Chevy Tahoe, Cold-start rattle in exhaust

Chevy Tahoe, Cold-start rattle in exhaust

PostBy: Rob R. On: Mon Nov 05, 2012 10:08 am

Alright Chevy guys, lets see if you have any ideas for this one... Now that it has gotten cold in the mornings our 2010 Tahoe 5.3L occasionally makes one hell of a rattle when first started. It sounds like it is coming from the converters, but by the time I can get crawled under it the noise has pretty much stopped. When I pull out on the road and accelerate, it also makes a rattle noise for a few seconds...but after that, you can drive it all day without a sound.

All of the heat shields are tight, and I can't find anything loose. Whatever it is only happens on a cold start, once everything is at operating temperature there is no noise.

I have had the material inside a converter break up before, but that rattled all the time...I'm stumped on this one.
Rob R.
 
Stoker Coal Boiler: EFM DF520
Hand Fed Coal Stove: Hitzer 50-93
Coal Size/Type: Lehigh Rice
Other Heating: Dad's 1953 EFM Highboy

Re: Chevy Tahoe, Cold-start rattle in exhaust

PostBy: 009to090 On: Mon Nov 05, 2012 10:21 am

Yeah, my first guess would have been the heat sheilds. They came loose on every car we have owned.
009to090
 
Stoker Coal Boiler: EFM 520 HighBoy
Hot Air Coal Stoker Stove: DVC-500 x 2
Coal Size/Type: Anthracite Rice

Re: Chevy Tahoe, Cold-start rattle in exhaust

PostBy: KLook On: Mon Nov 05, 2012 10:28 am

Second guess is the catalytic converter. I had a 2004 Silverado that had the comb inside break and it rattled all around. Warranty job if new enough.

kevin

You mean that has been check and replaced and it still rattles?? Hmmmm
KLook
 
Stoker Coal Boiler: Harman VF 3000
Coal Size/Type: rice, bagged, Blaschak
Stove/Furnace Make: Harman (Back In Maine)
Stove/Furnace Model: VF 3000


Re: Chevy Tahoe, Cold-start rattle in exhaust

PostBy: freetown fred On: Mon Nov 05, 2012 10:50 am

Just had that problem with the girl friends ( that's right, this old grump has a girl friend) newish Subaru--definetly converter heat shield--hers didn't seem loose either--I took a long walking stick &, from the top, pushed down on the converter shield & that was it--right where the pipe goes into the converter in the rear==I know this is Freetownish--but I took an axe handle steel wedge & ball peened it between the pipe & converter shield--I know--real rustic, but it worked---stop over thinkin it & give it a try ;)
freetown fred
 
Hand Fed Coal Stove: HITZER 50-93
Coal Size/Type: BLASCHAK Nut/Stove mix

Re: Chevy Tahoe, Cold-start rattle in exhaust

PostBy: Rob R. On: Mon Nov 05, 2012 11:25 am

There are no heat shields around the converters themselves, just around the manifolds and above the converters on the floorpan. I have pulled and tapped on all of them, and also the converters...still can't replicate it. I read online that the oxygen sensors can rattle...but I won't go that far until I have tried the Freetown wedge & mallet method.
Rob R.
 
Stoker Coal Boiler: EFM DF520
Hand Fed Coal Stove: Hitzer 50-93
Coal Size/Type: Lehigh Rice
Other Heating: Dad's 1953 EFM Highboy

Re: Chevy Tahoe, Cold-start rattle in exhaust

PostBy: KLook On: Mon Nov 05, 2012 11:35 am

Nothing you can't fix with a ballpeen hammer!! :shock: :roll:

Kevin
KLook
 
Stoker Coal Boiler: Harman VF 3000
Coal Size/Type: rice, bagged, Blaschak
Stove/Furnace Make: Harman (Back In Maine)
Stove/Furnace Model: VF 3000

Re: Chevy Tahoe, Cold-start rattle in exhaust

PostBy: 009to090 On: Mon Nov 05, 2012 11:52 am

KLook wrote:Nothing you can't fix with a ballpeen hammer!! :shock: :roll:

Kevin

My favorite tool.... the BFH
009to090
 
Stoker Coal Boiler: EFM 520 HighBoy
Hot Air Coal Stoker Stove: DVC-500 x 2
Coal Size/Type: Anthracite Rice

Re: Chevy Tahoe, Cold-start rattle in exhaust

PostBy: offcoursey On: Mon Nov 05, 2012 10:35 pm

Try searching.....gm knocking noise when cold....on the net.
Alot of 5.3L GM motors do this. My 1999 Silverado does.
Glynn
offcoursey
 
Hand Fed Coal Stove: Glacier Bay
Stove/Furnace Model: Glacier bay

Re: Chevy Tahoe, Cold-start rattle in exhaust

PostBy: Rob R. On: Mon Nov 05, 2012 10:45 pm

I am familiar with the piston slap of engines from that period, this is something totally different.
Rob R.
 
Stoker Coal Boiler: EFM DF520
Hand Fed Coal Stove: Hitzer 50-93
Coal Size/Type: Lehigh Rice
Other Heating: Dad's 1953 EFM Highboy

Re: Chevy Tahoe, Cold-start rattle in exhaust

PostBy: SMITTY On: Tue Nov 06, 2012 10:24 am

Get used to it Rob. It's "today's" Chevrolet. :P :lol: My Silverado makes more noises than my '94 K1500 did with 266,000 miles on the clock. What pisses me off the most about it is I could've bought 10 K1500's for what I paid for this thing. :mad:

But anyway ...sounds like it's definitely exhaust related. It's the only place where things expand enough to stop a rattle, besides inside the engine. Mine has noisy lifters & piston slap when cold too. :roll:
SMITTY
 
Stoker Coal Boiler: Patriot Coal - custom built by Jim Dorsey
Hand Fed Coal Stove: Harman Mark III (not currently in use)
Coal Size/Type: Rice / Blaschak anthracite
Other Heating: Oil fired Burnham boiler

Re: Chevy Tahoe, Cold-start rattle in exhaust

PostBy: Rob R. On: Tue Nov 06, 2012 11:51 am

This morning I eliminated the manifold heat shields as a cause, and determined that the noise is down in the transmission area. This morning it almost seemed like it could be the torque converter, but the cat. converters are right near it so who knows. I will keep trying to narrow it down, but it is tough to diagnose when the noise doesn't last long.
Rob R.
 
Stoker Coal Boiler: EFM DF520
Hand Fed Coal Stove: Hitzer 50-93
Coal Size/Type: Lehigh Rice
Other Heating: Dad's 1953 EFM Highboy

Re: Chevy Tahoe, Cold-start rattle in exhaust

PostBy: freetown fred On: Tue Nov 06, 2012 11:56 am

I know I'm showing my age---BUT--do you have a dust shield to get up at the TC---I know I had that problem on the old (78) plow truck & could spin the fly wheel & tighten the VERY loose TC--remember---kids at BOCES rebuilt this whole thing--they kinda did good, but weren't real good at tightening bolts LOL Intake manifold bolts were finger tight double LOL---friggin kids triple LOL
freetown fred
 
Hand Fed Coal Stove: HITZER 50-93
Coal Size/Type: BLASCHAK Nut/Stove mix

Re: Chevy Tahoe, Cold-start rattle in exhaust

PostBy: Rob R. On: Tue Nov 06, 2012 12:49 pm

10-4 on the TC shield, didn't find anything loose there. What I need to do is park it on ramps the night before, that way I can quickly get under it after a cold-start. Maybe I will get lucky and something will really start making a racket...easier to diagnose that way. :lol:
Rob R.
 
Stoker Coal Boiler: EFM DF520
Hand Fed Coal Stove: Hitzer 50-93
Coal Size/Type: Lehigh Rice
Other Heating: Dad's 1953 EFM Highboy

Re: Chevy Tahoe, Cold-start rattle in exhaust

PostBy: Rob R. On: Wed Nov 07, 2012 1:26 pm

Haven't had time to get back under it, but here is a short video of the "rattle", easiest to hear towards the end.

http://youtu.be/pp6XsIOsL0o
Rob R.
 
Stoker Coal Boiler: EFM DF520
Hand Fed Coal Stove: Hitzer 50-93
Coal Size/Type: Lehigh Rice
Other Heating: Dad's 1953 EFM Highboy

Re: Chevy Tahoe, Cold-start rattle in exhaust

PostBy: freetown fred On: Wed Nov 07, 2012 1:52 pm

Ya checked your flywheel ring??? I know you were in there --BUT-- I'd check that back & forth/ side to side. Unfortunatly if it's not there, it sounds real internal. That's automatic, yes???
freetown fred
 
Hand Fed Coal Stove: HITZER 50-93
Coal Size/Type: BLASCHAK Nut/Stove mix