Sudden Loud knocking

[qwikz28]

Josh does all my work. It's hard to get the car there because of the sheer distance. I was hoping to get a rough diagnosis before deciding whether to take it now, or let it sit. I was eventually hoping to do a LS3 setup, so if this is going to be more than 2k or so, I'll just park it until I can afford to spring for the new setup. That's at least what I'm thinking right now.

Is my thinking logical, at least?

[BonzoHansen]

AAA+ goes 100 miles. Just saying.

[bobbyn362]

is it a low pitched knocking or tapping? it could be a bent pushrod. if you pull your valve covers you can feel all the push rods and rockers and if it s a wiped out lifter or lobe on your cam that can eliminate the whole valve train in ten minutes.

[qwikz28]

Originally Posted by BonzoHansen

AAA+ goes 100 miles. Just saying.

Very good point. Josh is about 97 miles from me.

Originally Posted by bobbyn362

is it a low pitched knocking or tapping? it could be a bent pushrod. if you pull your valve covers you can feel all the push rods and rockers and if it s a wiped out lifter or lobe on your cam that can eliminate the whole valve train in ten minutes.

It is definitely a low pitched knock.

I think I'm going to try Curt's idea of fishing around in the oil for metal and cutting open the oil filter, and then I'll pull the plugs to see if I can find any evidence of a failed cylinder. If I still can't figure it out, I'll make it Josh's problem.

Edit: I found the TTP invoice. It basically just shows that they ripped the engine apart, cleaned it, and installed new "King Rod Bearings." It says nothing regarding the crank being machined or anything like that.

[S.J.SLEEPER]

Originally Posted by MyFirstZ

Would a compression test show a broken ringland/piston. ?

normaly but not always.

JAKE: if you find no metal, you can also pull the plugs, if a piston broke, ringland broke, usually it damages the electrode on the plug but may still fire which you will not notice a miss. (check #7 first, always seems to be the one to break)

As for flywheel bolt and such. If you had a automatic, I would say posibly cracked flexplate.(i have seen some make horrible knocking noises) but your a stick, so highly doubt it any trouble in clutch/trans.

[qwikz28]

Originally Posted by S.J.SLEEPER

normaly but not always.

JAKE: if you find no metal, you can also pull the plugs, if a piston broke, ringland broke, usually it damages the electrode on the plug but may still fire which you will not notice a miss. (check #7 first, always seems to be the one to break)

As for flywheel bolt and such. If you had a automatic, I would say posibly cracked flexplate.(i have seen some make horrible knocking noises) but your a stick, so highly doubt it any trouble in clutch/trans.

I see. Thanks. I'll check the plugs then tomorrow. Looks more and more like the car is getting parked.

[S.J.SLEEPER]

any update?

[qwikz28]

Ah yes. I was going to pull the plugs, but it was cold. I did though cut the filter open, didn't find anything out of the ordinary. No metal that could be picked up with a magnet:

I also checked out the oil again. No metal that could be picked up with the magnet, but a bronzish film has accumulated on the top of the oil. It leaves a trail as you stir it. I tried to catch it on my phone, but this is all I could muster:
http://www.youtube.com/watch?v=dAn9Q..._order&list=UL

[alamantia]

I dont think bearings are magnetic.

edit:

I'm just busting on you by the way. Slide a magnet across the bottom of the pan and towards the oil drain hole, any pieces not caught on the drain plug magnet could be drawn towards the hole.

[qwikz28]

Alright, Anthony (Alamantia) is loaning me a compression tester and timing light to do more diagnostics tomorrow (it's too cold today!). So I'll be starting her up after I fill her back up with oil and then pulling the plugs to do the compression test. To be continued!

[Lt1_8U]

good luck! keep us updated

[Slow-V6]

Does the sound get louder the longer the car is running or the warmer the car gets or does the sound go away? Is it there throughout the RPM band? Does the sound go away when the clutch is pushed in?

I drove my V6 firebird around with 2 spun bearings for about 12,000 miles or so before I was ready to do my motor swap. I put 3 qts of 20W50 and 2 qts of Lucas oil stabalizer. The knocking went away. I also broke a piston on another 3.8 motor and it sounded the same as when I spun the bearings but when I did my 20W50/Lucas oil trick it didnt help in making the knocking not as loud..

[Lt1_8U]

even though you have oil pressure are you getting oil to the top end of the motor? i broke a connecting rod and it wiped out my oil pickup tube, i still had 40lbs of pressure but no oil up top and it made a knocking sound like your describing.

[alamantia]

I went there and that was by far the weirdest noise I have ever heard come out of a car ever in my life. I put my timing light on it, and as soon as it fired up I thought it was backfiring sporadicaly. I placed my hand on the air filter lid and it felt as if someone was under the car hitting the oil pan with a mallet. This horrific knocking shook the entire engine compartment and no way was in any sort of sync with the strobe on mt timing light. The engine ran fine aside from the starter not working one of the times we tried starting the car. At first I thought maybe a roller busted off a lifter and the lifter was wedging itself on the cam lobe. But only on every 5th or 6th revolution? On my way home it occured to me that perhaps the starter solonoid was shot and the starter gear is rubbing up agenst the flywheel and every now and again catching a flywheel tooth. I hope thats it, that would be an easy fix, much easier than tearing the motor down or towing the car. Im keeping my fingers crossed for it being the starter.

[Lt1_8U]

that would definitely be great if it was just the starter

[qwikz28]

Much thanks to Anthony (Alamantia) for coming by to lend his expertise and take a look at my car. As per his recommendation, I peeked into the flywheel to look for any indication of wear from the starter, and this is what I found:

I'm not really sure how much wear should be on the flywheel otherwise, but there is definitely some nicks in it.

[alamantia]

It would be nice to have someone spin the crank pulley with a wrench while you check the flywheel as it makes one full rotation and see if there is any contact between the starter gear and the flywheel. I know you can shim a starter going up and down. The two starter bolts are knurled to center the starter. Its tough to see from the picture exactly how far away from the flywheel it is. I dont know if there are any aftermarket clutch clearance issues. If its possible to eyeball a measurement between the starter gear and the flywheel the way it sits right now, how much space do you see between the starter gear and the flyeheel, should be at least 1/4 of an inch if memory serves me correctly. You could loosen the bolts a touch and try to pry the starter away from the flywheel and retorque them. Dont over tighten them, I think they only tale about 55 ft/ lbs

[qwikz28]

Should I be able to push the gear in?

[WildBillyT]

I wonder if it's worth trying to bump start the car to see if the noise is gone.

[98F-1camaro]

Originally Posted by WildBillyT

I wonder if it's worth trying to bump start the car to see if the noise is gone.

I was thinking the same thing.

[qwikz28]

Nevermind. The starter gear is already retracted. I can pull it out and it seems to be going back in quite normally.

Originally Posted by WildBillyT

I wonder if it's worth trying to bump start the car to see if the noise is gone.

Not really much room for that. It doesn't really seem like the starter at this point. It appears to be functioning normally and I don't see a significant amount of wear that you would expect from such a loud banging noise. The starter is an aftermarket unit and is clockable so I'll see if I can bolt it back up and see if it is still aligned well. I'll try and start her again after that.

[qwikz28]

Starter is back in. She's in there good and still getting the noise. Also tried running it with the belt off, still making the noise. so that rules out the water pump and other accessories. Caught a quick clip with my phone, but it didn't pick up the knock so well. You can hear it faintly, but it is much louder than it sounds in the video. My sewing machine of an engine is most of what you can hear:

http://www.youtube.com/watch?v=F07ci...j_gl79XeWVgU6Q

[alamantia]

I hear the loud knock we are talking about like 3 times in that clip, but I hear a lesser tap more in sequence with the RPM of the motore in the backround. Maybe this is stupid thinking here but is it possible that a broken exhaust pushrod or rocker is allowing the cylinder to fire and that loud bang is a backfire thru the intake? Is that possible or am I stupid? Its not hard to yank valve covers...

[sweetbmxrider]

Did you check to make sure all of the plugs are in? It kinda sounds like its just blowing compression out but it seems a little too infrequent for both the compression and fire strokes.

[1984camaroz28]

Pull the valve covers...