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

[RAMurphy]

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

Thank you, I will check. Still running fine this morning.

 

[Rocket Man]

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.

Might only leak when the brakes are applied hard. Have your gf start it up and step on the brakes while you look at all 4 wheels as well as the MC and also the brake lines themselves. Hopefully you don’t have rusted lines.

 

[Scottydoggs]

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.

no vacuum to the booster nets a rock hard pedal nothing more. would feel like if you pump the brakes engine off. the pedal gets rock hard in 3-4 pumps. even with hydro boost, engine off pump the pedal. rock hard. and this vac leak to the booster would also cause a lean code and lots of idle surging.

 

[Walchit]

@Tonyrodz my line rusted out right above the rear end on the drivers side. I didn't see the leak until it was on the lift at the alignment shop the second time.

 

[Tonyrodz]

@Tonyrodz my line rusted out right above the rear end on the drivers side. I didn't see the leak until it was on the lift at the alignment shop the second time.

Thanks for the heads up on that. Mechanic replaced all those lines when the rear was swapped out, but I will check all connections.

 

[MassHoe04]

no vacuum to the booster nets a rock hard pedal nothing more. would feel like if you pump the brakes engine off. the pedal gets rock hard in 3-4 pumps. even with hydro boost, engine off pump the pedal. rock hard. and this vac leak to the booster would also cause a lean code and lots of idle surging.

Thank you for teaching me some new stuff here @Scottydoggs ... Anytime I can learn, is much appreciated!

 

[MassHoe04]

Quick scan and go this morning...

This is why I keep my Zurich scanner in the center console.

So I don't even have to get out in the unusually heavy downpour, go inside to get the scanner, just to find out the CEL is only the P0442 code (one stored and on pending) I can ignore for now. Off to work I went, with no worries!

Looks like the Purge valve replacement took care of my "Tighten Gas Cap" messages and CEL codes for Large Evap Leaks, but looks like I'll be checking vent/canister/tubes when warm weather returns next spring...

 

[Tonyrodz]

Quick scan and go this morning...

This is why I keep my Zurich scanner in the center console.

So I don't even have to get out in the unusually heavy downpour, go inside to get the scanner, just to find out the CEL is only the P0442 code (one stored and on pending) I can ignore for now. Off to work I went, with no worries!

Looks like the Purge valve replacement took care of my "Tighten Gas Cap" messages and CEL codes for Large Evap Leaks, but looks like I'll be checking vent/canister/tubes when warm weather returns next spring...

View attachment 384929
View attachment 384930

I'm right there with you.

 

[Scottydoggs]

Thank you for teaching me some new stuff here @Scottydoggs ... Anytime I can learn, is much appreciated!

keep in mind. if the pedal goes to the floor engine off. the master is bad, or a line blew for sure. but if all is working right it will be hard.

 

[Fless]

I'm right there with you. View attachment 384931

Unless you have a wiring problem in that circuit, a new purge valve on the engine should cure that.