Timing Belt Idler Pulley
10-23-2007, 08:06 PM
#1
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Timing Belt Idler Pulley
I purchased an '86 944 for $400.00 that has/had some issues. The clutch hit the floor and stayed there so I flushed the fluid and bled the clutch slave cylinder. Clutch Fixed.
I also heard a belt whining when the engine was running and would get louder as the throttle was increased. After searching I determined it may be the Balance Belt (not to be confused with the timing belt). So I pulled off the air filter and the plastic case that seals the timing belts. When I pulled the case off a large bolt fell down into the timing gears. I fished it out with a magnet and determined it is the bolt that was used for the Timing Belt Idler Pulley.
OK, this is what I dont get. Even if i were to put the bolt and pulley on it wouldnt even touch the timing belt. I have attached some pictures so you guys can see what I'm dealing with.
This is my first porsche.
Thanks in advance for any help.
I also heard a belt whining when the engine was running and would get louder as the throttle was increased. After searching I determined it may be the Balance Belt (not to be confused with the timing belt). So I pulled off the air filter and the plastic case that seals the timing belts. When I pulled the case off a large bolt fell down into the timing gears. I fished it out with a magnet and determined it is the bolt that was used for the Timing Belt Idler Pulley.
OK, this is what I dont get. Even if i were to put the bolt and pulley on it wouldnt even touch the timing belt. I have attached some pictures so you guys can see what I'm dealing with.
This is my first porsche.
Thanks in advance for any help.
10-23-2007, 08:31 PM
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What is an eccentric roller setup? I have been using the following link as a reference:
http://www.clarks-garage.com/shop-manual/eng-10.htm
http://www.clarks-garage.com/shop-manual/eng-10.htm
10-23-2007, 09:59 PM
#7
Burning Brakes
That's a (non-eccentric) idler
The idler doesn't necessary rotate hard against the timing belt. It's there to limit belt movement in the middle of the long span. (You don't really want it causing too much drag and friction.) Put it back in!
And change the balance belt! Look at those teeth... half gone. Maybe that's where the whine is coming from, though there can be multiple sources (too tight, too loose, bad rollers, etc.) difficult to trace down.
And change the balance belt! Look at those teeth... half gone. Maybe that's where the whine is coming from, though there can be multiple sources (too tight, too loose, bad rollers, etc.) difficult to trace down.
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10-23-2007, 10:08 PM
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10-23-2007, 10:47 PM
#9
Burning Brakes
idler
DainBramaged: I've heard about things coming apart in there several times before. Not sure why. Clean the threads really good (in the block and on the bolt) and use loctite 574 when reinstalling. (Lack of cleaning + loctite by mechanics in a hurry may be why they come out.)
10-23-2007, 10:57 PM
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DainBramaged: I've heard about things coming apart in there several times before. Not sure why. Clean the threads really good (in the block and on the bolt) and use loctite 574 when reinstalling. (Lack of cleaning + loctite by mechanics in a hurry may be why they come out.)
10-23-2007, 11:36 PM
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OK, I loosend the balance belt idler roller and moved it down some and that stopped the whining noise at idle. It still has a little bit of a whine as the RPMs go up but much much less than before. SCHWEET!
10-24-2007, 01:22 AM
#12
Racer
It almost looks as if the balance belt is rubbing on the water pump pulley.
See how the water pump pulley is "polished" on the tapered part. This may have be caused buy the belt rubbing on the pulley.
The taper on the water pump pulley also matches the wear on the balance belt.
This was probably caused because the balance belt idler was set to far up, causing the belt to be forced up, contacting the water pump pulley when it rotates.
Change the belt, and I would also double check all the other rollers and gears for correct installation and tightness.
See how the water pump pulley is "polished" on the tapered part. This may have be caused buy the belt rubbing on the pulley.
The taper on the water pump pulley also matches the wear on the balance belt.
This was probably caused because the balance belt idler was set to far up, causing the belt to be forced up, contacting the water pump pulley when it rotates.
Change the belt, and I would also double check all the other rollers and gears for correct installation and tightness.
10-24-2007, 02:19 AM
#14
Not Special
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Replace the belt, absolutely. Belts are cheap. Rebuilds, not so much. If you're serious about doing it yourself, get (or find someone near you who has) the Arnworx tools for measuring the belt tension. Yes, you can do it by feel, but if I were a timing belt virgin, I'd want the numbers to back it up. 
I had someone HELPING me retension after my cam tower gasket from hell and was still scared to turn the key!
I had someone HELPING me retension after my cam tower gasket from hell and was still scared to turn the key!
10-25-2007, 01:48 AM
#15
Burning Brakes
whining
That balance belt roller just below the balance belt in your last picture is a common source of whine when it's bearing gets worn. It's got an adjustable eccentric to set it's spacing from the belt where it wraps below it. (Porsche wants you to set it real close... I don't remember the number of millimeters. They have a special tool for setting it.) If the spacing is real close, it will turn about at belt speed when the engine is running and things are vibrating, though it will spin freely with the engine stopped. If you open the gap up, it will stop turning when the engine runs. If the whine then goes away, then that was the source.