I have an odd rattling sound that comes from the engine when it is cold. It sounds like a loose baffle on the exhaust but it is not. The car has 236,000 miles. I am not sure if the tensioner was replaced at the last timing belt.

The noise diminishes as the car warms up and it is never to be heard again until the next cold start. I got out the stethoscope and went poking around. The place that makes the most noise seems to be the upper tensioner bearing for the power belt. The alternator, power steering unit, compressor seem to be in good shape.
Has anyone run into the problem or have a place for me to go look?

 

This morning I started the car and went listening with the stethoscope. The upper tensioner bearing is noisy...not bad but not great. It didn't seem to be the noise source. I removed the plastic engine cover and sent probing some more. Comparing the front bank to the back bank, the noise was in the back. Then I compared one cylinder to another with the source seeming to come from the middle cylinder. I could hear the ticking noise come and go as the engine warmed up.

My guess is a loose valve that rattles when cold and then as the engine warms up, the lash clearance changes making the noise go away.

It has been 4 years and 30,000 + miles since I last adjusted the lash. Time to get in there and check them all once again. Not a big project just a pain to get the feeler gauges in those tiny spots.

 

I give you credit for persistence. I have a buzz sometimes in the first mile after a cold start. It's similar to what I've heard on other cars when a weld holding the catalytic converter heat shield breaks and the metal is in only intermittent contact, except this one comes from the engine compartment rather than under the car. But it goes away so quickly and occurs so irregularly that it defies search.

 

Tony thank you for your post. I am not 1005 sure I have found the rattle, but when you go listen with a stethoscope you know what is good and what is bad. Today I think I will go dig around the backside of the engine some more and verify if what I have head is the source. You said about the heat shield, and there is one on the backside of the engine I believe and it is worth looking into.
For sure the tensioner is going to get replaced and it can't hurt to check the valves, for just the cost of a set of gaskets/seals.

 

I owe the readers an update on the RL noise. After poking around with the stethoscope and isolating the noise to the rear head, I ordered a gasket set. I tore down the engine to get to the valves. What was the first tip-off was the rear center ignition coll came out with oil on it. Bad plug seal. I removed the spark plug and it was soaked in oil, and I was amazed it even ran. The plug looked perfect on the tip. I cleaned up the hole and reinstalled the plug.

Next was to get the valve covers off. The front one was easy enough, but getting the rear cover out with that wiring harness over the top of it is one major pain
Grabbing the .008 & .012 feeler gauges I started to adjust the valves. Yep, the rear head center exhaust had on that was really loose. That must have been the onewith the ticking noise. One set of exhaust on the front head had a loose set of valve adjusters.

Once I got all the valves adjusted, I put it all back together, started the car and the noise is gone. Nice to have my car back to normal.

Does anyone have a tip to get that rear cover off and back on with that wiring harness in the way? I slipped my cover in from the drivers side while lifting the harness.

If the cover gasket keeps falling out, I used some trim cement to hold it in place. Works like a charm. I also used some anti-seize on the bolts. Some of them were really tight to get off.

 

Fabulous! I wish I had useful advice for you about the rear cover, although I don't. I just came on to say great work! and thanks for the informative post.

Lately, just for the hell of it, I've been poking around on sites like cars dotcom and autotrader with the usual thought exercise: If my car quit or got totaled, what would I want? To my own surprise, I'm finding there's very little out there at any price that, for my personal priorities, compares favorably to my RL. The refined road manners, quiet ride, tune-in ride-handling compromise with the combo of stiffened springs and forgiving shocks, the smooth J-Series V6 power, the wonder of SH-AWD, expensive-feeling yet intuitive controls, terrific driving position, the looks inside that I continue to love, the modest maintenance requirements and reasonable cost of ownership. Glad yours is back in tune and you can resume enjoying the many things this car does so remarkably well.