the engine rattle when I start

[BYprodriver]

Originally Posted by Daniel R

Mine rattles constantly at idle but the noise goes as soon as the revs are above about 1,000rpm. It also rattles at low revs if the engine is laboured (ie in too high a gear).

Any ideas what causes this? Someone suggested it could be either a belt tensioner gone bad, or possibly a bent conrod.

All thoughts appreciated.

Maybe a chain tensioner?? I would fix this problem A.S.A.P. take it to the most qualified mechanic/shop you can find, it will be cheap compared to waiting. I would stay away from whoever said it could be "a bent conrod"

[Daniel R]

Originally Posted by BYprodriver

Maybe a chain tensioner?? I would fix this problem A.S.A.P. take it to the most qualified mechanic/shop you can find, it will be cheap compared to waiting. I would stay away from whoever said it could be "a bent conrod"

The guys that suggested bent conrod are in fact the best guys in town for Porsche! Why they would have suggested such a thing I have no idea, I am not thoroughly informed when it comes to these things so I will take your word for it that it is a ridiculous suggestion.

What does replacing chain tensioners entail? Just a rough guide to labour hours, I can search the part prices online.

Thanks.

[autodoctor911]

my 99 with 140k miles made the same noise on startup for 1-2 seconds. but I switched from that awful mobil one 0w40 to lubrimoly 10w60 gt1 full synthetic. I think it came out for bmw m cars. anyways noise is gone. I will do an analysis as soon as I get to the track.

[Blue-S]

Originally Posted by Jake Raby

This noise is coming from looseness in the timing chains due to the hydraulic tensioners.

Clean or replace the tensioners or change oil brands. One brand of oil made the noise completely disappear in my Wife's 996 Land Speed car, when I changed brands again the noise returned.

Wear on components like variocam wear pads, timing chains, cam drives and etc will make the noise louder and occur more often. There are solutions, you don't have to live with it and it isn't good for the engine.

How does one clean the tensioners? Can the timing chains and guides/tension arms be replaced without complete engine disassembly? For example, on Mercedes engines it is possible (with the correct tools) to break the existing chain, temporarily link a new chain to it, bar the engine over manually to feed the new chain through, then connect the ends of the new chain permanently using a chain pin staking tool.

[JoeFromPA]

Try Mobil One 15w50....it's a phenomenal flowing synthetic oil . Anything down to 40 degrees fahrenheit and you won't notice a difference.

I'm going to swap it in close to thanksgiving, I'll try to make a note of any sound changes.

[BYprodriver]

Originally Posted by Blue-S

How does one clean the tensioners? Can the timing chains and guides/tension arms be replaced without complete engine disassembly? For example, on Mercedes engines it is possible (with the correct tools) to break the existing chain, temporarily link a new chain to it, bar the engine over manually to feed the new chain through, then connect the ends of the new chain permanently using a chain pin staking tool.

Submerge the tensioner in clean engine oil & pump the plunger in & out to suck in the new oil & purge the old oil & hopefully any contaminants. This works better & easier if the oil is heated to 250 degrees & you "cook" the tensioners in the oil for several hours. The cams must be removed to replace chain or wearpads.