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Hello everyone, I have a question concerning my sisters 2003 Impala (3.4L V6). First off, the car has about 148,000 miles. About 2 months ago, it started to run hotter than normal (normally it runs about 180ish, it was about 220) only when stopped. I changed the thermostat, did a fluid flush, and bled the system. After that it stopped overheating, but when we had it running, I noticed white smoke coming out the exhaust and a rough idle. I turned it off thinking it was a head gasket, and checked the oil. It was not milky, so I thought well, it probably nothing. Next day there was no white smoke, but it still had the rough idle. So we took it down to Autozone, and he said it sounded like a vacuum leak. He said it was ok to drive. Well, Sunday (May 31st) She said she smelled a burning smell. So I looked around and saw no leaks or anything. Everything looked ok, so I left it alone. Well, the next day (Monday, June 1st), on her way home, it lost power. She said she pressed on the gas, and it would not accelerate and it made a ticking noise. So she pulled over at a small church and my mom picked here up. We called our mechanic up and he said to listen for the fuel pump. So yesterday (Tuesday, June 2nd) we went to check the fuel pump, and it was making its buzzing noise. I went to the front and took the radiator cap off, and noticed it was low. I checked the oil and it was one notch fuller than the day before. After checking around a little, we attempted to start it. When it started, there was a loud knock, so I told here to cut it off. (forgot to mention, she said the a/c was not working very good right before she broke down, if that makes a difference.) A little while later a guy pulled up that was part of the church. He happened to be a mechanic. He told her to start it, and it sounded the same, a loud knock. He said it sounded like is was coming from the bottom part off the engine, and most likely a rod knock. What do you think? I researched online and some people said that engine had problems with the rocker arm bolts ripping out. I can’t do anything to it because we have not got towed yet, and it is still sitting at the church. I don’t want to take the engine out to find it was something else. But, is really does sound like a rod. It sounds like some dude with a hammer is beating away inside the engine. I have my moms s10 in the garage right now that I am rebuilding the engine. I guess now I will have another to rebuild. lol. What are your thoughts? anything I should check? I don’t really was to run the engine and makes things worse. And sadly it has a dummy light and not a gauge for the oil pressure. Please let me know what you all think. Thanks
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I just listened to the video a couple more times and am now inclined to think valve train issue as the knocking wasn’t completely consistent with rotation. Although it is hard to tell for sure with the recording mic being so far away from the engine. If you have a stethoscope or long screwdriver you could take a listen near the top end and bottom end to see where the noise is loudest. As it is for now, rocker arm just went to the top of the list.
I’m still surprised, though, that the OP didn’t take a sample of the oil from the oil pan and look at some on a white piece of paper in bright light to check for metal. It’s an easy test that only takes a couple of minutes. If a lot of metal dust is in the oil, then that pretty much confirms worn bearings. A little to no metal glitter in the oil would exonerate the bottom end and point toward a top end issue. It only makes good sense to perform as many tests as possible that don’t require tearing the motor apart first.
I am inclined to believe valve train as well. I concluded that earlier but, had pm’d Fopeano because I was not sure because after it sped up it sounded more like a rod knock.
Removing the spark plug does not confirm rod knock. If anything it points to valve train or fuel more now. The engine still rotates at the same speed without the spark plug in there due to the way computers are setup in the car they compensate with the other cylinders when you have a dead miss. Since it is spinning at the same speed it should make the same noise unless it is a spun bearing. If you think about the way the rod is if it broke the rest of the rod would smack everything else. Regardless of where it broke. A spun bearing would go along with this because it wouldn’t be getting forced into the crank just pulled around.
What you did is remove combustion which would remove detonation from happening. Yet you said it was all but, gone which points me to the valve train for that cylinder or the aforementioned spun bearing It could be piston slap but, that sounds different. It doesn’t sound like piston slap to me because of the intermediacy when you had just started it.
Leak down and Compression test would be the best way to verify.
To me though it sounds like a bridge is messed up but, In your case it would be a rocker arm. It could be because a pushrod snapped etc.
The consensus between us all is valve train though so I would pull the valve covers and look around.
Pulling the spark plug wires one at a time is a tried and true test for rod knock. It is called a power balance test. It is useful for testing rod knock because the noise diminishes when you take away the detonation that causes the rod to smack the crank so that the rod is just pulled along by the crank. I agree that it is not conclusive IF it is the ONLY test performed, which is why we have all suggested additional tests to be done. While I can concede that it may be rocker noise, given the evidence presented and history of these type of engines having rocker issues, I am still not 100% convinced. I hope for the OPs sake that it is a rocker issue, as that is much cheaper and easier to repair. There is still just a bit of doubt in my mind, that’s all.
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