Closed thermostat pressures

[mjoekingz28]

Ok, when your thermostat is closed, I believe coolantis basically just sitting static YET the water pump is always turning, so is there something of a relief valve?

 

[A_Harman]

No, there is a bypass hose that takes the coolant from the water pump discharge and returns it to the inlet. When the t-stat opens, it doesn't open all the way, and sends part of the coolant to the radiator for cooling. The t-stat divides flow between the bypass and radiator in different proportions to regulate coolant temperature to a steady value for most operating conditions. You have to be running at high power on a hot day for 3-5 minutes to get the thermostat wide open and sending all the flow to the radiator.

 

[NHGUY]

The waterpump is not a positive displacement pump.When dead ended it will just cavitate....paddling water with no flow.

 

[GS1000S]

Also, you have a flow from the pump through the heater core that is not dependent on T stat opening. Sometimes there is a valve controlling this flow and sometime it just flows from the pump, through the core and back into the engine.

 

[4wheeldog]

Originally Posted By: NHGUY
The waterpump is not a positive displacement pump.When dead ended it will just cavitate....paddling water with no flow.


Actually, closing the discharge just causes a centrifugal pump to......Stop pumping!

Pressure is a product of momentum, so there is no pressure developed. Closing the suction would cause cavitation......Cavitation = bad! If you need to idle a centrifugal pump, close the discharge. Never close either, on a positive displacement pump.......Closing disharge = boom!

 

[wirelessF]

Here's an interesting video showing the coolant flow through an LS engine water pump.