TB Woes – Just did TB Job – Now has a Bad Moaning Noise
07-27-2004, 02:11 AM
#76
Rennlist Member
Measure the bearing resistance - wind some light cord around the pully, and pull it with a spring balance, noting the steadiest reading you can. Compare with new pump when it arrives....that way you have an objective measurement at least.
jp 83 Euro S AT, with a quiet pump...
jp 83 Euro S AT, with a quiet pump...
08-02-2004, 03:41 PM
#77
Instructor
Thread Starter
Join Date: Feb 2004
Location: Houston
Posts: 100
Likes: 0
Received 0 Likes
on
0 Posts
Ok – I went back with another new Tensioner Roller, 2nd new rebuilt water pump, and another new T-Belt..
No more belt hunting on the cam gears – yes!
4 minutes later of idling, the dreaded moaning noise returns after things heat up. Crap!
The noise only returns after idling a cold engine after 4 or 5 minutes to warm things up. Then the noise slowly gets louder and louder (picture excessive stress / heat somewhere, generating the noise in center front of engine). It almost sounds like a belt is too tight, but that’s been ruled out multiple times.
Replaced so far during the project:
Timing Belt - twice
Water Pump - twice
Tensioner Roller and Bearings - twice
Tensioner Idler Roller and Bearings
Tensioner Bushings - twice
Tensioner Arm Pivot shaft / bolt
Also Rebuilt Tensioner
1st newly replaced water pump was definitely bad. Superheated WP pulley, noisy bearings after removal from engine, discolored impeller and pulley shaft, crud (small metallic fragments on end of impeller shaft). Also belt starting “hunting” fore and aft on cam gears after it was installed.
2nd newly replaced water pump (still on car) fixed the belt hunting on the cam gears issue.
Yet the moaning type sound (picture excessive stress / heat somewhere, generating the noise) has stayed. Timing Belt also apparently getting too hot still.
I don’t know what else to do at this point. But here’s a shot in the dark: When dropping the T-Belt over 1-4 cam gear, I then “let go” of the cam gear spring pressure, thus tightening the slack between cam gears and over the WP pulley. Could this be too much tension? All slack is between 1-4 cam gear and the tensioner, but could I be letting the cam gear pull the belt too tight over the WP pulley?
Stymied – still….
No more belt hunting on the cam gears – yes!
4 minutes later of idling, the dreaded moaning noise returns after things heat up. Crap!
The noise only returns after idling a cold engine after 4 or 5 minutes to warm things up. Then the noise slowly gets louder and louder (picture excessive stress / heat somewhere, generating the noise in center front of engine). It almost sounds like a belt is too tight, but that’s been ruled out multiple times.
Replaced so far during the project:
Timing Belt - twice
Water Pump - twice
Tensioner Roller and Bearings - twice
Tensioner Idler Roller and Bearings
Tensioner Bushings - twice
Tensioner Arm Pivot shaft / bolt
Also Rebuilt Tensioner
1st newly replaced water pump was definitely bad. Superheated WP pulley, noisy bearings after removal from engine, discolored impeller and pulley shaft, crud (small metallic fragments on end of impeller shaft). Also belt starting “hunting” fore and aft on cam gears after it was installed.
2nd newly replaced water pump (still on car) fixed the belt hunting on the cam gears issue.
Yet the moaning type sound (picture excessive stress / heat somewhere, generating the noise) has stayed. Timing Belt also apparently getting too hot still.
I don’t know what else to do at this point. But here’s a shot in the dark: When dropping the T-Belt over 1-4 cam gear, I then “let go” of the cam gear spring pressure, thus tightening the slack between cam gears and over the WP pulley. Could this be too much tension? All slack is between 1-4 cam gear and the tensioner, but could I be letting the cam gear pull the belt too tight over the WP pulley?
Stymied – still….
08-02-2004, 04:08 PM
#78
Range Master
Pepsie Lite
Lifetime Rennlist
Member
Pepsie Lite
Lifetime Rennlist
Member
You sure the moaning is not coming from your fans or another accessory? I am just grasping at straws here, I sure wish I could look at the car and hear the noise for myself.........
08-02-2004, 04:21 PM
#79
Instructor
Thread Starter
Join Date: Feb 2004
Location: Houston
Posts: 100
Likes: 0
Received 0 Likes
on
0 Posts
I know, I'm grasping at straws myself. The words "flatbed towtruck" and "I surrender" are actually starting to sound plausible. Perish the thought...
It has ran without belts, and fans / shroud, and still the noise is there.
I wonder what the odds are of 2 bad rebuilt water pumps - back to back - are?
It has ran without belts, and fans / shroud, and still the noise is there.
I wonder what the odds are of 2 bad rebuilt water pumps - back to back - are?
08-02-2004, 04:48 PM
#80
Range Master
Pepsie Lite
Lifetime Rennlist
Member
Pepsie Lite
Lifetime Rennlist
Member
Get someone to come by and look at it..........wish I could do it for you........Another local 928er who has done a TB job. Two sets of eyes are better than one set. AND DON'T GIVE UP DAMN IT. That ramp truck talk is for quitters..........you can do this man................be patient.
08-02-2004, 05:21 PM
#81
Rennlist Member
Join Date: Dec 2002
Location: Southern New England
Posts: 1,975
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by geekapalooza
I wonder what the odds are of 2 bad rebuilt water pumps - back to back - are?
08-02-2004, 05:25 PM
#82
Fleet of Foot
Rennlist Member
Rennlist Member
I've been watching this thread awhile... Thought I'd throw this out. ALL timing belts that I have ever replaced (a lot) on any kind of engine make a moaning sound for around 1-2K miles, even properly tensioned, probably until the belt begins to seat or stretch. They will really howl if the belt is overtensioned, basically warning you that you may have a problem. I am beginning to wonder if what you are experiencing here is actually a normal condition??? I realize of course you were having a hot pulley on the WP itself, but I am wondering if this may just have been normal heat tranfer due to hot coolant in the WP radiating to the pulley. Are you still having a tracking problem? May be a totally separate issue. I had a tracking problem (bad tensioner bushings) and there was no noise associated with it. Just some thoughts... 
Hope this helps!
Hope this helps!
08-02-2004, 06:10 PM
#83
Rennlist Member
Join Date: Mar 2003
Location: Nashua, NH
Posts: 4,328
Likes: 0
Received 0 Likes
on
0 Posts
I hate to say this, but it sounds like you've got another bad water pump. If you've identified the problem correctly and the symptoms are the same, then it's likely that the cause is the same.
Will you say where you got your water pumps? If there's a bad batch out there we need to know and you may be able to source from a different rebuilder through one of the big three.
Will you say where you got your water pumps? If there's a bad batch out there we need to know and you may be able to source from a different rebuilder through one of the big three.
08-02-2004, 06:16 PM
#84
Range Master
Pepsie Lite
Lifetime Rennlist
Member
Pepsie Lite
Lifetime Rennlist
Member
Bill brings up a good point..........the question of the overly hot waterpump pulley.......does this condition still exist? The symptom in the first case was a burned belt. Is the belt still being burned? How loud is the moan? does the sound volume or pitch change with engine speed?
Damn, you got me cogitating on this again...............
Damn, you got me cogitating on this again...............
08-02-2004, 06:43 PM
#85
Drifting
I too had a slight moan from a brand new belt, but it was pretty faint. I kept stopping and checking to see if it got any worse, after a few hundred miles it stopped and this is the first time I've thought about it since (7k later).
08-02-2004, 07:08 PM
#86
Rennlist Member
It may be the second pump, but it's a bit like the line of "lightning never strikes twice ...." so, what can it be?
Where did the metal fragments on the 'bad' pump come from? Was there any scoring on the block face? If the impeller was not fully pressed onto its shaft ( due to improperly seated bearing, seal, or old fashioned stupidity) , then with expansion to operating temp, the impeller may be moaning away against the block. Was the impeller plastic or cast iron? - same in the latest pump? What is the face to face dimension from pump pulley to impeller? ( to be efficient pumps, must impellers are very close to their casing halves - the block being the second half).
Where is it appear to get the hottest - at the pump, at the crank?
As far as installing the belt, as long as the timing marks line up, you cannot over tension the belt in any one span!(by turning cam gears, etc.). All tension is induced by the tensioner alone when the indices are "on".
Water level is great - ditto for oil we conclude.
Does the crank spin freely when setting belt tension? Does it take any more effort to turn (by hand) after the moaning starts? If so, that would call for dropping the lower bell housing cover to verify 'you - know - what'.. The fact is at least I don't know - so excuse the thinking out loud: Just exploring the possible ...
Where did the metal fragments on the 'bad' pump come from? Was there any scoring on the block face? If the impeller was not fully pressed onto its shaft ( due to improperly seated bearing, seal, or old fashioned stupidity) , then with expansion to operating temp, the impeller may be moaning away against the block. Was the impeller plastic or cast iron? - same in the latest pump? What is the face to face dimension from pump pulley to impeller? ( to be efficient pumps, must impellers are very close to their casing halves - the block being the second half).
Where is it appear to get the hottest - at the pump, at the crank?
As far as installing the belt, as long as the timing marks line up, you cannot over tension the belt in any one span!(by turning cam gears, etc.). All tension is induced by the tensioner alone when the indices are "on".
Water level is great - ditto for oil we conclude.
Does the crank spin freely when setting belt tension? Does it take any more effort to turn (by hand) after the moaning starts? If so, that would call for dropping the lower bell housing cover to verify 'you - know - what'.. The fact is at least I don't know - so excuse the thinking out loud: Just exploring the possible ...
08-02-2004, 08:22 PM
#87
Fleet of Foot
Rennlist Member
Rennlist Member
The impeller into the block would definitely start out grinding, not moaning. Metallic debris could be left over from original pump failure and an insufficient flushing of the cooling system afterward (BTDT). Can you try to describe what the moaning sounds like, speed dependent, etc.? Is it kind of a 'warbling' sound?
08-02-2004, 10:33 PM
#88
Rennlist Member
Another wild shot in the dark or two... With the crank at 45° and the TB off, rotate each cam one full revolution to check for binding. Also see if the oil pump turns freely. Do this VERY carefully... I'm not positive that 45° absolutely insures against valve interference, you might want to double-check that. If you haven't had the oil pump out for seals, now is a good time. It will be easier to check if it isn't trying to build pressure...
08-04-2004, 11:47 AM
#89
Instructor
Thread Starter
Join Date: Feb 2004
Location: Houston
Posts: 100
Likes: 0
Received 0 Likes
on
0 Posts
Sorry for the late response guys. Busy as heck lately…
The 1st new rebuilt WP was a PCNA approved rebuilt. Came from a Porsche Dealer in San Diego, then shipped to Devek, then to me. Auto-Pac was the rebuilder. It had a plastic impeller. The impeller came out looking good, no rubbing on the block whatsoever. The tiny fragments were on the end of the shaft (impeller side), apparently a by-product of the bearing inside the WP going bad. Coolant drained clean as a whistle. The engine is one of the cleanest running engines I have ever owned. The coolant and oil always stays new looking all the time so far. Too bad I can’t drive the thing.
The 2nd WP is Auto-Pac also, directly from 928 Intl. This one has a metal impeller. I guess the difference in a PCNA approved WP from the rebuilder is the Plastic vs metal impeller. Jim B. thoroughly checked it out for me before shipping, so I’m confident that I have not received 2 bad WP’s in a row. Thanks Jim!
Also while on the subject, I just have to throw out a hearty “thanks” to all of the Big 3 for putting up with me on this project, since I have pestered all 3 of them during my “project from hell”. And thanks again to all you guys here on this thread for the help, much appreciated!
Anyway, back to business. Last night I Pulled the TB cover – passenger side (it’s hot outside in the garage these days, time to install an A/C unit in the garage!). Sure enough the newest T-Belt got too hot again, and left impressions where it parked on the WP Pulley and Tensioner roller, after shutting off the motor. I re-checked T-Belt tension again, still in spec as usual, but on the low side. BUT - I did notice when installing the T-Belt, that tension fluctuated when adjusting. I would turn the crank 2 revs, set tension, turn crank 2 revs again, adjust tension once again, and so on. It seemed like there is some variance in the tension setting every time I spun the crank 2 revolutions. Each time it was within the window, but was on the high side of it one time, and on the low side of it the next. The variance never perfectly flattened out. I probably turned 2 revolutions and re-adjusted at least 5 to 7 times. Thoughts?
The next plan I guess, is to put a laser thermometer on the pulleys while motor is running, with the center cover off again. I paid a visit to a local BMW, MB, Porsche repair shop yesterday. “Hans” was nice enough to loan me one to use. This Laser Thermometer is one very cool little device!
Hans also gave me a number to a towing company. Never!!! Quitting crossed the mind for a sec, but is not in the vocabulary (yet).
The puzzling thing is all pulleys turn smooth and good, were never messed with during the project, and the old TB / WP / Rollers worked smooth as silk before I jumped in to do nothing more than just proactive preventative maintenance.
Thanks,
Rob (Can now do a 928 TB / WP project with eyes closed)
The 1st new rebuilt WP was a PCNA approved rebuilt. Came from a Porsche Dealer in San Diego, then shipped to Devek, then to me. Auto-Pac was the rebuilder. It had a plastic impeller. The impeller came out looking good, no rubbing on the block whatsoever. The tiny fragments were on the end of the shaft (impeller side), apparently a by-product of the bearing inside the WP going bad. Coolant drained clean as a whistle. The engine is one of the cleanest running engines I have ever owned. The coolant and oil always stays new looking all the time so far. Too bad I can’t drive the thing.
The 2nd WP is Auto-Pac also, directly from 928 Intl. This one has a metal impeller. I guess the difference in a PCNA approved WP from the rebuilder is the Plastic vs metal impeller. Jim B. thoroughly checked it out for me before shipping, so I’m confident that I have not received 2 bad WP’s in a row. Thanks Jim!
Also while on the subject, I just have to throw out a hearty “thanks” to all of the Big 3 for putting up with me on this project, since I have pestered all 3 of them during my “project from hell”. And thanks again to all you guys here on this thread for the help, much appreciated!
Anyway, back to business. Last night I Pulled the TB cover – passenger side (it’s hot outside in the garage these days, time to install an A/C unit in the garage!). Sure enough the newest T-Belt got too hot again, and left impressions where it parked on the WP Pulley and Tensioner roller, after shutting off the motor. I re-checked T-Belt tension again, still in spec as usual, but on the low side. BUT - I did notice when installing the T-Belt, that tension fluctuated when adjusting. I would turn the crank 2 revs, set tension, turn crank 2 revs again, adjust tension once again, and so on. It seemed like there is some variance in the tension setting every time I spun the crank 2 revolutions. Each time it was within the window, but was on the high side of it one time, and on the low side of it the next. The variance never perfectly flattened out. I probably turned 2 revolutions and re-adjusted at least 5 to 7 times. Thoughts?
The next plan I guess, is to put a laser thermometer on the pulleys while motor is running, with the center cover off again. I paid a visit to a local BMW, MB, Porsche repair shop yesterday. “Hans” was nice enough to loan me one to use. This Laser Thermometer is one very cool little device!
Hans also gave me a number to a towing company. Never!!! Quitting crossed the mind for a sec, but is not in the vocabulary (yet).
The puzzling thing is all pulleys turn smooth and good, were never messed with during the project, and the old TB / WP / Rollers worked smooth as silk before I jumped in to do nothing more than just proactive preventative maintenance.
Thanks,
Rob (Can now do a 928 TB / WP project with eyes closed)
08-04-2004, 01:30 PM
#90
Rennlist Member
Quote: " Rob (Can now do a 928 TB / WP project with eyes closed)" ..... and, lest we forget, " wallet open .... "
If you are using the Kempf tool at TDC and on the closest tooth to the center cover ( or same tooth location w/o cover), I've never seen any varience after the first two full cycles (4 revs). If you have the 9201 tool, it could be quite easy to get variation. Anyway, the former is not a micrometer - so it depends on the magnitude of variation seen. 1/4 turn on the adjuster can take it 'out of the window'. Re. the tensioner, even if the guts were scrambled, the thing would hold constant while setting tension - it would just behave differently - later ...
Interested in the temp readings ....
If you are using the Kempf tool at TDC and on the closest tooth to the center cover ( or same tooth location w/o cover), I've never seen any varience after the first two full cycles (4 revs). If you have the 9201 tool, it could be quite easy to get variation. Anyway, the former is not a micrometer - so it depends on the magnitude of variation seen. 1/4 turn on the adjuster can take it 'out of the window'. Re. the tensioner, even if the guts were scrambled, the thing would hold constant while setting tension - it would just behave differently - later ...
Interested in the temp readings ....