belt tensioners?

[Russian007]

It's difficult to get the required 1/4" of belt tension on my Volvo 2003 diesel. Supco and others make belt tensioners available on Amazon. Any opinions on these?

[SohoSail]

No brainer, get one.... makes the job a whole lot easier. I have one of the Supco ones and it's fine. It's not a complicated tool....

[rslifkin]

As long as it's a decent design and will work reliably, I see no downside to adding an auto tensioner. Not having one from the factory is just a cost saving measure.

[Mickeyrouse]

My belt tensioner came from Balmar, but I’m sure what O’Reilly sells is just as good. I regret having gone so many years without it.

[Uncle Bob]

Hi, have seen a turnbuckle with an eye fitting each end used in lieu of the adjustment arm, looked very practical.

[Rumrace]

Toss the whole mess go to the auto mod nuts and find the right sized billet serpentine pulleys. I have Honda on a Yanmar blue anodized. A serpentine tensioner is a wonderful thing. Lovely water cooled alternators. Got one from a rolled X5 BMW.
Volvo has always been a hard brand like Yanmar to follow. Most the Gas Volvos were GM short blocks.
I’m not sure which brand your block is. But you may find a full serpentine parts list from its truck equal.
The “V” belt has some real issues the worst of which is salt water eating the pulleys Belt dressing spray no matter which way you go.
In the case of Yanmar it’s a Kubota Tractor Block and the various Honda aftermarket pulleys had the correct shaft size,? diameter or bolt pattern. The rest are tractor parts. As soon as you add marine to the search engine parts triple.

[Bowdrie]

Are you running a high-output alternator?
If not, have some restraint on belt tension.
Many engines that only use the belt to drive the coolant/freshwater pump and a lower amp auto style alternator off of the crank pulley do not need high tension.
You only need enough to eliminate slip, anything beyond that only increases alternator bearing heat and side loading of the water pump, (whose bearing is already subject to large cantilever loading.
You're not running a 5,000rpm V8 in a speedboat, go easy with the tension and all is happy and cool.

[glenn.225]

Originally Posted by Uncle Bob

Hi, have seen a turnbuckle with an eye fitting each end used in lieu of the adjustment arm, looked very practical.[emoji2]

These work great and simple to make it you have room. I mostly use a hammer handle or pry bar to hold the alt/pump/etc very snug against belt while tightening adjustment bolt. Works 99.9 % of the time, there always one where the adjustment bolt moves a bit with the assembly and you can't get it really tight.
One of the simplest and easiest adjustment I ever saw was a small gear nut on a adjustment arm with a sawtooth along the edge, you simply loosened holding nut and then turn the adjustment nut till belt tight and tighten holding bolt. Not sure if it was on a vw or not.

[Russian007]

Originally Posted by Bowdrie

Are you running a high-output alternator?
If not, have some restraint on belt tension.
Many engines that only use the belt to drive the coolant/freshwater pump and a lower amp auto style alternator off of the crank pulley do not need high tension.
You only need enough to eliminate slip, anything beyond that only increases alternator bearing heat and side loading of the water pump, (whose bearing is already subject to large cantilever loading.
You're not running a 5,000rpm V8 in a speedboat, go easy with the tension and all is happy and cool.

It's a 50amp alternator and the belt also spins the fresh water pump. The owner's manual says .20 inch of belt play. How do you determine if the belt is slipping? Squealing? doesn't do that.

[Bowdrie]

If a new belt shows "glazing", a shiny appearance after some usage it's an indicator of slip, but it can also indicate overloading, (too much tension/heat).
Of course, a new belt will stretch a bit after being run-in for a while.
The "cogged" belts are much preferred as they can travel over the small diameter alternator pulleys with less stress.
Depending upon the un-supported distance between pulleys, most any belt will show some "flutter" at some specific rpms, (it has to do with harmonics).
A bit of flutter is ok, even under recommended tension there will be some at some rpm, (usually a fairly small rpm range).
It contributes to belt life to avoid that rpm for continuous operation.

[Bowdrie]

Addendum.
I just measured the slack in the new belt I installed ~3 weeks ago, with perhaps ~2 hrs. use.
With 9" of unsupported span between crankshaft pulley and water pump, I can, with not much effort deflect the belt ~3/8ths in. either side of "rest", if I "push" I can get 1/2" each side of rest.
So that's about .750 total, an inch with some push.
It runs just fine; I'll keep an eye on the stretch as it settles in, and probably add a smidge of tension.
Never have had any "belt dust" or glazing, but the small alternator I have, (charges starter batt only,) has little loading.

[boatpoker]

Originally Posted by Rumrace

In the case of Yanmar it’s a Kubota Tractor Block .

Incorrect.

[Pete7]

Originally Posted by Rumrace

Toss the whole mess go to the auto mod nuts and find the right sized billet serpentine pulleys. I have Honda on a Yanmar blue anodized. .

Its an old engine that hasn't been made for 30 years, good luck with that. Still if you find one for us at a sensible price, do let us know. I look forward to seeing the results.

Pete

[Pete7]

Originally Posted by Russian007

It's a 50amp alternator and the belt also spins the fresh water pump. The owner's manual says .20 inch of belt play. How do you determine if the belt is slipping? Squealing? doesn't do that.

Did you get the water pump fixed? If so I would settle for what you have and just go with it.

[SohoSail]

Just as an added data point 007, I have gone to using Gates XL HD belts, the green cogged ones, nice belts. Mine is a Yanmar 4JH3 series, low usage and std alt. Point made about over tensioning is wise. When you hear squealing, your belt needs tightening. Mine is pretty easy to check so I am pretty good about checking it, especially having had one break previously, which will never happen at a "good" time. One of those things it's good to stay on top of.