300SD, 300TD, Why does the alternator have two belts?
 

I am replacing my alternator in my 300SD. I went to a local rebuild shop, and they had one that was identical, but the pulley is only for 1 belt, not two.

When I look at the car, it appears that the two belts connect from one double pulley to another double pulley. It was the same in my 300TD when I had it. What's the purpose of that? Could I get bye with just one belt?

thanks

In case one fails. It also turns the fan. Its one of the few weakpoints of the NA 617...

The NA 617 has only one belt, the turbo has two. at least on my cars.
two belts give you more surface area to handle the load of the massive 65A alternator...riiiight. OM vehicles tend to get oil on everything. maybe MB decided that slippage might be reduced with the extra belt... cooling is important.
John

Why not just swap the double sheave for the single on the "new" alternator? Very easy for a rebuild shop... RT

I would if I could... the nut fell off the shaft and the shaft and pulley were damaged in the process... the alternator is probably fine electrically.

My daughters 240D has one belt. It broke and so the water pump does not turn. My daughter was stranded on the side of the road comming home from college.

300TD has 2 belts. I had one break and the other one is fine. So the car can be driven and no overheating. I have a new set, I just haven't installed them.

I would install both belts just for peace of mind.

Dave

Two belts is a great idea. The only thing better is a serp.

I had 'matched set' belts on my Merkur. They lasted forever.

If one breaks, you'll make it home. Two belts seem to grip better than one.

You can run a lower belt tension, which is good for the bearings.

Serpentine belts, which are fairly new to me, are fab. It sort of scares me that I might eventually throw one, but so far I haven't.

ok ok two belts it is...

So, anyone have a spare double pulley laying around??? :cool::sultan:

not exactly a spare, but I have 4 parts cars... pm me.
John

Its typical Mercedes overkill. Things like that are why they cost more.

Sure you can get by with one V belt, most cars do. But Mercedes takes it a step further, having a second is better. Most cars lack them because such a set up costs more, but the engineers spec'd two because cost wasn't an issue.

That double belt has saved me a couple of times, it will run with one, but it will slip unless it's pretty tight. Last time I broke one I was in VT, and I drove around for a week before I had a chance to replace it. Sure beats having to do it on the side of a highway someplace.

On a Merkur, the belts surely last longer than the motor.......;)

Well put!!

2 Belts....
 

Liebchin....because ve zaid zo........

SB

Also kudo's to Mercedes for making the belts cheap. Last I checked I think replacements were like $10 each!:D