Are new belts hard to tension?

[Cap Bill Des]

Are new engine belts difficult to tension? I just put a new belt on our Universal M25. I ended up using a long lever pulling up on the adjusting arm( this alternator bracket has the pivot on top and the adjusting arm attaches to the alternator below the pivot)- and even with me levering up and another person tightening the pivot arm the belt still bounces around much more while running than I am used to.

Do belts have to be" run in" before it is possible to get good tension?

On another forum someone mentioned a "reverse turnbuckle" tool for less than$10 that is used for tensioning and then removed once the pivot arm is bolted tight. Does anyone have a link to this tool? I can't find it

Thank you!

[a64pilot]

Yes, they do break in and will need retensioning soon.
I’ve seen turnbuckles used as the upper arm, and my Miata has a nut welded to the arm that you turn a bolt to tension the alternator.
But other than DIY, I don’t know where you can buy an arm that would fit your engine

How about this, just found it on a search, never used one myself
https://www.amazon.com/Supco-Belt-Te...s%2C154&sr=8-1

[SVTatia]

Originally Posted by Cap Bill Des

...

On another forum someone mentioned a "reverse turnbuckle" tool for less than$10 that is used for tensioning and then removed once the pivot arm is bolted tight. Does anyone have a link to this tool? I can't find it

Thank you!

Check:
https://forums.sailboatowners.com/in...n-easy.188775/

[Suijin]

Be REALLY careful tensioning the belt on the M25 as the alternator mount is on the block. Break and you have a real problem. There is a kit for fixing this design flaw.

Some more info on it.

Evaluating the alternator mounting upgrade

[GordMay]

I think you’re referring to a Male Turnbuckle, or Jack Screw.

[hellosailor]

Bill-
You might ask in a Harley shop or forum about that. They were among the last places that had belt tension gauges and other "old" tools. V-belts are sadly obsolete these days, and it is very possible you've got one that is the right belt length--but the wrong profile. Then it will slip in the pulleys no matter how much you tension it.
With a small crowbar or a large screwdriver, it should be easy to put enough tension on any engine belt. Sometimes you need a third hand to tighten the bolts and keep that, sometimes one person can do it all. If you've really got to lay into the crowbar, something is probably wrong.
The belt jacks and belt tensioners might be available on ebay from folks clearing out their old tools. And ALL V-belts need to be re-tensioned after break-in, the belt maker can tell you what's right for their particular belt, how many hours of use.

[captain465]

The "belt tensioning jack" that a64pilot references is a good tool for tensioning a belt by yourself. I have had one for years. You can also look at J C Whitney automotive catalouge for this great tool.

[RossD]

I have one also, it is a fine tool for tensioning in tight areas single hand and does not require prying upon another engine part with a bar.

[Stu Jackson]

I have an M25 and use the belt tensioner. Don't make it too tight or you'll put unnecessary pressure on the water pump bearings.


Engines 101 - The BIGGEST & BEST collection of M25 Series Universal Engine Information on the Internet, plus some M35, too

Diesel Engine - c34.org

[hamburking]

Belts don't need much tension. If you over tension they will break fairly quickly. I've never used more than a long screwdriver as a lever to tension while tightening the bolts.

[GeneM]

My experience - yes! Just go back later and retension.

[BlackHeron]

Belts should be almost loose enough to slip. Any tighter than that and you risk bearing issues and even alignment issues. If it doesn't slip or squeel then it is tight enough.

Bearings and oil seals are MUCH more expensive and difficult to source and repair than belts. Err on the too loose side. Stock extra belts, they are easy to change if they wear too fast from slipping.

If you want a better guide as to how tight a belt should be invest in a "Kricket" belt tension tester. Most any auto parts store will have one if you ask. They are cheap, well inder $20, and don't take up much room in the tool box or roll. They are only the size of a magic marker.

Many old-time mechanics laugh at them saying they just "know" how tight a belt should be by feel and that is all well and good for them. But how do you learn what the right tension feels like without some sort of guide? Is the old-timer going to come on down and check your belts for you every time you install one until you get to that point yourself?

Just get a Kricket and use it as a learning guide. When you feel confident in your "feel" you can give it away, or put it in the back of the tool box -whatever.

A trick to get extra purchase on a tricky installation is to use a big screwdriver as a lever. Put hand tension on the bolt and dial a bit more tension into the alternator or pump by carefully levering it around the pivot bolt. Be careful not to break anything, especially cast mounting flanges and be aware at the red wire that goes to the alternator is always HOT even with the key off on many engines so don't short it out to ground with the big stupid screwdriver and scare the living S out of yourself with a massive DC arc (done that!)

Gates (Kricket) 91107 Belt Tension Tester https://www.amazon.com/dp/B000MUTAGS..._el..CbQPCB86Y

[Stu Jackson]

heron's right, but save the money for the kricket. It's right when you can turn the longest length between the camshaft pulley and the alternator 90 degrees with your fingers. Without breaking your fingers.