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4.0 V8 Water Pump Confusion


garrycol
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As some will know the water pump on the Rover serpentine belt engines turn the opposite direction to V belt driven water pumps. Looking from the front of the engine the serpentine water pumps turn counter clockwise.

I have this water pump to go onto my engine.

Waterpump2_zpsjsqiberh.jpg

The wiggly red arrow indicates the direction the impeller turns when looked from the rear.

Here is a different view of the impeller.

Waterpump1_zpsdj2s0nlp.jpg

Notice the direction of the teeth on the impeller.

Here is my confusion - when this impeller is turning in the correct direction as per the red arrow the teeth seem to be the wrong way around - basically the impeller seems to be running backward - as if the water pump should be turning the opposite direction.

Now the shown pump is supposedly the correct pump and I have found the same examples in the internet being sold for the same application.

So can someone explain why the impeller seems to turn the wrong way on these pumps.

Thanks

Garry

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Does not the flow go in the pipe and out through the sides? Through the block and out the top hose, wouldn't this be the correct direction then?

So I guess the question is if the vanes are correct? Sorry if this is me playing catch up?

Marc

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On centrifugal fans the forward facing vanes are the best angle for ventoring the most amount of air, but it doesn't have the ideal stall characteristics of backward facing blades which can generate more pressure. So in this case I am guessing they are right if it has a thermostat to block the flow?

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Your picture matches the drawing in Rave. The pump sucks coolant from the intake channel (center) and pushes it outward, to the galleys connected to the engine block. This impeller design is the most efficient (for the given pressure and speed) as it uses mainly centrifugal forces to drive the fluid outward without making it spin in the housing too much.

So yes; this is the correct pump and the impeller properly designed for it's purpose.

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Thanks for the comments - my teaching of hydrodynamics would indicate it would be more efficient if the blades were the otherway round - would increase suction through the inlet pipe in the housing. I guess there is some logic there but not sure what it is - maybe it prevents cavitation which can cause major corrosion,

Cheers

Garry

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If the blades were the other way around, the impeller would be pushing the coolant out through the center. To do that, it needs to overcome the centrifugal forces due to rotation. Designed as it is (as most pumps) the rotation creates a centrifugal effect, from the center outward. Just like for example the compressor on a turbocharger. At such high speeds reducing friction with the fluid is important to prevent losses, hence why the blades are curved to 'guide' the fluid instead of 'forcing' it.

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