2500 RPM+ clicking? - Page 5 - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


1992-1999 Series I L27 (1992-1994 SE,SLE, SSE) & Series II L36 (1995-1999 SE, SSE, SLE) and common problems for the Series I and II L67 (all supercharged models 92-99) Including Olds 88's, Olds LSS's and Buick Lesabres Please use General Chat for non-mechanical issues, and Performance and Brainstorming for improvements.

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Old 10-16-2003, 09:36 PM   #41
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Quote:
Originally Posted by DrJay
haha now you're getting too creative for your own good! I dunno how much air can make it past the supercharger, that valve isn't very big. May be enough to idle though. hahaha I dunno what to even think bout it. I guess if the supercharger will let enough air past its possible to use it to rule out the waterpump. Really I'd just pull the spark plug and if it makes more noise you know its not your water pump and all it takes is pulling a plug wire, ya know?
OK Dr Jay, I'll pulled one wire at a time but didn't give it gas. There was no change in the noise level attl all. I pulled one plug at a time, then started the car. It idled fine with no noise on the start up or shut down. Please shed some of your wisdom on this situation. Is Willwren right? I'm starting to think maybe. Please help! You too Jarhead!
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Old 10-16-2003, 09:44 PM   #42
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hmm...okay this is some info I found that may be helpful


Try to track the noise down with the stethoscope tip or the end of the hose suckered onto the engine surface, sealing the end. Spend a full ten minutes putting the hose all over the engine, not just where it is loudest. Try to envision the parts moving inside the engine. You are training your ear, not just listening, so don't get in a big rush except to be sure that the engine doesn't overheat. A trained ear can tell you which piston is slapping or which rocker arm is clacking from outside the engine so if you come out from under the car proudly saying, "it'* the bottom end" get your dumb-*** back under there until you can tell me it'* coming from the oil pump or the 3rd piston back on the driver'* side or the flywheel or the camshaft.

Rod knocks are loudest at higher speeds (over 2500 RPM) Feathering the gas pedal may result in a distinctive back rattle between 2500 and 3500 RPMs.

Bad rod knocks may double knock if enough rod bearing material has been worn away allowing the piston to whack the cylinder head in addition to the big end of the connecting rod banging on the crankshaft rod journal. It will sound like a hard metallic knock (rod) with an alternating and somewhat muffled aluminum (piston) klock sound.

Wrist pin knock in modern engines is very rare today but is a favorite for the misdiagnosticians.

Determining which cylinder contains the noisy parts may be aided by shorting out the plug wires one by one with a common low voltage test light. Now you won't get the bulb to light up but it is a convenient way to short the cylinders without getting zapped or damaging the ignition coil.


Attach the alligator clip to a convenient ground, away from fuel system components, and pierce the wire boots at the coilpack or distributor end of the wire.


If the noise is changed when the plug wire is shorted to ground, you can figure that the problem is in the reciprocating bottom end parts. (piston, wrist pin, connecting rod or connecting rod bearing)


The reason the sound changes is that when you short the cylinder plug wire you are stopping the combustion chamber explosions that are slamming the piston downward making the inside of the big end of the connecting rod bang against it'* connecting rod journal. Or in the case of piston slap, no explosion changes how the piston is shoved hard sideways against the cylinder wall.

If you get a change in the sound when you short a cylinder out it may become moot as to what the problem is because the oil pan and cylinder head must be removed to correct the problem. [Generally speaking, an engine with damage to reciprocating parts (pistons, rings, connecting rods, wrist pins or rod bearings) and more than 70 thousand miles is not cost effective or risk free enough to attempt to repair. Replacing a crankshaft, for example while the rest of the engine has 70k perfectly maintained miles on it is risky enough but whatever killed the crank has scored the rings and packed the lifters with debris and smoked the piston pin bosses etc.]

If the sound doesn't change, look at parts other than the reciprocating ones. In many cases of rod-knock or piston slap, more than one is banging so even if you eliminate the noise from one rod the other one will still be a-banging away with a different, more singular tone.
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Old 10-16-2003, 09:59 PM   #43
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Quote:
Originally Posted by DrJay
hmm...okay this is some info I found that may be helpful



Rod knocks are loudest at higher speeds (over 2500 RPM) Feathering the gas pedal may result in a distinctive back rattle between 2500 and 3500 RPMs.

If the sound doesn't change, look at parts other than the reciprocating ones. In many cases of rod-knock or piston slap, more than one is banging so even if you eliminate the noise from one rod the other one will still be a-banging away with a different, more singular tone.
1 Should I have given it gas (to the 2500-3500rpm) as I checked each cyl?
2 Does the lack of change at this point mean I should look at some thing like the water pump as the cause?
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Old 10-16-2003, 11:46 PM   #44
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Justin, did you pull the plug wires, or the plugs themselves (one at a time)?
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Old 10-16-2003, 11:50 PM   #45
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wires off the plug one at a time, and shut down and started after each plug. I didn't rev the motor though. I just started it and let it run for a few seconds. It purred at idle.
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Old 10-16-2003, 11:59 PM   #46
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I'm wanting to go out there now with the low-voltage test light as stated in DrJays post, but I need to know if I should bring the rpms up while doing it. Any ideas?
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Old 10-17-2003, 12:21 AM   #47
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OK went out with the test light. Reved' on every cyl and no noise change! I'm thinking at this point I should be feeling pretty good. Should I be feeling good or am I getting ahead of myself?
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Old 10-17-2003, 01:44 AM   #48
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I think the idea was to pull a PLUG.....one at a time, and start the car. If it'* a rod or cylinder related problem, it'll be louder when the correct plug was pulled. In this particular case, considering where the noise seems to be located, I'd pull #5 first (face the car, right front closest to the airbox), then pull #1, where we heard the noise at the header......right below the SC nosedrive.

Is it louder on #1 than #5?
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Old 10-17-2003, 01:49 AM   #49
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There'* no differance at all in any cyl.
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Old 10-17-2003, 01:50 AM   #50
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Even with the plug completely removed? That'* probably good news. You buy a stethescope yet? Or do I have to come over again

Time to listen UNDER the car, methinks.

This is probably good news.
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