JPTL

Hope to find out today....I'll post when I learn something.

UKKid35

BTDT, except in my case I reversed the bolt, this made a loud clicking noise as it rubbed over a balancing hole in the damper. But it was not a grinding noise as described by JPTL

mark kibort

water pumps usually make howeling noises, that can be heard using a stethascope on the surface of the water pump. fan belt noises can sound like bearings, but spraying brake cleaner on them, can determine if thats what it is. (just quick shots sprayed on the inside of the belt . If the noise goes away or changes, its the belt)

JPTL

So today, I got started in. Removed the belly pan and noticed fresh metal shavings - mostly on the pass. side, but in the middle front as well (so that's what belly pans are good for!) Also some on the top of the oil pan. Clearly external component & not something behind the covers I was still thinking air pump bearing, and that the scrapings had come from the bearing and somehow migrated around the front of the engine. Didn't explain the shavings under the pulley on top of the oil pan, and I've never seen a bearing spin off shavings like that.
When I began to loosen components for hand turning, I noticed that the crank pulley had an odd sound when I tapped it with the wrench.
So.......
Ding, ding, ding! Malcolm, good job in identifying a loose crank bolt as the culprit! Not only would I never have guessed it, but I thought that your suggestion was off base, because I'd torqued it to 225 ft. lbs and used Permatex Blue Threadlock on the bolt. The washer was oriented properly as well (confirmed this upon installation, and today on removal). When I originally removed the bolt for the t-belt job, that sucker was either LocTited to the max. or it was torqued upward of 600 ft. lbs. It took me a breaker bar and a 3' section of galvanized pipe to get it off. Maybe the Porsche shop who did the prior t-belt job knew something.....
The crank pulley 'group' had been spinning on the A/C pulley, and apparently being harder steel than the pulley group was grinding away at the pulley group. Explaining the horrendous 'bearing' sound and the ample metal shavings.
So what the hell? How come this bolt came loose? I'm positive that I torqued it to specs and positive that I used threadlock. Is it possible to get a 'false seat' like you can get with a lug bolt on a wheel?
Could the vibration damper & A/C pulley not have been seated, and still didn't seat after 225 ft. lbs?
I don't get it.
Anyway, it's a good day. April 15th still sucks, but April 16th rocks!
Thanks to all of you who weighed in on this. Your suggestions were invaluable. They helped me to approach this with a clear head, without haste and considering all possibilities.

dprantl

Did you have the flywheel lock tool in place when you did the torquing, or was it in gear with the brake applied?

Dan
'91 928GT S/C

JPTL

The groove or recess in the washer was facing rearward - against the A/C pulley (the flat, non-recessed side of the washer was against the bolt head).
Flywheel lock was in position when I torqued it.
I'm stumped. The only thing that I can imagine is that the flywheel pulley and/or the vibration damper was seated, but not fully....slightly cocked. Torquing the bolt wasn't enough to fully seat it. Either that, or 225 ft. lbs and thread lock isn't enough.
Does the shop manual recommend checking the torque of the crank bolt along with the t-belt check after 1,500 miles?
Anyway, I couldn't be happier with the cause. I was preparing to have to go deep.

mark kibort

thats weird. How is that possible????

mk

aggravation

Did you use a torque wrench that has a range well above the 225? The reason I ask is I've found that most things, especially things with a mechanical component to them, that are designed to measure something and only are able to do so within a certain range are not very accurate at the ends of their range. I don't know if this is true of torque wrenches but it's a rule of thumb that has served me well with other devices, scales, thermostats etc.

OK, so that's my wild *** guess, now for the dumb question:

You didn't use the old one foot on the bathroom scale method did you?

WICruiser

Is it possible that your crank bolt is longer than the thread depth / part stack up required resulting in the bolt being very tight in the crank but not actually clamping the damper and pulley? Check the thread depth and the part stack up to make sure there is not a washer missing or a piece of an old bolt down in the crank threads.

JPTL

Torque wrench has a 250 ft. lbs. max. I can't imagine it being so far off to the tune of 25 or 30 ft. lbs.
Crank bolt is the original. Threads were very clean & the bolt looks nearly new.
Keeping in mind that it's a very snug fit on the shaft I'm still leaning toward the A/C pulley and/or vibration damper not being fully seated - like a bearing slightly askew in a race. The more pressure you put on it, the more it gets wedged. It/they eventually seated with vibration and revs. thus leaving the bolt loose. Just a theory.

the flyin' scotsman

The only reason I suggested it was when I did the project I managed to move the engine even though the flywheel lock was in place; the lock, if not exactly installed perfectly, can allow slip and perhaps false readings of torque on the crank bolt.

Glad it was not more serious; now about the Porkentensioner

Mrmerlin

make sure to check this bolt after 50 miles of driving, my guess is that the pulley isnt seating fully onto the crank nub, pay careful attention to the crank keyway this could be part of the problem, also did you replace the timing belt drive pulley ? maybe this isnt seated

JPTL

If I can't find the reason for this w/in a good amount of certainty, you can bet I'll be checking this bolt!
Didn't replace the t-belt drive pulley. Left that alone. Everything behind the covers looked really good, including the 10 year old timing belt.
Your thought about the crank keyway is interesting. I don't recall it w/too much detail. It's not a movable key that fits in an beveled groove is it?
FYI, the crank nub now protrudes through the A/C pulley just over 5mm. I have no idea what that measurement was initially when I put on the pulley group & torqued the bolt after the t-belt job. Wish I knew.
The correct amount of protrustion of the crank nub @ the A/C pulley isn't documented is it?

the flyin' scotsman

what?????????? I thought you replaced the belt

JPTL

I did.
It's just that the almost 10 year old belt (12k miles) looked great. Hardly any signs of wear and no cracking whatsoever. I replaced the water pump as well. That looked/felt fine too. I know that looks can be deceiving, but I'd venture a guess that they both had many more miles left in them. I just didn't want that gamble, so I replaced them.