Hi there,

I've no idea why there are two.

My take is this is a 240 quirk that takes some getting used to.

Because (as I tell my kids) they all squeal at one time or another, I've put a lot of head scratching into this peculiar arrangement at the alternator. First, I don't subscribe to the redundancy theory, for avoiding breakdown. What good is redundancy without alarming? No, I believe there are two belts because with three pulleys there's not enough wrap on the small alternator pulley to hang on to it under peak loads with only one. Fact is, the later cars can't hold on to it with two.

The cars you are used to and 7/9 cars don't need two belts because, prior to the serpentine arrangement in FWD, alternators had their very own belts to get them whizzing at 2-3x engine rpms. As the 240 progressed from the 55A alternators in '76 to the 80A powerplants in the 90's, nothing changed in the geometry or rubber support of the three pulleys.

I also don't hold with the notion these belts have to be matched pairs. The fact is, we crank on the adjusters in every case to force the front belt to be tighter, so if they would have equal tension, an unmatched pair with the shorter belt inside would be better practically. That's the side effect of mounting the alternator on rubber bushings.

Anyhow the net result of this quirk, on the later 90's cars is, you pull the belts tighter to keep it from squealing in the morning, but the pulleys and belts get glazed, the bushings take a set, and you're doing it again, and again, until eventually, the coolant pump side load scares you into replacing the bushings, belts, and deglazing the pulleys.

Here's what the adjuster mechanism should look like.


--
Art Benstein near Baltimore

My father said there are two kinds of people in the world: givers and takers.
The takers may eat better, but the givers sleep better.