Serpentine Belt Tensioner Heads-Up

seans

Member
I hope this thread isn't too cold, you guys really got my attention. My 2004 647 has almost 100K on it, and the battery light has been flickering on and off. I took a look at the belt, and it and the tensioner look like the fluttering bad example in the videos above. So I have been reading through this great forum contemplating my next steps. What I could see of the belt looked pretty good, but it is the original. I bought a spare belt from europarts five years ago. It is a Contitech PN 6 PK 2260. Different than the number Vanven had in post 29 for the 647. Would anybody else like to weigh in on the correct Contitech PN for a 647 belt?

I need to decide how deep to go, so I will look to see if the water pump is leaking, check the alternator pulley, maybe check for reasonable torque and smooth movement in the tensioner, look for any breakage in the idler, and replace only with MB parts! This is a passenger van with the aux rear AC, so there are two condensors in front, and a second small cogged V-belt in front of the serpentine. I will check the tensioner and replace that belt also.

In post #37 Steady-Eddie mentioned replacing the pulley on the alternator. Where can you get a replacement alternator pulley? I read in another post that MB only sold the complete alternator. I assume that there area couple special tools involved in removing the pulley from the alternator.... is that correct?

Thanks for any help ...
Wow - sounds a lot like what I'm in the middle of. See this post I made today on the water pump replacement thread.

(from that thread:)
tornapart.jpg

I'm replacing the alternator, belt, tensioner pulleys, and I'm considering replacing the water pump and other hoses. I have non-OEM parts and am considering doing a temporary repair now and a permanent full repair (replacing the non-OEM parts with Mercedes parts) in the spring when it is warmer.

If you follow the instructions from an earlier post (which I've linked to in my post) you will find that by removing a lot of parts including the bumper, you'll have a LOT more room to work and inspect. I found I had to remove the turbo resonator to get to the top alternator bolts, and this would have been a LOT easier if I had moved the radiator first.

I want to, but have stopped short of removing the transmission cooler lines to swing the radiator out (per the instructions mentioned in the link above). I have never pulled them before but there are a number of threads where people are complaining of transmission fluid leaks at the radiator. I really want to get a better view - I think I might have a weeping water pump seal - but if you remove the wrong fittings you might be asking for trouble aka replacing the radiator. More people need to weigh in on this. See talkinghorse43's posts adjacent to this one (which is just before the other post and includes my guess of which are the danger fittings.)

Can you please post a link to the Doktor A 85K mile maintenance item post?

Thanks and good luck!
 
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CruisnDiesel

New member
I think I read through some earlier posts on the 647 water pump replacement thread. Looks like you are pretty far into it. It is tough to decide how far to go with replacing parts while you have easy access. I haven't seen any indications of leakage from my water pump, so I may just replace the belts and alternator for now. I think I can do this from underneath without taking much else apart. I see you also have the Aux rear AC compressor. Here is the link to the Doktor's 85K suggestion: https://sprinter-source.com/forums/showpost.php?p=222164&postcount=145
Sorry best I could do on the link ....
 

MightyGopher

New member
Thread kinda got lost in the facts. The Dr. is 100% correct. I replaced my OE tensioner at 236K because it had a little slop in the wheel. Do not use any tensioner that is not MB or Litens. Dayco sells the same tensioner as europarts, mine fractured at 12K just exactly like Talkinghorse. Napa sells the litens OE tensioner for a few bucks more, but well worth it. The dayco model will leave you stranded without warning and if you do not notice the missing belt, perhaps a engine!
 

vanven

Member
Continuing...

The ends of the spring shown in the exploded view in the post above fit into recesses in the tensioner body and the inside of the top of the tensioner to provide torsional resistance to pivoting. The spring is also compressed on assembly and provides clamping force to hold the back plate in firm contact with the plastic insert. This effectively makes the back plate/plastic insert a brake or shock absorber, apparently meant to dampen oscillations. I haven't disassembled the OEM Litens brand tensioner because I plan to use it as a spare part in the future, but experimentation with the torque wrench shows me there is no such damper in the Litens brand tensioner. The 1st pic below shows the top of the tensioner body and the cavity for the central spring. Also, this shows the top sleeve bearing for the central shaft. Again, this bearing appears to be coated with PTFE, which is partially worn away.

The last pic shows the central shaft attached to the top of the tensioner. The surface of the shaft in contact with the two sleeve bearings is corroded, which accounts for the increased pivoting torque and the overload failure of the roller mounting arm. Note also where the shaft meets the top of the tensioner. It can't be clearly seen, but an O-ring like the seal at the bottom is also fitted here. This is where I believe the water responsible for the corrosion of the central shaft entered. Since the design of the tensioner depends on the friction between the back plate/plastic insert to provide damping, that friction pair will lose thickness due to wear which will remove the top O-ring from contact with the sealing surface (top of the central tube of the tensioner body) allowing the seal to be lost.

Therefore, the very design of this tensioner dooms it to early failure.
Thanks to this analysis Europarts-sd (Steve) emailed me to offer me a free replacement for my INA (second one). He did this w/o me requesting it. Thanks again talking horse.
 

SRT2

Hi-Miler
When a belt tensioner does not pivot smoothly, in spite of heavy spring tension, it MUST be replaced.

Easy to evaluate with a long flex head wrench w/17mm, 12 point socket, from under the vehicle.

Beware of aftermarket tensioners.

Doktor A
While I have "strayed" when replacing A/C compressors, power steering pumps, and alternators, I will only use OEM Mercedes parts for the tensioner, water pump, and idlers. Nothing shuts a truck down quicker than chucking a belt, and keeping the correct tension is a must. Good advice, Dr. A! :thumbup:
 

tat1642

Member
Hello.
I wanted to research about tensioner here but busy days,, so I just discovered this thread last night. It happened same for my t1n 2006 Sprinter back in April 2013.
Just exactly 60000 Miles(2 years and 11 days)after: I replaced brand new Bosch Alternator 150 and tensioner kit(tensioner, 2Pulleys and belt) from Europarts SD. That day, I was driving on interstate for easy 60m/h, had big sound, suddenly needed to pull over side of the road.

I remember there was a little squeaky sound from serpentine belt somewhere a week ago. But I couldn't locate problem by visual check before the trip. Even engine heat up and sound was gone, so I knew something going on but it was very little warning.
Fortunately, I kept old Tensioner in my van and replaced side of interstate, dangerous, dark and took me 3 hours.
Next day, I went to Freightliner parts shop, they had one. It was $110. Replaced it to new quickly at outside of parking lot.

Somehow, I assume this tensioner is just BAD made of material. I know there is different opinion and also I saw video in this thread.
What is the best solution for this? Should i replace pulley for Alternator?
Appreciated your advice.
tat
 

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hulagun

Haulin' A** since 1974
I'm still scratching my head over what belt pulleys work on my 2005 OM647 motor, and what pulleys do not. The threads are not really that clear and cross reference each other in an endless loop of confusion.

Europarts sells Litens tensioners now. They also recommend using 2 large (65-70mm?) ribbed pulleys. That is different from the factory combo of one large, one 55mm smooth pulley set up.

Here's the Gates dayco page listing their replacement pulleys. I can't really make sense of it until I know more details on the factory pulley dimensions, but they may offer a more affordable alternative than the $25-$40 OEM ones.

http://www.dayco.com.au/products.as...xdHmgc88K9zqluXcSIvEiSWAn+QafmjG6HrOc2XPGpSg=
 

hulagun

Haulin' A** since 1974
I ordered the whole belt tensioner replacement kit from Europart-SD. Litens tensioner, 2 INA large ribbed pulleys, and a ContiTech belt.

Interestingly, the "new" belt is marked 6PK2257. The web says it replaces MERCEDES PART NO 0089977092.

I also have a unused new ContiTech belt spare, from when I bought the van 2 years ago. It is marked 6 PK 2260. The web says it replaces MERCEDES PART NUMBER 0149970692A. IIRC, it came with my van.

Curious about all the different numbers, both belts appear to be *about* the same length.

Update: I installed the PK2260 belt and the smaller idler pulley (nearest the tensioner) because it felt loose and sounded dry. Everything else looked good (knock wood). Took me about an hour, working slowly and carefully, and I encountered no real issues with the belt.

Based on recommendations from Dennis at Linden Eng. (https://sprinter-source.com/forums/showthread.php?p=270979#post270979), I may go ahead and just have the tensioner and the other idler swapped out when my van goes in for AC repair soon.
 
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dronsin

Member
FIX for Broken Upper Tensioner Mounting Bolt (UGLY) My tensioner failed by breaking a bolt- the top one, which allowed the belt tension to pry it down and break off the lower ear, It all fell into the fan shroud.
So I had a lower bolt to remove, easyn but the top bolt had broken off just about flush with the Timing Chain case into which these bolts are threaded. They seem undersize, ( I think a bad alternator clutch pulley made for a lot of belt tension cycles and failed the upper bolt in fatigue as it had no/insufficient preloaD)

In any case, I was faced with extracting the upper bolt, broken flush with the aluminum case. Drilling the bolt and extracting it was nearly impossible, even with the radiator swung open - hinging on the AC hoses on the drivers side. Access was much improved. The upper bolt is on a section of case cover that is beyond the chain case.....meaning drilling through would not involve the internals of the timing chain drive. so I was lucky -- I drilled on both sides of the stub bolt, angling inward, to create a two through holes to the backside of the chain case. There are casting ribs on that backside, but the holes both exited in a web space. So, I chiseled the remaining bolt out that was inbetween the drilled holes, resulting in a major opening. I cleaned that up with somethingf like a 3/8 drill bit. So now I had a hole through, not a blind tapped anchorage. I was able to install a socket head bolt from the rear, the exited the front acting like a stud - to mount the tensioner ear with a nut. I think that is probably a great improvement on the original design actually.....a larger upper atachment ( had to slightly overdrill the tensioner ear hole. I had to grind the socket head flat on one side to allwo it to seat deep in the backside web, abd ut fut well.
Wish I had some good photos. To recap - I replaced the upper tensioner mounting bolt by overdrilling through the timing chain case and installing a through bolt as a replacement for the original tapped screw arangement. Dale

 
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220629

Well-known member
... So now I had a hole through, not a blind tapped anchorage. ... Dale
Nice recovery. Thanks for the tips. :thumbup:

Belt length may be critical and could contribute to excessive tension on the system. Some discussion is here.

https://sprinter-source.com/forums/showthread.php?p=329917#post329917

Talkinghorse had several catastrophic tensioner failures. Perhaps the tensioner shouldn't be blamed? Perhaps the tighter 2257 belt put the tensioner into the upper limits of its operating range?

Cal
Good memory and observation! :thumbup:

Along the same line...

The OM647 OEM smooth idler pulley(s) are 56 mm diameter. The presently recommended lipped idler pulley is 70 mm in diameter.

"After further reflection...

Personally I would choose the flat style pulley as designed. (Edit: Maybe not. Read further.) Have fun. vic"
******
20111123 edit to Stoopid Things: There is a note in red on the Europarts listing that the grooved pulley is now listed by Dodge for the 2004 - 2006 OM647 engines.

If your Sprinter is a 2004-2006 model and the original upper pulley fitted to your engine is smooth and slightly smaller (56 mm) in diameter, this slightly larger ribbed pulley is to be used as a replacement unit. This is the pulley now specified as the correct replacement for both upper and lower idlers on the Dodge parts diagram.

The part link should be here: (Updated Oct. 2012)
http://europarts-sd.com/serpentinebeltidlerpulley-small2002-2006.asp

If the link is no longer valid use these search words/info at Europarts.
Sprinter 2002-2006 Engine Cooling System
Serpentine Belt Idler Pulley-Small 2002-2006
Ribbed surface
2 required
Sold in increments of 1
70 mm O.D.
27 mm Thickness
There are two of these on all 5-cylinder engines.

*If your Sprinter is a 2004-2006 model and the original upper pulley fitted to your engine is smooth and slightly smaller (56 mm) in diameter, this slightly larger ribbed pulley is to be used as a replacement unit. This is the pulley now specified as the correct replacement for both upper and lower idlers on the Dodge parts diagram.

******
My guess is that as a practical matter it has been discovered that the pulley alignment on the OM647 engine is OK for the grooved pulley design. It does mean that you now only need one pulley on hand as a spare if you trust the Europarts comment. I don't mean to suggest that you shouldn't trust the comment. I would be interested to know how much more tension that extra diameter adds to the belt system and therefore to the bearings? It's probably negligible. FWIW. vic
Even if the 70 mm diameter pulley measurement includes the lip and not just the belt contact surface, it is a larger diameter than the OEM 56 mm. So the combination of both the shorter 2257 belt and the larger replacement idler pulleys would make things even worse.

:cheers: vic
vic
 
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syncro_G

Member
Ouch, I've been bit by the INA tensioner bug! Both mounting bolts were sheared off about flush with the timing chain case.

A new INA tensioner was installed 10K miles ago (along with idlers and belt) by the previous owner's mechanic.

So now i'm disassembling the front end so I can get a drill and extractors in there. Since I'm at it, I'm reading up to see what else I should inspect while it's all apart.

  • Belt looks great,
  • Tensioner will get replaced
  • Two idlers seem ok
  • Alternator pulley looks to be working but I need to test it again tomorrow with the rotator fixed
  • Water pump? seems fine
  • Harmonic balancer? The van was built in 11/2006 so I've been under the impression the HB would be fine.
 
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billintomahawk

Guest
Hello everyone,
I'd like to resurrect this old thread and add to it.
I am in the process of bringing my 'gifted' '02 Freightliner OM612 T1N, 94k back to life.
I am new to Sprinter vans.
The engine makes a screaming sound on startup emanating from the drivers side front of the engine. This sound goes silent after 10-30 seconds but returns if an electrical load is applied or the air conditioner is activated.

As a second problem I have corroded transmission and other lines under the radiator.

A third problem is that I have no ideas if other non OEM parts have been installed on the engine iike a non OEM water pump.

My idea is to expose the front of the engine but I'm not familiar with exactly how that is done?

Since I need to change out the coolant and the transmission fluid it sounds like I should make things right with the belt, hoses and lines first....

Would someone help me with steps to swing the radiator out to expose the work.

If there is a thread on this please post a link.

Thanks,
bill in tomahawk
 
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billintomahawk

Guest
Vic, Keith
Thanks so much.
The threads are perfect.

bill in tomahawk
 
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tybostwick

New member
Bill

My '06 Sprinter was making the same sound when the ac was on. I ended up replacing the condenser, accumulator, and thermal expansion valve. I'm sure it was either the accumulator or the TXV making the noise but the condenser had a leak so it had to go. Anyways after replacing, flushing, vacuuming, and refilling the sound is gone and I have ice cold air again [emoji300][emoji300]️[emoji300]️

The HVAC manual was useful to know the amount of pag oil and freon to put in

Cheers and good luck.

Tyler

Sent from my ONEPLUS A3000 using Tapatalk
 

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