Turbine-like whine that follows engine rpm
06-06-2009, 09:46 PM
#46
Burning Brakes
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At the same time, I started getting 'cam belt service' warnings from the dash computer. Naturally assuming a connection, I arranged to have waterpump, cam belt and rollers changed. Turned out one of the roller bearings was very bad (despite apparently being replaced by the PO less than 3 years / 26.000 km ago)
No more warnings so far, but noise still there after this. Had a few other 928/944 guys listen to it at a meeting and the general opinion was that it wasn't internally from the engine, but rather the alternator, servo pump or perhaps just a belt making the noise.
Had my mechanic remove the belts today, and it didn't remove the noise
He's used a listening device on it and it still sounds like a bad waterpump, seemingly coming from the area around it, but since sounds wander, it's very difficult to say with any certainty.
No more warnings so far, but noise still there after this. Had a few other 928/944 guys listen to it at a meeting and the general opinion was that it wasn't internally from the engine, but rather the alternator, servo pump or perhaps just a belt making the noise.
Had my mechanic remove the belts today, and it didn't remove the noise
He's used a listening device on it and it still sounds like a bad waterpump, seemingly coming from the area around it, but since sounds wander, it's very difficult to say with any certainty.
07-11-2009, 04:41 PM
#47
Racer
Thread Starter
Finally able to provide you guys with an update on this.
Took a while to source the small outside roller for the timing belt, and when I finally got it, mechanic went on a two-weeks holiday, so thus the long delay.
At long last got it replaced this week, but it didn't solve the problem
Inspection of the old roller seems to support Mrmerlin's assertation that it normally doesn't rotate, as it has caked dirt on the roller surface, which I would expect to have been rubbed off if it touched the belt.
Everything around the timing belt looked good according to mechanic; no outward signs of trouble.
He's out of good ideas though, recommending I continue driving, keeping a very wary ear on the noise for any changes. He bases this on 1: The noise isn't all that bad. 2: It has hardly changed over 3000 miles of driving.
Not at all comfortable doing this, as I may have a ticking time bomb under the hood, but on the other hand, continuing to more or less randomly replace parts in the hope of finding the culprit, could eventually bleed me dry too.
Have set up an appointment with the Porsche specialist I mentioned earlier, for him to listen to the car, in the hope he might recognize the type of noise. They're booked solid though, so it won't happen until the end of this month unfortunately.
Regards,
Erling
Took a while to source the small outside roller for the timing belt, and when I finally got it, mechanic went on a two-weeks holiday, so thus the long delay.
At long last got it replaced this week, but it didn't solve the problem
Inspection of the old roller seems to support Mrmerlin's assertation that it normally doesn't rotate, as it has caked dirt on the roller surface, which I would expect to have been rubbed off if it touched the belt.
Everything around the timing belt looked good according to mechanic; no outward signs of trouble.
He's out of good ideas though, recommending I continue driving, keeping a very wary ear on the noise for any changes. He bases this on 1: The noise isn't all that bad. 2: It has hardly changed over 3000 miles of driving.
Not at all comfortable doing this, as I may have a ticking time bomb under the hood, but on the other hand, continuing to more or less randomly replace parts in the hope of finding the culprit, could eventually bleed me dry too.
Have set up an appointment with the Porsche specialist I mentioned earlier, for him to listen to the car, in the hope he might recognize the type of noise. They're booked solid though, so it won't happen until the end of this month unfortunately.
Regards,
Erling
06-26-2013, 01:38 AM
#48
Three Wheelin'
back from the dead...
I recently bought an 81 928 with the 4.5L L-jet engine. 55K miles, 5 speed.
The whine I have is RPM dependant, and can get VERY LOUD. more RPM, louder it goes. At 3K+ RPM it sounds like a fire truck. Seems to be from front of engine...but hard to tell. easy to hear when driving, at idle also ( but quieter)
not stuck AC compressor. check.
not AC or Alt rubbing on belly pan.
I have yet to pull the belts and try process of elimination.
when driving, If I push in the clutch and coast, and let the engine goto idle, the sound diminishes. so not drive-line related.
Records show water pump and timing belt done 4 years and 1500 miles ago.
I recently bought an 81 928 with the 4.5L L-jet engine. 55K miles, 5 speed.
The whine I have is RPM dependant, and can get VERY LOUD. more RPM, louder it goes. At 3K+ RPM it sounds like a fire truck. Seems to be from front of engine...but hard to tell. easy to hear when driving, at idle also ( but quieter)
not stuck AC compressor. check.
not AC or Alt rubbing on belly pan.
I have yet to pull the belts and try process of elimination.
when driving, If I push in the clutch and coast, and let the engine goto idle, the sound diminishes. so not drive-line related.
Records show water pump and timing belt done 4 years and 1500 miles ago.
06-26-2013, 06:02 AM
#49
Racer
Thread Starter
Back from the dead indeed.. 
Your problem sounds different from mine - or more developed perhaps, as my noise never was (is) as loud as you describe.
In my case, I haven't found the reason yet. In many thousands of miles since I first noticed it, it really hasn't changed, so I'm none the wiser.
In your case, I would start with removing the belts, to check for the 'easy' explanations. Best of luck with solving it.
Regards,
Erling
Your problem sounds different from mine - or more developed perhaps, as my noise never was (is) as loud as you describe.
In my case, I haven't found the reason yet. In many thousands of miles since I first noticed it, it really hasn't changed, so I'm none the wiser.
In your case, I would start with removing the belts, to check for the 'easy' explanations. Best of luck with solving it.
Regards,
Erling
06-26-2013, 01:28 PM
#51
Team Owner
Erling have you ever checked the crank end play and if the flex plate is preloaoded?
06-26-2013, 06:12 PM
#52
Racer
Thread Starter
Thanks for the suggestions.
Terry: no airpump in my car anymore (gone already when I got it), but perhaps something to check for granprixweiss928, when removing the belts.
Stan: It's a manual, so no flex plate if I'm not mistaken. The crank end play you mention, is it only relevant in connection with the flex plate, or applicable for a manual too ?
Regards,
Erling
Terry: no airpump in my car anymore (gone already when I got it), but perhaps something to check for granprixweiss928, when removing the belts.
Stan: It's a manual, so no flex plate if I'm not mistaken. The crank end play you mention, is it only relevant in connection with the flex plate, or applicable for a manual too ?
Regards,
Erling
07-06-2013, 01:47 AM
#55
Three Wheelin'
tonight I pulled my v-belts one by one. Car is an 81 so no Serp belts. not any of them. the only one that was slightly suspect was my smog pump, bearing might be getting tired. But the whine still is there, and LOUD at about 2K rpm. I locate it in the forward section of the engine, in the V, so my guess is water pump of oil pump or a bad/failing tensioner. I removed the upper timing cover to inspect the belt there, its fine. anyone ever heard an engine sound like this??
watch the video, Ill rev the motor and for abit hold it when its really loud. in this video none of the accessories belts are connected.
watch the video, Ill rev the motor and for abit hold it when its really loud. in this video none of the accessories belts are connected.
07-06-2013, 08:42 AM
#56
Three Wheelin'
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Last year I had a similar whining noise to yours, a few months later after not discovering what it was.., the air-con compressor gave up and smoked, since replacing the compressor it,s noise free.. just saying really ?
Ken
80 928 S
5 Speed
UK
Ken
80 928 S
5 Speed
UK
07-06-2013, 02:38 PM
#57
Under the Lift
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Since you have removed all the accessory belts, that rules out the air pump, ac compressor, power steering pump and alternator. To me, that leaves only the water pump and tensioner roller bearings. Theoretically it could be the oil pump, but I've not encountered that. If it does not localize to the tensioner by using a heater hose as a listening probe, I'd go with water pump. Hopefully others will notice your post is a new addition to this thread and will chime in with other suggestions.
tonight I pulled my v-belts one by one. Car is an 81 so no Serp belts. not any of them. the only one that was slightly suspect was my smog pump, bearing might be getting tired. But the whine still is there, and LOUD at about 2K rpm. I locate it in the forward section of the engine, in the V, so my guess is water pump of oil pump or a bad/failing tensioner. I removed the upper timing cover to inspect the belt there, its fine. anyone ever heard an engine sound like this??
watch the video, Ill rev the motor and for abit hold it when its really loud. in this video none of the accessories belts are connected.
MOV 3228 - YouTube
watch the video, Ill rev the motor and for abit hold it when its really loud. in this video none of the accessories belts are connected.
MOV 3228 - YouTube
07-22-2013, 07:31 PM
#58
Three Wheelin'
update to my issue
I picked up a Kempf gauge and pulled my upper covers. timing belt was a bit tight, the pointer was towards the rad fan about 1/8" PAST the notch in the gauge. I backed it off so that it is within the window. the noise is still there, but it is less loud now. far more tolerable. So I think this is tensioner related, and the noise seems to localize to that area. TB is only 1500 miles old, but was installed in 09. so 4 years like that. maybe the tensioner bearing is done now.
I picked up a Kempf gauge and pulled my upper covers. timing belt was a bit tight, the pointer was towards the rad fan about 1/8" PAST the notch in the gauge. I backed it off so that it is within the window. the noise is still there, but it is less loud now. far more tolerable. So I think this is tensioner related, and the noise seems to localize to that area. TB is only 1500 miles old, but was installed in 09. so 4 years like that. maybe the tensioner bearing is done now.
07-22-2013, 07:37 PM
#59
Race Car
What did the timing belt teeth look like? I would also take a peek at the cam gear teeth to check for wear and also to see if they are shiny or not.
Dan
'91 928GT S/C
475hp/460lb.ft
Dan
'91 928GT S/C
475hp/460lb.ft
07-22-2013, 10:37 PM
#60
Addict
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Have you examined the lower front engine cover? (Not the upper covers that encase the distributors and cam gears, but the lower cover that encases the water pump, oil pump, and crank damper...) It can rub on the rotating parts like the damper, as well as the waterpump and oil pump gear shafts, and trick you into thinking you have a turbine in your engine bay..
Did you take a look at the alternator cooling inlet.. It could have sucked in a leaves or debris, and it could be just making little noises in the rear alternator shroud.
One possibility could be the cam gear plate (the plate behind the cam gear, between that and the head) could be bent, and ir touching the back of the cam gears..
Have you examined the distributor caps and rotors for marks..?
First point I have experienced, others are just thoughts on rotational things..
Regards,
Did you take a look at the alternator cooling inlet.. It could have sucked in a leaves or debris, and it could be just making little noises in the rear alternator shroud.
One possibility could be the cam gear plate (the plate behind the cam gear, between that and the head) could be bent, and ir touching the back of the cam gears..
Have you examined the distributor caps and rotors for marks..?
First point I have experienced, others are just thoughts on rotational things..
Regards,