How to extend the life of pulley tensioner arm? - PeachParts Mercedes-Benz Forum

Father Of Giants · #1 12-07-2017, 03:21 PM

It's only been, about 10,000 miles and idler pulley is already starting to get cocked again, probably because the tensioner arm is worn out again. Do these things really live such short life spans? Is there anyway I can help them last longer?

The last one I purchased was an INA tensioner arm.

Diseasel300 · #2 12-07-2017, 03:36 PM

Replace all of the tensioner components together. Pivot arm, pulley, spring, and shock. Make sure you have the plastic caps that cover the pivot bearing and the pulley bearing. If you don't, order them. I forget which brand mine is, but it isn't OEM or INA and it's still tight as a drum after ~9K miles.

Father Of Giants · #3 12-07-2017, 03:53 PM

Quote:

Originally Posted by Diseasel300

Replace all of the tensioner components together. Pivot arm, pulley, spring, and shock. Make sure you have the plastic caps that cover the pivot bearing and the pulley bearing. If you don't, order them. I forget which brand mine is, but it isn't OEM or INA and it's still tight as a drum after ~9K miles.

I replaced all of those componetns before I put the car on road, hmmm, i'll inspect it tommorw and see what's shot.

What I do know is the plastic cap is missing on mine and that probably caused premature failure on it. I'll order a new one cap along with a tensioner arm.

torsionbar · #4 12-07-2017, 06:16 PM

There is a metal sleeve bushing in there. I'm not sure if this bushing is available separately, but it would be the first thing to wear out. The original pivot with 150k miles was flawless when I last removed it from my car last summer. I have to imagine something is wrong to cause such dramatic premature wear in your case.

Texasgeezer · #5 12-08-2017, 06:51 PM

I'm doing work on my 95 E300D

One of the items being installed is a 'one way pulley'.

I'm doing this in the hope it smooths out the serpentine belt vibrations and hopefully the life of the tension components. The other belt driven components might benefit from smoother belt action... AC, Fan, Power steering pump - don't know haven't looked for that.

This thread provides good information.

Alternator Pulleys 101: Clutch type / one-way pulleys

I believe your solid pulley is the same fitment as my old one. If your alternator takes a m16 x 1.5 thread nut, then it should be a fairly easy swap out.

There is a probable better design ' overrunning plus one way pulley ' but I haven't found an applicable pulley. There are a couple that might be shimmed to fit but haven't checked them out yet.

I'll be taking my tensioner components off this weekend, hopefully. Life keeps getting in the way of my projects. I plan to try to figure out if there is a way to reduce tensioner arm failure in addition to the new type pulley.

BillGrissom · #6 12-08-2017, 08:40 PM

Interesting that guys pay big bucks to retrofit blingy serpentine belt systems on classic 1960-70's engines. In newer cars, people have nagging problems w/ serpentine belts oscillating or coming off. V-belts do take up more axial space, but they are much more forgiving of mis-alignment.

Texasgeezer · #7 12-14-2017, 12:08 PM

I've just ordered an INA tensioner arm. Hopefully I won't regret it. A little worried since yours failed at 10,000 miles. I will try to look at build quality before installing and also include a small grease zert positioned top middle. Then use a low viscosity grease. If I'm in to this area again, I'll use a needle grease tip and make sure the tensioner pulley has sufficient grease. Hopefully that will extend its life.

On my car I've found that the water pump is probably in early failure mode and guessing that was contributing to extra bouncing and noise from the tensioner assembly.

Have you checked your alternator, power steering, compressor, and water pump for smooth uniform movement? One of those could be adding extra tension to the belt.

It has surprised me that the belt, pulleys, and tensioner can be so troublesome. I've seen where other posters have resorted to removing the vendors painted info from the smooth side of the belt, lightly cross sanded the tensioner pulley to gain traction, and rigorously cleaned the grooves of pulleys in an attempt to reduce chirping noise & reduce problems.

My reading is telling me that 'out of the ordinary' tension movement is probably an early indicator of another components failure.

Diseasel300 · #8 12-14-2017, 02:57 PM

The number of problems with the 60x engines with the tensioners is due to the diesel engine, not the pivot design. Adding a Zerk to your tensioner is wasting your time. Unless you completely disassemble the tensioner assembly and remove the seals on the bearings, you're greasing nothing but the shaft bushing.

Diesel engines have very abrupt acceleration/deceleration cycles as the pistons compress the air/fuel mixture, then accelerate as the mixture combusts. Gasoline engines don't suffer the acceleration/deceleration issues that the diesels do. This all translates into oscillations and harmonics on the belt drive system that create extra stress on moving parts. The tensioner design is much more reliable than a coil-spring design that a lot of manufacturers use since it actually has a damping shock to help absorb some of the vibration and belt flutter.

Texasgeezer · #9 12-15-2017, 05:25 PM

Diesel300, I'm confused about the part where you say 'completely disassemble the tensioner assembly and remove the seals on the bearings'. My old pivot arm is just cast metal with what looks like a very thin sintered split bushing pressed into each side.

My old pivot arm was dry and showed a tiny bit of wear on the inner sintered bushing. I probably could keep using it, but my new one arrived today.

In my case a future failure would probably be due to lack of lubrication between the sintered bushings and the big pivot bolt.

I've attached a picture of my new & old arms & a picture of what I call the sintered bushing. New one is not oiled or greased.

Diseasel300 · #10 12-15-2017, 10:03 PM

On a sintered bearing, the very last thing you EVER want touching it is grease. Forget the Zerk, injecting grease in the bearing will ruin it. If you're concerned about lubrication, some non-detergent oil is all that should go in there. Grease will block the pores in the bearing material and kill it in very short order. It's counterintuitive, but grease is BAD for sintered bearings and bushings.

Texasgeezer · #11 12-16-2017, 03:36 PM

Thanks Diseasel300, I'll try to find an appropriate oil.

Diseasel300 · #12 12-16-2017, 06:17 PM

Zoom spout oil or 3-in-1 oil in the blue can for "Electric motors" are both good choices for non-detergent oil. They're also useful for oiling just about anything that needs oiling (squeaky hinges!!!)

Father Of Giants · #13 12-16-2017, 08:24 PM

I read the Alternator Pully 101 thread numerous times but it doesn't make sense too me. Everything just goes over my head honestly. My feeble mind can't comprehend it.

Diseasel300 · #14 12-17-2017, 12:21 AM

It's worth noting that the tensioner pivot arms in the 604/5/6 and 601/2/3 seem to be different in the bearing department. The later ones use a sintered bushing style bearing, the earlier ones use ball bearings. The sintered bushing should be more reliable in the long run due to much less 'slop' in the overall design. Pivot arm wear and failure is fairly common on the 601/2/3 engines, it doesn't seem to be as much of an issue in the later engines, probably due to the change in bearing design.

Texasgeezer · #15 12-17-2017, 03:29 PM

I must be getting 'oldtimers', this is the 3rd time I've tried posting this. Guess I'm dozing off before completing it.

For quite a few hours I've been reading about sintered bearings and their lubrication. In the early days of sintered bearings some greases were made by adding clay to an oil. This clay would quickly block the pores and stop the lubrication.

What I think I've found is that Krytox ( spin off from a Dupont product line) makes oils and greases that are compatible with sintered bearings.

Some of the websites I looked at:

http://www.nationalbronze.com/News/self-lubrication-options-for-bronze-bearings/

BryCoat Tungsten Disulfide (WS2)

https://www.chemours.com/Lubricants/en_US/products/Products_Greases.html

https://www.chemours.com/Lubricants/en_US/assets/downloads/krytox_auto_brochure_L14353.pdf

https://www.chemours.com/Lubricants/en_US/tech_info/Index.html

This is fairly long, but if you look towards the bottom of this web page, it show how good Krytox is for pretty much eliminating galling:

Why use only DuPont Teflon Bearing Grease? really thorough testing of several lubricants

There is a space age product that will probably be available more in the future and mixed with oils and greases. From what I've read it will adhere itself to stainless steel and other metals. It is 'WS2'. This website is one that provides info about it.

BryCoat Tungsten Disulfide (WS2)

For my tension pivot bolt and arm I'll probably be using Krytox gpl-204 due to its temperature range and viscosity. If I think WS2 might be a good additive then I might mix it in at about a 4-8 percent ratio.