Cooling systems

[vlad01]

I thought it said sexdaily?

[immortality]

That's EXACTLY what i said

[psyolent]

WHERE WHERE?

[pman92]

Thanks for the detailed description pman. Unfortunately I still can't visualise it (I'm a hands on visual learner) so I'm just going to have to trust you on that one.

I'll do more research before I jump in at the deep end with this idea.

Haha that's fair enough, I didn't understand how it worked either for years until a mate who is actually a fitter and turner explained it to me, when I had a water pump off and he saw it and said "that's a centrifugal pump". He hadn't probably ever seen one before and I didn't know what he was on about and said "what do you mean centrifugal, it's just a bloody water pump".

Imagine the coolant in between 2 of the fins on the impeller. As the pump turns it spins that coolant around and around in circles. Now imagine getting a rope with a steel ball on one end, you grasp the other end of the rope and spin it around and around above your head like a cowboy with a stock whip. The faster you spin it the harder it is to hold onto it, and when you let go it flys off in one direction, it doesn't continue going around in circles. There's centrifugal force pulling the ball away from you. The same thing happens with the coolant, the faster you spin it in circles the harder the force wants to push it towards the outside of the circle. That is the force that pumps the coolant.
A water pump/centrifugal pump is different to say a vane or a gear pump (used for power steering and oil pumps) in that it is NOT a positive displacement pump. It doesn't displace X amount of fluid for X RPM. Say for example 10cc per RPM, if it was doing 100RPM it would displace 1000cc, if it was doing 50RPM, it would displace 500cc. A water pump is not like that. If you don't spin it fast enough it will not pump anything. The centrifugal force has to overcome a certain force (the pressure difference between inlet and outlet) before it has any flow at all, until then coolant goes no where.
You can see this by removing the pressure heater hose, connect the suction side to a bottle with the end cut off and half fill it with water to create a reservoir. Then hold the pressure end you removed over the reservoir and see how high above the water level you can hold it before it stops flowing out. The lower you hold it, the more coolant flows out, as you lift it up above the water level in the reservoir it flows less and less until it stops flowing completely. What you are doing is changing the pressure difference between pump inlet and outlet and the flow changes to suit. If you then rev the engine up it will start flowing again, as your increaseing the pump speed and available centrifugal force in the pump. If you measure the distance above water level it stops flowing, there is actually a mathematical formula to calculate the pressure the pump is producing. Obviously capable of more and more pressure as pump speed goes up and up. This is a very good way to test pumps are working. I've done it many times to confirm pump failure on VW golfs, which have a plastic impeller pressed on a steel shaft. The plastic ages with heat and breaks off the steel shaft, the pump stops working and the customer drives the car until it overheats usually.

[vlad01]

long explanation there. I just know it as conservation of angular momentum.

[MAGP]

Pman you've done it.
I didn't connect centrifugal with centrifuge until just now. I know, I know, I should have but I didn't . As soon as I made that connection, because of your explanation, I could see it. Now I have a vivid memory of year 8 tech class when I was in high school cause we had a centrifuge. I also, unfortunately, have vivid memories of the dentist who had a centrifuge.
Thanks for your patience, it is very much appreciated

[vlad01]

http://www.gumtree.com.au/s-ad/sunshine ... 1117284873

[immortality]

Yeah, seems there are a few on aussie. Seen this one as well on ebay

http://www.ebay.com.au/itm/GMB-WATER-PU ... SwmtJXXLz1

However I would like to see if I can get one from a local supplier.

[vlad01]

Thats the exact ones I end up with, even has the purple texter mark on the impeller shaft.

[Charlescrown]

The construction is driven by cost. Who was the astronaut going to the moon that said to himself "all the parts in this rocket were made by the lowest tender"? My general feeling is if it does the job reliably it's good enough to fit. I agree all the older cars had cast impellers but there again the didn't have coolant. Plastic is another story.