What pulley for a 5.0 water pump? - PeachParts Mercedes-Benz Forum

GGR · #1 10-05-2009, 07:28 PM

I am slowly putting back my euro 5.0 engine after rebuilding the timing. I ended up with two water pump pulleys of different dimensions. I believe the original one is the bigger one, while the smaller one must be out of a 4.5. I am thinking of fitting the smaller one to increase water circulation and improve cooling. I also noted that another type of 5.0 water pump, with both inlet and outlet on the side, had the smaller pulley. Any thoughts if this is a good idea?

Thanks in advance!

cth350 · #2 10-06-2009, 06:59 AM

As long as the groves are in the right place, why not? Except doesn't using a smaller pulley mean the accessory turns less, not more? http://www.csgnetwork.com/pulleybeltcalc.html

BTW, can the toothed gear be mounted on the back of the pulley?

-CTH

GGR · #3 10-06-2009, 07:05 AM

Thanks CTH. We are talking of the pulley on the water pump, not on the crankshaft. So the smaller it is, the quicker the water pump turns. I was concerned by cavitation at high rev.

I checked and the groves align properly with bot pulleys.

Tomguy · #4 10-06-2009, 08:07 AM

The water pump shouldn't need to turn any faster. I'd imagine that a 5.0 water pump is more efficient than a 4.5 - I could be wrong, but I would hope in the 9 years or so since inventing the 4.5 that MB came out with a more efficient design.

I'd use the larger one. It'll add 1-3 HP. Maybe more. And yes, that's seriously why I'd use it. That and it's probably the right one. I do remember the 4.5's being fairly big. Compare it with your 3.5 - the 3.5 and 4.5 use the same one.

GGR · #5 10-06-2009, 08:24 AM

The smaller one is the same size as on the my 3.5. Note that at least at the beginning the 5.0 will run with the 3.5 radiator without an expansion tank as on the 450 SLC 5.0 it came out of. The rad capacity may also be a bit less on the 3.5 rad. I read that some people fit smaller pulleys for racing. So having the liquid circulating faster may compensate for the slightly smaller rad capacity. On the other hand, faster circulation means less time in the rad and therefore less temp exchange... I really don't know.