Startup Rattle on a 99 911 manual

Has anyone cured startup rattle on early M96? Owned the car for 8mo and I have replaced the key switch, starter, three external chain tensioners, oil pressure relief spring and piston, running 5w-50. Opened up the cam covers and changed actuator pads on both banks, retimed motor to dial in cam deviation to 0.0 and -1.0. Timing had jumped a tooth Bank 2 was -21deg, bank 1 -3.0deg (it still ran perfectly fine). Cause unknown. Motor runs very strong and no faults. 1st Cold start sounds like the starter was held too long for 1-2 sec. Subsequent starts are normal, but it may do it again on the same day if left to sit for a few hours. Severity of the rattle is not consistent. Sometimes barely noticeable, other times distinct grinding sound. Trying to avoid $3k for new variocam actuators on a guess. Durametric activation causes engine to stumble at idle for each bank, so they are working, but maybe lazy to pump up right away? Chain guide material was found in sump before all the work was done (by me) and the cam pads were definitely worn but nothing crazy. Oil pressure is excellent and comes up right away to 5 bar on cold start, 1.2 bar hot idle (not verified with mechanical gauge, but I do have a new OEM sending unit installed). Is this just the way these engines are, or should I keep trying to fix it? I haven�t found any reference online where someone actually solved this. Most replaced tensioners with no change. Its not my daily so its taking some time to get enough miles on it so I can drop the sump again to inspect for any new debris. Had a Mahle filter amd Mobil 0-40 in it when I got it. Changed to LiquiMoly 0-40 with a new Mahle, and now while I try out the mobil 5w-50, a WIX from Oreillys. No debris found I have driven the car an avg 100mi per month. Any help is appreciated!

Can you record a sound clip or video and post it here? If it is a starter solenoid hanging too long, that a cheap remove , clean solenoid and reinstall type DIY. But this doesn�t cost a rattle, just a slightly long starter engaging sound.

Mine had developed a brief starter grind over the winter. It wasn�t a rattle. It was a distinct grinding sound from the starter motor being dragged by the flywheel. I thought it was a sticky starter solenoid not retracting the gear. Turns out to be a sticky ignition cylinder/steering wheel lock (the mechanical cylinder linked with the steering wheel lock, not the electronic ignition switch). Sprayed it down with WD40 and worked it loose, then lubricated it with dry lube for locks. It�s held up so far.

Sounds to me like you have the common " starter bendix squall "... These Bosch starters have a brass bushing at the nosecone of the bendix, that if it gets dry will make a horrific squalling sound for a couple of seconds as the starter speed slows down after the engine is running.. The recommended repair is to replace the starter because the screws holding the starter together are Loctited in and very difficult or even impossible to remove.. You need to post a sound recording of the noise you are concerned with so it can be diagnosed whether it is a Starter Squall or a Timing Chain Rattle.. ( or something else )

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I will record the sound, but I have already replaced the key switch and the starter with zero change to the startup noise. This was my first thought, starter hanging up, but didn�t fix it. Also removed the serpentine belt and started it up. Still did it, so nothing to due with the engine accessories either. Then I bought Durametric, and discovered the cam deviation issue, fixed that and retimed the engine. New deviation values have been steady. This has a dual row IMS bearing. 46k miles on the motor. I am hoping to make it quiet when I start it! Research seems to point to oil bleeding down from the heads causing a delay in oil getting back to the tensioners at startup. My old tensioners were still firm, when removed and the new ones didn�t fix it, so I dont know.

My guess: hydraulic lifters that bleed off oil and need to be filled again after engine start to get valve lash back to zero, during which the valve train rattles.

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When I did the timing work, I took each lifter out of its bore and inspected it, tried to squeeze with fingers, they all felt the same and nothing obvious to be found. Not sure how to test them further without just replacing all of them? I was however getting some lifter ticking about 5sec after startup for about a minute before it cleared up. I did add some LiquiMoly lifter additive and that noise has since gone away completely. Parts cannon on these cars gets expensive fast�

Same exact issue. 2001 C2. Actually seen a couple of threads on this, but haven�t seen anyone say they�ve solved it. I�m hesitant to start throwing parts at it, so any help appreciated on my end, too.

Here�s a cold start on mine. You have to listen carefully right as it starts. This time it wasn�t a brief buzzing noise like it usually is, but was a longer noise. Ignore the other noise � just found out I need a passenger side muffler. Engine sound YouTube

The rattle is most likely the cam chains and lifters making noise until the oil pressure comes up. My 99 has this start up rattle as well. I suspect they all do. The previous owner, a friend, said it is normal. He used the car for 10 years as a daily driver. I have had the car about five years and also drive it daily. The rattle has not changed in the 50k miles I have added to the car, which is now at 193k total.

I have a 2003 996. I actually don't hear anything unusual with your start-up. (Does the noise that you hear come through in the video)?

Sounds like my 01 has for the last 6 years, sometimes I crank it a couple times without letting it start and the noise is much less and sometime does not make that noise at all when I do that

My ‘99 has been in the family since 2002 and has always made a raspy chain rattle for a couple of seconds on cold start up. Also, a bit of lifter ticking noise that can range for a few seconds to a minute. Car has nearly 183,000 km on it now. Uses no oil. No smoking, etc. If memory serves, when the car was younger, my Dad asked the dealer about it and their response was asking him if he’d like to go out back and listen to ones that are more noisy… I asked my independent mechanic about it a couple of years ago and he also said that throwing money at it may not change much.

I made a startup video of the rattle. Car had been sitting for over 48hrs since last start. The LiquiMoly lifter additive did cure the ticking after startup. Sounded exactly like the video above by 9eighty6. Now it sounds good apart from the startup rattle. Highly recommend that stuff. Youtube link to startup video

That�s the sound! It�s driving me crazy.

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'98 build (1999MY) checking in... During (and only during) cold start mine has done this exact same thing for the last 5 years i've owned it. Even that knocking rattle. Had the car bore scoped and it was totally clean. also changed variocam pads/chains/tensioners. Still makes the noise. I just think its normal at this point and pay it no mind. After about 15 seconds it goes away and the idle smooths out.

lol..that little noise ? My 99 has been doing that for 18 years 194k miles and has been ran hard and put up wet ( but taken care of ) .... I wouldn't sweat it ..

Can add a couple things to this thread. My 996.1, 2001 C2 has made this rattle ever since I can remember. Its cam dev has slowly increased to currently 4.7 on 1 bank, this cam dev hadn't changed the rattle at all. My 996.2, 2002 C2 has never made this noise ever. No 996.2 I've owned or driven has ever made this rattle, unlike every 996.1 I've experienced... So must be related to something in the different valve trains used in the VarioCam & the VarioCam+ in the .1 vs .2 m96. What it exactly is, no clue. Compared to 0-40 or 5-40 oils... When switched to 5-50 oil, the noise went too 1/2 way gone, sometimes barely rattled for 1 second or not at all. When switched to 20-50 oil, noise went at least 3/4 gone. Big difference in volume of noise and duration. Sometimes no noise at all, then sometimes after prolonged down time a muffled rattle for 1/2 second then completely quite. In my anecdotal experience, Big difference in oils used as far as rattle is concerned. The 20-50 Valvoline racing full synthetic seems to have almost cured the worst of this rattle for the most part... JMHO

^^^^^ Yeah, it the rattle of the 4th and 5th timing chains/actuators on the 5--chain engines that causes the noise....... It is an inherited straight that all of them that have any miles on them will have .. It's like the gear rattle on the Turbo/Mezgers after they have 30K miles on them.... An annoying noise but will still last forever

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I am glad you guys don�t think its a big deal! I did change the 4th and 5th chains, but if I change the actuators, it will be quiet? For $3k in parts alone, need a guarantee! 😂 20w-50 might be too thick in the winter months? Not really planning on driving the car much but occasionally Ill take her out if theres no snow�

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I've actually not seen anyone obsess over that noise enough to actually replace it all... It like the rattle in the Turbo/Mezgers at idle, I asked the Porsche Instructor while I was in P10W Training about the noise because I had a customer that was still in CPO Warranty, and he basically said Porsche says it is an Inherited Noise in the design and they didn't consider it a failure...

I can live with it however, want to know why it had skipped time by a tooth and bank 2 cam dev was -21deg? Can they get enough slack in them to allow that? The chains seemed very tight when I removed the threaded rod on the actuators after changing chains and pads. Don�t want to have to do that work over again but if it prevents timing issues, and that startup rattle�might be worth it.

No, the 4th and 5th timing chains cannot slip a tooth.....it is not physically possible ..... Someone who had the cams out of the engine allowed them to slip a tooth while they were trying to re-install them .... I have seen that many times, .....But they cannot slip a tooth after they are installed..

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Thats good to know! The previous timing work was done by a Porsche dealer by previous owner. I was able to get the paperwork. This was five years ago at around 40k miles. They did bank 2 and I confirmed they put in new pads (zero wear in 7k miles since) with the lighter tan material. They didn�t touch bank 1. I can�t believe they would let it go out the door like that, which makes me think something else happened�car threw a timing code a couple hundred miles into ownership.

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It doesn't surprise me. Even really good Dealer Techs who know their way around a toolbox and an engine will get tunnel vision while retiming 5 chain M96 engines and make stupid mistakes the first few times they work on one.. I have seen this one a lot and even more frequent is the Scavenge Pumps not correctly oriented..... We had one here recently that went 10k miles with one Scavenge Pump 180 degrees out of time..

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I had a Scavenge Pump 180 degrees (bank 1) out after PO had the engine rebuilt by a 'famous' Sydney Porsche shop. I think the PO put up with it for 2 years before selling it. I got it, ended up suffering smoke pouring out of the exhaust after turning right at around 0.5-0.7g.. I was in tears. I ended up talking to The Oracle, PT3, and in that wonderful southern accent (as an Aussie - we don't hear it that often) the Oracle stated "you said the engine has recently been rebuilt? check the scavenge pump... One of them is out" And sure enough... it was. In fact it was at another very reputable porsche tech who initially dismissed my pleadings to check but sure enough. it was. If PT3 is saying the timing being out for reasons stated... he's likely right. Thanks again Charles. PS my mechanic during the 1st week of Aug will be,finally, fitting the UAOS I bought Sept last year.