I have had significant belt tensioner noise at idle for a couple of months. I got around to replacing the tensioner damper and that quieted about half the noise, but the tensioner was still moving significantly at idle, and idling more than a few minutes led to the damper becoming hot.
I had picked up a made-in-China "DB Electrical ABO0269 Alternator (For Mercedes Benz Cl S Sl Class 4.2L 5.0L 6.0L 150 Amp 1994-2002)" from Amazon last Fall in anticipation of removing the original Bosch 115A unit for potential overhaul, which I know to be original because I have all the receipts on this car from new. With over 160k miles, I normally replace starter/alternator/water pump on my cars; the alternator is top of my list for this one. That alternator application is reputed to be a direct replacement for the original, with higher current capacity.
Because replacing only the tensioner damper did not solve the noise-at-idle problem entirely, I figured that I now have a good reason to swap out the alternator and check the OAP (Overrunning Alternator Pulley), which is designed to prevent just this sort of situation. When removed, I found that my original, OEM OAP was/is locked solid. The alternator I purchased comes with a solid pulley, so I also bought an INA 602-150-00-60 OAP.
And, I needed a pulley tool set, in addition to my regular shop tools.
These proved to be a bolt-in replacement for the 115A Bosch.
DB Electrical ABO0269 Alternator (For Mercedes Benz Cl S Sl Class 4.2L 5.0L 6.0L 150 Amp 1994-2002), $126
INA 602-150-00-60, $57
Lisle 57650 Alternator Decoupler Tool Set, $26
Physical comparison:
I assume an impact wrench is needed to remove the 22mm nut to remove the solid pulley, but other methods have been used. As I'm not re-using the pulley, I could have used a regular ratchet and strap wrench, vise, etc. but because I was not certain that I wouldn't have to return this alternator, it was best if I left no tool marks
Rear view of the INA OAP:
Front view of the INA OAP:
Getting ahead of myself, front view of the old, OEM INA OAP. It is locked up solid, and was the reason for my noise and excessive tensioner movement at idle:
Lisle 57650 Alternator Decoupler Tool Set
Lisle 57650 pulley R&R tool set:
I used the 31T Spline and 10mm triple square tools:
I used a 7/8" wrench for the 31T spline adapter, and a box-end 10mm for the 10mm triple spline, but I definitely needed more leverage for that small wrench. The 18" pipe section was truly necessary:
I was originally going to remove the intercooler pipe section and drop the alternator out the bottom. I used this tool to loosen the alternator's top bolt:
However, after loosening with that perfect tool, the top bolt would not clear the fan.
Therefore, I figured I had to remove the fan to proceed. After fan removal, I then didn't need that GearWrench ratcheting E14 wrench and could have used a std. E14 socket, which is what I used on the alternator's lower bolt (using a 1" 3/8" extension; not everybody has a shorty 1" extension, but I'd run into this kind of problem before).
Kris will be pleased to note that after I removed the fan, I decided to leave the fan & fan clutch off. I've run fanless on other (older) vehicles many times, and Kris' testimony about running his E300 diesel fanless for years gives me confidence.
[Removing the fan is bitchy. There isn't enough room to manipulate tools or the screws that retain the plastic fan to the fan clutch. There are only three socket-head screws, 5mm hex wrench to remove them, but no room for even a 1/4" air ratchet: I removed them all by hand and it was probably twenty minutes' work, with lots of use of my magnet-on-a-stick tool, as I dropped the wrench a half-dozen times at least. I do not want to do that job more than twice. And access to everything up front is so much nicer with the fan & shroud out of the way!]
Fan clutch removed:
Not shown: removing the splash panel and disconnecting the two leads for the rear of the alternator (13mm for the charge lead, 10mm for the D+). One is supposed to disconnect the battery when doing this.
Imagine my surprise when I was able to then remove the alternator out the top! The cardboard is there to protect the radiator fins from damage, and it was needed, but while tight the lower radiator hose did allow enough room to snake the old alternator out and the new one in:
Rear of alternator after installation. The alternate placement ("clocking") of the rear makes the charge lead appear taut, but it's not. I will monitor this to see if a shiny spot develops on the intercooler pipe; if so, I may remove the alternator and attempt to re-clock it (if possible) to provide more slack. Lack of slack may or may not present a future problem.
I started it and it seems to work OK. I have not driven it, but I feel this was a success. There is no more tensioner movement or noise at idle.
I had picked up a made-in-China "DB Electrical ABO0269 Alternator (For Mercedes Benz Cl S Sl Class 4.2L 5.0L 6.0L 150 Amp 1994-2002)" from Amazon last Fall in anticipation of removing the original Bosch 115A unit for potential overhaul, which I know to be original because I have all the receipts on this car from new. With over 160k miles, I normally replace starter/alternator/water pump on my cars; the alternator is top of my list for this one. That alternator application is reputed to be a direct replacement for the original, with higher current capacity.
Because replacing only the tensioner damper did not solve the noise-at-idle problem entirely, I figured that I now have a good reason to swap out the alternator and check the OAP (Overrunning Alternator Pulley), which is designed to prevent just this sort of situation. When removed, I found that my original, OEM OAP was/is locked solid. The alternator I purchased comes with a solid pulley, so I also bought an INA 602-150-00-60 OAP.
And, I needed a pulley tool set, in addition to my regular shop tools.
These proved to be a bolt-in replacement for the 115A Bosch.
DB Electrical ABO0269 Alternator (For Mercedes Benz Cl S Sl Class 4.2L 5.0L 6.0L 150 Amp 1994-2002), $126
INA 602-150-00-60, $57
Lisle 57650 Alternator Decoupler Tool Set, $26
Physical comparison:
I assume an impact wrench is needed to remove the 22mm nut to remove the solid pulley, but other methods have been used. As I'm not re-using the pulley, I could have used a regular ratchet and strap wrench, vise, etc. but because I was not certain that I wouldn't have to return this alternator, it was best if I left no tool marks
Rear view of the INA OAP:
Front view of the INA OAP:
Getting ahead of myself, front view of the old, OEM INA OAP. It is locked up solid, and was the reason for my noise and excessive tensioner movement at idle:
Lisle 57650 Alternator Decoupler Tool Set
Lisle 57650 pulley R&R tool set:
I used the 31T Spline and 10mm triple square tools:
I used a 7/8" wrench for the 31T spline adapter, and a box-end 10mm for the 10mm triple spline, but I definitely needed more leverage for that small wrench. The 18" pipe section was truly necessary:
I was originally going to remove the intercooler pipe section and drop the alternator out the bottom. I used this tool to loosen the alternator's top bolt:
However, after loosening with that perfect tool, the top bolt would not clear the fan.
Therefore, I figured I had to remove the fan to proceed. After fan removal, I then didn't need that GearWrench ratcheting E14 wrench and could have used a std. E14 socket, which is what I used on the alternator's lower bolt (using a 1" 3/8" extension; not everybody has a shorty 1" extension, but I'd run into this kind of problem before).
Kris will be pleased to note that after I removed the fan, I decided to leave the fan & fan clutch off. I've run fanless on other (older) vehicles many times, and Kris' testimony about running his E300 diesel fanless for years gives me confidence.
[Removing the fan is bitchy. There isn't enough room to manipulate tools or the screws that retain the plastic fan to the fan clutch. There are only three socket-head screws, 5mm hex wrench to remove them, but no room for even a 1/4" air ratchet: I removed them all by hand and it was probably twenty minutes' work, with lots of use of my magnet-on-a-stick tool, as I dropped the wrench a half-dozen times at least. I do not want to do that job more than twice. And access to everything up front is so much nicer with the fan & shroud out of the way!]
Fan clutch removed:
Not shown: removing the splash panel and disconnecting the two leads for the rear of the alternator (13mm for the charge lead, 10mm for the D+). One is supposed to disconnect the battery when doing this.
Imagine my surprise when I was able to then remove the alternator out the top! The cardboard is there to protect the radiator fins from damage, and it was needed, but while tight the lower radiator hose did allow enough room to snake the old alternator out and the new one in:
Rear of alternator after installation. The alternate placement ("clocking") of the rear makes the charge lead appear taut, but it's not. I will monitor this to see if a shiny spot develops on the intercooler pipe; if so, I may remove the alternator and attempt to re-clock it (if possible) to provide more slack. Lack of slack may or may not present a future problem.
I started it and it seems to work OK. I have not driven it, but I feel this was a success. There is no more tensioner movement or noise at idle.