Turbine-like whine that follows engine rpm
05-29-2009, 06:43 PM
#31
Racer
Thread Starter
Again thanks everyone for the suggestions and input.
No conclusion yet, but a very interesting development today nonetheless.
Went to the shop and had a chance to listen with the mechanic's stethoscope myself this morning. To say that it was bloody difficult to locate the source of the noise would be an understatement. For example, if you put it at the end of the cams, it wasn't audible, but touch the upper, outer bolts on the cam belt covers and it was very clear. Likewise audible down around the water pump / oil pump, but just not possible to pin down decisively.
While chatting back and forth, one of the mechanics mentioned an extra, tiny roller that wasn't included in the cam belt / waterpump / rollers kit. Not involved in the belt tensioning, but still rotating with it, it could perhaps be the source.
Although suggesting it themselves, both mechanics were sceptical about the oil pump being the culprit, as pumps like the 928's hardly ever go (Just like some have mentioned here)
We ended up agreeing that I should try contacting an independent Porsche Specialist; one I know does handle 928s too, to get a second opinion.
When calling the specialist later today to set up an appointment, I described the problem and what's been done so far to the owner of the place. He dismissed the oil pump too and then starts talking about a tiny extra roller, and it quickly becomes clear it must be the same one mentioned by my regular mechanics earlier. According to the specialist, it can run dry and then make an awful racket. Not being essential, it can be removed briefly for diagnostic purposes.
But - and this is when things get really interesting - he then mentions that if an unoriginal oil filter has been fitted, it can make a turbine-like noise too. The filter fitted at the service is very likely unoriginal, and since the noise was present when I picked up the car after the service but not before, this could quite possibly be the cause.
Managed to drop by the specialist after work today to pick up an original filter. Do have tools to remove an oil filter, but only have the tool set jack and I won't get under the car with that one holding it, so swapping the filters will be done next week.
Will keep you all posted about the result.
Regards,
Erling
No conclusion yet, but a very interesting development today nonetheless.
Went to the shop and had a chance to listen with the mechanic's stethoscope myself this morning. To say that it was bloody difficult to locate the source of the noise would be an understatement. For example, if you put it at the end of the cams, it wasn't audible, but touch the upper, outer bolts on the cam belt covers and it was very clear. Likewise audible down around the water pump / oil pump, but just not possible to pin down decisively.
While chatting back and forth, one of the mechanics mentioned an extra, tiny roller that wasn't included in the cam belt / waterpump / rollers kit. Not involved in the belt tensioning, but still rotating with it, it could perhaps be the source.
Although suggesting it themselves, both mechanics were sceptical about the oil pump being the culprit, as pumps like the 928's hardly ever go (Just like some have mentioned here)
We ended up agreeing that I should try contacting an independent Porsche Specialist; one I know does handle 928s too, to get a second opinion.
When calling the specialist later today to set up an appointment, I described the problem and what's been done so far to the owner of the place. He dismissed the oil pump too and then starts talking about a tiny extra roller, and it quickly becomes clear it must be the same one mentioned by my regular mechanics earlier. According to the specialist, it can run dry and then make an awful racket. Not being essential, it can be removed briefly for diagnostic purposes.
But - and this is when things get really interesting - he then mentions that if an unoriginal oil filter has been fitted, it can make a turbine-like noise too. The filter fitted at the service is very likely unoriginal, and since the noise was present when I picked up the car after the service but not before, this could quite possibly be the cause.
Managed to drop by the specialist after work today to pick up an original filter. Do have tools to remove an oil filter, but only have the tool set jack and I won't get under the car with that one holding it, so swapping the filters will be done next week.
Will keep you all posted about the result.
Regards,
Erling
475hp/460lb.ft
06-05-2009, 05:03 PM
#34
Racer
Thread Starter
Just a quick update guys:
Oil filter was a blank unfortunately. Specialist sold me a Mann filter, but it turned out to be a Mann filter already fitted by my regular mechanic at the service, so no point in swapping them.
I'm now going to replace the tiny roller mentioned before. More specific, it's this one:
https://www.928gt.com/ps-25878-78-ti...bly-90-95.aspx
Rich asked earlier if it made any difference to the noise with the clutch in or out. It doesn't, as far as I can tell.
Regards,
Erling
Oil filter was a blank unfortunately. Specialist sold me a Mann filter, but it turned out to be a Mann filter already fitted by my regular mechanic at the service, so no point in swapping them.
I'm now going to replace the tiny roller mentioned before. More specific, it's this one:
https://www.928gt.com/ps-25878-78-ti...bly-90-95.aspx
Rich asked earlier if it made any difference to the noise with the clutch in or out. It doesn't, as far as I can tell.
Regards,
Erling
06-05-2009, 05:43 PM
#35
Chronic Tool Dropper
Lifetime Rennlist
Member
Lifetime Rennlist
Member
Erling--
The bearings in those guide rollers can be changed from the pin and the roller. IIRC, it's a very common 201 bearing with seals and shields (ie: 201FF) and an off-the-shelf part at any good parts seller. Cheapst part inside the front covers, shame it wasn't replaced. It's a snug fit in the roller, but comes out easily with a couple sockets in a bench vise. Someplace I have a video of changing mine during the last TB swap and can dig itout for you if you need it. But there's no magic to changing it. You will want new circlips to hold the little cast bracket to the pins on the block and the bearing on the bracket pin, and plan to use some really thick grease on those block pins so the bracket doesn't rattle/vibrate and wear on the pins over time. I used common aftermarket C circlips on a recent job, but Jim Bailey supplied me with originals when I did mine a few years ago now.
That roller is there only to help avoid flutter on the belt making it to the crank sprocket. On my car, it doesn't touch the belt at all while the engine isn't running. You should be able to localize the noise to that area below and slightly to the left of the crank nose if this is your problem. It's actually behind the center cover and the damper, so no way to listen directly once installed.
The bearings in those guide rollers can be changed from the pin and the roller. IIRC, it's a very common 201 bearing with seals and shields (ie: 201FF) and an off-the-shelf part at any good parts seller. Cheapst part inside the front covers, shame it wasn't replaced. It's a snug fit in the roller, but comes out easily with a couple sockets in a bench vise. Someplace I have a video of changing mine during the last TB swap and can dig itout for you if you need it. But there's no magic to changing it. You will want new circlips to hold the little cast bracket to the pins on the block and the bearing on the bracket pin, and plan to use some really thick grease on those block pins so the bracket doesn't rattle/vibrate and wear on the pins over time. I used common aftermarket C circlips on a recent job, but Jim Bailey supplied me with originals when I did mine a few years ago now.
That roller is there only to help avoid flutter on the belt making it to the crank sprocket. On my car, it doesn't touch the belt at all while the engine isn't running. You should be able to localize the noise to that area below and slightly to the left of the crank nose if this is your problem. It's actually behind the center cover and the damper, so no way to listen directly once installed.
06-05-2009, 06:16 PM
#36
Racer
Thread Starter
Thanks Dr. Bob.
A Swedish Porsche parts supplier I'm in touch with actually suggested the same, but mechanic wasn't keen on it. Fearing the roller or something else might be damaged in the process, he would rather just replace the whole deal.
As I would be paying him to do the bearing replacement, the savings might be relatively small anyway, and if something went wrong, the car would be stranded at the shop until a new part could be sourced.
Thus I figure; replace the whole part, but don't toss the old one. Without risk of the car getting stranded, I can try to have the old one's bearing replaced and if successful, I'll have a replacement ready for the next timing belt job (or whenever the new one's bearing gives up the ghost)
Regards,
Erling
A Swedish Porsche parts supplier I'm in touch with actually suggested the same, but mechanic wasn't keen on it. Fearing the roller or something else might be damaged in the process, he would rather just replace the whole deal.
As I would be paying him to do the bearing replacement, the savings might be relatively small anyway, and if something went wrong, the car would be stranded at the shop until a new part could be sourced.
Thus I figure; replace the whole part, but don't toss the old one. Without risk of the car getting stranded, I can try to have the old one's bearing replaced and if successful, I'll have a replacement ready for the next timing belt job (or whenever the new one's bearing gives up the ghost)
Regards,
Erling
06-05-2009, 08:02 PM
#37
Team Owner
just buy a 9.00 bearing the 170.00 dollar part is not warranted
06-05-2009, 08:22 PM
#38
Rennlist Member
I had a terrible whinning sound on the 84 when I first got the timing belt done. Turned out the clutch on the A/C compressor was bad and was just as loud as could be.
I could hear it in the driver seat and outside the car but just couldn't find it. It was pretty embarrassing driving the car with that darn loud whine.
A person mentioned the A/C clutch and when I removed the belt - aahhhh relief
Now I just need a new compressor (or clutch) - $$$
I could hear it in the driver seat and outside the car but just couldn't find it. It was pretty embarrassing driving the car with that darn loud whine.
A person mentioned the A/C clutch and when I removed the belt - aahhhh relief
Now I just need a new compressor (or clutch) - $$$
06-05-2009, 09:24 PM
#39
Rennlist Member
I just replaced that exact bearing on the rip van winkler 32 V 85 because it didn't operate smoothly. The $9 bearing was $20 at NAPA chain store (typical) here in the states but it was easy with a light duty shop press to remove and replace. My little roller was slightly damaged (nicked) in the process, but simple use of 400 grit oiled wet paper, followed by 1000 grit, then rinsed with solvent, made the roller surface absolutely fine again.
In my opinion the immediate thing to do is disassemble and totally inspect all aspects of the timing belt path. It may actually be a combination of things. The car shouldn't be run much until its solved. If you can take a series of about 20 digital snapshots of the set-up, one of us can diagnose the problem in conjunction with your mechanic, if he is willing to go down this path.
On my car, also, the tensioner roller shaft was missing a critical split ring that locates that roller. The roller was just starting to contact the body of the tensioner arm. You could see it happened a tiny bit from the slight wear, then the car was parked and left for about 10 years, as the scratched roller then corroded at the scratches. The belt was just starting to track off somewhat. Wasn't quite the noise you described, but I heard something as I fired it up a couple weeks ago.
Installing a crank pulley washer in reverse could also cause a noise and degradation.
On a 944, I mixed up an aftermarket balance shaft tensioner with the timing belt tensioner. Stupid rookie mistake. Timing belt contacted the rearmost plastic cover and created a pronounced whine and a bit of damage.
So, I am highly suspicious that whoever addressed the timing belt could have made a mistake in the reassembly. This seems obvious from your diagnosis with the use of the stethescope, also.
In my opinion the immediate thing to do is disassemble and totally inspect all aspects of the timing belt path. It may actually be a combination of things. The car shouldn't be run much until its solved. If you can take a series of about 20 digital snapshots of the set-up, one of us can diagnose the problem in conjunction with your mechanic, if he is willing to go down this path.
On my car, also, the tensioner roller shaft was missing a critical split ring that locates that roller. The roller was just starting to contact the body of the tensioner arm. You could see it happened a tiny bit from the slight wear, then the car was parked and left for about 10 years, as the scratched roller then corroded at the scratches. The belt was just starting to track off somewhat. Wasn't quite the noise you described, but I heard something as I fired it up a couple weeks ago.
Installing a crank pulley washer in reverse could also cause a noise and degradation.
On a 944, I mixed up an aftermarket balance shaft tensioner with the timing belt tensioner. Stupid rookie mistake. Timing belt contacted the rearmost plastic cover and created a pronounced whine and a bit of damage.
So, I am highly suspicious that whoever addressed the timing belt could have made a mistake in the reassembly. This seems obvious from your diagnosis with the use of the stethescope, also.
06-05-2009, 09:27 PM
#40
Rennlist Member
NOTE: This information is worth what you paid for it.
06-05-2009, 10:52 PM
#41
Racer
Thread Starter
Again thanks everyone for the input.
Chris, the noise was present before the timing belt was replaced, so I don't think it's related to any of the parts that were replaced in that process.
Regards,
Erling
Chris, the noise was present before the timing belt was replaced, so I don't think it's related to any of the parts that were replaced in that process.
Regards,
Erling
06-06-2009, 12:11 AM
#42
Team Owner
that bearing that your going to replace is a guide to prevent the belt from jumping a tooth on the crank gear if it should lose tension.
With the belt tight ,the belt doesnt contact it, i find it hard to figure that the bearing is making noise if its not turning
With the belt tight ,the belt doesnt contact it, i find it hard to figure that the bearing is making noise if its not turning
06-06-2009, 09:43 AM
#43
Rennlist Member
Would squirting WD-40 on each roller's bearing, one at at time, with the engine running stop it long enough to find the "squeaky wheel"? It wouldn't last long--but maybe it'd help find the culprit..
06-06-2009, 10:17 AM
#44
Team Owner
but you risk contaminating the timing belt with oil ( not good)
06-06-2009, 10:29 AM
#45
Rennlist Member
Could be a lot of things. At least you have eliminated all the easy stuff systematially. The mechanic will need to disassemble and assess all. I'd start with the easier part of inspecting the timing belt apparatus and water pump, then move to the valve train chain guides etc afterwards.
It is possible on the 85/86 to reassemble without the 3 front covers and listen to each part while in motion. Should be doable on later car as well. I'd use a screwdriver to attenuate the sounds into the stethescope and keep my digits out of there, though.
I
It is possible on the 85/86 to reassemble without the 3 front covers and listen to each part while in motion. Should be doable on later car as well. I'd use a screwdriver to attenuate the sounds into the stethescope and keep my digits out of there, though.
I