early 944 whining sound
10-16-2016, 05:29 PM
#1
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early 944 whining sound
My 1984 944 has been running well for the last few years. All belts have been changed about 3 years ago (15k miles ago) by the previous owner. (have receipts)
Few days ago I noticed a rattle from the exhaust, only happened at around 3,000 rpms. Today, the rattle seems to be gone, however, a new problem developed. There is a very noticeable high pitched hissing/ whining sound (a bit similar to a super charger whine) when the engine runs. It's most noticeable at idle, but it is also present while driving/ higher rpms.
I've been reading that this could be a balance shaft belt. But would a sound like this happen all of the sudden? Engine has been perfect for the last 3 years, only belt that I have touched/changed is the alternator belt a few weeks ago. From my understanding, balance shaft belt whining usually happens after changing/tightening the belt.
Link to video: https://www.youtube.com/watch?v=wXZK...ature=youtu.be
Car runs and drives fine, no loss of power.
Any input is appreciated.
Few days ago I noticed a rattle from the exhaust, only happened at around 3,000 rpms. Today, the rattle seems to be gone, however, a new problem developed. There is a very noticeable high pitched hissing/ whining sound (a bit similar to a super charger whine) when the engine runs. It's most noticeable at idle, but it is also present while driving/ higher rpms.
I've been reading that this could be a balance shaft belt. But would a sound like this happen all of the sudden? Engine has been perfect for the last 3 years, only belt that I have touched/changed is the alternator belt a few weeks ago. From my understanding, balance shaft belt whining usually happens after changing/tightening the belt.
Link to video: https://www.youtube.com/watch?v=wXZK...ature=youtu.be
Car runs and drives fine, no loss of power.
Any input is appreciated.
Last edited by edmrex; 10-16-2016 at 10:53 PM.
10-16-2016, 07:09 PM
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10-16-2016, 07:35 PM
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Could the exhaust rattle be related to the whining that I am experiencing now? To me, it seems like two unrelated issues.
10-16-2016, 09:31 PM
#5
Balance shaft wine is normal, you can make it less loud by slacking. The sound in the video is the t-belt rubbing on the belt guard, remove covers and inspect for belt shavings or a fresh rub mark on the top outer side of the t-belt. T-belt rubbing will sound like its coming from the cam tower and be very noisy like the video.
10-16-2016, 09:46 PM
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Just removed the alternator belt, and the sound was there. So it is not the alternator belt.
Balance shaft wine is normal, you can make it less loud by slacking. The sound in the video is the t-belt rubbing on the belt guard, remove covers and inspect for belt shavings or a fresh rub mark on the top outer side of the t-belt. T-belt rubbing will sound like its coming from the cam tower and be very noisy like the video.
How sure are you that this is a t-belt rubbing on the guard? I have to drive to work 10 miles tomorrow, how serious do you think this is? If it is the timing belt rubbing I'd rather not risk it.
10-16-2016, 10:08 PM
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That, my friend, is your balance shaft belt a wee bit too tight or one of the roller bearings are on it's way out. When was the last belt change? Where are you located? Perhaps a forum member could assist... I definitely would if you're in the New England area.
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10-16-2016, 10:17 PM
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I would not think that the balance shaft belt would be too tight, since I have not tightened the belts in the last 15k miles. A belt would not just become too tight overnight, right?
I'm leaning towards the roller bearings. Is there a way to diagnose bad roller bearings? How immediately would I need to fix a bad roller if it is the problem?
10-16-2016, 10:48 PM
#9
While the accessory belt was/is off, take the front cover off to check for rubbing as was suggested. You might also be able to find a bad bearing/roller then with a long screwdriver or mechanic's stethoscope.
The 3k rattle could also be a loose O2 sensor.
The 3k rattle could also be a loose O2 sensor.
10-17-2016, 01:38 PM
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How easy is it to take the timing belt cover off? Any tricks to it?
I will take the cover off tonight.
I drove the car for about 15 minutes today, and the whining sound was very minimal/almost couldn't hear it at the end of 15 minutes, when I pulled into the driveway.
I then shut it off and restarted it, and the sound was back.
Does this mean anything?
10-17-2016, 08:57 PM
#11
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It really helps if you drop the fan assembly out first, only takes 10 minutes but gains you a bunch of room.
Check the bearing/pulley shown below to see that it has 1mm clearance to the belt (on the bottom side). About the thickness of a credit card. It should spin freely without wobble.
Check the bearing/pulley shown below to see that it has 1mm clearance to the belt (on the bottom side). About the thickness of a credit card. It should spin freely without wobble.
10-17-2016, 09:36 PM
#12
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There are about 11, 10mm bolts to remove once the accessory belts are out of the way. You'll get a better view of what's going on at that point. There's also a vacuum hose to be removed running from the air box to the timing belt cover.
10-18-2016, 12:31 AM
#13
No need to pull the fans. I never do. As pfarah said, a handful of bolts requiring a 10mm socket to pull the front covers. Hopefully the hose from the airbox to the timing covers has already been deleted.