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Hello, have a 1986 944 Turbo and have replaced all rollers and belts but still have whine. Can get the whine to be quieter by loosening the balancer belt, however, when we loosen it to the point that the noise goes away we can actually hear the belt flap. Anything we are missing here? Have looked through as many threads as I can find about it but still cannot get the whine to go away.
I would check 2 things. First, that when adjusting the tension on the balance shaft belt, be sure that you are moving the eccentric pulley clockwise. Second, there is an idler pulley that needs space of 1mm between the lower and upper surfaces of the balance shaft belt. When I adjust mine, I actually remove the idler pulley while doing the tension adjustment and then set the idler pulley. You should hear a slight to no whine when finished.
Assuming that the rollers are okay, balance shaft whine is caused by overtightening. The belt should be loose enough so that you can twist it by 90 degrees by hand at the longest stretch between rollers. But no so loose that you can hear it flopping.
Assuming that the rollers are okay, balance shaft whine is caused by overtightening. The belt should be loose enough so that you can twist it by 90 degrees by hand at the longest stretch between rollers. But no so loose that you can hear it flopping.
Some people are saying 270. Are you sure you are referring to the balance belt and not the timing belt?
Below are the factory manual pages, showing the oft-forgotten method of setting up the idler pulley. Its purpose is to keep the long upper run of balance shaft belt from flapping. Set your basic tension as described below (90 degrees twist is a good rule of thumb; I have the expensive factory belt tension tool and that gets you just about there), and then set up the idler pulley.
If everything is set up properly (belt tensioner pulley properly oriented so that clockwise=tighter), it is possible to achieve both the 0.5mm clearance between the lower run of the belt and underside of idler pulley and the upper side of the idler pulley applying a slight amount of tension (just under a mm) to the upper run as shown in the second pic.
There should be a slight whine but not too high-pitched.
Yep: the drawing clearly shows "pre-load" of the idler pulley of 0-1mm. I tighten my balance belt just enough to take the slack out which results in a very easy twist past 90 deg. I end up with whine on cold start that completely disappears on warm up...
Some people are saying 270. Are you sure you are referring to the balance belt and not the timing belt?
Get a factory tensioner or the Arnnwrox tensioner. Trying to do it by feel without a ton of experience is a total shot in the dark. Even with a ton of experience, it's a shot in the late dusk. But, if it's whirring until loose enough to make flapping noises, I'm with Seattle -- very likely either the tensioner is turned the wrong way or the idler pre-tension isn't set right.
Get a factory tensioner or the Arnnwrox tensioner. Trying to do it by feel without a ton of experience is a total shot in the dark. Even with a ton of experience, it's a shot in the late dusk. But, if it's whirring until loose enough to make flapping noises, I'm with Seattle -- very likely either the tensioner is turned the wrong way or the idler pre-tension isn't set right.
Our own@Tom M'Guinn is too modest, he wrote a great article for the PCA Panorama magazine comparing the various belt tension tools, including the expensive factory one that I have at my shop.
Tom’s article is really informative and entertaining. If you haven’t yet read it please do. Issue is that, as Glue Guy said, the belts are critical on 944s and unless you want to be “in the dark, or at best dusk”, get a tool...don’t mess with this one. One belt can take out the other, skipping teeth because your tension is loose can also cause damage as these are interference engines. Unless you are very experienced and have done this a kajillion times you are best to either leave this with Droops or Tom or buy the tool and do it properly. Not trying to be nasty, just really trying to get the point across.
BTW, if you have a spring tensioner, do not use 33 ft-lbs (in the WSM above - applies to idler pulleys on a stud only) but rather 17 ft-lbs on the nuts.
Our own@Tom M'Guinn is too modest, he wrote a great article for the PCA Panorama magazine comparing the various belt tension tools, including the expensive factory one that I have at my shop.
I could only find a link to the first page of that article. Can you post up the article in its entirety. The first pager was a rollicking good read. I would enjoy more
I could only find a link to the first page of that article. Can you post up the article in its entirety. The first pager was a rollicking good read. I would enjoy more
I should have mentioned that you have to be a Porsche Club of America (PCA) member to view the entire article via the link I posted. Perhaps someone has a scanned copy of it or something . . . .
FWIW I have always adjusted the idler pulley on the balance shaft belt with clearance rather than with any preload, going against the recommendation in the FSM. There was no way the idler pulley would not squeal like a pig, cold or hot, with even the lightest preload. It also didn't prevent me from driving 65k miles troublefree over 10 years with the same balance shaft belt and idler pulley. YMMV.
04-01-2021, 02:41 PM
1986 944 Turbo belt whine won't go away.
But, if it's whirring until loose enough to make flapping noises, I'm with Seattle -- very likely either the tensioner is turned the wrong way or the idler pre-tension isn't set right.
