[Gotter]

No idea what it is, what caused it... so here are all the details, relevant or not:

No prior indication, upon completing a normal left turn on even ground a sudden sound begins. It sounds like I am dragging a piece of plastic of fiberglass on the ground; sortof a grumbing or tumbling. Maybe like a few tumbling rocks...

It is related to RPMs, but not speed. I am within 1.0 miles from home, so I go slow (20MPH) and coast when possible. When not in gear, the sound persists with the idling engine. The final stretch of road to my driveway is uphill. I have to put her back in gear, still going 15-20 MPH. Near the top the grumble/tumble sound abruptly stops, only to be replaced by a WHIR. Same symptoms, same MO, different sound. I coast into my garage. No leaks, nothing dragging on ground, no distinct smells. No seemingly loss of power... but again, I was trying to keep it under 20MPH....

WTF is it? And please tell me it's a weird noise gremlin that only come out on the 14th of October and that it's cure is to wash the car...

Thanks everyone.

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[Gotter]

Quick update: Just opned hood and cranked up the car for 15 seconds to locate the sound.... seems to be coming from the center of the engine bay, not sure if top or bottom. Def. not belts right behind radiator...further back.

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[banditsc]

Clutch in or out the sound is the same? Sounds gets louder with revs or?

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[Gotter]

As far as I remember, the position of the clutch had no bearing on the sound. Don't believe the revs influenced the volume, but as I said, it did affect the speed or intensity of the sound...

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[banditsc]

Pull the belt off the alternator and see if the noise goes away.

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[Gotter]

Here is the video of the engine bay... once YouTube processes it.

http://www.youtube.com/watch?v=TeZWBvmM_0I

banditsc ---> I did have a bout with an uncharged battery a couple days ago, but thought it was b/c I ran radio for a few hours with the car off... Hmmm...

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[banditsc]

I think I'd start with checking the alternator, pulling the belt off and firing it up should tell you if that's it. If it's not then it has to be behind the timing belt cover.

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[Johannvb]

To me it sounds a lot like something is not happy in the belst area maybe a failed belt pulley?

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[jfrahm]

Check the timing and BS belts, and the cam chain if no problems are seen with the belts. I would not run the motor again without some checks.

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[Ceenit]

Any verdict on the cause of the sound yet? You got me paranoid, and now I think I hear it from my engine (although a bit quieter) . It sounds like a sewing maching running in harmony with the engine. I'm guessing it is either a pulley/bearing sound of some sort. My water pump has already been replaced once, otherwise I'd guess it is that. I'll pull my front covers off next weekend.

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[gryphon]

Have you tried a stethoscope?

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[Gotter]

No, the car went into the shop yesterday afternoon... but the plasticy rumbling wasn't regular, it was a random tumbling sound... like i was dragging a milk jug on the pavement.

more on the diagnosis later when i hear from the shop...

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[Gotter]

OK, so heard from the shop.... and the majority rules. A roller broke. Might have been the original roller... the bummer is that the result was a stripped intermediate belt. Which led to the alternator not charging. They are repairing (waiting on belt and rollers to come in)... Gonna set up a poll for s#!+s and giggles to guess how much the bill will be.

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[jfrahm]

Someone is confused. There is no roller on the alternator belt and no intermediate belt.



I imagine you lost a balance shaft idler (which would be weird) and stripped the BS belt but that would have no effect on the alternator.



The balance shaft belt runs very loose and breaking a roller on that belt is somewhat unlikely, unless maybe the belt shredded and grabbed the idler somehow. In any event if they are telling you the alternator is involved I would question the shops competence and integrity.



-Joel.

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[flash]

agreed - there are no rollers associated with the alternator (unless you added the D1R AC Tensioner kit)



rollers are associated with the balance belt

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[randall968]

Similar experience here day before yesterday in the '94; suddenly sounded like something caught under the front of the car as I'm coming onto a frontage road. At the intersection I turned to find a place to pull off & check it out & the sound stops; great, whatever it was must have worked free. About 3 miles down the road the sound abruptly returns; hmmmm, very odd.



As I shift into 1st to pull into a business driveway the engine dies; a thorough top, bottom, & engine compartment check reveal nothing so I hit the ignition. Wow; that sounds ominous...& definitely not something from the road.



After towing the car to the shop & removing the timing covers I discovered the issue. The timing belt tensioner arm pivot stud had sheared dropping the arm assy onto the crank timing gear which was the noise I heard. As the sound seemed to come from the rear of the engine/firewall area I presume it was transferring through the flywheel/bellhousing assy.



Needless to say, without tension the timing belt eventually disengaged which is doubtless why it died. Presumptively I'm safe in assuming I will have multiple if not all bent valves...joy!!! The annoying aspect is that all items were new as of Feb 09 with only 16/17k on them & so should have been good for another couple of years. Oh well...whatcha' gonna' do???



After looking into it further today I had expected to find the stud seized in the tensioner arm but it actually was not. Although a little stiff from the cold grease & o-rings it would move back & forth easily with a 19mm wrench. I pulled it out & there was no scoring or abrasion marks so apparently the stud just gave it up...go figure.



This was my first & only broken timing belt on my 968's or 944 Turbo's after a combined mileage of 350k+ on street & track so I guess I can't bitch too much...at least it wasn't a 32v 928...lol



I will certainly be adding a new pivot pin to the parts list on all future belt/roller replacments from now on...



Hopefully, your repair turned out to be less 'impactful'...

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[RS Barn]

We had a track 968 which had stud break with very bad results. An exhaust valve collided with piston and punched a hole in it. Worse yet was damaged bore. Block was wrecked.

We change TB tensioner pivot to '95 model with "O Rings" to retain grease any time we do belts

Pete

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[randall968]

Hey Pete; 'Zup??!!

I was wondering about that as I noticed the part number change for the '95. Mine must have been a later production '94 as the pin has the 2 o-rings.

BTW; do you use anything 'special' for the pin lube??

Randall

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