Jump to content

Alternator problem


Recommended Posts

Help, do I need to be afraid?


We have a Laika Kreos (and we love it) motorhome built on a Mercedes 316cdi bought new 2001 now with 55,000 miles on the clock.


After, a recent journey from our home in Suffolk to Cornwall, I noticed that there is what I describe as a squeaky rattling sound, only when hot and idling, coming I know from the alternator.


So my question is, can I ignore it during the meanwilst and go on another 600 ish mile outing?


I will have it changed, but the timing is not good at the moment!


To sum up will a squeaky alternator bearing suddenly fail or will it go on for years just complaining? (some say, as I do)


Thanks in advance, Geoff.


Link to comment
Share on other sites

Hi. Is it the bearing or the belt making the noise.? If it is the bearing it will probably be the front one. As a temporary measure I would try to spray some lubricant into it, into the bearing only though. Then if the noise persists replace the bearing or the alternator asap.

Brian B.

ps I had a similar problem, and just replaced the bearing.

Link to comment
Share on other sites

If its the alternator front bearing giving notice I would expect it to be noisey irrespective of temperature.


Consider the possibility of the noise coming from the belt tensioner or possibly water pump or even the timing chain tensioner. Dont ignore any of these items giving notice as total failure can be very expensive.


Rough ball bearing rarely respond to lubrication. Its lack of it or excess belt tension that normally kills alternator ball bearings. If the bearing disintergrates the rotor will possible contact the windings damaging the unit so that it cannot be exchanged.


If its the belt sqealing, try very lightly damping with water to proivide temporary lubrication.. Lack of belt tension and it attendendent slippage and squeal usually shows up immediatly after starting when the belt is heavily loaded as the alternator is rapidly replacing starter battery charge.


If certain its the alternator the easiest advice ( I am not paying) is to replace the alternatar ASAP. Its likely to be far cheaper than a call out and a lot less hassle.








Link to comment
Share on other sites

  • 2 weeks later...

Most Merc engines have a serpentine belt that drives all the auxiliary items. It is held tight by a spring loaded tensioner. However, there is a small shock absorber near the alternator that damps vibration at this point. With age this deteriorates and causes the alternator to bounce and rattle at idle speed. One of the symptoms can be a flashing alternator light at tickover as the alternator struggles for drive. If you look at the alternator during tickover you can sometimes see it bouncing. If this shock absorber is allowed to deteriorate it can result in the serpentine belt jumping off. It is a low cost job to have the shock absorber replaced and any Merc specialist or Merc main dealer will know of the problem. If you don't get it fixed the serpentine belt will wear and jump off leaving you without an alternator, cooling devices, power steering and aircon.



Link to comment
Share on other sites


This topic is now archived and is closed to further replies.

  • Create New...