What have I done? Video attached: Bad sound after oil change on ol' Blue
 

Anybody recognize this sound from the linked video below? It's definitely metal hitting metal and I'm worried I'm headed for damage if I don't find it soon.

Today I gave the 1969 GMC 1500 (inline 6 250, 3 on the tree, no modifications) an oil change. I went to drive it after and once it had warmed up, I started hearing this loud, irregular TINK TINK noise from the front of the truck. The noise became more frequent as I continued to drive it back home. It is also more frequent with the truck in gear and getting gas.

Only other thing that happened to the car today was that I had taken it down the hill and turned it around and gunned it up the hill in reverse to get it in position for the oil change in my driveway. It's kind of a steep hill and to keep it from rolling down on my I admittedly clutched it at high RPM and it did "kangaroo" on me pretty hard on the way up. Enough that I gritted my teeth and thought, "oh that wasn't good for it." But I didn't notice anything wrong at the time as I pulled it in the drive for the oil change. I put in 5 qts 10-W-30 and a new oil filter.

Anyway, later, trying to figure out where the noise was coming from, I initially thought oh no, I must have messed up something in clutch or drive train with that hard gun uphill in reverse, but the sound is not coming from there. It's coming from the front end, from the fan area or maybe up to a foot behind it. I can't isolate it with the stethoscope, listening to the engine block, alternator, or radiator. Putting my hand on those areas, I also don't feel a vibration when the clang happens. The fan doesn't seem to be intermittently hitting anything. It's a TING/TINK/CLANG kind of sound. I put a link to video below.

I'm not sure how the hard reverse or the oil change itself would start this noise happening, but it's definitely from something that happened today. It's been driving fine to work and back for the last month since I got it running reliably and fixed all the electric stuff to get her street legal after buying it from the previous owner. I haven't done anything particularly invasive to the truck, just rebuilt carburetor, replaced I/O manifold gasket, steering wheel, and a lot of work on stuff like taillights , horn and heater. I did put some radiator stop leak in it a few days ago too.

Any ideas where I should look next for the cause of this? Worst case scenarios to check out first to prevent damage? I'd appreciate y'all's thoughts, I'm afraid to drive it like this and I want to find the issue fast without letting any additional damage happen from whatever is banging around in there.

Thanks!
-Will

Video link below:

https://youtu.be/K9P0g_WFMww

Re: What have I done? Video attached: Bad sound after oil change on ol' Blue
 

Sounds like something is hitting the fan blades. Sounds nuts but maybe it's leaking coolant and that's water hitting the blade????? Or is there a zip tie loose near the blades?

Re: What have I done? Video attached: Bad sound after oil change on ol' Blue
 

Sounds like the fan blade hitting that bent blade cover over the radiator.

Re: What have I done? Video attached: Bad sound after oil change on ol' Blue
 

That does sound like the fan intermittently hitting something. Can you grab the fan blades and wiggle them a little, after shutting the engine off, of course? Maybe your water pump bearing is going out, looks like there is a little drip of something on the crossmember under the fan.

Re: What have I done? Video attached: Bad sound after oil change on ol' Blue
 

That's definitely the fan hitting something. Call me crazy but perhaps letting the clutch fly ripped one of the motor mounts just enough that now the fan is pinging that "shroud" that gm graciously put on there. Take the belt off and spin the fan to pin down what it's hitting

Re: What have I done? Video attached: Bad sound after oil change on ol' Blue
 

sounds like the bearing in the pump is howling too, slip off the fan belt and see if the noise
leaves

Re: What have I done? Video attached: Bad sound after oil change on ol' Blue
 

Sounds like the fan

Re: What have I done? Video attached: Bad sound after oil change on ol' Blue
 

x2

Re: What have I done? Video attached: Bad sound after oil change on ol' Blue
 

Well, once again the collective wisdom of this board is spot on. Thanks everyone! It was the fan. I still couldn't see or feel the PING hit when the truck was running, but looking at the base of the radiator, there was a piece of metal placed under it to support it (the frame piece is rusted out underneath) and this looked like it had gotten chewed up a little bit. I took the fan off and sure enough, could see the bright spots at the end of the blades, where the fan was contacting that piece of metal.

Attachment 2342129

Attachment 2342128

All I actually had to do was smack that metal slab with a hammer to tap it back out of reach of the fan. And the TINK was gone! (Yeah I'm gonna have to bolt that thing down I guess.)

Those of you who mentioned that you hear the sound of the water pump bearing going bad, thanks for the tip! That low howling sound does indeed go away if I unhook the fan belt. I had noticed that sound before but had decided it was the sound of air intake through the cleaner! I inspected the weep hole, but it was completely crusted over with grease and S Alabama clay , so it didn't tell me much. But I'll order a replacement pump and get that replaced before it fails on me. Y'all's educated ears may have saved me a breakdown! (I have been getting most of my parts from Classic Industries. Does anyone have experience with their replacement water pump, or have a superior one to recommend?)

One final note that you guys will think is funny. Yesterday when I was scratching my head over the bad noise, I noticed that there was a little oil stain in my driveway that I hadn't noticed happen during the oil change. Now to my surprise, sitting right in the middle of it was this:

Attachment 2342130

That's the thimble from a Monopoly set. I just stared at it sitting there in the oil puddle thinking, how the heck did that get there (I don't own the board game), and what if that TINK TINK noise is the sound of MONOPOLY PIECES RATTLING AROUND IN MY ENGINE? :lol:

And then I spent a minute trying to decide if the noise sounded more like the dog or the top hat. :lol::lol::lol:

Thanks again, all, for weighing in. I'm glad my problem turned out to be super simple, borderline stupid actually. But I thought I'd ruled out fan contact because I couldn't see or feel it happening, but your consensus to the contrary was spot on and put me back on the right track.

-Will

Re: What have I done? Video attached: Bad sound after oil change on ol' Blue
 

I have ordered cosmetic, trim, plug and adapter parts from Classic Industries and like them, but when it comes to mechanical parts that make the truck stop and go I get them from the local car parts stores such as O'Reilly or Autozone and I get whatever they have with a lifetime warranty which is usually their store brand. I keep receipts in a folder, and make copies of receipts that are printed on thermal paper.

Re: What have I done? Video attached: Bad sound after oil change on ol' Blue
 

>> at the base of the radiator, there was a piece of metal placed under it to support it (the frame piece is rusted out underneath) and this looked like it had gotten chewed up a little bit.<<
>>All I actually had to do was smack that metal slab with a hammer to tap it back out of reach of the fan. And the TINK was gone! <<

Did you do something during that oil change that would have caused that cross member to be moved into the path of the fan?

>>turned it around and gunned it up the hill in reverse to get it in position for the oil change .... I admittedly clutched it at high RPM and it did "kangaroo" on me pretty hard on the way up.<<

You need to check the motor mounts.