Last weekend I took the car out for a cruise. Just nice driving, no WOT blasts or anything. Everything worked perfectly.

Since then I have changed my water pump and crank pulley to CVF pieces (beautiful pulleys btw):

http://www.cvfracing.com/oldsmobile-pulleys-s/148.htm

I have done nothing else to the car.

So, yesterday when I took the car out I immediately noticed some kind of tinny, metallic sound. It sounded external to the engine, not internal. After driving for a bit it became more frequent and presented itself when i put load on the engine. It would not appear when I revved the engine in neutral.
After driving a couple of miles the sound is now stronger and it now appears without load, not as loud though. Check out this video:


It almost sounds like small stones are being thrown out the headers
I removed the torque converter cover thinking it got bent and contacted the flexplate - no change. I have inspected the underside of the car but didn't find anything suspicious.
The new pulleys look perfect and doesn't make contact with anything. Fan isn't touching anything either.

What the h*ll is this?

Car idles just fine and has no loss of power. Except for this it sounds and works just like normal.

 

Just a guess, but is fan blade loose?

 

i did see stones bouncing around in the video

excess fan activity blowing driveway stones onto the underside ??

 

Did you get pulleys with the correct offset? Everything line up correctly? You could take the belts off and see if the noise goes away. This may help pin point noise.

Don W

 

Check and see if your alternator fan is rubbing a bolt. I had one do this to me once.

 

No, it's good. I'll check it again though.

No, it's way louder than that. Doesn't really come through in the video though.

Pulleys line up good. I'll take the belt off and check, can't hurt to try.

But the sound seems too be coming from the back off the engine and down low.

I'll check that too.

 

 

You said tinny sound under load not while revving. Could something have gone hay wire in the distributor and its possibly detonation. I agree as mentioned before run it with the belt off to isolate the issue to the belt drive system . if it remains then into the engine you go.

 

w/p to fan bolts or studs too long?

 

Detonation possibly enhanced by the engine running warmer with the aftermarket pulleys (assuming they are different diameter than factory)? Just a thought.

 

I checked the fan blades and bolts possibly interfering with the belt last night - nothing. I will take the belt off and control timing after work today.

I'll check but I don't think so. I used the same bolts and the new aluminum pulley is a little thicker than the stock steel one.

Pulley kit has a slight underdrive but engine doesn't run hot, it's very stable at 180 degrees. Plus this sound is present with engine cold right after startup.

 

My first thought when I heard this sound was detonation but it really sounds external - like something rotating hitting some kind of sheetmetal. At one time it also made a grinding noise.

It doesn't really come across in the video but this sound is loud! If it was detonation I think I would have pieces of piston spit out the tail pipe. Hope not...

 

Maybe a broken weld or crack in one of the header tubes??? I watched the vid, that is definitely a strange sound.

 

I thought about that too, they do hang very low and get punished from time to time. I'll check it out.

 

Id go at the torque converter or flywheel clutch assembly.

 

I've checked the flex plate and converter housing and they were ok from what I could see.

I won't be able to diagnose anything tonight, I'll get to it tomorrow.
Thanks for your suggestions everyone, keep em coming!

 

I agree. This is what my torque converter sounded like at the beginning of failure. The fins inside had started to contact each other and this is what I was hearing.

I would pull the trans dipstick and check for silver in the fluid. You may not have much at this point as it sounds like it just started, but you'll want to head it off at the pass if that's what it is.

This was what my trans pan looked like:

misc032.jpg

misc035.jpg

misc033.jpg

misc034.jpg

 

That does sound possible - awesome... Since the sound is present even in neutral now I'll disconnect the converter and see if it goes away. Good times...

 

Make sure to push it away from the flexplate when you do so.

 

I did a quick test tonight with the belt off - no improvement. The sound gets worse everytime I start the car, it now sounds a little bad even at idle.

More and more points to the torque converter, the sound definitely comes from that location. I checked the dipstick but didn't find any silver (a little clutch material was visible though).
I think I'll drop the pan before anything else. Won't be until next week though, stay tuned!

 

Do the unbolt the converter test first then drop the trans oil pan. Have a good look at the flex plate where it bolts to the crank. Ive heard a similar noise from a fractured flex plate. You sure as hell don't want a flex plate coming unglued.

 

I'll be willing to bet he has a cracked flexplate now too.
Unfortunately, you will have to either drop the trans or take it way
back to get a good look at it.

 

Do you have crossover plugs in the heads?
Mine made a very similar noise that seemed to come from the header when my passenger side plug came loose.
I was so convinced something was in the header that I bought a bore scope from Harbor Freight and removed the collector and probed around inside the header, and couldn't find anything.
I took the header off, thinking something was in one of the tubes. Nothing.
When I looked into the center exhaust ports with the scope I found the loose plug.

 

Been there, done that. No plugs in heads, intake installed as stock.

I had my plugs start to rattle in the middle of nowhere during a 400 mile road trip, didn't know what to think! Oh, the memories...

 

Ok, problem located and corrected!

Turns out it was the starter. The bracket holding the fork inside the starter was damaged. This created play in the mechanism and the pinion gear could slide out over 1/8" without force. This was enough to make contact with the flexplate and the noise was actually the pinion gear bouncing against the flexplate.

 

I made a new bracket and voila! - the noise is gone! Good thing I had a spare pinion gear lying around

 

Nice.

 

You win! Now to locate the genius engineer(s) who thought an injection molded piece in that location was a good idea....toss that person(s) into the flywheel! Poor validation. That cast aluminum fork is next? Is that a USA made high torque?

 

Haha! Yeah, not the best idea... It seems to be made out of POM plastic - a good polymer if you get it right but mess up the injection parameters and it's about as strong as crisp bread. Yes, I work with injection moulding.

We'll see how long the fork holds up.

This is a USA made RobbMC Gen I mini-starter. Robb told me the forks were a problem on some of these Gen I starters. The Gen I starter is based on a GM PG260M starter so that's were the fork and bracket comes from. He's now selling the Gen II piece which hopefully has improved on this point.

 

Good info. Looks like someone did a little R&D with some six sigma? Nice to see the improvement. Your fabbed piece looks nice as well.