Loud engine knock, but no codes. Please help.
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Cruising
Joined: Aug 2015
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Loud engine knock, but no codes. Please help.
About 1 year ago i took the Corvette to a car wash, when it left the wash I could not start it, tried and tried and a loud grinding noise would sound. Finally got it started and a loud engine knock happened, i could barely drive it, had to be towed home, code was multiple misfire. Finally got around to looking at it again, changed the spark plug wires, now the engine has a loud knock coming from the drivers side but no CEL. its not drivable, IDK what could be wrong with it now, now the starter is grinding and wont even start the car anymore, so i need to fix that but I need to know what could be causing this crazy knock! Im so lost, no codes or anything. I tried attaching but i couldnt, i will keep trying any info or help will be greatly appreciated.
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From: South Hill Wa
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I was gonna say and I mean this non offensively that the engine didn't look cleaned via pressure wash.
I could hazard about 10 different things that could be wrong including coincidences.
Wondering if it sucked water into the engine when you were in the wash through the dual cone air filter and bent a rod. Sometimes when that happens on LS motors it compromises the starter pad on the aluminum block.
What is the history on the engine? has it ever been touched or modified?
I could hazard about 10 different things that could be wrong including coincidences.
Wondering if it sucked water into the engine when you were in the wash through the dual cone air filter and bent a rod. Sometimes when that happens on LS motors it compromises the starter pad on the aluminum block.
What is the history on the engine? has it ever been touched or modified?
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From: South Hill Wa
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It almost sounds like you can hear a rocker arm rattling around secondary to the knock.
Bottom line, it's hard at least for me to pinpoint without the thing in front of me.
Where are you located?
Bottom line, it's hard at least for me to pinpoint without the thing in front of me.
Where are you located?
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From: South Hill Wa
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Do you have the ability to take the valve covers off?
If not, you might as well find the closest best shop you can get it into.
If not, you might as well find the closest best shop you can get it into.
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That’s a loud metallic clang. Sounds (95% sure) to be a rod knock.
I dont think its valve train as misfire codes would’ve been showing with a valve issue that severe.
You dont have codes because the piston is still moving as it should, it’s just the rod bearing is screwed hence the noise.
You will need an engine replacement, at the very least a short block.
I dont think its valve train as misfire codes would’ve been showing with a valve issue that severe.
You dont have codes because the piston is still moving as it should, it’s just the rod bearing is screwed hence the noise.
You will need an engine replacement, at the very least a short block.
Instructor
Joined: Jan 2018
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From: LA (lower Alabama)
Rod bent? Broken valve spring, valve hitting piston? Did you rule out that you drove over something in the car wash and damaged something from under the engine? Hard to tell from the video but clearly something is not happy. I had a '73 Olds back in the day that I took to the car wash and washed the engine and it tossed the timing chain when I cranked it back up. Total coincidence, which might be the case with your problem.
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I'm still debating in my mind if the car wash had nothing to do with this. Totally coincidental. I definitely agree with the bent rod synopsis but I swear I hear a secondary clatter that sounds likes its in the valve train that is on top of the rod knock sound.
OP what is your oil pressure like?
OP what is your oil pressure like?
Le Mans Master
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From: Wisconsin
I'm still debating in my mind if the car wash had nothing to do with this. Totally coincidental. I definitely agree with the bent rod synopsis but I swear I hear a secondary clatter that sounds likes its in the valve train that is on top of the rod knock sound.
OP what is your oil pressure like?
OP what is your oil pressure like?