For the Zen masters among us?

[elkaboom]

What is the sound of a failing main bearing? A koan, submitted for your approval.
I've lately experienced a disconcerting "noisy engine" sound that's got me really worried.
It's essentially a metallic knocking, combined with a pinging sort of sound.
However, it's not rpm related, nor has it effected either my performance or fuel economy.
My car still has the same giddyap and pep that I expect, fuel efficiency is still the same (23-28mpg), and for the most part, nothing about my car is diferent except this f'ing scary noise. btw, it's pretty loud.
It's definitely not a rod knocking or valve tapping, or even noisy lifters.
WTF....?!
Main bearing..? deteriorated exhaust valve?... Man, I'm at a loss.
Is it possibly something in the tranny -something banging around the bell housing? Despite the sounds, the oil is reasonably clean -some suspect material when I dump the sump-, but the oil filter is pretty clean (i cut it open ** cross sectioned it**); a little unindentifiable material (gasket or ring material?). nothing magnetic.
Maybe I'm riding a horse that's about to drop, but I'll keep driving it until it quits. Otherwise, this car is immaculately maintained.
I'm stumped.

[scottzg]

When does the noise happen? What happens if you roll along in neutral? Does it get louder when you accel harder? How about when you idle?

[elkaboom]

It happens all the time: from start up to shut down. It's not loud, loud... but it's loud enough to be a "damn, what in the Hell is that?" kinda sound.
brat4x4 and I could'nt point either of our respective fingers at it; I thought a water pump failure maybe... either way, I think it's bad.
-little help here...

[douglas vincent]

Broken piece of Catylitic in the front cat?

[fishbone79]

A done main bearing has a pretty dull knock, and doesnt sound metalic at all... it sounds exactly like knocking a wrench wrapped in a rag agains the block.

A cooked exaust valve has more of a tick than a knock (in my experience).

However, both of those things would change with RPM, if it doesnt d with RPM, it shouldent have anything to do with the guts of the motor (unless its intermittant top end, I would think). It shouldent be anything peripheral to the engine either, for that matter, H2O pump and oil pump d with RPM, as does PS pump (although, I would definitly check that).

An interesting idea, when I had shot motor and tranny mounts, I would get a similar sort of noise when I got on it or decelerated rapidly, and it turned out to be in my tranny. When I had the tranny out, I jerked it side to side roughly, as if it were getting a change in load from the motor, and it made the noise. It turned out to be the internal shift linkage clanking against the casing with movement (a dumbfounding revelation after you pull a tranny completely appart in search of loose parts ). But i guess that would only happen when you were driving, not when the car was stationary.

Im begining to think maybe my post is fairly useless, I guess i will let you be the judge.
Cheers!

[ultrasonic]

Possibly a rattling heat shield? That would be something that wouldn't change in rate along with engine speed. Although there often is a "resonance" effect- the rattling gets louder at certain engine speed.

Get a 3 foot long piece of garden hose, or something like that. Put one end close to your ear, and move the other end around various locations of your engine compartment. You might have to go underneath, while the car is on ramps, to listen to exhaust and heatshield noises. You'll know it when you get close, it will be much louder listening through the hose. It's an easy was to localize noises.

Let us know what you come up with.

[Brat4by4]

It was very weird. It sounded internal to the engine. But you couldn't get it to change with any throttle inputs. I would have him hold the revs high and then release to see if it go louder when a load was lifted, but nothing different. The sound ticks/knocks to its own drummer. It confused the mess out of me.

Maybe we should compression test it? Or maybe a scope into the spark plug holes would reveal a little ball bearing or something floating around in one of the cylinders

Only thing I could think of due to its location is maybe the throttle plate is rattling? And maybe a new OEM tranny mount to eliminate that possibility?

[fishbone79]

Wait, does it get faster or slower at all with RPM, or is there simply no change with RPM what so ever?

[professor]

I think the water pump is a real possibility. If the shaft is failing but not (yet) the seal, thay can make a racket with metallic, expensive sounds. The frequency of banging should change with RPM, though.

I agree with probing with a hose for where the noise is coming from

[entirelyturbo]

It very well could be a water pump, that's exactly what mine did and that's exactly what I thought was going wrong (spun bearing! )

But needless to say, that sound would have to come from the water pump, which is in front of the engine, under the A/C compressor.

[douglas vincent]

I still stand by a loose piece of converter in the front header cat since it appears the area of the sound has yet to be determined.

[fishbone79]

I'm goin with a squirrel from an 80's hair band in your oil sump.....



Seriously though, my power stearing pump made a hell of a racket when it went... sort of a clanking and a popping noise that was intermittant at first. Did you ever find where it was coming from?

[Legacy777]

yeah my ps pump made god awful noises.

Take the belt off and turn the ps pump by hand when the car's off. If it turns roughly or not smooth.....you found your problem.

[entirelyturbo]

I'm goin with a squirrel from an 80's hair band in your oil sump.....

LOL!!!

I think the best thing to do is accurately describe to us where exactly the noise is coming from, a pinpoint location.

[elkaboom]

Well, turns out it was, in fact, the waterpump. Sumbitch took a crap on me this afternoon (fortunately, only 1/4 mile from my destination; temp gauge was climbing, but never made it to the red zone *whew*).
Looks like I get to dismantle the front of the car this weekend. Yay.