OHV 4.0 Chain Rattle?

[Runnin'OnEmpty]

Hi all. The Sport has a 4.0 OHV with 156K miles. Lately it's had an off-and-on rattle when it's
warm and at low rpm. Also a slight miss or hesitation upon acceleration. It's quiet as a mouse
when it's cold and before the engine oil warms up. The noise is definitely coming from the
front of the engine, behind the radiator, and only at near idle speeds. It will rattle when in gear,
and when shifted into neutral the rattle goes away. (When engine rpm slightly increases.)

My thoughts are that the chain tensioner or guide has broken and allowed slack in the chain
causing the rattle, particularly when the oil is hot and thinner. This might be throwing the cam
timing off and also causing the miss? There are no pending or current codes, and this missing
and noise started at the same time.

I'm familiar with the SOHC tensioner problems, but this is an OHV engine.

Anyone have ideas on this before I start taking it apart? Thanks.

 

[koda2000]

The OHV engine does not have a timing chain tensioner or guide. I'd be thinking more water pump bearing or a serpentine tensioner/idler pulley bearing. With the engine hot, remove the serpentine belt and see if the noise goes away.

Edit:
According to the video provided below, I stand corrected regarding the OHV timing chain tentioner/guide. I've never seen these components of an OHV V6/V8 engine, but I'm still going to stay with my original comments on the origin of the noise.

 

[donalds]

 

[Runnin'OnEmpty]

Thanks for the replies, guys. I'll be removing the belt tensioner in the process, so I'll check it very
carefully. Might get lucky.

I've read a lot about the "marbles in a can" noise these engines make, and most posters say to
ignore it, it's harmless, but mine has suddenly gotten worse. I'm afraid to drive it now and getting
stranded, so it's time to have a look at the chain...

 

[donalds]

Thanks for the replies, guys. I'll be removing the belt tensioner in the process, so I'll check it very
carefully. Might get lucky.

I've read a lot about the "marbles in a can" noise these engines make, and most posters say to
ignore it, it's harmless, but mine has suddenly gotten worse. I'm afraid to drive it now and getting
stranded, so it's time to have a look at the chain...

cool let us know how it works out please thanks.

 

[Runnin'OnEmpty]

Finally got the timing chain and gears out today, and nothing was loose or broken. The area looked clean with
no sludge buildup; just a light coating of varnish in some places. The tensioner had only slight wear and the
oil hole was clear. I suspect the cause of the rattle was varnish buildup on the end of the tensioner plunger,
causing it to stick in it's bore and allowing the chain to slap against the tensioner arm under low rpm conditions.

I'm installing a Sealed Power chain kit (made in Japan), and I noticed the kit tensioner spring was considerably
weaker than the original. Maybe the high spring tension was a problem? I've read that lots of low mileage OHV
engines had this rattle, so it could have been a design defect. I believe Ford had a TSB out at one time stating
this noise was 'normal' and there was no fix for it. "Normal'...yeah right.

The new chain kit is going in, along with a new harmonic balancer, water pump, belt tensioner, CPS, radiator
hoses and heater return hose. Basically anything that could fail in the near future. I'll report back when it's
running again.

Thanks for the replies.

 

[donalds]

Finally got the timing chain and gears out today, and nothing was loose or broken. The area looked clean with
no sludge buildup; just a light coating of varnish in some places. The tensioner had only slight wear and the
oil hole was clear. I suspect the cause of the rattle was varnish buildup on the end of the tensioner plunger,
causing it to stick in it's bore and allowing the chain to slap against the tensioner arm under low rpm conditions.

I'm installing a Sealed Power chain kit (made in Japan), and I noticed the kit tensioner spring was considerably
weaker than the original. Maybe the high spring tension was a problem? I've read that lots of low mileage OHV
engines had this rattle, so it could have been a design defect. I believe Ford had a TSB out at one time stating
this noise was 'normal' and there was no fix for it. "Normal'...yeah right.

The new chain kit is going in, along with a new harmonic balancer, water pump, belt tensioner, CPS, radiator
hoses and heater return hose. Basically anything that could fail in the near future. I'll report back when it's
running again.

Thanks for the replies.

thanks for the update

 

[Runnin'OnEmpty]

OK it's running again. Took it for a short test drive last week and the engine is very quiet. No more
chain rattle. Due to a radiator hose leak, the test drive was only about 3 miles, but the engine got up
to operating temperature and it sounds good so far.

Upon closer inspection of the old parts, I noticed two grooves worn into the chain tensioner by the
outer sides of the chain links. This might have caused the chain rattle, no way to know, but that was
all I found that had any wear. As I mentioned, the new tensioner had a much weaker spring installed,
so the new setup shouldn't wear nearly as much as the original. After 156K miles I can't complain too
much, but man that was a lot of work just to replace a small part...

 

[donalds]

yea its a *****