What Was That?

2009SierraZ71 · April 30, 2010

I started up my truck at lunch today and heard a clunk from the front end as soon as it fired up. It was one of those sounds where you go, "What the he** was that?" Seems to run fine and moved around the parking lot fine. I can't see anything out of the ordinary. Any ideas on what it might have been? (I'm not expecting many responses to this)

Metro12 · April 30, 2010

Cat on the engine? Did you pop the hood and check?

DMurphy · April 30, 2010

That's the first thing I thought too.

Cat on the engine? Did you pop the hood and check?

2009SierraZ71 · April 30, 2010

Cat on the engine? Did you pop the hood and check?

Yeah, I popped the hood and checked - no kitty. Everything looks normal. No giant puddles of oil under it, either. Really weird. I can't fathom what it could have been if it's nothing serious. Guess I'll find out on the way home.

Nytemare · April 30, 2010

Your starter could have stuck and can make a very loud clunk when the bendex is retracting.

hockeypro1411 · April 30, 2010

Your starter could have stuck and can make a very loud clunk when the bendex is retracting.

We already decided that it was a cat.

Nytemare · April 30, 2010

Your starter could have stuck and can make a very loud clunk when the bendex is retracting.

We already decided that it was a cat.

There we go...LOL

hockeypro1411 · April 30, 2010

Your starter could have stuck and can make a very loud clunk when the bendex is retracting.

We already decided that it was a cat.

There we go...LOL

Hahaha

Sir Dan · May 1, 2010

Mine does this sometimes too. It's the A/C compressor kicking in with a loud clunk. It only does it on the first cycle, then it is quiet. I think there is a TSB on this and I've been meaning to ask my dealer. Something to do with re-programming the system to engage the compressor differently...

Anybody else know about this one? Rich maybe...

Bish · May 1, 2010

Mine does this sometimes too. It's the A/C compressor kicking in with a loud clunk. It only does it on the first cycle, then it is quiet. I think there is a TSB on this and I've been meaning to ask my dealer. Something to do with re-programming the system to engage the compressor differently...

Anybody else know about this one? Rich maybe...

+1 I hear mine every morning and it is definitely the ac compressor clutch. I just ignore it

caddycruiser · May 1, 2010

I think my '09 Avalanche has done this too. Second day I had it & started up with my brother around, clunk, and we all heard it and looked...nothing wrong...just an odd sound at start up. Sounded compressor related, as mentioned above.

2009SierraZ71 · May 1, 2010

Thank you for all the replies, guys. I'll ask the dealer about it when I take it in for an oil change since someone mentioned there might be a tsb on it. Very interesting.

I have to get the brakes looked at, too. The whole truck pulses when I apply the brakes at highway speeds - about 70 mph. I've seen other threads on this one and doesn't seem uncommon.

I'm glad I didn't find a mangled cat in there. I might have thrown up a little.

music · May 1, 2010

Report back on the TSB if it exists. I have noticed the same thing (odd, but it's only the first a/c clutch engage that does it). Still, I'd go with the cat idea...

2009SierraZ71 · May 10, 2010

Report back on the TSB if it exists. I have noticed the same thing (odd, but it's only the first a/c clutch engage that does it). Still, I'd go with the cat idea...

Not sure the TSB applies to the 2009. They couldn't find anything as it did only do it one time. But, they did verify there was no cat and no bullet holes.......which is good.

And they turned the front rotors as they were warped. Really? After only 9000 miles? My 93 that I drove the same didn't warp any rotors. What the heck. Has anyone replaced their rotors with something better?