Strange whine

[rodknu]

Hope I don't sound like an idiot in this post. My 2011/12 Mercedes diesel Sprinter makes a significant whine when starting in 30-40 degree weather.Goes away once everything is completely warmed up. My thought was, initially, that it was low pitched turbo, or power steering cavitation, or tranny.

Here are the symptoms/clues/investigations I have done so far and have concluded nothing.
1. Checked Belts and pullies which seem ok
2. Suspected Turbo but whine is not that high... inconclusive
3. Suspected power steering and have noted intermittent change in whine when approaching terminal left or right limits... inconclusive
4. Suspected Transmission; cannot locate a dipstick, research indicates there may not be one??? no leaks shifts ok but seems sluggish in reverse while whining... inconclusive
5. Using stethoscope listened to engine, turbo, power steering, tranny, alternator, etc. and could hear whining everywhere! (meaning I could hear the whine ANYWHERE I touched the probe around the engine and attached parts) ...inconclusive

Still looking but open to any and all comments and recommendations. I have owned the unit about 8 months and driven about 10K miles. I have owned numerous motorhomes and numerous diesels. I am not an expert mechanic but I have done numerous dye automotive projects over the past 60 years or so.... Thanks in advance, Rod

[ITSNO60]

Fastest way to rule out belt driven accessories is to remove the belt and start the engine briefly. Do not attempt to drive it and only run it for a minute. (You may get codes related to power steering and alternator which can be cleared).

You are correct that there is no transmission dipstick, you have to purchase a service dipstick and some new seals to seal the tube after using the service dipstick. I use this one: https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1 just be careful not to let the end get curved during storage and make sure you understand that you will feel the ears at the bottom hit the stop in the transmission when it is fully inserted, the end in your hand will still look like it has a ways to go but don't force it, once those ears bottom it's in all the way. The length is made to accommodate different models.

Has the transmission been serviced? Fluid and filter change are recommended at 80,000 regular duty and 40,000 arduous duty (as Mercedes calls it) which includes a motorhome IMO.

[rodknu]

Brian, thanks for the input and I will order a dipstick and pull the belt to test.

Unit had right at 80K on it when I bought it and I will research all the invoices that came with it to see if tranny fluid was changed but I am thinking I should do that anyway.
Rod

[ITSNO60]

There are a number of pulleys with bearings, removing the main serpentine belt will rule out the two idler pulleys and the tensioner (and of course accessories like the alternator) There is a second belt that runs the cooling fan which is mounted to a bracket that also contains a bearing. That belt is a stretch belt with no tensioner or adjustment and is a fair bit of work for a DIY especially without the special MB tools. It should always be replaced once removed.

The serpentine can be removed by pulling back on the tensioner with a 17mm 12 point socket then carefully threading it behind the fan, into the shroud and out. Some people remove the fan /clutch/shroud which all have to come out together. I've done it both ways. MB recommends replacing the belts after 4 years, there is a date on them, however mine were on there for over 10 years and 60,000 miles.

Pics below show belt diagram, one pic has the fan belt removed, the second has it installed. (The serpentine can be removed with the fan belt still in place, it will fit around it). If you are not a fairly advanced DIY you may want to have some help with this job. It also helps to have access to the MB workshop manual but there is a good thread at Sprintersource from several who have done it. Believe it or not the actual Serpentine is easier than the little stretch belt that runs the fan.

[rodknu]

Thanks, that helps. I kinda gather you are thinking it is a pulley bearing and that would make sense to me as anywhere I touched the block or accessories the noise was just as loud.

[ITSNO60]

Originally Posted by rodknu

Thanks, that helps. I kinda gather you are thinking it is a pulley bearing and that would make sense to me as anywhere I touched the block or accessories the noise was just as loud.

I'm not going to guess, it could be a lot of things. One thing for sure though, if your rig has not had belts and tensioner replaced it's getting close to that time with 80,000 miles. I would also replace the fan pulley and bracket assembly, if that fails on the road you are dead in the water. In order to replace it you have to remove everything, both belts, fan, clutch, shroud and upper idler or "guide" pulley. You also cannot remove the bolt from the upper tensioner without removing the fan pulley so it makes sense to do it all at once.

Here is one man's saga on his serpentine system failing on the road:
https://sprinter-source.com/forums/i...threads/91134/

[rodknu]

yikes! Thanks for the advice and the link for the breakdown thread. I am like him and out in the Montana sticks and don't need his problems for sure! Again thanks.

[pfm41]

Check your power steering fluid level. If the fluid gradually gets low it will make a very distinctive sound when it sucks a little air. As the fluid warms it will expand, no more sucking air, no more sound.

[rodknu]

Excellent suggestion... I have checked it twice but will renew my check method and reevaluate the level reading as what you describe fits my situation....maybe?