DR911s

I have a 2017 C2S that I purchased CPO with 14k miles over 4 years ago, and it now has almost 36k miles. All oil changes were performed by the original selling dealership until April of this year when I did it myself, and only Mobil 1, 0W-40 European Formula has been used. I have occasionally observed the valve lifter ticking, and it has varied as to which engine bank, but has most frequently occurred on the right [passenger side] cylinder bank. When I took the car for its first annual service after I purchased it and drove it for a year and about 5k miles, the dealership service receipt listed a charge of about $60 for an oil flush in addition to the normal oil service charge and parts charges. After that service, the ticking has rarely occurred at startup, and only if the vehicle has sat for many days to many weeks, and quickly disappears upon driving the car. Most of the times, even after storing the car for weeks or even a couple of months during winter, there is zero lifter ticking upon startup.

Overall, I would not be concerned about this noise on that used 991.1 given that it went away after warming up the engine. As others have said, it's best to drive the car gently after cold startup rather than simply let it idle. Everything warms up faster if the vehicle is driven. German vehicle manufacturers have recommended driving the vehicle after cold start up for a very long time; those directions were specifically expressed in the owners' manual of the 1962 MB 220sb that my parents bought in 1962!

I also note that the hydraulic valve lifters of my 1993 BMW 325i and the 1995 M3 SB50 engine that I later had installed would occasionally make slight valve lifter/tappet noises upon startup... but in that car, they might also begin making slight tapping noises following a vigorous autocross run, likely due to some oil starvation, yet that engine was still running strong after more than 100k miles and many, many track days.

neanicu

The only flush I know is a wallet flush...very common flush. Doing a flush to an engine that has had regular oil changes is like taking a pregnancy preventive pill for a headache : it has zero effect but your headache might go away simply from the brain stimulation that you took something for that headache.

barncobob

i never understood engine flush, how is it done?

neanicu

There are different ones,some you add a chemical to your oil,some so called " professional " replace your entire oil completely and you run the engine at 2000 RPMs for 20-30 min,then you drain,replace that chemical with another chemical,replace the oil filter again,run the engine...and eventually you flush that out and finally fill up with oil and a new oil filter AGAIN.
I would never recommend doing this wallet flush : even on poorly maintained,heavily gunked up engines,especially if the engine was running ok before doing it. You are basically looking for trouble by moving the gunk from a place where it was " resting just fine " to a place where it might clog up vital oil passages,pressure ports for variable valve timing actuators etc. Not to mention that you are just asking for oil leaks by moving the dirt and gunk that was sealing the deteriorated oil seals.

B Russ

Back in the day those flush's involved the use of transmission fluid in the oil

neanicu

Transmission fluid is an excellent cleaner. Yeah they were using all kinds of crazy things,diesel,transmission fluid etc. Just change your oil in time gents and you'll be just fine. Remember,oil is cheap,engines are expensive. Or just buy electric,do a couple exciting launches until you get bored and then sell it!

DR911s

I recently used Liqui-Moly engine flush when doing an oil change on my 2013 Audi Allroad which has a 2L turbo, direct injection engine. This type of engine is known to produce carbon soot that is introduced into the motor oil, and some allegedly knowledgeable writers who post on the internet state that such carbon together with other combustion by-products can add up to "carbon varnish" on pistons that can adversely affect the functioning of the rings. That Allroad vehicle is driven mostly on short, urban trips, and currently has over 57k miles on it. The L-M flush comes in a ~half litre can and from its smell it appears to be kerosene based. L-M's instructions say to add it to a warmed engine and let it idle for 10 minutes before changing the oil, and that one can is to be used for every 3 to 5 L of motor oil. I used one can, and this was the first time I used it. But this Audi engine can be very well drained with each oil change, unlike our Porsches. Per L-M's data chart, for my 2017 C2S a complete dry fill of the engine oil system is over 11 liters!

Here's an email exchange I had with L-M's technical correspondent regarding use of their oil flush in my Porsche:
(I hasten to add that I have not used any engine flush on my Porsche.)

DR911s

So is brake fluid, but I certainly wouldn't use that! Obviously, transmission fluid is oil based and has lubricating properties for moving metal parts, not so with brake fluid which is formulated for working with elastomeric seals that are mounted on moveable metal parts. But brake fluid has been used by several engineers I know for cleaning disassembled automotive components and other items.

neanicu

Don't do it Dave,just my opinion... I'm sure others will chime in with their experience.
Just change your oil with quality synthetic oil 5K miles or 1 year whichever comes first and you'll be just fine.

B Russ

Ill tell you my 2.2L 5 cylinder Audi that I did it to had a knock after I did that process back in 1989

Charles Navarro

You hit the nail on the head. You don't want to use any flush product in a modern engine. Moves the gunk to places it shouldn't be.

B Russ

I guess its safe to say Dont mess with any oil flush process. Just do timely oil changes and live happily ever after.

DR911s

Excellent point!

Here's a copy of the Porsche Dealership Service Receipt from the time they charged me for an engine oil flush... They apparently "automatically" added it to their charges for the major [4 years or 40k miles] service. My car was then past 5 years in service. I'm the second owner; I purchased this car as a Porsche CPO vehicle with a little over 14k miles from the dealership that first sold it to the first owner. All service on this vehicle through this one were performed at that dealership. I do not recall complaining to them that I was hearing valve train noises upon cold startup. Usually my car doesn't make any noises upon cold startup even after sitting for weeks in a storage garage, and it almost always fires up instantly when the starter [key in dash] is turned.

I'm guessing that I should go back to the dealership and ask them specifically what they did, and what product they used, and why...

They haven't worked on my car since this April 2022 major service since I decided to try changing the oil myself and did so in spring of 2023. I also recently changed the OEM diverter valves via the "long route" as described in the Flat 6 Motorsports video that is online. The oil change is very easy comparatively.



BMW E36 US Specification M3 3L engine with over 100 k miles and much track time. Various brands full synthetic oils were used, mostly Castol and Mobil 1 at annual intervals at 5k to 8k miles with new OEM specifcation cartridge filter each time. Fuel used was 93 octane pump gasoline. Engine had Conforti ECU chip and upsized fuel injectors and upsized intake air filter and mass sensor, and OEM stock 1993 325i exhaust.




As you can see, everything remained quite clean!

Here's what Amsoil has to say about using their engine flush chemical: https://blog.amsoil.com/is-an-engine-flush-good-or-bad/

jan86

Hello, if 991.1 have lifters with valve stem there is possibility. But 991.2 have lifters with inner ball and piston mechanism. The lifter cylinder is always in touch with valve where is slapping happen is between cam and tappet housing of hydraulic adjuster until oil build up pressure to remove clearance by plunger which raise up tappet housing to cam and remove clearance. So if car sitting for 1-2 months or so the open valves will bleed out and also create this ticking noise until oil build up pressure inside, bigger issue can be if lifters doesn't bleed and lifter stuck hard it can happen with bad oil sludge.

Bud Taylor

They are hiding something and their bad experience was they got busted hiding something before.