Loud Engine Knock is coming and going

[SweetLou0222]

Hey guys,

New to the forum. I have used it plenty for information on my truck since I purchased it December 2017. I have an issue that is really bugging me and my mechanic and I am looking for some guidance or advice.

 

Last week my fiance was out driving my truck and reported a very loud engine knock that came on suddenly and was so alarming, she only felt comfortable having the truck towed to a local mechanic. After 2 days, the mechanic said they could not replicate the knock. but noticed my valve covers were leaking oil and I had them replaced. Drove around for a week, including 30 miles of highway and probably the same city.

 

Just yesterday, driving the exact same stretch of road, the knock came back with me behind the wheel. Loudest thing I have ever heard. I pulled up to the first side street because the main road we were on had no pull off space on the side. By the time I pulled into the side street, the knock was completely gone. I got lucky and thought to jump out right away on the main road to get a video recording the has the "very evident" knock recorded on it before pulling to the side road. I have attached the recording below.

Looking for any ideas?

 

The only thing that made this stretch of road any different than any others is that I had to go through 3 round-abouts/rotaries, with the sound occurring as I was exiting the third. 

 

My truck has given me nothing but issues since I purchased it, including 2 engine replacements, new heater core, $3,000 in handling and suspension, etc.... Any serious inquiries or help, feel free to ask about any past history.

 

Please Help! This truck has put me into debt and have no other options.... : /

[davester]

2 engine replacements, $3K in handling and suspension, it sounds like you beat on the truck...

 

Anyway, check the exhaust system, as it might shift a bit as you turn left & right, so you hear the exhaust, then shifts back over time so you can't hear it as much.  Make sure all the bolts are in and tight in the exhaust manifolds to the heads and the up pipes to the manifolds.

 

Also check oil level and what the oil pressure is when this sound is happening.

[SweetLou0222]

I appreciate the response! I will pass that on to the mechanic as it is still in their possession. 

 

I wish I could blame myself for all of the repairs, it would make things easier. Unfortunately, I do not know anything about cars, and when I bought the truck, the dealership "forgot" to tell me that the previous owner had taken the truck airborne. I myself have never even taken this truck off-road, as much as I want to.

 

I only use the truck as a daily driver. First engine replacement done 2 weeks after purchase, and then again 2 months later. Both covered by extended warranty, which is no good now, and therefore I had no choice when it came to them putting in a re-manned engine instead of a new one. 

 

The previous owner took no care for this truck and now I am stuck dealing with it. 

[Mikebtte]

Given the consistency of the sound I would say it is coming from engine or drive train. Something rotating is producing the sound. My first inclination is to check the engine as this is the most common on a Ls engine but look at the belts and pulley system. Have seen a chuck of belt come off and make a hitting sound and I have had tread come off at tire and sound like a rod knock. Just look it over and keep poking at it. 

 

What year is this truck you are driving? If 07-13 you have an AFM engine. If not you still have a push rod engine 

[newdude]

Open the transmission inspection hole cover and see if you can see the flexplate.  Vortec LS are known to crack the flexplate and cause that kind of noise.  Or have your guy pull the trans and look at the plate.  They usually crack around the 6 bolts that hold the plate to the crank. 

[Zeekster]

check out the guy putting your motors in...looks to me maybe he has a boat payment coming up...lol

[daleone3]

I had the same issue with my Silverado. Sounded like a loud bottom end rap. Happened driving about 50mph, slowed the truck down, stopped and shut it off. Waited about ten minutes before I started it and never happened again. I would have bet anything that I spun a bearing but will never know. Good luck but not sure you will ever know


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