I’ve got a 1997 Honda CRV. Recently when you start it up in the morning there is a terrible clatter coming from the engine. Yet, once the car warms up, the clatter totally subsides and the car runs and drives normally. Turn the car off and then start it again, the clatter comes back - but then in a minute or so the clatter is gone and all is well. I’ve checked the fan area and belts - nothing is caught in there. Seems like the sound is coming more from the engine. Can’t figure it out. By the way - did I mention that the car now has 338,000 miles on the odometer? Other than that, the car runs fine. Is it time to give up the ghost?
First, congratulations on getting over 300k miles out of this vehicle!
As to the source of the problem, the likely possibilities–as I see it–include:
Lubrication problems due to engine sludging (not unheard of, especially at over 300k miles)
Valves in need of adjustment (something that should really be done every 60k miles or so)
Piston slap (not very likely if the noise only began recently)
I’ll guess carbon buildup on top of the piston. It could be slamming into the top of the cylinder head until it heats up a little.
I’d try a de-carbonizing treatment.