck, stuck a new bulb in and it still didn't work. Grabbed my meter and spent about an hour troubleshooting only to find that the new bulb was the problem.

 

Did they adjust the booster push rod when they replaced the booster or master cylinder?

 

Not sure, I haven't been back to the dealer since they replaced the booster. Only spoke with the service manager on the phone and he said he "wasn't convinced that fixed it"

 

Assuming they did, tearing into the rear brakes is probably next.

 

Did the parking brake work ok?

 

Yup. It did when the issue first occured, and when I dropped it off 2-1/2 weeks ago.

 

I am going to say it is a leak or air in the lines. If it is a leak make sure any residue is properly cleaned off. Brake fluid eats paint

 

possible...unless the new booster is different dimensions it shouldnt be a problem...but same note, if its that new of vehicle it should have this problem in the first place...

 

power bleed brakes

 

what is the sub-assembly?

 

good question... This is the order email I got from them with the part they ordered:

SPO Number:
Description: CYLINDER SUB-ASSY, B

 

They did. Multiple times now.

 

The assembly the reservoir sits on; in front of the booster.

 

appears to be a master cylinder...according to google fu now that I looked it up could be a vacuum leak somewhere like someone said...

 

Nvm

 

that should take out all existing air in the lines, that cured my brake issue