My truck started making a noise when I left work today. It sounds like a baseball card in bicycle spokes. It makes this noise while idling as well as driving. The "clicking" intensifies with the throttles and then when the engine reaches higher RPMs it crescendos into a short of "rattlesnake" like sound. I pulled over and looked, nothing in the fan, belts look fine, it sounds like it's coming from the top of the motor in the back towards the cab.

Any ideas?

 

Sounds like that Ford timing chain issue, the guides wear out and the noise comes from the lose chain.
I can never remember what years were affected though, but Ron and others will know.

 

+1 ^^^

Google: 4.0l SOHC timing chain rattle

2001 Rangers and up had the 4.0l SOHC engines, to 2004/5 they had older designed Tensioners that would fail.
This would cause timing chain to hit against the chain guides(cassettes), these would eventually start to break apart and you would start to hear the "rattle".
So the rattle is the end phase of the problem, not the start.
You can try installing new tensioners, you need them in any case, and it may allow you to get a few more miles on it before having to repair it, but may not.

You have to pull out the engine to fix/change rear timing chain.

One thing you can try just to make sure it isn't a belt/accessory issue
When engine is cold loosen and remove fan belt from Crank pulley
Start engine
Battery light will stay on because alternator is not turning.
Listen for the rattle noise
If you still hear it then it is timing chain noise

Don't run engine more than 2 minutes this way, water pump is also not turning

 

Thanks for the response. So I could fix the tensioners but will have to replace the chain anyway, so if I have the money I should just replace the chain?

 

If it is a timing chain that is rattling, then yes you will eventually have to replace the chains, there are 3 chains on 2WD Rangers and 4 on 4x4 Ranger(counter-balancer shaft inside engine).
Changing the rear chain requires pulling out the engine, and the rear one is the one that usually rattles/fails first

 

The mechanic says it is indeed the tensioners. I asked if I should then need to replace the chains and he said no. How should I answer this? If they fix the tensioners would the chain then break spontaneously down the line?

 

It's such a big job that it doesn't make sense not to replace the chains and sprockets.
Chains do "wear", they become longer as each link union wears, this causes the chain to grow in length.
When this happens, the chains don't fit on the sprockets correctly any more which can be noisy too.
Not as much noise as worn guides, but some.
The sprockets do wear with the chain, but the chain always wears more then the sprockets, that's why when you're in there, it's a good idea to replace everything.

 

On my truck the tensioners can be replaced without removing the engine.

 

In that case, see how it goes with just replacing the tensioners.

 

If I just replace the tensioners, would there be some noise indication in the future that the chain needs replacing or would it just spontaneously fail?

 

That's hard to say, but in all my years, working on engines with timing chains, I've never had one fail before.
It would have to get quite noisy to hear it over the regular engine noise.
I'm sure Ron would know more then I do.