300 sounds like a bucket of bolts at higher speed acceleration

[FrazerJames]

Got the Bronco out on the highway for the first time today and was pleasantly surprised by the handling. Barely any movement in the steering wheel! What did surprise me is the noise coming from the 300. I mean, I know it’s a loud engine, but this seemed out of the ordinary.

1. At idle and normal around town driving speeds it’s not too loud. It’s a tractor engine, but not ridiculous by any means… (Idle at 650 and smooth up to 2000 rpm)

2. Acceleration in city driving seems normal sound wise. Or at least doesn’t shock me. I can also cruise at 65 between 2300 and 2500 rpm and it sounds fairly normal. (It’s a 3.08 and a C6 transmission)

3. Try to accelerate when already driving above 55mph and it sounds like it’s going to rip apart. Lots of loud clanking. RPM never goes above 3000 and I’m not at WOT because it sounds terrible. Also, it’s extremely slow to get moving (as if passing) at those high speeds, but that part doesn’t surprise me.  

I suspect it could be any number of things - any thoughts on what I should chase first?

[kramttocs]

My first thought when just reading "bucket of bolts" + acceleration is pinging.

[FrazerJames]

Yeah, there’s not much to go on… I thought the higher speed might be an indicator on something in particular, but it’s a shot in the dark.


I’m just going to start with the basics… Timing, spark… And then I guess I’ll just go from there.

[kramttocs]

And it's definitely from the engine? Just noise and no vibration?

[FrazerJames]

No vibration, no. Just noisy as hell.

[ratdude747]

Check your flexplate nuts... I've heard of people not getting them tight and making all sorts of noise like that.

I'd also suggest the harmonic balancer but usually that's also an idle noise.

If it's pinging, better get it fixed. Such was likely what broke the 5 of the upper compression rings in my 300 and forced a rebuild and bore job.

[1986F150Six]

Ignition timing? If you can, check the timing with a timing light or vacuum gauge. If the fuel tank is almost empty, put in a few gallons of premium and see if the engine sounds better.

Is the vacuum line attached to the distributor advance cannister?

[FrazerJames]

Thanks all. I’ll update on what it ends up being. It’s probably a bad pulley.

[FrazerJames]

Ratdude, I think you may have nailed it. It a little quiet at idle, but I think I hear a rattle coming from the driveshaft pulley. Either that or the water pump.

Anybody think it’s a bad idea to remove the belts and start it up to for a minute to see which one? Although, I wonder how the sniper will react to no alternator power…

[Gary Lewis]

You'll be fine w/o the belts for a minute or two.  Take the front belt off and see if that kills the noise.  Then the back belt if you still have the noise.

[FrazerJames]

I don’t think I can remove the back one without moving the 2nd one. Basically If I take them all off the big thing I’m losing is alternator and water pump. Everything else is accessory right?

So running for 2 minutes will be ok on a cold start I’m gathering.

[Gary Lewis]

Yes, you can run for a couple of minutes on a cold start w/o the water pump. But keep it as brief as you can.

[FrazerJames]

Got to taking all the belts off today. The noise ended up being the water pump pulley. It’s kind of a dull thump when turned by hand. I suppose it’s new water pump time? Any other alternatives?

[Gary Lewis]

So it is actually the water pump itself?  I’d replace it as that surely means the bearing is failing.

[FrazerJames]

Yeah the whole pulley is sloppy. Ordering up a pump. Might as well do my Saginaw upgrade as well - I’ve got all the parts for it.

[Gary Lewis]

Yes, now is the time to make the swap.