Reply to "Weiand water pumps, what's up? ACCOBRA"

Ron,

If you are running a thermostat, the motor MUST have some way to recirculate coolant, bypassing the radiator, when the thermostat is closed (motor is cold).

On some cars, the heater core flows coolant full time. Not so with the Pantera, our heater cores only flow coolant when the valve is open.

The other way to recirc coolant is with a bypass. On the Windsors, that's the little hose with the 90 degree bend between the water pump & intake manifold. The Windsor bypass flows full time, never shuts off, therefore it is intentionally a small passage.

The Cleveland bypass passage is internal to the block, it's the passage below the thermostat that leads to the passage missing in the Weiand water pump. Ford engineers designed the Cleveland coolant system this way because they can recirc more coolant during warm up, this speeds up the warm up time, prevents steam pockets from forming in the cylinder heads and allows the motor to warm up more evenly. It also means if you install the wrong thermostat, the car will have a tendency to over heat under heavy loads, because too much coolant is bypassing the radiator FULL TIME.

Here's the problem with the Weiand water pump on a Cleveland motor. You have a thermostat installed in the block, as normal. You are also running the Weiand water pump that defeats the motors ability to recirc coolant internally. Your heater valve is also closed. In this situation, when the motor is cold & the thermostat is closed, the water pump CANNOT pump coolant, it is pumping against a dead head. This is not a good situation, and poor engineering. This is why you'll never read me recommend the Weiand pump.

The Weiand pump must be used with a Windsor thermostat, AND some method to allow the engine to recirc coolant, or with no thermostat at all.

Your friend on the DTBB, George