I recently picked up a 2005 Grand Caravan with the 3.3L, it has 111,000km on it right now and was seldom driven by the old man before me (about 3000km/year for the last 4 years), but it had its oil changed every year and was up to date on all other maintenance items. After taking it home I started it in my garage the next morning and noticed it makes a bit of a clacking noise on a cold start (not a rapid ticking but more of an intermittent clacking) which I have now noticed is present all the time at idle, perhaps slightly louder when warm. The oil had last been changed in January 2011 at 107,000km and the van had 110,000km on it when I bought it so I figured it was at least partially from being overdue for an oil change so I used an engine flush product and switched the oil to a thicker oil (I believe it had 5W20 in it, I switched to 5W30 synthetic) to see if it would quiet the clatter (thinking it was lifters/rockers). After it had no impact on the sound I started doing some poking around. Using a stethescope I have checked the following:
Front valve cover - quiet
Rear valve cover - quiet
Water pump - quiet
Alternator - quiet
Transmission - quiet
Oil pan - You can FAINTLY hear the clatter through the oil pan, it does NOT sound like bottom end noise

Looking around on various forums I BELIEVE I am dealing with a rattling timing chain. I don't have a video of my van making the noise yet, but it is identical in sound and location to this one:
http://www.youtube.com/watch?v=Cwn2ni_JqSc

I was planning on checking the oil pressure to make sure I don't have a bad oil pump, but after that my next thought was to check the timing chain. However, I have some questions and I was hoping somebody here knows the answers:
What is considered normal for oil pressure? I have a mechanical gauge I can use to verify oil pressure at the sending unit location
When replacing the timing chain, is it also customary to replace the gears? What is the best source for the chain and if necessary, gears?

Any commonly forgotten parts that need to be replaced when I dive in to change the timing chain (assuming that's what the noise is)? I know the coolant transfer pipe on the bottom commonly rots out, and since my van has spent its whole life in Canada I suspect mine will be rather rotten, so I plan on replacing that and the O-ring that goes with it, which means I will also be replacing all of the coolant since it's pretty much due for that anyway. Anything else?

Thanks in advance!

 

Welcome to DF
First thing I would do is isolate the noise. Remove the fan belt and see if the noise is still there. If it is, then check the oil pressure. But sure it will be fine. I have seen problems with the number 4 or 6 rod bearing causing the same type of sound. But remember, that may not be what is wrong with your van.

 

The noise is present even with the serpentine belt removed. If it is a rod bearing would that show as low oil pressure? Or will I have to drop the pan and pull the big end caps to tell?

 

You may have to remove the pan and inspect the bearings one at a time.

 

Can I pull the caps and re-install them without replacing the bearings, or do I need to change the bearings if the caps are removed?

Also, do you have a good guide for any additional steps required for removing and replacing the rod caps? Are there special torquing procedures? Is it necessary to plasti-gauge the bearings?

Also, what is considered acceptable for oil pressure? I was hoping to test that first.

 

Well without any answer on acceptable oil pressure I decided to go ahead and test anyway. Here are the results.
Idle: 55psi
2000RPM: 60psi
3000RPM: 70psi

My old school training is that I should have 30+psi at idle with 10psi/1000RPM above that until you hit the bypass valve (usually around 70-75psi).

So what do you guys think, is my oil pressure okay?