996TT crank pulley loose

[AngelOfGrief]

Hello.

My 996tt's crank pulley has gotten loose lately. It fell off and I had to DIY screw it back with the help of my nephew right on the street. We removed the tensioner pulley and screwed the bolt back with a regular wrench. The bolt got a bit damaged, so we filed it a bit to restore the grooves.

I was able to drive back to my parking place, expecting to take the car to get serviced later, however yesterday I decided to replace the battery (it died afterwards)

and when I started the car and drove it around the parking I heard loud squeaking. Then the 'charge' light went on, steering became heavy: the pulley was loose once again, but I was able to catch the moment: I shut the engine off and the pulley did not fall off, but the crank bolt was loose -- I could see it thru the air filter.

I have already gotten a new crank pulley bolt and the cylindrical locking pin also. I am not going to service the car myself, but I have a few questions and I want to make sure the mechanic does it right.

1. What's the deal with the cylindrical pin? It's mentioned in the service manual and there is a cavity for it in the crankshaft and the pulley, but the pin is not shown on PIWIS PET page for 996 turbo engine, only for 996 GT3. Is it supposed to be there, actually? I don't know if it was there originally, since it might have just gotten lost: I haven't found it in the engine compartment.

2. The 996tt service manual does mention the pin, and it also states the bolt has to be tightened to 170 Nm. Does that mean no glue/loctite is to be used? There was no trace of glue on the old bolt.

I would appreciate any comment on this, please.

Edited November 1, 2013 by AngelOfGrief

[JFP in PA]

Hello.

My 996tt's crank pulley has gotten loose lately. It fell off and I had to DIY screw it back with the help of my nephew right on the street. We removed the tensioner pulley and screwed the bolt back with a regular wrench. The bolt got a bit damaged, so we filed it a bit to restore the grooves.

I was able to drive back to my parking place, expecting to take the car to get serviced later, however yesterday I decided to replace the battery (it died afterwards)

and when I started the car and drove it around the parking I heard loud squeaking. Then the 'charge' light went on, steering became heavy: the pulley was loose once again, but I was able to catch the moment: I shut the engine off and the pulley did not fall off, but the crank bolt was loose -- I could see it thru the air filter.

I have already gotten a new crank pulley bolt and the cylindrical locking pin also. I am not going to service the car myself, but I have a few questions and I want to make sure the mechanic does it right.

1. What's the deal with the cylindrical pin? It's mentioned in the service manual and there is a cavity for it in the crankshaft and the pulley, but the pin is not shown on PIWIS PET page for 996 turbo engine, only for 996 GT3. Is it supposed to be there, actually? I don't know if it was there originally, since it might have just gotten lost: I haven't found it in the engine compartment.

2. The 996tt service manual does mention the pin, and it also states the bolt has to be tightened to 170 Nm. Does that mean no glue/loctite is to be used? There was no trace of glue on the old bolt.

I would appreciate any comment on this, please.

The pin is a locking pin that goes through the belt pulley, and it is put in before torqueing the center bolt. The OEM manual does not call for Loctite on the center bolt, but a dab of the red stuff would be a very good idea:

[AngelOfGrief]

Thanks for the info. Do you happen to know by any chance: is it possible to access the pulley without lowering the engine and/or removing the muffler?

[JFP in PA]

I don't think you are going to be able to get at it with the car assembled.

[AngelOfGrief]

Update.

It was enough to remove the bumper and the heat shield underneath it and also another small plank to actually get full access to crank pulley and its bolt. We were also able to remove the pulley by removing the belt tensioner (bolt on the back, nut on the front). It turned out the crank pulley is all messed up and needs to be replaced. (( The crankshaft is fine however, luckily. The weird thing is that partnumber on the pulley is misspelled: it reads 996 102 170 71, whereas correct number is 996 102 017 71. For my VIN, PIWIS PET shows p/no 996 102 017 72 that fits all turbo range Porsches 996-997.

Should I get any type of a tuned kit like this one? Is it worth it?

http://www.amsperformance.com/cart/evoms_porsche-996-997-gt3-lightweight_pulley-kit.html

Edited November 9, 2013 by AngelOfGrief

[JFP in PA]

Update.

It was enough to remove the bumper and the heat shield underneath it and also another small plank to actually get full access to crank pulley and its bolt. We were also able to remove the pulley by removing the belt tensioner (bolt on the back, nut on the front). It turned out the crank pulley is all messed up and needs to be replaced. (( The crankshaft is fine however, luckily. The weird thing is that partnumber on the pulley is misspelled: it reads 996 102 170 71, whereas correct number is 996 102 017 71. For my VIN, PIWIS PET shows p/no 996 102 017 72 that fits all turbo range Porsches 996-997.

Should I get any type of a tuned kit like this one? Is it worth it?

http://www.amsperformance.com/cart/evoms_porsche-996-997-gt3-lightweight_pulley-kit.html

Not sure that fits the turbo cars (they are different than the 996 cars), plus I don't see what advantage it would add for all that cash.

[AngelOfGrief]

Well, they actually do have a pulley for the turbo cars, and I was asking about the advantages -- are there any? The "tuned" pulley is slightly smaller diameter, they claim it poses less load on the engine thus increasing horsepower...

[Loren]

And your current pulley is balanced with the engine crankshaft and rods.

If I were rebuilding the engine and re-doing the balancing I might consider it -- but otherwise I would skip it.

[AngelOfGrief]

And your current pulley is balanced with the engine crankshaft and rods.

If I were rebuilding the engine and re-doing the balancing I might consider it -- but otherwise I would skip it.

Loren, are you sure the old pulley is balanced with the engine? I've got a feeling it's balanced separately, because it's got its own part number and can be purchased separately.

The old pulley is totally messed up: its mounting place is ruined, and also the cyllindrical pin's place, the whole thing is out of balance which can be observed while the engine's running. :(

[Loren]

Yes - when I rebuild engines it is.

Each part is individually balanced - then when assembled as a rotating mass - you balance it again for any harmonics that have been created by the rotating assembly.

The Porsche replacement parts are going to fit within a spec range - that will minimize any balance issues. I guess you have to trust the third party company on that one.

[AngelOfGrief]

Here is the manufacturer website for the underdrive crank pulley:

http://www.evoms.com/product_p/epk-gt2.htm

The idea behind is: it's diameter is smaller, thus it gives us about 10-15 hp on the wheels.

[RFM]

Update.

It was enough to remove the bumper and the heat shield underneath it and also another small plank to actually get full access to crank pulley and its bolt. We were also able to remove the pulley by removing the belt tensioner (bolt on the back, nut on the front). It turned out the crank pulley is all messed up and needs to be replaced. (( The crankshaft is fine however, luckily. The weird thing is that partnumber on the pulley is misspelled: it reads 996 102 170 71, whereas correct number is 996 102 017 71. For my VIN, PIWIS PET shows p/no 996 102 017 72 that fits all turbo range Porsches 996-997.

Should I get any type of a tuned kit like this one? Is it worth it?

http://www.amsperformance.com/cart/evoms_porsche-996-997-gt3-lightweight_pulley-kit.html

Given the cranckshaft pulley (driver) is smaller in diameter, all other OEM pulleys, waterpump, alternator, steeringpump, etc. will rotate slower. This can cause all sort of problems at lower speeds as city traffic, idle, etc. These products are suitable for racing purpose where always high engine speeds are achieved, not for cars that are used on public roads.