My 98 ml320 with 134k starting to make a clack-clack-clack sound in the morning when engine is cold. Very noticeable. Not valve train noise. Usually, it goes away after 5 minutes of driving. The car drives fine other wise. Still has some oil sludging that collects on the engine cap and uses about a quart of oil every 3-4K miles. I look at the belt, it looks fine. The harmonic balancer was replaced at 60k miles.So far I can't trace this noise. Any thoughts. Thanks.

John

You say it's not valve train noise. But couldn't it be a hydraulic lifter making that noise because it does not get enough oil pressure initially?

I am assuming that hydraulic lifter and valve noise are like click-click sounds. I am used to it on my early 911 Porsche(however, the lifters are not hydraulic). This is definite louder, one can hear it across a room. Yes, the oil was low at that time. Wife reports that she didn't hear it this morning after oil was added the day prior. I will continue to monitor. Car is due for an oil change. Will do it this weekend.

John

The Porsche 993's have hydraulic lifters and while I've not had any problems with my lifters, I've had friends who have. The described the noise as a tapping sound. And sometimes on start up there is no tapping sound. In some cases the lifter is sticking sometimes but not always so the sound is not present. I've been told that is the sign of a failing lifter; at least in a 993.

As above.

Thanks,

John

My understanding and I’m not an expert is that at least with Porsches that have , hydraulic lifters, the majority of the hydraulic lifter failures are due to infrequent oil changes and excessive running temperatures. The loud ticking occurs on start up, because the hydraulic lifters cannot build pressure and pump up. The noise that you are hearing in this situation is from the increase in clearance in the lifter causing greater lash.

In other words it's like the valves are out of adjustment because the lifters don't let them open and close the valves as they should. That's how it has been explained to me. It would be nice it a real expert could explain this.

Is your harmonic balancer failing and starting to rub against the timing chain cover?
I had a new balancer that had to be replaced AGAIN less than 15,000 later.

__________________
Jim

Same noise was made by my 98 ML320 b/c the harmonic balancer started causing other problems (timing chain cover). Also, check your serpentine belt tensioner which failed on mine.

Chris Warner, Lt, USAF
AC-130 Pilot