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Nonong
Regular
Date registered: Apr 2006
Location: Manila, Philippines
Vehicle(s): 1995 290GD LWB white; 2016 G500 silver
Posts: 88
| problems with my belt tensioner-shock absorber
I'm having problems with my 290GD's engine belt lately. The belt tensioner shock absorber fails after about 1,000km only!! The engine would become noisy which can be traced to the belt rattling heavily. After inspection, you can see that the belt tensioner-shock absorber has already lost its stiffness. I've already replaced it two (2) times and the same thing happens again after about 1,000kms. This belt tensioner shock absorber I'm referring to is the small shock absorber like that counter's the spring on the automatic belt tensioner assembly. This is present with the 601, 602 and 603 diesel engines. As of the moment the color code of my spring is yellow. I have seen in some pictures that they have a green color coded spring. Would the spring be a factor in the belt tensioner's failure? I'll appreciate any thoughts on this matter.
Regards,
Nonong |
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Alaskagwagen
Date registered: Dec 1899
Location:
Vehicle(s):
| RE: problems with my belt tensioner-shock absorber
I wonder if you have a bad belt or pulley which is causing the spring to work too hard. Does the tensioner move when the engine is on - ie does it compress and extend?
Adam |
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AlanMcR
Expert
Date registered: Apr 2006
Location: US, CA, Los Altos
Vehicle(s): G300DT E300DT 230SL
Posts: 3500
| It's most likely the one-way clutch on the alternator
Most modern diesels have a one-way clutch hidden inside the pulley for the alternator. If that seizes you get exactly the symptoms you mention.
The high compression and quick burn of the diesel design leads to the belt being driven in pulses. The larger alternators mounted on modern engines have a lot of mass that doesn't want to speed up and slow down. The solution has been to put a one-way clutch on the alternator shaft. The belt keeps kicking the alternator around and everything is great. If the clutch seizes then the alternator and motor play tug-of-war with the shock being the loser.
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Nonong
Regular
Date registered: Apr 2006
Location: Manila, Philippines
Vehicle(s): 1995 290GD LWB white; 2016 G500 silver
Posts: 88
| Re: problems with my belt tensioner-shock absorber
Hi Adam,
Yes, the tensioner moves when the engine is running. It does extend and compress. Sorry I forgot to mention that the rattling only happens in a certain RPM ie 700rpm at idle. When I turn on the aircon which brings down the RPM to about 600rpm, the rattling disappears. The rattle also disappears when the rpm is more than 700. At around 800 rpm up to 3,000rpm, there is no ratlling of the belt.
I have also replaced the belt and pulley the last time around but the problem came back after 1,000 km.
Regards,
Nonong |
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Nonong
Regular
Date registered: Apr 2006
Location: Manila, Philippines
Vehicle(s): 1995 290GD LWB white; 2016 G500 silver
Posts: 88
| Re: problems with my belt tensioner-shock absorber
Hi Alan!
Thank you for the information. I will try to talk to my mechanic about this clutch and see if he does know about it. Hopefully he does and we can check the clutch on the alternator shaft.
Regards,
Nonong
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AlanMcR
Expert
Date registered: Apr 2006
Location: US, CA, Los Altos
Vehicle(s): G300DT E300DT 230SL
Posts: 3500
| Checking the clutch
It is pretty easy to check the clutch. Take off the belt. Grab the pulley with your hand. Sharply twist the pulley clockwise and counterclockwise. It shoud grab in the clockwise direction and slip in the counterclockwise direction. If not it needs replacement. The fastner requires a special internal spline tool. Find an alternator rebuild shop. I had mine replaced for $45, parts and all.
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Braingears
Expert
Date registered: Apr 2006
Location: St Petersburg, FL
Vehicle(s): G320 & ML320
Posts: 1450
| Re: problems with my belt tensioner-shock absorber
Also look for any pulleys that may be out of balance.
Does the engine run rough at 700 RPM? Is there any lunging in the engine? |
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Nonong
Regular
Date registered: Apr 2006
Location: Manila, Philippines
Vehicle(s): 1995 290GD LWB white; 2016 G500 silver
Posts: 88
| Re: problems with my belt tensioner-shock absorber
Hi Chuck!
We already checked the pulleys before and everything seems ok. The engine does not run rough at 700 rpm. My mechanic made a test before. He poured a little water between the belt and the pulley while the engine is running and the rattle disappears. Once the water dries up, the rattling comes back. He told me that it shows that the belt is slipping. We change the belt and the tensioner but after some time, the rattling came back.
regards,
Nonong |
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Roly
Elite Veteran
Date registered: Apr 2006
Location: Australia
Vehicle(s): 1999 G500
Posts: 661
| RE: problems with my belt tensioner-shock absorber
Check the centre bearing on the arm which holds the pulley. It can get worn and requires replacing |
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Nonong
Regular
Date registered: Apr 2006
Location: Manila, Philippines
Vehicle(s): 1995 290GD LWB white; 2016 G500 silver
Posts: 88
| RE: problems with my belt tensioner-shock absorber
Just want to let you know and share with you guys that after a couple of months and a lot of arguments from different mechanics including the Mercedes' Philippine distributor , my belt problems was finally solved. Thank you Alan for your input and suggestions.
After inspectiing the alternator pulley of my 290GD, I found out that it did not really have the clutch bearing. However we found out that the Mercedes Vito van with the 220CDI engine had this clutch bearing on its alternator pulley but it does not fit the alternator of my 290GD.
Anyway what my machanic did was buy a clutch bearing or they call it here a "one way bearing" and had a shop fabricate an alternator pulley which will fit this bearing and yes, my problem was solved!!!!
Again, thanks to the this forum and its great members.
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