16V - Mystery Ticking\Tapping from Valve Cover

doabarrelroll · 09-01-2009, 08:31 PM

Like many of you have described in the past, my 87' 944S has the ticking/tapping sound coming from the valve cover. I took off the valve cover today and nothing seems to be abnormal. I'm running 15W-50 Mobil 1 and recently did a complete service on the car. In addition, I re tightened the exhaust flanges to 15 ft/lbs as it says in the manual. The head was rebuild at about 85k (107k now) after a timing belt failure. All exhaust valves were bent, yet, the cylinders turned out to be fine.

When I first fire it up in the morning, the sound is not present. After 10-15 minutes of driving, the sound begins. The sound is only audible at idle when near other cars or buildings. It increases in frequency when I begin to accelerate and then masked by engine noise at that point. I've read through the various posts regarding this issue and still seem to find no definitive answers.

Anyone reach any sort of conclusion on this issue or made any headway?

JD159 · 09-01-2009, 09:31 PM

ya...i know what your saying...i've got the same problem...i read somewhere once a worn or broken valve seat?...but am not quite sure what thats referring to...

thill944 · thill944's Garage

When you had the cover off did you check your timing chain slides. They are located on your hydraulic chain tensioner. They deteriorate over time. You can replace them. If one is bad it could cause a little slap of the chain. I doubt this is your problem but if you pull the cover again be sure to check these.

doabarrelroll · 09-03-2009, 09:40 PM

I made a quick video tonight of the sound itself. Maybe this will shed some light on this mystery issue.

http://www.youtube.com/watch?v=tFdXAUTDLio

rb101 · 09-04-2009, 04:03 AM

I would
1. Check the timing belt. When I got the 996, the 944 sat only being run once or twice a month for about 9 months. As I started teaching my daughter started to drive it, I noticed a tapping. I checked the belt and it was missing a few teeth. The belt had about 30K on it, I thing the sitting did the damage.
2. Check the chain in the head and the tensioner pads.

Hard to tell in the video, but it does sound like the noise is up top. Injector....

bazar01 · bazar01's Garage

It sounds the same as my hydraulic lash adjuster when it was still getting pumped up with oil after the head gasket replacement and head refresh. But after 10 minutes the tapping was gone.

You probably have one hydraulic lash adjuster that is collapsing. Have you tried mixing some ATF with engine oil?

You may also need to check to make sure the ignition rotor is not hitting the post inside the cap.

mallard ducks · 09-04-2009, 05:53 AM

I had the EXACT same noise a while ago... my guess is lifters because after running ATF before oil changes a couple of times it went away

HondaDustR · 09-04-2009, 07:37 AM

Try Seafoam added to the oil. It does the same as ATF, but is alot stronger. Don't run it too long without changing the oil (no more than ~30 miles I think), since it thins the oil out. Would be good to do right before an oil change.

rickharrison · 09-04-2009, 10:28 AM

Maybe the timing belt/balance belt are hitting the cover?

+1 on ATF or Seafoam...clean her out, then add new oil.

I use 20W50 (no winter driving for me).

rickharrison · 09-04-2009, 10:29 AM

...oh. It should idle @ 850-950 area...not 1300 rpm.

doabarrelroll · 09-04-2009, 10:54 AM

The noise is much more pronounced after the car has been running. Here is how it sounds after about 30 min.

doabarrelroll · 09-04-2009, 10:54 AM

http://www.youtube.com/watch?v=EXgRe0YNB80

rb101 · 09-05-2009, 05:54 PM

From the second video, it seems much louder on the exhaust side, correct?