Discussion
my faithful 2001 996tt had a bad weekend. Now, only when the motor is warmed up, car stationary, clutch peddle pressed down, or clutch up makes no difference, it sometimes makes a clear noise as if two gears are trying to engage but unsuccessfully, i.e a sort of tearing gear grinding noise. It does it best when you blip throttle and as it comes down from say 3500 rpm to 2500 rpm there comes the noise suddenly and then it fades out as it returns to idle, and then is gone again. It is loud enough to be noticed by people outside the car. Sounds like engine, not gearbox as it happens when clutch is in (so gearbox disengaged). Pressing clutch in and out makes not difference. I can also feel the grinding very slightly through the clutch peddle for some reason.
surely not the intermediate shaft on a 996 tt?....
surely not the intermediate shaft on a 996 tt?....
Crimp a Length! said:
It could be the IS but they all make a timing chain rattly type noise quite common, when you rev past 2.5k it should disappear
Intermediate shaft?? Turbo lump is same as GT3 and GT2 i.e derived from GT1 race car lump so doesnt have the same god awful chain driven setup as per normal M96 and M97 Carrera/ Boxster engines so not that!! How many miles has the car done? Have you checked all pulleys such as on water pump etc? Very difficult without hearing it obviously.
Edited by TOENHEEL on Monday 5th March 23:56
speedbird1000 said:
my faithful 2001 996tt had a bad weekend. Now, only when the motor is warmed up, car stationary, clutch peddle pressed down, or clutch up makes no difference, it sometimes makes a clear noise as if two gears are trying to engage but unsuccessfully, i.e a sort of tearing gear grinding noise. It does it best when you blip throttle and as it comes down from say 3500 rpm to 2500 rpm there comes the noise suddenly and then it fades out as it returns to idle, and then is gone again. It is loud enough to be noticed by people outside the car. Sounds like engine, not gearbox as it happens when clutch is in (so gearbox disengaged). Pressing clutch in and out makes not difference. I can also feel the grinding very slightly through the clutch peddle for some reason.
surely not the intermediate shaft on a 996 tt?....
Probably not the IMS or layshaft or whatever this is called in the Turbo engine.surely not the intermediate shaft on a 996 tt?....
As a knowledgeable someone else noted the Turbo engine has a different IMS design than that of the N/A engines, a design that does not use a roller bearing and relies upon a gear drive from the crankshaft.
My 03 Turbo made a 'dry bearing noise' that proved to be from a bad idler roller bearing up near the power steering pump.
Thus before you tear apart the engine you need to id or have someone id where exactly the noise is coming from.
One way to eliminate the noise source as being from an idler roller bearing or noisy accessory drive is to remove the serpentine belt (note carefully its routing and direction of rotation) and then start the engine and only run it long enough to verify the noise is still present or not. Now I've never done this for the Turbo and I suspect it is harder to do that for say my Boxster (which I have done when searching for what proved to be a noisy water pump).
This assumes the noise appears from cold (or warm start) and right away. Obviously if it takes minutes of engine run time to reproduce the noise you can't use this technique.
Now even with the belt removed and even if the noise is still present it might not be coming from the engine. The car needs to be on a lift, in the air and making the noise and someone under the car listening carefully to pinpoint where the noise is coming from.
'course the above is done with the belt properly reinstalled!
Even if the car's quiet, all heat shields, exhaust pipes need to be checked for any play, looseness.
A loose exhaust hanger, a loose heat shield can make a noise that can have one convinced the engine's coming apart.
Cars that are driven year 'round, where the roads are salted, are really prone to having exhaust system hangers fail/come loose or heat shields come loose due to corrosion attacking the hardware/fasteners.
Also, a loose underbody panel or air dam or something similar can also be the source of the noise.
You need to clearly id from where the noise is coming from and once this is known then what to do about it is easier to determine.
Sincerely,
Rockster.
Thanks Rockster useful comments.
Had an Indy take a look and, no this engine design is a true great it seems, verdict is the dual mass flywheel is the culprit, 75% certainty given. will find out shortly.
been running at 1 bar for 2 years with free flow exhaust,i.e say 490 hp, so fair play as the clutch is still stock
Had an Indy take a look and, no this engine design is a true great it seems, verdict is the dual mass flywheel is the culprit, 75% certainty given. will find out shortly.
been running at 1 bar for 2 years with free flow exhaust,i.e say 490 hp, so fair play as the clutch is still stock
speedbird1000 said:
Thanks Rockster useful comments.
Had an Indy take a look and, no this engine design is a true great it seems, verdict is the dual mass flywheel is the culprit, 75% certainty given. will find out shortly.
been running at 1 bar for 2 years with free flow exhaust,i.e say 490 hp, so fair play as the clutch is still stock
It is a great engine derived from a Porsche race car. Made of granite. Pleased to hear you've found the source of the problem. Your car doesnt have the IMS that would cause problems like many talk about on here. Hope its all sorted soon! Had an Indy take a look and, no this engine design is a true great it seems, verdict is the dual mass flywheel is the culprit, 75% certainty given. will find out shortly.
been running at 1 bar for 2 years with free flow exhaust,i.e say 490 hp, so fair play as the clutch is still stock
er..so.. i "found" these Pauter rods 
new intergear in place with locktighted bolts, stock oil pump back in too...
Gassing Station | Porsche General | Top of Page | What's New | My Stuff