What did you do to your NBS GMT800 Tahoe/Yukon Today?

[Rocket Man]

A new issue popped up with my 03. When stepping on the brake pedal to stop, the pedal slowly goes to the floor. Letting up and then stepping on it again the pedal feels normal, then again slowly goes to the floor. There's vacuum going to the black canister that's bolted to the booster. Also my abs AND brake lights are lit on the dash--but it's been like that for months. Brake fluid level is good. The pedal issue is new. Any ideas or clues?

But the trans is ok after the latest issue?

 

[Tonyrodz]

But the trans is ok after the latest issue?

Well......coming home tonight merging onto the highway the trans felt like it went into neutral/slipped and then back into gear. So idk....maybe there was water or something on the road--I hope anyway.

 

[Tonyrodz]

Regular vac-boosted or hydro-boost?

If vac-boost, I would suspect possible leak in the canister.

Sometimes, the canisters get damaged or have pinholes rust through.

There is also a rubber diaphragm and rubber valve seal inside. They can get old and start to disintegrate, become brittle, causing bad seal or leaks.
Here is a cut-away of vac-boost canister...
View attachment 384753

If you have hydro-boost, other than checking fluid level and looking for visible leaks, I know even less about those systems. Still new to me.

It's regular vacuum brakes, no hydro boost. So you think it could be the booster?

 

[RAMurphy]

Sooooo, my plan was to install my TBSS intake this weekend - but on my way home from work I stopped at the naval base pharmacy to pick up some meds (because I'm old) and when I walked back out to my baby, she started but would not idle. Because this girl has never left me stranded, I managed to keep the RPMs up and got her home. It was exciting at times especially around tight turns when she would die (no power steering). Got her in the garage. Had dinner and a glass of wine with my wife. Went out to the garage, hooked up my scanner and no codes. Started her up and guess what she is running perfectly. Took her out for a long test ride and recorded her parameters and she ran perfectly and there does not appear to be anything obvious from the readings I have in front of me. I hate intermittent problems. My first thought -fuel pump. I did replace the pump (OEM) 2 months or so ago though. Thoughts?

 

[ivin74]

Anything aftermarket so if that’s just the stereo, yes. As long as it doesn’t get power, the system won’t try to communicate with it and you’ll be safe to flash a tune.

What happens if you don't pull the fuse to the aftermarket radio??

 

[ivin74]

Sooooo, my plan was to install my TBSS intake this weekend - but on my way home from work I stopped at the naval base pharmacy to pick up some meds (because I'm old) and when I walked back out to my baby, she started but would not idle. Because this girl has never left me stranded, I managed to keep the RPMs up and got her home. It was exciting at times especially around tight turns when she would die (no power steering). Got her in the garage. Had dinner and a glass of wine with my wife. Went out to the garage, hooked up my scanner and no codes. Started her up and guess what she is running perfectly. Took her out for a long test ride and recorded her parameters and she ran perfectly and there does not appear to be anything obvious from the readings I have in front of me. I hate intermittent problems. My first thought -fuel pump. I did replace the pump (OEM) 2 months or so ago though. Thoughts?

Check the air intake and the mass air flow connections. Sometimes they loosen up and cause it to die.

 

[Fless]

What happens if you don't pull the fuse to the aftermarket radio??

When programming? It either won't finish programming (typical) or it'll brick the module (rare, but possible) you're trying to program.

 

[Rocket Man]

What happens if you don't pull the fuse to the aftermarket radio??

The programming can hang. In my case, I was programming my HVAC control head in my 08 Silverado when it happened. I think it was at the point it had completed and then went to check all the modules for version info. But anyway, everything stopped and wouldn’t complete. I let it sit for a couple hours.I called tech support first she had me pull the stereo fuse, and when that didn’t work she took control of my laptop and tried everything before she said all I could do was disconnect the laptop and tech2 and hope for the best. The display on the HVAC module stayed blank and it wouldn’t communicate. It was bricked. She told me to always pull the fuse on any aftermarket electronics before programming modules or it will cause a hang.

 

[MassHoe04]

It's regular vacuum brakes, no hydro boost. So you think it cou6be the booster?

I don't claim to be an ASE mechanic or brake expert. But, based on the facts that your pedal goes squish to the floor, has some pedal after a pump then squish to the floor...

If there is no fluid spraying onto the driveway, hoses are still attached/intact and fluid level is good, I would suspect vacuum booster is leaking by somewhere.
It is pretty much the only other thing between your foot and the brakes that might make the pedal do what it is doing.

This is my bet on what you have going on.

I certainly welcome all opinions from people who really are more qualified than I am.

 

[Tonyrodz]

I don't claim to be an ASE mechanic or brake expert. But, based on the facts that your pedal goes squish to the floor, has some pedal after a pump then squish to the floor...

If there is no fluid spraying onto the driveway, hoses are still attached/intact and fluid level is good, I would suspect vacuum booster is leaking by somewhere.
It is pretty much the only other thing between your foot and the brakes that might make the pedal do what it is doing.

This is my bet on what you have going on.

I certainly welcome all opinions from people who really are more qualified than I am.

I appreciate your input. I'm def no mechanic myself. I looked at the fluid level again in the master cylinder yesterday and it does appear low now. Still no leaks on the ground or under the master cylinder.