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Bob Jones’ 2002 Porsche 911/996 Engine Tapping Issue


I know this is sort of a repeat of my previous thread but the following includes some updates and additional information that may help ferret out some suggestions or solutions.


January  21, 2017 bought car with 48,484 miles on odometer.


February 16, 2017, with 49,595 miles, had new IMS bearing and Direct Oil Feed Line installed.


About mid April, with 52,665 miles and warmer weather, noticed significant tapping noise at idle of 850 RPMs on cold start up


Sometimes on cold start the RPM’s are 1100 and there is no tapping, but when it warms a bit and the RPM’s drop to 850 the tapping begins.


Tapping noise stops if RPM’s are raised to 1K; or, car is driven about 3 miles; or 180 degree operating temperature is reached.


I can't really tell exactly where the tapping noise is coming from but to me, based on my experience, the noise sounds like a lifter that has bled down during the cool down period.


So on July 7, 2017 the 0 W 40, Mobile 1 oil was replaced with 5 W 50, Mobile 1 Oil, and the tapping appears to be not quite as loud.  The engine overall appears quieter.


Another thought is it might be a bad bearing in one of the belt driven accessories, ie.  alternator,  A/C compressor, etc.


Suggestions???    Maybe go to 15 W 50 Oil???  Something else ???


Thanks in advance.



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A sound/video clip will help a lot in this case. Usually tapping is not from a lifter but rather from bore scoring. To eliminate the pulleys, you can remove the serpentine belt and hand spin each pulley and feel for any grittiness and noise. If it's bore scoring, a thicker oil can only mask the symptoms.

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Thx for your suggestion.


Given you are a forum moderator I assume you must have a bit of knowledge and exposure to this specific issue and if so I have a couple of questions.


So, if your bet is correct, that removing the DOF line and plugging the source on the right cylinder head stops the tapping noise:


Why would it take 2 months and 3,000 miles from the time the DOF was installed to the time the noise started?


Is your suggestion that something in the engine is not getting enough oil due to the DOF pulling off oil pressure?


If so, what specifically are you suggesting is tapping to make the noise?


If you are correct what is the down side to avoiding cold 850 RPM idling as much as possible and otherwise ignoring the noise?


In speaking with the DOF installer, he said these noises come and go; change to a heavier oil; and don’t worry about it.  He has installed 20 or more of these DOF’s and comes highly recommended by those I respect.


FYI, the DOF manufacturer’s test suggests less than 2 psi of oil pressure drop and the change to 5 W 50 caused a PSI increase in oil pressure of twice that at idle and normal operating pressure.


Thanks in advance.

Bob Jones


Edited by Bob Jones
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  • Moderators

My shop, and others, have encountered noise and VarioCam problems on cars equipped with the DOF, which went away when the oil line off the cylinder head was disconnected and plugged.  The exact reason this happens to some installations and not others is not clear, but  as oil circulation in these cylinder heads is already a known issue (usually the result of either "varnish" build up or debris in the rather small oil passages found in the heads and particularly in the cam followers or lifters) low oil flow is suspected.  So while you may have decent pressure as measured at the oil sender, the actual flow rates inside the cylinder heads may not be adequate, resulting in noise and/or insufficient oil to operate the VarioCam components correctly.

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If that's the true cause, that means the oil pressure is lower than designed (which makes some metal parts tap). You question will be the same as asking what would happen if I keep driving the car if it's oil pressure is too low.

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Duncan is correct.  When you hear cam follower/lifters tapping, you have excessive metal to metal bounce contact because the lifter hydraulic system is not keeping them in contact with the cam lobes.  Over time, that will lead to both lifter "mushrooming" and wear on the cam lobes themselves, which are only soft cast iron.  Valve train noise is not your friend.

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" Why would it take 2 months and 3,000 miles from the time the DOF was installed to the time the noise started? "

Speculatively :

1. It took that long for the reduced oil pressure/volume (DOF) to cause sufficient valve train wear to then cause ticking ?

2. It took that long for the fresh oil to be sheared to the point where it was much too thin- which is why the noise decreased when you put fresh oil in ?

3. Some debris was dislodged and found it's way to the 'dead end' some tappets inside the buckets ?

4. The bores in the lifter cradle are worn = 996.104.105.53 84,824  ?

The easy tests are to plug the DOF as suggested .Then fill with the best oil for the M96(separate Thread). Those 2 issues will eliminate the obvious/simple.

Recently lifters have become much cheaper.The labor not so much ....

Theoretically, the Lifter Carrier/cradle can be bored and sleeved .Check these bores if/when you replace lifters.Replace  all the Lifters on whichever side is ticking because they are cheap enough now.They have been upgraded also.

Edited by Schnell Gelb
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  • 3 weeks later...

Many thanks to you all for your input.  I appreciate it.


I went through the suggested exercises without any positive results.


Afterwards, I did, however, change the oil again to Mobile 1, 15 W 50, (including a new OEM oil filter) which the 2002 Owner's Manual calls for over 50 degrees, and the issue is resolved.


Thanks again.



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3 quick and modest points:

1.  try Red Line 10-40.

2.  this thread seems to argue against installing the DOF to the IMS.  I'll be facing this issue in approx 25k miles when I plan on a new LNE bearing.

3.  Carefully listen to the cats.  I had a clicking sound similar to what you describe that was driving me crazy, and my inde heard it in the left cat.  Replaced.  Solved.

Good luck...



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  • 2 months later...



Turns out my declaration that the change to 15 W 50 oil resolved my taping noise issue was premature. 


The heavier weight oil sure quietened down various other cold engine noises but not the one I was concerned about. (Long story)


Sorry if I misled anyone.


After more research and input gathering, I opted for the idea that the noise might be coming from one or more noisey fuel injectors.


Having used Chevron Techron in a previously owned 1986 944, I put one bottle in the tank of our noisy 911 and after about 350 miles the noise was reduced to about half the volume.


Given the instructions on the Techron bottle noted that more than one application might be necessary, I put another bottle of Techron in the tank and after another 200 or so miles the noise was gone, and I have driven the car another 400 miles and it has still not come back.


Solved???   Hope so!  May need to add a bottle every 3K miles as per the instructions on the bottle.


Re. the DOF modification, I would do it again.  I know several who have, and shops that have installed it, and no one has mentioned any issues with it.





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An Engine Ear would have conclusive diagnosed the Injector vs Lifter noise.

The solenoid inside a lifter  always  has some ticking - it is just the design of it. The Lifters on the other hand ....

Speculation = It is almost as unlikely that  a different weight oil will "fix" a noisy M96 Lifter as Techron will fix a noisy injector solenoid.

The solution to both problems is usually replacement.

Glad to read your situation was the exception because Lifter replacement with the engine in the car is challenging even with practice .

Injector change is fiddly and awkward but much easier and faster than Lifter replacement. There are no obvious upgrades to our old lifters but several part number revisions. Injectors  have been upgraded. Check the new 15 ohm version from Bosch .I am trying them now.

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