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Thread: 3.8 with an upper engine knock

  1. #1

    3.8 with an upper engine knock

    I just dropped a known good engine from a 2001 Buick Park Avenue into a 2002 Pontiac GTP. I had driven the Buick for several months to ensure the engine ran good and put about 3000 miles on it. Once I had the engine swapped, it ran great. However, after about 100 miles or so when slowing down to turn there was a ticking sound. Once slight acceleration, there was a knock. I was in my yard at that time, so I ran it back into the shop and the crankcase was full of gas. Drained and replaced the oil and then started it again. The knock was still there. Its fairly loud but not from the bottom end. Any ideas before I tear into it?

    If you need any more information, I can sure see if I can get it.

    Thanks,

    Wes

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  3. #2
    Full Throttle Extreme!
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    Crankcase was full of gas? When you say it was full of gas, how much total volume of oil and gas came out when you did your oil change? Sometimes if the car is running rich, gas fumes can work there way into the crankcase. Knock usually comes from the bottom end and ticking is usually from top end. Before you get into the motor, check your flexplate. I once inherited a car because the flexplate bolts became loose and it sounded just like an engine knock. Also check for any cracks in the plate they normally appear around the crank bolts. Take a hammer and tap the flexplate, it should have a ring to it. If it is cracked it will make a dull kinda sound.

  4. #3
    Quote Originally Posted by 3.4 grape of wrath View Post
    Crankcase was full of gas? When you say it was full of gas, how much total volume of oil and gas came out when you did your oil change? Sometimes if the car is running rich, gas fumes can work there way into the crankcase. Knock usually comes from the bottom end and ticking is usually from top end. Before you get into the motor, check your flexplate. I once inherited a car because the flexplate bolts became loose and it sounded just like an engine knock. Also check for any cracks in the plate they normally appear around the crank bolts. Take a hammer and tap the flexplate, it should have a ring to it. If it is cracked it will make a dull kinda sound.
    I'm not sure of the amount of gas in the oil. I wasn't home and my grandson drained it. He said it was full. I suspected the gas pressure regulator or an injector dumped the gas. Took it to a tech I know and he put looked it over after replacing oil and now it's got the knock. It doesn't sound from the bottom end but I'm now thinking there's nothing else it could be. Maybe a rod bearing? I do know my grandson coasted about half a mile to my place and then on slight acceleration he could hear the knock. I haven't yet checked the flex plate. You thinking the bolt may not have been tightened when reinstalling the engine?

  5. #4
    Full Throttle Extreme!
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    I would just check the flex plate bolts to the torque converter and the flex plate bolts to the engine before getting into the engine.
    Remove torque cover inspection plate (4 bolts) and have a peek.

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