I recently changed the oil in my 99 996 c2. I also changed mufflers from 3.4l stock to 3.6l stock. I now have a rpm related engine tapping sound. It is constant, faster with increased rpm's. Seems to be coming more from the passenger side of the engine. I read that if not enough oil is added after an oil change that you may here valve tapping. I have checked a million times and I sufficient oil. I have a 914, my 996 now sounds similar to the 914 (at least the valves). The car runs great. Other than the mufflers, everything is stock. Has about 55k miles. No known problems other than a minor RMS leak.

Anybody familiar with this issue? I do not know if it is normal and I had never noticed it before or if it is related to the oil or muffler change?

Thanks again for your help

 

I bet its the muffler. The baffles inside mught have came loose making a rattling sound. Oil related tapping sound are usually always present and not just because of an oil change unless something went wrong with the change that blocked an oil circuit which is unlikely.

 

I've noticed that it will be there sometimes and not others. Sometimes it is louder than others. I have good oil pressure. If I clogged the oil system somehow, shouldn't I have a decrease in pressure?

The sound really sounds like valve tapping however it is not characteristic. I actually changed the mufflers because of a broken baffle in my old ones. This sound is different- more of a tapping than a rattle. Is it possible that an exhaust leak could cause a tapping sound?

Thanks

 

An arching ignition coil can also produce a tapping sound.

 

Got any good ways to diagnose an arching coil other than just looking at it. I looked and I saw no eveidence of arching.

Thanks for all of your help!!!

 

The flat six is harder since you can't look directly at the coils from above. If it was arching badly, you may see it in the dark. On a lift, you can remove the heat shields and look and often, spraying a bad coil with water will change the sound.

Make sure you are not simply hearing the egr valve located inline to the throttlebody right above the alternator. To eliminate this as the source of the noise, simply disconnect the electrical to the valve while engine is running.


Valve noise will also decrease when the viscosity of oil is increased.

 

I think that you may have solved the problem. I did change the viscosity from 0w-30 to 10w-40. The sound doesn't really bother me- it reminds me of the air-cooled porsches.

Thanks,
Steve

 

-Also, A good way to take a look at the coil is with a flexible borescope. It is somewhat hard to see details but it is fun to use.

 

Could be a small exhaust leak

Check clamps on the cat

Realign and retighten the exhaust tips

Only thing that changed was the oil and exhaust

 

Yes, only thing that changed was the oil and exhaust. I believe that I may have a slight leak from the cat clamp. Also, for some reason, I had an unusually difficult time aligning the tips. Does anybody have any hints for tip alignment, it is such a pain.

 

No tip, It's a pain in the A**

I tighten it enough so that it's tight but still can move with a little force. Worked for me