This is a bit off-topic, because the motor is in my 1985 Chevy 1/2 ton pickup, but it's the same basic motor in my "real" car. Here's the deal: 305 4-barrel, auto trans, 2-wheel drive. 140,000 miles. Bone stock motor. Drove it every day for 2 years, and for the past 2 years I only drive it maybe once a month when I need to haul something. Last time I started it up it was making the most awful death-rattle I've ever heard. Not a knocking (I've heard bad bearings) a pinging (I've heard detonation) or a ticking (I've heard bad lifters), but a rattle that sounds external. I looked and looked and couldn't find where it's coming from. It's not the water pump or alternator (both new) or power steering pump or air pump (removed years ago). It was rattling and shaking at an idle, or going down the road at a steady speed, but would completely disappear if I accelated OR let up on the gas. I thought maybe the flywheel or torque converter had come loose, but the noise pretty much went away after the second time I drove the truck. It's running smoother now, too. What the heck could make that much noise and vibration AND stop doing it? The truck runs fine now, and only makes the noise a little bit at fast idle. Otherwise, it's quiet. Any ideas?
Thrust bearing. the noise you're hearing is one of the counterweights hitting a main web. Or your balancer is coming apart-but that's alot less "innermitten" than that.
did you hit something with your oilpan? or jack up the engine from your oilpan? sometime the crank hits the OP or walls inside and makes weird noises. TP
No, I haven't touched it at all any time recently, other than to climb in and start it up. I figured something like a bearing going out, or the balancer, but I can't understand how either of those would be so loud and constant, and then just as quickly go almost completely away. And even when it does make the noise now, it's very quiet. Before it sounded like someone rattling metal to metal. Now it's just a short-term, muted noise. I really thought the motor was going to come apart, and all of the sudden it's running fine. I suppose I should have mentioned that it made a much milder version of the same noise when I bought it (after sitting for several years) and that noise went away after driving it for a few days. I bought it thinking it was the air pump, but it wasn't. Can a harmonic balancer be going out, but sometimes be okay? I'm not much of a mechanic and this has me completely stumped.
Put your hand on the oil pan while its running, you'll feel a tap if it is hitting. I've had to fix a crank tapping on the oilpump pickup tube bracket too. At least it will take that potential issue off the list. TP
It does go away if I put it in gear, but it was almost constant for a while and now it's almost completely gone. It's been so long that I don't even remember: can you get to the converter bolts just by dropping the dust shield, or do you have to pull the trans?
Thanks. I'll be crawling under my truck this evening to pull the shield and check the torque converter bolts.
I had a really odd rattle in my 96 chevy truck when it was about 3 years old. Turned out to be the catalytic convertor. Doesn't quite sound like your problem though. I have heard loose convertor bolts, they make a hell of a racket.
. Broken off chunk of cylinder head carbon?? Can sound like a really bad main or rod/piston knock, intermittent and highly metallic noise. Gm top engine cleaner used per instructions or some water (be careful) will make it go away....H
Id be willing to bet on cracked flexplate too. I took one out in two pieces cracked in a circle around the bolt holes like Flipper said.
And the winner is...Fordcoup! (And Flipper and fiftyfiveford). The flexplate was just about to go to pieces. I'm pretty sure if I'd kept driving it, it would have let go and taken my trans, converter, and/or block with it. Thanks to everyone - and bless the HAMB!
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