Odd "tunk" sound
 

The new (to me) 2000 Blazer has a weird sound about a minute after I shut it off after driving it for awhile. It sounds like a metallic "tunk" and seems to be coming from the rear of the vehicle - perhaps from the exhaust. Is that normal or ab-normal? And any ideas what may be the source?
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RE: Odd "tunk" sound
 

Never heard anything like that. Only thing I can suggest is next time the conditions are replicated, lie down beside the truck and listen for it tomake the soundso you can get a better idea where it's from.

RE: Odd "tunk" sound
 

OK - got under the Blazer after driving today it and the hollow metallic "tunk" sound is coming from the catalytic converter. It also crackles like it's cooling off after driving it -- is that normal or is it signs of a failing cat? It idles ok, drives ok and doesn't smell like rotten eggs or anything like symptoms I've read in other threads from doing a search on catalyitic issues.
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RE: Odd "tunk" sound
 

Some of these vehicles are known to have exhaust cooling thunks and tings for a bit after shutting it down. If you aren't having any driveability or fuel mileage concerns, I wouldn't worry about it. If your catalyst was failing, it would be characterized by a rattling during operation or reduced performance/mileage.

RE: Odd "tunk" sound
 

Yep it seems to drive ok - took it out on the Parkway today and got quickly up to 80mph with no noticeable performance issues. Just was a bit concerned about the crackling and then the "tunk" sound - it sounds like say if you sucked a vacuum on a 5 gal metal gas can and then let the air back in ... or conversely (and more concerning since it's a cat) pumped a bunch of air in and then released the pressure. Guess it's just the cooling of the metal?
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RE: Odd "tunk" sound
 

It's not uncommon for the muffler or cat converter to make the "tunk" sound as it contracts a little as it begins to cool.
I've seen this many times.

RE: Odd "tunk" sound
 

It mostlikely is either a heat sheild or the outer case of the cat warping under heat and returning to its cold shape with a tunk.

RE: Odd "tunk" sound
 

Thanks a lot guys - you've really eased my mind regarding the issue. I was getting worried that I was looking at replacing the cat too -- I've already put new front wheel hubs on both sides, front shocks and tires on my new ride. Wasn't really looking forward to adding a cat to the list right now -- but it's probably inevitable eventually since it's got nearly 150K on it. I figure I still got a deal on it as I only gave $2995 for it and with what I've added in the last couple of weeks since buying it I now have -- let's see here -- 2 front shocks Gabriel Pro Guard @ $20per, Timken wheel hubs @ $165per (used my Autozone Rewards for -$20ea - gotta love it) and 4 Firestone 235 70s (Road Force balanced - thaks to a tip seen on this board) about $400 = $770 all told. I figure I'm still ahead as when I bought it evidently somebody at the dealership screwed up and put it on Autotrader for $2995 and it was supposed to be $4995 but they honored the price for me - it was indeed changed the next day online to $4995 when I went back to buy it. My salesman said he was the one who traded for it and they only made $237 on the deal ;) Dunno if they were putting on a grand act for me but whatthehell I'm happy and I absolutely LOVE the Blazer :)

And allow me to add - I am extremely grateful to everyone for the helpful info I have found here at this forum - I can't thank y'all enough. I've still got a few projects ahead of my yet so you haven't heard the last of me. Got the usual pesky door pin issue and an EVAP code to deal with yet... I just hope I can learn enough about the Blazer to be able to give back to the community eventually. :eek:
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RE: Odd "tunk" sound
 

Read up and post up if you have more questions on those issues! We're here to help!!