2002 4.7 Engine Chatter at Start Up w/ Good Oil Pressure.

[Savatreatabvr]

Hello guys new member here, I hope you can help with my issue. Like the title says, when I do a cold start the engine clatters for a good 60 seconds then slowly goes away. When at operating temperature the oil pressure stays normal. The truck has 138k miles and runs great but I can shut it off for 15 minutes start it up and no clatter but if I shut it off for an hour or so it clatters again on start up.

I would think that would be the signs of a weak oil pump but I read that some 4.7s have a problem with oil passages in the top of the engine being blocked and not allowing oil to drip back down to the oil pan which means no oil to pump back up. So has anyone dealt with this situation before?

 

[ViolentMouse]

3.7/4.7 both suffer from timing chain tensioner failure. not sure what, or why, but the tensioner spring fails and allows slack in the chain during startup. This is a spring/hydraulic unit, so once you build oil pressure it goes away, and as long as oil stays in or near the tensioner it will not make noise, let it sit long enough for the oil to drain out and the internal spring does not maintain enough pressure to stop the chain from slapping.

My Jeep commander 3.7 suffered from this for almost 3 years. I replaced the tensioner when I did my heads after a blown head gasket, the problem was solved for over a year, then it started to happen again.

I pulled the timing components off and replaced them, and tore the tensioner down to inspect it and found the spring was broken. I never bothered to look into the original one.

I suspect if allowed to continue long enough it might cause damage, but I do have a customer with a 4.7 commander who has had the startup rattle for almost 10 years.

Not sure if there is an updated part number, been a long time since I personally experienced this issue, but it was not an oil problem, it was a tensioner problem.

 

[Savatreatabvr]

If the timing chain tensioner makes noise until it gets oil wouldn't that mean the oil pump is weak? The oil pump should start pumping immediately the second the engine start turning over. The analog oil pressure gauge on my dash takes about 2 seconds before the needle shoots up to the middle of the gauge and holds steady even at idle.

I'm sure replacing the timing chain tensioner is not a 2 hour job and with limited tools I don't think I can do it myself. After 40 years of working on my own vehicles this Dodge RAM may be the first vehicle I've had that goes to an actual mechanic shop.