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AR15.COM
11/16/2010 7:20:37 AM EDT
So, I’ve essentially got 72K of problem-free miles out of my 06 H2.

I was out of town for a few days. On Wednesday, my H2 drove fine. On return, I had my two little boys in the H2 to go to the park to kill some Orcs or something. On my slightly-sloped driveway, I put it into reverse shortly after starting up the vehicle. As I gently rolled back, as always, I put the brakes on to slow out of the driveway. The brake pedal felt entirely normal with pressure required to push it down, but literally nothing happened. It didn’t slow me down at all. By that, I mean that when I pressed all the way down on the brakes, it did not slow the vehicle down in the slightest. I got my boys out; sent them inside; and tried again a few times. Same result—forwards or backwards—the brake pedal had pressure, but did nothing.

I called Onstar, and they sent out a tow truck. The operator, tried it himself. He noticed that, in park, when he pushed down on the brakes, it made a screeching sound. In park. He immediately said something like: “It’s brake booster. It’s bad. It supplies power to the brake lines. In can tell from the sounds that that likely is what it is.” He towed it to the Cadillac dealership formerly known as the Hummer dealership where I bought it.

As it was well into the afternoon on Saturday, I knew it would be Monday before anything useful happened.

I talked to the service department yesterday, I reported all of the above, and the guy told me that they test drove it twice and found nothing wrong. The brakes worked perfectly. Before he could say much, I told him that I was not going to drive this 8,000lb vehicle until they figured out what was wrong. I don’t want to be going 65 mph when the brakes completely stop working. He said that they would look at it again today, but can’t find anything wrong––can't duplicate the error.

Does anyone know what might be wrong and what I should do? I don’t want to kill anyone with my unbrakable vehicle.

Thanks in advance for any advice.
11/16/2010 1:33:02 PM EDT
[#1]
I thought if the brake booster went, it sounded more like  rushing air under the dash board, not to mention the lack of feel to the pedal.

It does seem like that is the problem. Maybe you had a vacum leak in a hose that they fixed?

11/16/2010 1:58:08 PM EDT
[#2]
that is correct. booster going bad sounds more like a hiss or vacuum loss.

try it on an incline again. see if you can replcate that way.
11/16/2010 6:10:15 PM EDT
[#3]
Very strange problem...I have nothing to offer as far as a solution, but I think you are doing the right thing by insisting that they try to duplicate the problem again.

Losing brakes on any vehicle is serious business and I'm sure they will do everything they can to try to get the H2 squared away. The biggest problem here is duplicating the complaint at the shop so they can make a solid diagnosis and get it repaired. There are many instances where no matter how hard I try, the car simply won't act up while in the shop. Really sucks for both the owner of the car..and for the shop. For your sake I hope this isn't the case, but I had to put it out there.

Let us know what happens.
11/16/2010 6:34:32 PM EDT
[#4]
The ABS wigged out, and simulated an abs event. (closed isolator valves, but did not dump)Those have kind of a reputation for that according to my GM guys.

I don't know a fix offhand, but if  I find one out, I'll post it.
11/17/2010 4:44:19 AM EDT
[#5]
Thanks for all the helpful comments guys.  I will ask about trying to duplicate on an incline, which sounds like a good idea, and whether they have checked the ABS for errors, which I assume they have.  FWIW, I had two very brief "Service 4WD" errors light up briefly for only a second or two during the last month.  I told the dealer about this, but I assume this has nothing to do with my brake problem.  In the past, with my 2006 H2 and my 2003 GMC Sierra 2500, they have done this on average about once per year with no significance.

Thanks again for the suggestions.