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Balance belt idler roller adjustment
#1

I was re-tensioning the balance belt this morning and was unable to set the balance shaft idler roller per factory spec. In short, the manual says set the roller a half-millimeter above the lower gear, such that it preloads the belt above by between zero and one millimeter.

Well if I set the bottom correctly, the top of the roller is not even close to touching the belt above - it's several millimeters below. My basic technique is to lay a curved 0.5mm feeler gauge on top of the lower pulley, then push the idler to the car's right (my left facing the engine) until it's as close to the upper belt as possible. I have the slotted hole for the idler pulley facing such that it allows maximum travel (as you know if it's rotated the wrong way this limits the pulley's left/right travel).

Anyone encounter this? I don't recall this problem from previous belt work. Any opinions about which setting is the more critical - above or below?
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#2

It sounds like you just need to move the idler roller to another position. You are setting the tension correctly, so the problem must be with the orientatin of the idler roller. As for above or below being more critical, my personal opinion is above. Below, the belt rides over an idler and then the tensioner pulley. Above, the belt could flap and ossilate and hit the water pump pulley and get damaged. But I don't think you'll need to choose, it sounds like the idler is not cooperating.
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#3

thanks OL - I must be missing something obvious but can't imagine what that would be. Are the 968 rollers the same diameter as the 944-series? Maybe the new roller I put on last summer is the wrong diameter. Just a thought.

on edit: Ha - worrying about what you said I went back out and re-adjusted the idler roller favoring the top belt and set it just touching the bottom. This leaves several millimeters clearance at the bottom, as opposed to the .5mm spec.

Weird.

    [attachment=9648:fac_man_..._diagram.jp
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#4

Yes, I have the same situation. No way to get both dimensions. I have a new idler too. Maybe it is the wrong diameter. Hopefully I still have the old one and can compare. I'm going to go in there and try again within the next week or so. Apex, please post if you figure it out
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#5

the adjuster will rotate to 2 positions that provide tension - one of them will give you the dimensions indicated - one will not
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94 Midnight Metallic Blue Cab Porsche 968 w/deviating cashmere/black interior and WAY too many mods to list - thanks to eric for creating www.968forums.com



"It isn't nearly as expensive to do it right as it is to do it wrong."
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#6

Not in this case, flash. I've rotated the eccentric both ways. You're right - there is a "near" and "far" position. The near position results in "almost to spec" as described above. The far position results in "NFW". [img]style_emoticons/<#EMO_DIR#>/dry.gif[/img] Not even close.

Lear: Is your engine still out of the car? You might be in a position to take pictures that would tell the story. Pic or no - please post what you find out. Meanwhile I've set the roller as described and am driving that way.
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