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YOUR RESEARCHTiming chain tensioners
Reported or suspected cause
ims tensioner at the bottom of the engine
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Reported cause
The sound of chain flapping is caused by the IMS tensioner at the bottom of the engine.
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Suggestion
BTW, listened to the audio/YouTube clip several times, kinda tough to distinguish a particular sound from the rev on start up with the muffler delete, however, when the engine gets down to idle I hear a distinct rhythmic tap which may or may not be bore scoring, you may want to have your engine bore scoped to inspect for cylinder wall damage.
Leading evidence: 'ims tensioner at the bottom of the engine' (1 discussions report identifying this cause; no attributable repair resolution). Across 1 matching discussions, the most frequently mentioned possible cause is 'ims tensioner at the bottom of the engine' (1 discussions; 1 report identifying it and 0 suggest it). The most frequently discussed action is 'Inspect cylinder wall damage' (1 discussions). For that action, 0 discussions report a resolution and 0 report an unsuccessful attempt. No action has an explicit, attributable resolution report under the current rules. These are forum reports and suggestions, not a confirmed diagnosis.
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Performed · outcome unconfirmed
My cam deviation went back to (0,0) from (-3,-2) once the pads were replaced.
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you probably don�t need the tension era themselves replaced - only the pads.
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Performed · outcome unconfirmed
The shop that did my tensioner pads on both sides used Motul for the refill.
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Suggestion
BTW, listened to the audio/YouTube clip several times, kinda tough to distinguish a particular sound from the rev on start up with the muffler delete, however, when the engine gets down to idle I hear a distinct rhythmic tap which may or may not be bore scoring, you may want to have your engine bore scoped to inspect for cylinder wall damage.
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Inspect cylinder wall damage
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Suggestion
BTW, listened to the audio/YouTube clip several times, kinda tough to distinguish a particular sound from the rev on start up with the muffler delete, however, when the engine gets down to idle I hear a distinct rhythmic tap which may or may not be bore scoring, you may want to have your engine bore scoped to inspect for cylinder wall damage.
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Suggestion
The bore scoring noise would remain for the entire time that the engine is running, whereas lazy tensioner noise should go away after a minute or so once they get fully pressurized.
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Suggestion
The crank pulley has various holes in it , one is to lock the crank at Top Dead Centre, this is a datum point for the engine where cylinder one is at the top of its stroke and is deemed the beginning of the engines combustion cycle, it is used to set the bottom end of the engine I.e pistons with the timing of the cam rotations and valve openings to ensure everything runs properly and opens and closes as it should in the right time to make the engine work properly , in this case it just locks the engine at a certain point , the five chain which you have isn't bad for skipping chain links on timing when you remove the tensioners etc, that's why you have to pump up the new tensioner with oil so
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Suggestion
The crank pulley has various holes in it , one is to lock the crank at Top Dead Centre, this is a datum point for the engine where cylinder one is at the top of its stroke and is deemed the beginning of the engines combustion cycle, it is used to set the bottom end of the engine I.e pistons with the timing of the cam rotations and valve openings to ensure everything runs properly and opens and closes as it should in the right time to make the engine work properly , in this case it just locks the engine at a certain point , the five chain which you have isn't bad for skipping chain links on timing when you remove the tensioners etc, that's why you have to pump up the new tensioner with oil so
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Suggestion
On the 99 it's ok to just lock the crank at TDC and then remove the tensioners , two are really easy to do literally underneath the engine , takes like 30 mins for both no need for $$$$$, the ims tensioner and bank 1 tensioner , take the new tensioner out of box , place some oil in a plastic container , submerse the new tensioner in it, pump the piston with your thump until it pumps up, use a new crush washer and bolt in to correct torque, it's one of the easiest jobs I've ever done on my 996 , the hard bit is bank 2 the tensioner is on top of the cylinder head instead of underneath and I think you need to remove the air con compressor to get at it but I'd say do the two underneath and see i
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Outcome without a verified action link
I tried copy and paste from YouTube and it did not work.
^^^An arm and at least half a leg... you probably don�t need the tension era themselves replaced - only the pads. You can only do the cam chain pads. Probably in the ballpark of $1500 to $2k... In order to do the main and IMS tensioner pads, you need to split the crank case...Take it to a reputable shop for an estimate...Mo money!
The tensioners themselves are about �80 GBP each , it is worth changing them as when they get older the oil leaks out when the car is parked and on starting they have to pressurise from the oil system to give proper tension on the chain hence the rattle , I would say it's more the tensioner than the paddle myself really! On the 99 it's ok to just lock the crank at TDC and then remove the tensioners , two are really easy to do literally underneath the engine , takes like 30 mins for both no need for $$$$$, the ims tensioner and bank 1 tensioner , take the new tensioner out of box , place some oil in a plastic container , submerse the new tensioner in it, pump the piston with your thump until it pumps up, use a new crush washer and bolt in to correct torque, it's one of the easiest jobs I've ever done on my 996 , the hard bit is bank 2 the tensioner is on top of the cylinder head instead of underneath and I think you need to remove the air con compressor to get at it but I'd say do the two underneath and see if it improves any then look at maybe the other one after that!
If those two items are a question.. Stop and back slowly away from the engine.
Your many hours of reading and searching.. away from being ready to DIY this..
If your just messing with us ,,, well played...
Just did the tensioners on my 99 Boxster, was able to do all 3 without disturbing the AC compressor, however, there was much foul language which decorum prohibits the repetition of here. I think my head twisted around 360 degrees at one point ala Reagan in "The Exorcist" (or was that the great 996 coolant reservoir replacement debacle?) Anyway, I second pdxmotorhead's suggestion to the OP of doing much more research/reading before attempting this as a DIY, yer messing with your cam timing here and if you pooch the job you could have your timing chains skipping teeth on the timing gear inside the engine. Just sayin.
I just paid my mechanic to both bank tensioner pads on my �99 (64,000 miles). They were both worn. It was $4,000, including a $500 failed solenoid on one side.
Once the chain rails/pads start to wear, they go fast (I've read) and should be replaced sooner rather than later. Will new tensioners take up all the slack in a worn pad?
My cam deviation went back to (0,0) from (-3,-2) once the pads were replaced. I assume the chain slack is now tighter, but I would guess only on cold start. Once the tensioners have sufficient oil pressure (they are the last endpoint in the oil deliver system in the engine), I would expect the chains to be tight when the engine is running in either case.
I wouldn't say so , the tensioner will take up the slack anyway but new tensioners might reduce wear, I would say the point on start up where the pad is vibrating against the chain before the old tensioner pumps up is the worry causing excessive wear !
The crank pulley has various holes in it , one is to lock the crank at Top Dead Centre, this is a datum point for the engine where cylinder one is at the top of its stroke and is deemed the beginning of the engines combustion cycle, it is used to set the bottom end of the engine I.e pistons with the timing of the cam rotations and valve openings to ensure everything runs properly and opens and closes as it should in the right time to make the engine work properly , in this case it just locks the engine at a certain point , the five chain which you have isn't bad for skipping chain links on timing when you remove the tensioners etc, that's why you have to pump up the new tensioner with oil so the chain is not slack on start up causing a jump but I'm not sure if it would happen on the five chain , if you research locking engine off at TDC on here you will find the info you need , basically when the crank is in a given position the TDC hole in the crank lines up with a recess cast into the block behind allowing you to insert a timing fowl into to stop any rotation on the engine or just make sure it stays exactly on the TDC spot , you don't need the special dowel though , just use a bolt that fits in there quite well, but as others have said use a bit of caution if your not confident don't do it ! The only hard part of the job I had was once the tensioner is pumped with oil and your trying to insert it into the block and start off on the threads to screw it in it can be a bit hard to get started as it's extended and there's a bit of backwards force there , this requires a bit of pushing on the head of your ratchet to depress the tensioner into the whole so you can get on the thread and because it's a bit awkward there's a chance you could hit a cross thread but if your careful you should be fine , once you get on the thread just tighten up to the correct torque and that's it ! Another note , each tensioner is unique they are not all the same , one has a plain head ( the top of the nut) , one hasone ring groove on the head and one has two ringed grooves so you can identify them, it sounds like it's getting complicated this but it's really not !
Metty, just to be clear, on your 1999 996 5 chain engine there are three chain tensioners: one for each engine bank cam chain, and one for the crankshaft to Intermediate shaft chain. These are screwed into and out of the engine externally. Each of these chain tensioners has an oil pressurized plunger which acts upon an internal chain guide rail and pad which actually contacts the chain creating the required operating tension. Your rattle is most likely caused by the chain tensioners failing to hold hydraulic pressure after engine shutdown and being noisy upon engine start up until they pressurize. The chain tensioners are cheaper and easier to fix, if I recall correctly they were about $125 each or thereabouts. Your engine's internal chain guide rails may also be the source of your rattle, typically when the pads made of dark brown plastic material wear down from chain contact to the point that the chain is contacting the guide rail itself. or the guide rail has failed and is banging around inside the engine. The internal chain guide rails are much more costly to repair as the engine needs to be opened up to get at them. If you have been doing your own oil changes and dissecting your oil filters and have not found good amounts of bits and pieces of dark brown plastic type material, then I would suggest the rattle is more likely your external chain tensioners. If you have been finding good amounts of dark brown plastic type material in your oil filter at each recent oil change, then its most likely your internal guide rail pads. Me, personally, I would try the external tensioners first as they're cheaper and easier. If that doesn't remedy the problem, then you know its the guide rail pads. BTW, listened to the audio/YouTube clip several times, kinda tough to distinguish a particular sound from the rev on start up with the muffler delete, however, when the engine gets down to idle I hear a distinct rhythmic tap which may or may not be bore scoring, you may want to have your engine bore scoped to inspect for cylinder wall damage. Is this the "rattle" of which you speak because, if so, then that's a whole other kettle of fish (entirely different issue).
At the extreme risk of turning this into an oil thread, changing brands of oil might influence your startup rattle. I believe mine got better when I switched to Motul.
I agree...that does not sound good. But, it appears to happen when you hit the starter. It actually sounds like your stater bendix gear is getting stuck in the flywheel gear. Perhaps time for a new starter?
It seems to me that there should be an easy way to discern between bore scoring and lazy tensioners:
The bore scoring noise would remain for the entire time that the engine is running, whereas lazy tensioner noise should go away after a minute or so once they get fully pressurized. No?
Yes, lazy tensioner noise typically goes away after the tensioners re-pressurize and sound like a diesel engine idling (just like my 1999 Boxster), whereas bore scoring is a consistent clacking sound best heard at idle. Often when you rev a car with bore scoring, the clacking goes away, but returns at idle. I have personally never heard a failed guide rail/pad but I would imagine that noise would not go away and even increase with engine revs.
The sound of chain flapping is caused by the IMS tensioner at the bottom of the engine. The updated tensioner (2002 I think) has a preload spring to minimize slack & flap before the tensioner is fully pressurized with oil.
There is a update bulliten on this that a good search would reveal .
Exactly. Continuing to run an engine with lazy tensioners is a horrible idea. It can cause a catastrophic engine failure and will also damage the IMS bearing and can cause false brinelling due to these oscillations and vibrations.
