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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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Based on your description it does sound like a rod knock/spun bearing. You won’t know for sure until you take it apart, but all the signs are pointing that way.
I would say with it running hot more then likely you have an issue with combustion. Now whether that caused a broken rod or what I could not tell. My experience with broken rods is the engine tends to sound like a helicopter but, that has to do with where the rod breaks.
Stupid question, does it have a check engine light? Next stupid question, got a buddy with a scan tool? If there is no check engine light it would make me think detonation as that would go along with the symptoms from before and what you are hearing now. Problem is that is normally a precursor to a broken rod. As is a head gasket leak water doesn’t compress real well.
As for you making oil does it look like a milkshake? Does it smell like fuel? Does it taste like chocolate (jk please don’t taste it) When you first pull the dipstick is it clear right above the oil but still look wet?
How does your coolant tank look does it look black? How does it smell does it smell like exhaust?
Is your oil fill cap on top of your valves? If so how does it smell? How does it smell compared too the dipstick. Does it smell burnt? Does it smell like exhaust, coolant, a babies freshly marinated diaper?
Have you looked up videos online of rod knocks on you tube? Have you looked up videos of fuel knock on youtube? Have you looked up videos of detonation on Youtube? I would do all of that and compare to the sound you remember hearing. Preferably on the same motor or similar motor aka same manufacturer same pattern.
[quote=”MDK22″ post=138523]I would say with it running hot more then likely you have an issue with combustion. Now whether that caused a broken rod or what I could not tell. My experience with broken rods is the engine tends to sound like a helicopter but, that has to do with where the rod breaks.[/quote]
I’m not so sure the rod is actually broken. My experience with rod knocks is that if the engine sounds like someone is inside hitting it with a hammer making a metallic clanking sound, it has a spun bearing (or even more than one) and the noise is the rod smacking the crankshaft journal because the bearing is gone. Although a spun bearing does not, by itself, cause oil/coolant contamination. The condition of the oil does need to be verified, along with pulling a sample from the oil pan drain plug to check for bearing dust (“glitter”). A “sizzle test” can also be done with that oil sample to show conclusively if there is any coolant contamination.Rod knock can be tested by pulling spark plug wires one at a time. If the knocking goes away (or becomes significantly less) when the spark plug wire comes off, the problem lies in that cylinder. Pull the spark plug on that cylinder and see what it looks like. Also a cylinder leakdown test can be done to see if the head gasket has been compromised, but only after the bottom end is inspected, because if there is a bottom end problem the heads have to come off anyway.
Anyhow, the OP won’t be able to confirm anything until he gets it towed home and can check the oil and coolant situation, pull the valve covers to inspect the valve train, and perhaps also pull the oil pan to check the bottom assembly.
Thank you both for answering! No, the check engine light did not come on. Yes, I know some people with scan tools. I will check the oil and coolant when I get it home. The guy with the tow truck is going to tow it sometime this afternoon. I will let you know when I can. Thanks again!
The car is now here, so I can check everything now. The oil looks and smells normal, same as the coolant. Yes, the oil cap is on top the valves, it looks fine and smells the same as the dipstick. I opened the radiator and the coolant around the side of the rim looked normal, but I could not see down in there because it is low. The overflow tank has always been kind of dirty and black at the bottom ever since she got it, but the coolant looks ok. Should I pull the valve covers off and make sure one of the rocker arm bolts are not torn out of the threads? I have seen a lot of complaints about the threads letting go and make a loud knock noise. Although it does sound like it is coming from the bottom of the engine. I could take short video of it running so you can hear it.
Will it shock me if I take off the spark plug wire? I guess I am a big chicken, LOL. Just don’t want to get shocked
[quote=”Mechanic2001″ post=138575]Will it shock me if I take off the spark plug wire? I guess I am a big chicken, LOL. Just don’t want to get shocked[/quote]
It will, if you don’t handle it properly. Wear a pair of gloves to insulate your hands, use a pair of insulated pliers to grab the boot, and don’t become a ground path for the spark. Those three rules will keep you from getting shocked.As for the valve covers, do a compression test (and/or cylinder leakdown test) before removing them. Do all you can before pulling them off. You will have to eventually, though. And probably also the oil pan. But any tests requiring rotating the engine assembly should be done before removing the covers and pan.
I might look like the dumbest guy on the forum for offering this 2 cents worth. I do know the GM 3400 well. You’ve received some good advice here already. Check the water pump…Yes, the water pump… when the bearings get bad enough, it can resonate and actually sound like something banging inside the engine. A few weeks back, a friend called me who was told their car had spun a bearing. Honestly, it sounded like it. However, I determined and confirmed it was the water pump. When you remove the serpentine belt, you can easily spin the pump and listen/ feel for a problem. You can even crank the vehicle for a couple minutes with the belt off. It won’t hurt it. The water pump is right up top on this motor. Good luck…
I would check tomato farmers suggestion. You could check the valves but, it depends on how much of a pain it is. I like to perform a bunch of preliminary checks first and narrow it all the way down as far as I can before tearing into stuff. Saves me all day long at work from making unnecessary repairs.
I would check your pcv valve. Yes the pcv valve its often overlooked it and making sure air can flow through both passages on either side. It sounds stupid but, it can make it knock. Just take it out and shake if it rattles its good or you can always replaceit as it is normally only a 5 dollar part either way is fine. Another thing is do you have a MAF sensor. If you have a MAF sensor simply cleaning it with a 5 dollar can of CRC MAF cleaner may also remedy your issue. I know both of these sound stupid but, I start my way from stupid and run till i get to well its already totaled lets drop 6 cans of ether in it and let it eat. (Btw, never go full ether going full ether kills people)
Another thing that would be useful is lure one of those people with a scan tool over with promises of pizza and beer then when they say sure pounce like a lion on a gazel with and bring your scan tool. Get the stft and ltft along with any previously active codes if you can get them and the freeze frame data also if possible. This will help to give us a good jumping off point. The other thing that has me a little at odds is if it is an engine knock why has your knock sensor not set a code for it.
Because of what I said in the paragraph above check your shocks/struts by bouncing the corners of the car while it sits in your driveway. Also look for any loose driveline or suspension parts. Loose lugnuts etc. Was anything just “fixed” on the car. If so look there first.
I took a video of the car running and tried to post it here, but it would not work. I ended up uploaded it to Youtube.
Here it the link to the video: https://www.youtube.com/watch?v=2VTyIls4HtI
Pure speculation here. Judging from the quality of the noise, I’d be inclined to look at your roller lifters, push rods and rocker arms. That just doesn’t seem deep enough to be rod knock. Another culprit might be a rod’s small end or a wrist pin.
I have very little experience on these engines, though.
Plus 1 on Evil-i’s comment about the push rods rocker arms, etc. It sounds a little heavy for a lifter issue to me. However, a stuck valve might be a primary cause. It’s a pain to get the valve lifter off the back of that engine 🙁 I’d suggest once you do, have somebody turn it over by hand and watch all the roller rockers for movement, etc., You may want to remove the push rods one by one and see if any are bent/ damaged.
So that noise is an unfamiliar kind of sound to me, and I try to avoid working on pushrod engines, so my logic is that it’s a pushrod or rocker arm noise. I’ve repaired one of those engines with rocker arm studs that pulled out of the head. It was misfiring and making kind of a similar noise now that I think of it. Just the sound of that rocker arm kind of flopping around. Thing is though, you know a stud didn’t pull out completely because you would have a misfire due to the valve not opening. The real giveaway that it’s not a rod noise is that it’s got that random double tap sound. Rod and piston noise changes quite a bit based on how the engine is loaded/revved. Lifter noise is normally the same tap over and over that changes with RPM. Your noise sounds like the latter, but with that random double-tap sound thrown in there. That’s why I think it’s a pushrod/rocker issue.
EDIT: I asked for a 2nd opinion from the other senior guy here, who does a lot more with domestic/pushrod engines. He thought maybe a broken pushrod, but agrees that he’s pretty sure it’s a pushrod/rocker arm sound because of the same reasons I stated previously.
Thanks again to everyone who responded! I think I just confirmed rod knock. I took number 5 spark plug wire off and started it, and the knock was almost gone. I put it back on and started it again, and the knock was back. That confirms rod knock right?
Would it tick if it was a push rod/rocker arm problem if the spark plug wire is off?
In my mind, you’ve pretty much eliminated anything in the valve train.
Unless I’m missing something obvious here, it kinda points towards a rod’s big end, small end, or a piston issue.
Not to muddy the water here, but I don’t think the noise becoming more faint with the #5 plug wire disengaged proves the problem is in the engine block. Without detonation in that cylinder, a valve train related noise could become more faint as well. As previously noted here, the heads would have to come off anyway if the problem is in the block. I’d get those valve covers off and have a look up top if she were mine. You might get lucky and find something simple like a loose rocker arm. Keep us posted on what you find…
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