Rod Knock? Piston Slap? Rocker arm?

[WoR496]

I have a '96 Olds Ciera w/ a 3100. It has a knock at idle that almost sounds like a rod. But the past engines i've had w/ a rod knock, when you run them up a thousand or two RPM past idle they get worse, this one goes away. It still does it when the engine reaches normal operating temp. Has ~160k miles on it. I know you prob. can't tell me anything without hearing it but hopefully someone can give me a clue as to what type of knock has these characteristics.

[mr.rogers]

bad lifter? is it a tick or a knock? this is crazy troubleshooting over the net.

[WoR496]

It definitely is not a lifter. Its more of a knock.

[cujoe_da_man]

actually, it sounds exactly what mine does, same engine and almost same miles. If you drive it, does the knock get worse when you give it gas then all but go away when you let off the gas? It's probably just a spun bearing like mine. Usually anything else would show a loss of power, but like mine, I could get right on it like there was on problem, just the loud knocking.

[WoR496]

It only does it below say 2000rpm, and it doesn't seem to care how much throttle you give it, it doesn't get any louder. This is why i don't believe it is a rod bearing. Someone on another forum believes it may be excessive clearance in the piston for the wrist pin.

[tractorman]

Sometimes the only option is to tear it down and see what you find.

[WoR496]

Sometimes the only option is to tear it down and see what you find.

yea, i'm starting to feel that way. Guess i'll pull the oil pan off and check the rods, if that all looks good then i guess i'll just drive it till it gets worse or blows up.

[tractorman]

Let me know how that goes- pulling the pan. The pan gaskets on both of my 3100 engines leak, but it looks damn near impossible to pull the pan with the engine in the vehicle. I could be wrong... never been brave enough to try it. So if you manage to get the pan off, lemme know how it goes.

[95Grand-Am]

Does the sound come from the front of the engine maybe a streched timing chain or a guide? A clapsed lifter can be loud and deep sounding.

[WoR496]

Well if its anything like trying to get the pan off a 3800 in a '98 grand prix then i know what im in for lol... i had to undo all but the trany mount, pull the motor up from the passenger side, remove the axle nut so i didn't seperate the CV joint, take off the mount plate that bolts to the engine (about the hardest part), remove pan bolts, drop pan down as far as it will go (about 5"), reach in from the fender well (wheel removed obviously), remove the two bolts holding the pickup tube on (yes with the pan still halfway on the car), then get back under there and get it positioned just right and it will come out, with some force. Putting it back in isn't any better...

To me it sounds more like its comming from the rear of the motor but i didn't spend a whole lot of time moving around and listening.. will have to do again. I'll prob. run the car up on ramps and get my stethoscope out and listen around the pan.

[bszopi]

Not sure the 3800 has side-mount bolts in the pan, which is probably the hard part about pulling the pan.