The Mitsubishi Pajero Owners Club®

[Hilux]

I ran Toyota 4x4`s for 20 years - some with two alternator belts.

In changing double belts I noticed that there are subtle differences in pully diameters and certainly with incorrect/differing belt lengths (poor manufacturing tolerances) and ultimately the tension is determined by stopping the slackest belt squealing.

One of the ways to avoid this is to always use quality belts which are made to exacting tolerances and are the correct widths for the pulleys. Most belts are about 9.5mm and will squeal if used in 11mm pulleys. The belts should fill the `vees` not sit in them for maximum surface area contact which lessens the need for higher tension. I always use Gates belts (they invented them after all)

I also consider that the squealing and wear over the years polishes the pulley surfaces so use medium wet and dry to de-glaze them.

I recently changed the the three belts and carried out the same experiment on my 100k 3.2 as I did on a Landcruiser where I noted belt lengths and pulley tolerances are the key issue.

I set the printed manufacturers brand/label/name on the new twin belts in parallel on the pulleys and tensioned the belt so the alternator and fan pulleys couldnt quite be turned by hand. It started fine and was ok for a couple of journeys and then squealed. I checked the belts visually and wasnt surprised to see they were not now running parallel as there is a certain amount of settling in and stretch that must occur - albeit a small amount as these belts are designed to be stable in length - so re-set the labels in parallel and tensioned them further.

Another couple of short journeys and I got squeal on start up so checked the belts again and the labels were not running in parallel. So reset and tensioned further. No more squeal and the belts have moved from parallel but slowly. This was an exact repeat of my previous experiences.

Conclusion?

The alternator belt tension is always dependent upon belt lengths and pulley tolerances and is set by tensioning the slackest belt/pulley combination which means you tension them both differently ie: the tightest belt will be overtensioned. This cannot be avoided due to the inherent pulley tolerances but can be reduced by using quality belts. I dont know if the water pump is overtensioned but there is no other way.

Quality belts designed for the pulley's width (most are 9.5mm and the Did requires 11mm) means the pulleys sit on the grooves and not in them. Maximising side contact is the most important issue as they rise and fall within the pulleys in theory taking out any tolerance whereas thinner belts tend to sit lower within the pulleys contacting the bottom of the groove.

Just thought I`d share this nugget from many years of experiencing it and have no affiliation at all with Gates but any belts of any type or purpose I use on any engine are always Gates.

[Google]

[trekker]

In my engineering years, multiple belts were purchased as matched sets, regardless of manufacturer, though I don't know the position with small belts as on a Paj alternator.

[BenKenobi]

Good information. Some stuff I worked on used up to 6 belts but belt technology has moved on a lot since then and many use the single 'ribbed' serpentine type belts now. I wasn't aware of the 9.5 v 11mm on Mitsubishi either - very useful.

To add my two penneth ..

The belts when teamed up as in the alternator pair should always be replaced in 'teams' from the same manufacturer - you can't replace one at a time no matter what anyone tells you. I'd replace belts on an interval basis i.e. every 30,000 miles or 4 years perhaps and not when they are already goosed enough for the damage to be visible.

Attention needs to be paid to alignment also - I've encountered situations where the pulleys were not aligned correctly - this will rip belts to bits in no time. Same goes for a belt that is too narrow, once a belt is 'bottomed' in the groove the only part driving the pulley is the bottom part - the sides become 'unloaded' and slippage is certain, in these conditions many keep tightening thinking that the extra tension will shut things up - they will but only after the belts / bearings fail. Sometimes squeal just means the belts are worn out.

For what it's worth a belt tension tester is the only way to be sure, the deflection method is good too if properly applied on the belts longest run between pulleys - 0.4mm per 25mm length on this run (or 1/64 per inch). I don't agree with Mitsubishi's 'sounding' technique (I'm sure I read that they tension the belts then pluck them like guitar strings and use a special tool to listen to the noise made - can't find it at the moment)

Overloading the belts will destroy not only the belts but the bearings of whatever they are turning.

[Hilux]

I agree they should be sold in pairs (and used to be) but as they arent any more it's best to go to a manufacturer whose tolerances are good. Hence I will continue to recommend Gates belts all the time.

This I have learned from experience over many years.

A lot of 4x4`s have the wrong matched belts tensioned to stop the slack one squealing or they are the wrong width so necessarily over tensioned and then people wonder why alternator bearings or ancillary bearings fail.