Whats making this Knocking noise??? - TBSSOWNERS.com Forums - The #1 TrailblazerSS Dedicated Owners Forum

Boricua SS · Mar-22-12, 11:25 AM

ok everyone.. i fear that i have joined the dreaded bent rod club...

After getting my oil change today, i noticed that my motor made a really loud knocking noise... (see attached video for clerification at the 5 second and 15 second mark).. dealer seems to think its a bent rod/floating valve/rocker slap.. but im hoping its something more simple?? truck is an '07 and only has 40k miles on her and the only "performance" mods i have done to her is the Corsa Sport exhaust that came with it when i bought it...so im just trying to understand how this could come about... with the freakish 80* weather we've been having here in Ohio, i decided to bring the SS outta winter storage yesturday.. and SURPRISE.. she started knocking... so she hasnt been driven hard since september of last year..

what do you all think it could be?? oh.. and i have the GMPP, so im fully covered

any thoughts from the pros out there????

http://youtu.be/WAKfsMjBkeg

damnit.. i dont know how to add the youtube video, so i just posted the link to the video...

Bullnettles · Mar-22-12, 02:34 PM

No idea, but I really like your airbox. Looks good. Good luck, hope it doesn't stay down for long.

Boricua SS · Mar-22-12, 05:06 PM

thx bro... i painted them awhile ago.. my engine cover is also painted...

but upon further investigation, and letting my brother hear it (collision tech and ASE certified mechanic) we think that its something along the lines of a rocker slapping/floating valve meaning maybe a spring broke... at least thats what im hoping, so a complete tear down/rebuild isnt in order.. staying on the top end definetly would relieve my pain.. bottom end would just suck... since this noise is coming at the top end and not through the entire power band, the bent rod should be eleminated as the culperit.. at least i'd like to think so...

shes going to the dealership monday.. they said it could take anywhere from 2 weeks to a month.. so we'll see..

anybody else with ideas.. i read all kinds of horror stories about engine noises.. i know someone has some input out there...

martyjw597 · Mar-22-12, 05:23 PM

Damn ...two weeks to a month. They really know how to milk it, huh

TmanSC07TBSS · Mar-22-12, 05:51 PM

Well I couldn't really tell but doesn't sound like a Rod to me. Hopefully you have a good dealer and they will get it soon.

Boricua SS · Mar-22-12, 07:05 PM

Quote:

Originally Posted by martyjw597

Damn ...two weeks to a month. They really know how to milk it, huh

sure do.. luckily i have another car as my DD...

Quote:

Originally Posted by TmanSC07TBSS

Well I couldn't really tell but doesn't sound like a Rod to me. Hopefully you have a good dealer and they will get it soon.

yea, we're all leaning towards that as well, since the "slapping/knocking" only comes in when the RPM's go high or right when the tranny gets ready to shift.. i heard if it was through the whole power band in low rpm and high rpm that chances are it wouldve been a rod..

ZACAZ · Mar-30-12, 02:37 PM

Quote:

Originally Posted by Boricua SS

sure do.. luckily i have another car as my DD...

..

If you have GMPP, aren't they supposed to give you a rental to cover the time you are down?

Boricua SS · Mar-30-12, 04:13 PM

Quote:

Originally Posted by ZACAZ

If you have GMPP, aren't they supposed to give you a rental to cover the time you are down?

yes they are.. they offered me one, but i turned it down since i have my DD... wasnt really a big deal to me...

gn2beatu · Mar-22-12, 08:06 PM

Videos are always hard to tell, but heres how to diagnose it further. Get your friend that helped you to do it again. Next time dont raise the RPM's more than 100-150 over idle. And dont hold the RPM's there, just go up and down continually. Do this while the vehicle is on jack stands, or drive the front tires up a curb, and then crawl under the truck. When you listen to the noise, listen through a hollow tube (heater hose, metal pipe, pvc, anything). It will give you directionality that you wont have listening to open air noises. Open air has too much reflection of sound. Diagnose if its coming from the pan, or the top of the engine. Listen at the base of the plastic intake by each cylinder also. Any valve noise will echo in the nylon intake clearly and you will tell which cylinder its coming from if its top end.

The noise I heard does sound more top end, like valve or lifter, but laptop speakers dont do sound justice like in person. It is more high pitched like top end, but Im not saying it couldnt be bottom end either. It would be differant if I was there in person.

Are there any shavings in the oil? You can cut up the oil filter and look, thats a cheap way to check too. Id do a bit more diagnosing before the dealer gets ahold of it. Especialy if you have been tuned, they could void the warranty if they find that out.

Papabear · Mar-23-12, 02:10 AM

Any misfires?

Boricua SS · Mar-23-12, 10:54 AM

Quote:

Originally Posted by Papabear

Any misfires?

No misfires, drives fine. The noise starts happening at the higher end of the rpm range.. low end, everything is normal and no sounds... Dealership told me to drive it more, and report back if the noise still remains.. it hasn't gone away yet, so I'm taking it in monday

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Papabear · Mar-23-12, 11:20 AM

Was just curious. I had misfires and a noise at high RPMS dealer couldn't figure it out. Was misfiring crazy on ONLY ONE cylinder at real high RPM. Then a week later, rod knock. Turns out rocker arm failed.

PeteG06SS · Mar-23-12, 11:35 AM

I had a collapsed lifter that was knocking. I put a quart of tranny fluid in with the oil, ran it for about 1/2 hour, drained it, changed the filter , put new oil in it, ran it and did it again and the noise when away. Just make sure you get that tranny fluid out of there it'll screw up some shit if you leave it in there.

1FAST07SS · Mar-23-12, 12:54 PM

Sounds like it coming from the top, I think it sounds like a lifter or valve but either way that's not a normal sounding engine. Get it in as soon as possible!

BBA · Mar-23-12, 07:53 PM

Sounds like a lifter to me. You sure they didn't put used motor oil in it?

Boricua SS · Mar-24-12, 01:45 PM

Quote:

Originally Posted by 1FAST07SS

Sounds like it coming from the top, I think it sounds like a lifter or valve but either way that's not a normal sounding engine. Get it in as soon as possible!

that i am doing.. hasnt moved since the day i heard the knock start.. she goes monday afternoon...

we are all guessing top end as well.. be it lifters, rockers, or valves... either way, i just hope this doesnt change things.. im not too mechanically inclined with the motor compnents.. im more of an electrical/stereo/circuit boards guy.. so this is all new to me... i just dont want this to alter my driving of the truck when i get it back.. if i feel like its gonna "break" everytime i get on it or go to try and race it.. why keep it.. i can still get somewhere around 20k on a trade (at least up north at my dealerships around me lol) so why not get a fun little turbo'd car or something.. but these are just all ideas ive been having as i dont know how serious this issue is.. ive NEVER had a motor problem like this in any vehicle ive owned...

Quote:

Originally Posted by BBA

Sounds like a lifter to me. You sure they didn't put used motor oil in it?

yes im sure.. i buy my own oil and take it to them..

and thank you gn2beatu for the troubleshooting tips... gonna try that before she goes monday... my brother is coming up later on today.. so we'll see...

91RS · Mar-24-12, 02:29 PM

I hope mine never does this! As long as the dealer has a good heavy engine tech, they'll get it fixed no problem.

Boricua SS · Mar-25-12, 08:33 AM

Quote:

Originally Posted by 91RS

I hope mine never does this! As long as the dealer has a good heavy engine tech, they'll get it fixed no problem.

That's what I'm afraid of.. I've had to go back there a couple of times to show them how to fix something that I leanred on the foums.. so it scares me a little to know they're going to tear down the motor..

Ultimately what this boils down to (for me at least) is if this is going to effect my confidence in driving this truck without fear of breakage, then I might as well trade it in.. KBB on it is still at 21k and I only owe 8k on her.. so I'm banking on all that equity.. would be a nice down payment on something brand new..

But again, I'll just have to wait and see what they say.. if its just something simple, then I'll keep it..

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91RS · Mar-25-12, 09:35 AM

I wouldn't worry about it, just let them fix it and drive it. If it's on the bottom end, there's a good chance you'll get a new engine. Most likely though, it's a lifter issue.

TheCoach · Mar-25-12, 12:52 PM

When my rods spun the ticking noise was consistant and any rpm including idle. My guess is it's not a rod. But i dont know shit either.