E320CDI Snapped belt tensioner
 

Anyone else experienced this? Was sitting at a red light at idle last night in a snow storm, heard a screech and a pop. Then the charging light came on. Noticed power steering was gone, got it into a parking lot under its own power, popped the hood and the belt was on top of the engine, looked down and laying in the belly pan was the tensioner pulley with half of the tensioner arm still attached to it.

Called AAA at 10pm, they said it would be 12 hours. Just called them to ask if 12 hours was still accurate, they said it may actually be tomorrow before they can tow it. So I'm going to go recover it myself.

Anyone else had this happen? Could something else have caused this? (The belt tensioner arm cracking, not AAA being inundated with people crashing their cars in 1/2" of snow)

2006 E320 CDI

No.

How many miles are/were on your belt tensioner, pulleys, serpentine belt, and water pup's replacement/history?

The belt tensioner may not be the singular cause or culprit. Serpentine belts are often the victim of other part(s)/component(s) failure. Can you post pics of your serpentine belt? Both inside and out would be helpful. Also, is your serpentine belt OEM Mercedes-Benz? The tensioner may have snapped loose/off, because of the serpentine belt's being thrown.




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You may or may not have a secondary towing source without realizing it. I understand the service workload b/c of the inclement weather, but having only AAA, you're at a distinct disadvantage. My collective towing policies allow me to do some contractor sourcing in just a couple phone calls.

Belt is a dealership belt I put on December 12, 2015 looking at pictures in my cell phone. And that was at least 40,000 miles ago.

Water pump, tensioners, and pulleys are at least 90,000 miles old, I have not replaced them in the time I've owned the car.

I ordered a new belt and tensioner from the dealer today. Was just curious if anyone had experienced this as well, lots of other people with similar or higher miles to me. I wouldn't have expected your 73,000 mile car to have suffered this.

When I get the car towed back I'll do a detailed inspection, currently Monday-morning-quarterbacking the situation from my desk at work. I need to inspect the water pump, reading more and more threads of CDIs needing them around my mileage.

How many miles are on your 2006 CDI?


Problems with the entire scope of alternator, water pump, serpentine belt, pulleys, A/C, and tensioner can happen long before 73K miles. It is sometimes age related, or shoddy parts/component installation, or a QC, part/component issue.

Unless you bought the 2006 CDI from new, get a printout of your car's VMI history-report. Do whatever is necessary to procure it's in house, MB VIN report. The more history of your car you can learn, the better you'll be able to assess it's profile.

As a data point, I have never lost a tensioner on any of my CDIs. One with 302k, that I've had since 130k. Water pumps have gone, but not the belt tensioner.

I got my doubts too, about the tensioner going kablooey, as causation of the breakdown. The tensioner was quite possibly collateral damage to something else cutting loose, I'm thinking.




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No but I replaced mine after my water pump failed, glad I did as I read this.

I've read of original tensioners seizing, but not snapping (yet). There are many reports of aftermarket INA tensioners snapping though. INA blames seized clutched alternator pulleys (the pulley is recommended to be replaced every 100K), but the INA tensioner most parts retailers supply is an outdated/superseded design for either the OM647 or OM648 engine (installed in Sprinter vans and E320 CDI).


Litens is the correct OEM for the tensioner and as far as I know (besides buying OE MB), the only supplier to offer the Litens tensioner is Gates. INA is the correct supplier for the idler pulleys and clutched alternator pulley though. Use OE MB or ContiTech for the correct length serpentine belt.

Put a new dealership belt on and a new dealership tensioner (which has been superseeded a few times, may or may not mean something) and all is well.

Everything turned smoothly, no play in anything (looked hard at the water pump).

Car is back together and running well.

Car has 199,700 miles on it.

This is the post I was seeking when I made this thread.

The one that came off the car was a Mercedes stamped unit. But I did not know the alternator pulled was clutched or considered a wear item, it "felt" fine, but I will definitely give it a second look after reading this.

We've got three 05 CDIs in the extended family.

One has close to 300K on it, ours is at 210K, another is a "low mileage" car with 160K.

I'm not aware of any of them having snapped a tensioner pulley.
Of course, I wasn't aware of a clutched alternator, either.
Need to look into that.

On another note, it appears that springs in a W211 CDI are another maintenance item. Whilst ours are still original, my cousin TimFreeh recently replaced (@ 280K) all four on his CDI and reports a noticeable improvement. Another cousin, with the 160K CDI, told me he just had a broken spring in the rear replaced this week. He also reports that he really likes the 18 E300 4matic he got as a loaner......

Jim

The INA Overrunning Alternator Pulley (OAP) - Simply Explained!

When you turn off the engine you should be able to hear the alternator spin down for a second or two (If not, the pulley is seized and will need to be replaced). Excessive noise or vibration from the pulley or belt system are also signs of a failed alternator pulley.

Alternator pulley:
INA Alternator Freewheel Clutch (Part Number: 535 0086 10)

Required tool:
Professional Alternator Clutch Pulley Removal & Installation Tool (Part Number: KL-0284-28)

At 140k the alignment shop told me there was negative camber they couldn't get rid of they attributed to tired springs. I replaced them and all was well. I want to say my cost from the dealer was only like $56 for the springs each. So I can attest to 211s needing springs.