Chain noise?
 

Maybe coincidence but after replacing my worn engine mount and the crank pulley with underdrive one, now I am hearing what seems to be chain noise when giving very little throttle at low rpm, say steady-state driving below 50mph in 4th gear.

As soon as throttle is closed or open to decelerate or accelerate, noise immediately stops but it comes right back with slight throttle opening to keep steady speed.

I thought of tensioners but no chain noise at cold start at all, so they are OK I guess?

And ideas of the root cause, or is it one of those M96 engine habit? I have no fear with IMSB, but this is bugging me even though the engine runs smooth except the noise under this isolated condition.

It had been 60's or below and this noise was pretty much repeatable and reproducable with slight throttle opening at steady speed for the last a few weeks, and again it goes away immediately when I close throttle or press it to accelerate.

Today it got warmer over 80's, and I could not make the same noise at any throttle position... So whatever the issue may be, it is temp related, if this adds a clue.

Anybody with similar experience?

My best guess is: worn chain tensioners, worn chain rails, or worn vairocam rails if your car has them. Could be all three. It could also be stretching chains.

Have you checked camshaft deviations and, if so, do you have past numbers to check them against. I believe changing deviations over time suggest wearing rails or stretching chains

You could also check the sump for black or brown plastic pieces to see if the rails are wearing.

Tensioners are cheapest to replace; variocam rails next and internal chain rails are the most expensive requiring a complete tear down.

Thanks for sharing your thoughts. I have zero chain rattle at cold start-up, that really puzzles me to doubt tensioners/ rails. 3 oil changes in the past 15K miles of my ownership came out with zero plastic or metallic debris in oil filters, but it is due now so I’ll check it out again. My car has 85K miles and it runs like a champ and revs smooth beside this strange, very isolated noise.

I never checked cam deviation, I’ll look into it. Anybody here around Detroit with the proper scanner? I got Autel with no such ability...

My filter was clean in my first ever oil change. I then dropped the sump to install a guardian. There was little bit of those chain ramp plastic in the sump. I was always thinking they might never reach the oil filter because they are to heavy to suspend in the oil and reach the filter.

Do you also suspect worn tensioners to be the issue?

I have seen many posts with pictures of plastics debris caught in the oil filter paper pleats, but I might drop the pan too see. I got the drain plug with magnetic tip and so far metallic debris are nothing alarming.

My cam deviation is not bad. I will be assessing replacement of the pads next year. I just did the clutch, new flywheel and chain tensioners. My thinking is to either farm it out to an independant or drop the engine and DIY. If I could fond someone reliable the first option sounds better. I have rebuilt a V8 before, cracking open the boxster engine is intimidating.

Did you have classic cold start noise or other symptoms that prompted replacing tensioners? Did you change all 3 and notice any difference in noise or otherwise?

I had a little noise. I think it is a little better. I have no emperical evidence to support the reduction. I was in there doing the other work, the cams were locked. The funds were available, and compared with the moeny it would have cost me to have a indie do the work, I spent the cost savings on doing much more work.

chain noise
 

How difficult is it to change these rails,..want a 2001 S and has that noise on cold start only ?? Thanks

Still trying to figure out the issue.... Again this is not the issue with rattles on cold start!

The noise is still reproducable, most noticeable around 2,400 rpm with slight throttle just to maintain speed. Either giving more gas or closing the throttle immediately kills the noise, then crack the throttle tiny bit open and the noise comes right back... And the car runs great and revs smooth into red.

Any ideas guys????

Could it be an exhaust rattle?

Can that be throttle-position specific issue? Again, rattle is very repeatable with slight throttle under wide range of rpm but it immediately disappears with more or no throttle. I’m thinking exhaust rattle may be more rpm dependent, correlating to flow volume, engine vibration, etc.

Still chasing the root cause...

I read about 2005 987 owners complaining the same issue, that was resolved with the updated oil pressure relief piston with chamfered top edge and new spring.

So tried my luck with them for just $15, but it did not do the trick...

This rattle/ noise around 2,400 rpm, seems to be exposed after installation no new 987 engine mount (original was torn) and UDP that reduced noise from accessories, as did not notice it almost 2 years of driving before, even though mostly top down so harder to notice noises.

Related internet threads suggest intake noise/ pulsation as a suspect root cause. I use a larger 996 mechanical throttle body, but otherwise stock intake components, and I wonder my 996 TB, paired with UDP, has something to do with this noise issue isolated to very slight throttle opening.

I checked exhaust and heat shield, and they seem to be tight and rattle-free. This noise is only produced with car running/ engine loaded, and I could never reproduce it with car parked no matter how I rev the motor.

Any more thoughts out there?

I know generally cats can rattle if they go bad, but not sure about the Boxsters. Bang on yours with a rubber mallet, who knows? If your tensioners were worn, or your pads I think it would be odd to only hear the noise at a single rpm range and not at all on cold start. For giggles, check your rotating things. PS pump, alt etc. it might be that your alt has bad bearings and the change in rotation is making them more known, or possibly the alt pully. They can go bad as well.

Cat and exhaust: checked with mallet, no loose components
Pulleys: checked when I installed UDP and new belt, all smooth and little bearing play

As fas as the alternator pulley, it has overrun clutch, if I recall? What is the typical effect of failed alt bearing and can it cause my issue?

only when engine loaded? probably driveline related. only makes noise when clutch engaged? driving down the road at 2400 rpm and engine is making noise, push clutch in and what happens? shift into neutral and keep the engine at 2400 rpm and what happens?

Clutch in, noise gone.... I can not reproduce this noise not matter what rpm with the gear in neutral and car standing still. Only when car is running in gear, mostly in 3rd and 4th on the road, at steady speed with very delicate, slight throttle opening. Taking the foot off or pushing the pedal just a little instantly kills the noise, and back to the slight opening it comes back, very repeatable.

It seems as if combination of UDP, 996 TB and maybe 997 engine mount of recent changes is causing some kind of isolated system instability that the factory ironed out, and it woke up this noise ghost?:confused:

Does it sound like 5 pebbles in a coffee can?


Cuz I hate to sound overly simple here, but the conditions you're describing are perfect for detonation. Sometimes referred to as "pinging", and correctly known as "pre- ignition".



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Interesting thought, it kind of sounds like it, and more from right side of the engine (but of course I’m sitting in the left side.) If so what causes it, bad knock sensors, lean mixture due to vacuum leak? It makes noise when the engine is cold or warm, and I use premium gas and different brand made no difference. MAF, all 4 O2 sensors and spark plugs are less than 15K-mile old, and no check engine lights/ codes...

Still trying to diagnose.... Research suggested alternator pulley with overrun clutch, ah wa! But upon double-checking mine (from 1997, manual) is solid pulley... so something else yet to be IDed.

By the way, do I have the right pulley? Did all manual cars since 1997 come with clutched pulleys or just later car from 2000ish?

Following this - I have the same issue on my 2000S. I rebuilt the motor and it started after rebuild - right around 2500 RPM. I have all new chains/guide rails/vario ramps. I have 5 months of winter to debug and figure it out, but not sure on where to even start!

The clutch in making the noise go away seems to be pointing to your throw out bearing or perhaps a rattle/vibration in the release arm or spring.

As an aside, I had all sorts of fits with shifting in 1st gear making horrible vibrations until I replaced the single front engine mount. It's a cheap fix easily done in your garage.

Thanks for sharing this pain, it seems not a serious issue with no performance degradation etc but it sure is bothering!

I take your input basically eliminating those components. I have no record of those valvetrain parts replaced, but several oil changes and filter gut-check in the last 15K miles yielded zero debris to suspect excessivel wear on them.

Let’s hope for the resolution soon!

Clutch feels good and no vibration/ rattle is felt through the pedal.

As mentioned earlier, I installed new 987 engine mount with new side pads too, so that may not be it... even though it seems as if I started noticing this noise after new mount and UDP installation.

When I replaced motor and transmission mounts, found that I experienced a couple of new types of sounds: 1) tighter motor/chasis meant more vibration transmitted to interior of car, making existing engine sounds more pronounced. 2) New sounds from things inside the cockpit vibrating more - at around the 2,500 rpm mark, under certain conditions I heard a new very pronounced buzz - that sounded like it came from engine. After some hunting I discovered it was the mesh hoop insert that vibrated very breifly. Decided to leave it as it adds some character! Hopefully you are experiencing something similar - more pronounced sounds resulting from tighter mounts.

Yes, it seems as if the new mount, together with UDP that drives the accessories at lower speed, promoted or exposed this noise.

My mesh inserts are secured with multiple zip ties (so I won’t lose them knowing how ridiculously expensive these plastics are), so probably my noise won’t be it, but will double-check. I’m pretty sure it comes behind the firewall, thought.

Keep ideas coming! With running out of ideas myself, I’m planning to drive the car with the serpentine belt off to see if I can positively rule out all accessories and pulleys.

My mesh thingies vibrate as well, definitely a distinct buzz.

Hi Boxstard,

The issue you describe sounds very similar to a noise I’m experiencing. I also have a 1997 2.5L.

Every time I ‘feather’ the throttle, either gradually on or off, I hear a distinct ‘chatter’. Full throttle / No throttle and the noise disappears. Most of the time I hear it when attempting to maintain a steady speed when cruising, but it's amplified at high RPM's when easing off the throttle after a hard acceleration (when joining a motorway for example).

Interestingly, unlike you - I can replicate the noise with the clutch fully depressed and the car stationary, by carefully holding the revs around 2,500 RPM and slowly feathering in a little more gas. Are you sure you can’t achieve this ?

I’ve just had my front engine mount changed (for unrelated reasons) which made no difference to the noise.

Did you ever find a root cause?

Keylime,

Perhaps the noise comes from within the muffler (loose shield) or failing cat..?

Good to hear you pointing to the Release Bearing. Bell Housing condensation will rust a release bearing over time and it will rattle. With the Engine running clutch out it will rattle when shutting the engine down. Clutch in no rattle when shutting down the engine. DMF I doubt it's the problem.

I noticed the same noise recently. The car is parked, but I had to move it so I drove it around the block. Very noticeable because I don't have the carpet over my engine cover, and my soft top is removed.

Still chasing the root cause... and I could not reproduce the noise with the car parked, clutch in or out, no matter how I tried with gentle throttle around the ‘sweet spot’ of 2,400 rpm.

FWIW-black silicone holds the mesh windscreens securely. Isolating that noise took a while!

Bump! Anyone with experience fixing this issue?