TV Brake Quirks

[Global Driver]

Howdy y’all,

Got a situation that’s happened twice now. We have been backing into a spot and my driveway where I press the TV brake pedal and it has the slight resistance but goes full throw with little to no brake application.
The TT brakes is what’s stopping both vehicles. The TV brake pedal is fwd and I can use my foot to pull it back towards me, then it falls back fwd with pressure.
Once I unhook and let the TV chill, I can drive and all is fine.

Brake resevoir is full
Haven’t checked for air in the lines, as I thought that would have manifested itself already
Hot brakes maybe? I only drove an hour in light traffic.

Any other thoughts? Taking the TV for brake inspection tomorrow now that we are home.

[ctbruce]

JMO, But I think you're kn the right track to have a professional diagnose and treat this patient.

[CarGuy]

When brake fluid gets old it absorbs moisture, as the moisture heats up during brake applications the moisture boils turning into steam. Brake fluid is a liquid which cannot be compressed but the steam is a gas which can be compressed causing brake pedal to go to the floor with no brake action. This could be your problem or the old contaminated fluid will also cause brake master cylinders to fail, they work if you hit the brake rapidly but leak internally with slow application as when backing up. Brake fluid should be changed at least every two years. Not sure if this is your problem but you can test it by quickly jabbing the brake pedal then slowly depressing it, if the master cylinder is going bad it may leak during the slow application. This problem usually shows up when the weather gets cooler.

[travelin texans]

If the pedal doesn't come up on it's own you've got a master cylinder or pedal linkage problem. If you're not comfortable with doing this type of mechanical work let the professionals do it, immediately.

[sourdough]

If you're hitting the brake pedal, it goes down, then you hit it again and it gets better, you have an issue. If that happens there are many things that could be wrong; bad (oxenagated) fluid, bad (leaking) brake cylinders, bad master cylinder etc. In the vehicles that I have experienced that in I, 1) replace the brake cylinders, 2) drain/flush all brake fluid and replace with new, 3) replace the master cylinder, 4) replace all brake pads/shoes etc. Some of that may be overkill but unless you know exactly what your problem is you just need to hit if from every angle...and it's not a really big deal.

[Global Driver]

Thanks for all the quick reply’s and info....heading to the local shop for expert fix tomorrow morning.
Let you know what they say

[Global Driver]

Brake fluids lush and fill didn’t do the trick.
Took it to the Chevy Stealership and the service tech immediately identified it as vacuum pump failing.

This is a “well known and documented” problem with 2015 Tahoe’s and Suburbans. $512 part plus labor.

Writing up a report to the NTHSA about this known brake problem that GM seems to not care to fix.

[bob91yj]

I'm a service advisor at a Chevy dealership, I've seen the vacuum pump issue as well.

[Global Driver]

How often are you seeing this? Every documented instance I’ve read happen between 50-60K miles.
One visit fixes a brake issue and a loss of steering recall. Some info says GM is in a class action lawsuit over accidents caused by this issue.

Warm fuzzies indeed!

[bob91yj]

I really don't see it that often, just a handful of times at a fairly busy dealership. It happen's on Colorado's/Canyon's as well. The first time I encountered the problem the truck was at about 30k miles.