Hi everyone, I can’t figure this problem out. When the truck is cold it sounds as though it has a knock when I start driving. The only way I can describe it is it sound like a really bad exhaust leak. I’ve looked and can’t find any soot from an exhaust leak. I’m not sure what else to look for. Sometimes it’s worse than others, but it definitely didn’t make this sound before.
LBZ: Strange sound before truck warms up
- Thread starter Jon7891
- Start date
Use your hand to feel around the up-pipes while the engine is cold. You should be able to feel the leak. You don’t always get soot tracks with a leak.
No I’m not sure. All of my balance rates are Well within spec, the worst being around +2. Is there a way to test them without pulling them?
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Is it tuned? How long have you had the truck? Is the sound new?
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It is tuned. Not sure who’s tuning. I’ve had the truck for 2.5 years and the sound is definitely new. It started about 2 weeks ago.
Unplug one injector at a time on the side of the motor you think it’s coming from to determine which cylinder it is if it gets quiter. When cold You can always squirt some soap on the uppipes to see if you can see bubbles. Ike G’s Pro-Tip
I was thinking about this. The only thing is I can’t hear it at an idle, it’s only when I start driving. I’m sure it is doing it at idle but I can’t hear it
I asked about tuning because the are timing and fuel pressure tables that will cause a knock durring cold weather. But if your haven't had cooler then normal weather and the sound is new that's probably not the case.
Is the knock steady with rpm up and down? Get louder or quieter?
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Is the knock steady with rpm up and down? Get louder or quieter?
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Yeah it actually a lot warmer here than normal and it’s still doing it. The speed changed with the rpm, and does get louder the more throttle I give it.
Make sure you check the bellows on up pipes very closely , we just changed up pipes on an lbz because of that , one was cracked , it wouldnt make noise until on gas !
I took a video of it but I can’t post it for some reason. It’s 75 here today so it didn’t do it too bad. Tomorrow will be back in the 30’s so I’ll try again.
https://youtu.be/2BKtGwbdN38 This is me driving when truck is cold.
https://youtu.be/Hc4D3CH_YJQ this is where it sounds like it’s coming from. Engine is warm
https://youtu.be/Hc4D3CH_YJQ this is where it sounds like it’s coming from. Engine is warm
That's the only thing I hear is a possible exhaust leak.
How I find exhaust leaks is with a shopvac on blow mode. Conect it to the tail pipe. You can hear the leaks better and use soapy water to find them for sure.
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How I find exhaust leaks is with a shopvac on blow mode. Conect it to the tail pipe. You can hear the leaks better and use soapy water to find them for sure.
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X2 on what Iowa said remove the fender liners take a 4 foot piece of hose or long pry bar or mechanic stethoscope have a friend place vehicle in drive and load the engine a little power brake it if you will and listen through the hose on each injector and around the up-pipebellows to rule any culprits out and that should net you your problem hope this helps