unless you have a small exhaust leak?
LT-1 Engine Knock
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From: Evansville IN
St. Jude Donor '05-'06
LT-1 Engine Knock
I've noticed when I first start my '92 LT-1 up it has a knock to it. I can hear it more inside of the car than outside. It goes away after it warms up a little. I'm not sure if this is normal or not. I've had it for almost 1 1/2 years, and it has done this ever since I bought it. Could it be something other than the engine? Transmission maybe? 
Le Mans Master
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From: Myrtle Beach SC
St. Jude Donor '05-'06
My datamaster scans show a knock at start up on my car(I can hear it when it is cold enough) but it goes away immediately.I would say it is a sign of old age if it last longer than that.
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From: Evansville IN
St. Jude Donor '05-'06
Thanks guys. It's kind of weird the way it does it. I can start it up, drive 2 blocks to the bank, shut it off, come back out and start it up again, and no noise at all. It does have 95K on it, could it be just getting old? Other than that it runs great, uses about a pint of oil between 3,000 mile changes, which I am told is within tolerance for this engine.
Le Mans Master
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From: Myrtle Beach SC
St. Jude Donor '05-'06
Originally Posted by Kwikerthanu
It's kind of weird the way it does it. I can start it up, drive 2 blocks to the bank, shut it off, come back out and start it up again, and no noise at all. It does have 95K on it, could it be just getting old? Other than that it runs great, uses about a pint of oil between 3,000 mile changes, which I am told is within tolerance for this engine.
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From: Evansville IN
St. Jude Donor '05-'06
I've listened very closely for this noise, and it appears to be on the passenger side of the engine. It only does it after it has become completely cold, 8-10 hours, less than that and it doesn't do it. The noise isn't quite as bad if it is warm outside, say 60+°. This just a dull muffled sounding knock, not like metal to metal. I'm leaning towards the exhaust leak theory, as it does quit soon after starting, and driving.
I've been using Mobil-1 on a regular basis. It's just about as clean when I change it as it is when I put it in, so sludge doesn't seem to be a problem, but I did notice some seepage from the valve covers, this could be caused from not being used on a daily basis. It is driven every couple of weeks, weather permitting.
I've been using Mobil-1 on a regular basis. It's just about as clean when I change it as it is when I put it in, so sludge doesn't seem to be a problem, but I did notice some seepage from the valve covers, this could be caused from not being used on a daily basis. It is driven every couple of weeks, weather permitting.
Le Mans Master
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From: seattle WA
I find this interesting, cause I've never experienced a rod knock getting
better when the engine has warmed up-my experience has been just the opposite.If I ever experienced something like that I'd suspect the
oil pump.
better when the engine has warmed up-my experience has been just the opposite.If I ever experienced something like that I'd suspect the
oil pump.
Le Mans Master
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From: Santa Teresa New Mexico
Originally Posted by rick lambert
I find this interesting, cause I've never experienced a rod knock getting
better when the engine has warmed up-my experience has been just the opposite.If I ever experienced something like that I'd suspect the
oil pump.
better when the engine has warmed up-my experience has been just the opposite.If I ever experienced something like that I'd suspect the
oil pump.
Also a rod knock will get louder as rpm goes up and it should be constant. If its a lifter Marvel Mystrey Oil will lossen it up.
Power sterring pumps can make some strange noises.
Le Mans Master
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From: CLT, North Carolina
How to Find It!
It's definately not a rod knock. It is either piston slap which is harmless or an exhaust manifold leak. Both are temperature sensitive. I would get a length of rubber vacuum hose and while holding one end to your ear probe around the side of the engine with the other end until you pinpoint the source of the noise. The hose will work like a stethoscope and you will know when you've located the source of the noise. A long screw driver will work the same way for probing a running engine for internal noises.
Regards, Greg
Regards, Greg
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From: Evansville IN
St. Jude Donor '05-'06
I drove it again today, because it was so nice outside. Yesterday when I started it the noise was there for approx. 1-2 minutes then gradually went away. Today no noise at all. Maybe it's because it was used 2 days in a row, and the oil was coating everything better than yesterday. Yesterday was the first time in a couple of weeks it had been started. Guess it's nothing major, but it is annoying.
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From: Sioux City IA
Chevy 250's are known for lifter bleed-down after they have been sitting and with age. What happens is the lifter collapses when the oil drains out of it and it will knock a few times after start-up until it gets pumped up with oil. Nothing to worry about..very normal.
Le Mans Master
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From: CLT, North Carolina
Knocks, Slaps, Clicking or Clattering?
It might be an exhaust manifold leak if it makes a slapping sound rather than a knock when you rev it a little? Internal engine noises don't come and go except for possibly a couple of things. Lifters can make noise at first then quiet down after running a while but the noise they generally make is more of a clattering sound or a clicking if you have one or two acting up. Piston slap is another noise that is louder when you first start but will go away or diminish after the engine warms up. If you have piston slap it will sound like a little hammer in there when you rev slightly off idle and it will do it every time you start up cold. Piston slap is 100% harmless, just turn the radio on and forget it.
Regards, Greg
Regards, Greg
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From: levittown pa. usa Even a bad day with my `Vette, is better than a good day at work
St. Jude Donor '10
Originally Posted by Kwikerthanu
I've noticed when I first start my '92 LT-1 up it has a knock to it. I can hear it more inside of the car than outside. It goes away after it warms up a little. I'm not sure if this is normal or not. I've had it for almost 1 1/2 years, and it has done this ever since I bought it. Could it be something other than the engine? Transmission maybe?
