Macster

The plus side of hydraulic lifters is there is no need for periodic adjustment. The downside of hydraulic lifters is they can be noisy at times.

At cold engine start is one of those times.

In the case of your car the 10 or 15 minutes of tapping is a bit excessive. But this can be explained by a lifter is left under pressure when the engine is stopped because the intake valves are open. Over time the oil is squeezed out of the lifters.

If the engine sits a long time before its next start this gives more time for oil to drain out of the oil passages/galleys.

Upon engine start the engine fires and the DME as is normal brings engine RPMs up to over 1K for the normal fast cold idle.

Concurrently as the engine turns from the starter the collapsed and bled down lifters begin to move and as the oil from the pump rushes to fill all the oil passages pushes air ahead of it. The lifters instead of getting a dose of oil get air instead.

Because of the way the lifters are intended to work the air is sort of trapped. But because air is compressible the lifter is noisy and will remain noisy until the air is replaced by oil. This can take some time and is helped by the engine and oil getting warm up to temperature.

If you leave the car unused for days be prepared to hear the noise.

What you can do to minimize the likelihood the noise will be present, besides using the car more often, is run an appropriate viscosity oil for where you live/drive. 0W-40 is a pretty good oil. The "0W" is the low temperature viscosity index and the oil flows better than say "5W" oil at the same temperature.

Do not overfill the engine with oil but keep the oil level topped up. The reason is this increases the amount of oil in the engine and lessens the possibility the oil ingested by the oil pump pick up wil have any air in it.

These engines really thrash the oil and the oil gets quite aerated. There are defoaming pots to help remove the air from the oil but these pots do not work at 100%. So the oil with some air in it runs onto the oil already in the oil sump so by the time the oil gets down to the where it can be ingested by the pump it has lost its air content. Provided the oil level is not too low.

Do not run the oil too long. As the engine runs the oil gets contaminated with combustion byproducts, among these water. Water in the oil tends to thin the oil and contribute to foaming (and the generation of oil vapor). This increases the risk of aerated oil being ingested by the oil pump.

The bearings (main/rod) are (surprisingly) somewhat immune to small amounts of air in the oil. The hydraulic valves less so. In some cases of engine (good 'ol 'Merican V8s) dyno testing it has been observed that at near red line engine output falls off. This output fall off was traced to severely aerated oil that in being supplied to the hydraulic lifters caused them to partially collapse (air being compressible) and affect valve lift and timing at high RPMs.

In the case of your 991 engine if aerated oil is supplied to the engine you probably won't notice any drop off in performance. But what this does is it puts oil with some air in it in the lifters. If the engine is shut off before this oil can be replaced with oil with no air in it this can lead to noisy lifters at the next cold engine start.

Last but not least the Porsche techs tell me they recommend Swepco 502 oil improver for engines that are not used frequently, sit for long periods of time between uses. This oil additive (it contains 200ppm molybdenum (I had a bottle analyzed)) which acts as a lubricant and is claimed to help reduce lifter noise and especially at start up.

I have tried this stuff in both my Boxster and Turbo engines. (BTW, it takes *2* bottles of Swepco given the Porsche engines hold approx. 9 quarts of oil.)

With 2 bottles of Swepco in the engine oil I believe both engines are a bit quieter on startup but the difference is not earthshattering. However, I use both of my cars often, with neither car sitting more than a day or two between use and cold startup noise what there is is not very much and is rather subdued.

But try some Swepco and see if helps in your case.

kayjh

From a professional Porsche Shop mechanic in an article in Excellence Magazine:

"The 1995-1998 993-gen 911 and all water-cooled Porsches (except the early 924) use hydraulic valve lifters, which rely on a cushion of oil to maintain proper valve clearance. When hydraulic valve lifters “bleed down” or lose oil pressure, the excessive clearance will cause a tapping noise similar to that of loose solid lifters. Several seconds of lifter noise immediately after cold startup may be considered normal in the case of a Porsche that sits idle for long periods of time, but if the lifter noise becomes more and more frequent or does not cease after the engine oil warms up, replacement may be necessary. Collapsed hydraulic timing chain tensioners can also cause rattling on startup, which should be addressed immediately!"

I wonder what your service advisor would say in response to this mechanics (above) opinion? The opinion above seems to say few seconds is normal, but your car seems to go on for quite a while.

I think I'd have another chat with your dealer. It sounds like metal on metal noise without the cushion of oil. That can't be good for the engine long term (in my opinion).

GTSMeister

An excellent review on lifters and oil delivery.

--bob "trying to get my post count up!"

justabout

I agree this should not be present in any new car. They should fix it or provide a lifetime warranty on the lifters and camshaft. GM provided such a warrantee because of manufacturing issues but it took lawyers to make that happen. It's also kind of embarrassing on a high dollar car.

justabout

i wonder if synthetic leaks down faster than conventional oil. I have had cars that leaked synthetic but stopped when switching to conventional oils.

LexVan

I would NEVER recommend adding an oil additive to a Porsche. Especially one under warranty. I'd bet if you asked 100 Porsche certified mechanics, "should I use an oil additive" that 99 of them would say "NO!".

LC991.2

Excellent information, thank you. Will definitely get UOA done on next service.
So it seems "normal" (should not be) to hear tapping on these engines if left sitting for a period of time. I guess the question is what is acceptable frequency between starts and the duration of tapping before it stops.
Also, if there will be long term damage if left unrepaired.

Pags993

+1, 14 years working for a global major oil brand, don't do it!

LC991.2

I would not risk voiding warranty by using additives.

Would Porsche allow you to use heavier oil like 10W-50 without voiding the warranty?
Would it help to slow the oil drainage from the lifter?

LexVan

10W50 is not a Porsche A40 approved viscosity for the 9A1 motors. But Mobil 5W50 is.

seattle_sun

Since I got the 911, my wife has started driving the C63 AMG. After a couple of months of driving, she started noticing the ticking noise on startup. Took it to the dealer and they thought that the lifters had failed. However, the noise is very common in the AMG and there is a protocol that they follow before repair. Basically it's running the car at high revs. The service manager told me that this is to "reset" the lifters. Basically it happens because the engine isn't being driven hard enough. My wife drives in auto and basically it's shifting around 2500 and she does a lot of short drives. The service manager states that this can make the lifters stick.

I don't know enough about engines to wether this is true or not. Can someone with more knowledge confirm this? BTW, the ticking did go away.

AlBinVA

One easy, cheap and fun test is to drive it more often and see if it persists.

fast1

I disagree. I'd say 100 and not 99 would recommend not adding oil additives, assuming of course that they didn't have a vested interest in one of these products.

fast1

I agree. If nothing else I would recommend that this concern be documented, so that there will be a record of it in Porsche's database. So the car should be taken to a dealership and have it checked out. Porsche is much more likely to grant goodwill for a repair when the concern was documented during the warranty period.

Noah Fect

There's something to be said for this. I've occasionally heard (light) ticking from my 3.4L engine, and it's always, without exception, gone away after an Italian tuneup. I've always assumed the ticking was the high-pressure DFI system, though, not lifters. It's never been loud enough to be a concern.

If my car were making as much racket as some of the videos we've seen, my strategy would be to let it warm up thoroughly and then thrash the hell out of it. The idea would be to either fix the problem or force a catastrophic failure that the dealer can't answer with the usual "They all do that" BS.