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Hummer H2For those who like a little more gleam to their Hummer, the H2 offers a similar rugged look as the H1, but as a lower cost, and with more added features, making it almost a massive luxury SUV.
Hello All. purchased a pretty clean 2006 H2 Luxury a couple months ago. fixing little quirks and trying to do some research on a random noise.
The clunk is a vehicle shaking clunk,seems to come from front lower end, right when the engine is turning over and starts. Almost always when it sits overnight. Not too often after a recent drive. I have noticed the brake pedal jumping up to "high and hard" firm pedal but not as experienced with hydro boost if this is normal. Before I got ripping and tearing I figured I'd see if anyone else had some input or similar problem?
Check your skid plate bolts...loose ones will make creaking and often popping noises.
Motor mounts: Have a look at each one while someone starts the engine.
I'm wondering if you have an electrical issue, with the transfer case encoder motor. I would unplug it, start the vehicle....if no clunk, it's either the encoder motor, (Hopefully), or a short somewhere. (Shifting ranges in transfer case makes a loud clunk that you can feel ...that is normal. Not normal though, to have it attempting to shift range when starting. Could even be a problem in the switch on the dash. Usually though, it's the encoder motor. Takes 5 minutes and a 10 mm socket to replace it. Right on the back of the transfer case)
Brake pedal coming up is odd. I would suspect the hydroboost unit
Check your skid plate bolts...loose ones will make creaking and often popping noises.
Motor mounts: Have a look at each one while someone starts the engine.
I'm wondering if you have an electrical issue, with the transfer case encoder motor. I would unplug it, start the vehicle....if no clunk, it's either the encoder motor, (Hopefully), or a short somewhere. (Shifting ranges in transfer case makes a loud clunk that you can feel ...that is normal. Not normal though, to have it attempting to shift range when starting. Could even be a problem in the switch on the dash. Usually though, it's the encoder motor. Takes 5 minutes and a 10 mm socket to replace it. Right on the back of the transfer case)
Brake pedal coming up is odd. I would suspect the hydroboost unit
Thank you, also forgot, the 4WD switch selector top middle button cover popped off a few weeks ago, snapped it back on but was around the first time I heard/felt the clunk, I did get a svc 4WD pop up that went away and scan tool didn't read anything
Apply the emergency brake, place the transfer case in neutral and see what you get when you restart cold. This will eliminate the drive train from the picture and leave only the engine and transmission and make it easier to troubleshoot.
Also, keep your foot off the brake when starting, it is possible the hydroboost unit could be the culprit but first things first, eliminate the drive train.
2006 H2 cold start large random clunk
