Rick
After I posted that I got to wondering then went out and looked and wasn't
at all sure. Thanks for keeping me honest.
Probably doesn't really make any difference when I plumb the new heater but
it's nice to know.
Thanks
Dick
>
>> I think the line from the water pump end is the supply
>> and the line to the rear of the block is the return. I also think the
>> heater comes off before the thermostat. If this is true then the Shutoff
>> going to the heater is in the return line. Without looking inside the
>> water pump I don't know for sure. Does anybody know for sure?
>
>Dick,
> Actually, no. The water pump sucks coolant from the radiator AND the
>heater/preheat circuit, and discharges it directly into the engine via the
>front cover. From there the coolant flows rearward around the cylinders.
>Some of it migrates upward into the heads through the myriad small passages
>(these prevent air pockets in the block and insure some flow around the tops
>of the cylinders), but most flows to the back of the block where the largest
>passages in the head gaskets/heads send it upward. (This is where our
>heater/preheat hose is connected, and some coolant leaves the engine here.)
>Now the coolant does most of its work, picking up all that heat from the
>combustion chambers, valve seats, and exhaust ports, as it flows forward
>again. At the front of the heads, it turns inwards through the passage at
>the front of the intake manifold, to the thermostat and thence to the
>radiator inlet.
> When the thermostat is closed, the flow INTO the radiator is blocked, but
>some coolant bypasses the radiator via the small (what else?) "bypass" hose,
>which goes straight down into the water pump from the thermostat housing.
>This keeps the coolant circulating at all times, preventing stagnation and
>hot spots, and maintaining a flow past the thermostat element so it "knows"
>how hot the coolant in general is. Also, the coolant at all times flows
>through the heater (and water heater preheat) circuit. In fact that flow
>increases slightly when the thermostat is closed, due to the increased
>pressure differential between pump suction and outlet.
> We might note that this is not necessarily the most efficient coolant
>flow, just the easiest to accomplish. There has been some interest in
recent
>years in directing the flow first to the heads, where most of the heat is
>produced and where damage first occurs if overheated, then send that heat
>down to warm the cylinders, the bottom of which actually run too cold in a
>conventional engine, thus improving efficiency and reducing emissions.
>Unfortunately, this flow is directly counter to the normal "thermo-syphon"
>flow, and makes it harder to eliminate air bubbles, so I hear. For now we
>are stuck with conventional flow as described above, at least in our engines
>and most others.
> HTH.
>
>Rick Staples
>'75 Eleganza
>Louisville, CO
>
>
After I posted that I got to wondering then went out and looked and wasn't
at all sure. Thanks for keeping me honest.
Probably doesn't really make any difference when I plumb the new heater but
it's nice to know.
Thanks
Dick
>
>> I think the line from the water pump end is the supply
>> and the line to the rear of the block is the return. I also think the
>> heater comes off before the thermostat. If this is true then the Shutoff
>> going to the heater is in the return line. Without looking inside the
>> water pump I don't know for sure. Does anybody know for sure?
>
>Dick,
> Actually, no. The water pump sucks coolant from the radiator AND the
>heater/preheat circuit, and discharges it directly into the engine via the
>front cover. From there the coolant flows rearward around the cylinders.
>Some of it migrates upward into the heads through the myriad small passages
>(these prevent air pockets in the block and insure some flow around the tops
>of the cylinders), but most flows to the back of the block where the largest
>passages in the head gaskets/heads send it upward. (This is where our
>heater/preheat hose is connected, and some coolant leaves the engine here.)
>Now the coolant does most of its work, picking up all that heat from the
>combustion chambers, valve seats, and exhaust ports, as it flows forward
>again. At the front of the heads, it turns inwards through the passage at
>the front of the intake manifold, to the thermostat and thence to the
>radiator inlet.
> When the thermostat is closed, the flow INTO the radiator is blocked, but
>some coolant bypasses the radiator via the small (what else?) "bypass" hose,
>which goes straight down into the water pump from the thermostat housing.
>This keeps the coolant circulating at all times, preventing stagnation and
>hot spots, and maintaining a flow past the thermostat element so it "knows"
>how hot the coolant in general is. Also, the coolant at all times flows
>through the heater (and water heater preheat) circuit. In fact that flow
>increases slightly when the thermostat is closed, due to the increased
>pressure differential between pump suction and outlet.
> We might note that this is not necessarily the most efficient coolant
>flow, just the easiest to accomplish. There has been some interest in
recent
>years in directing the flow first to the heads, where most of the heat is
>produced and where damage first occurs if overheated, then send that heat
>down to warm the cylinders, the bottom of which actually run too cold in a
>conventional engine, thus improving efficiency and reducing emissions.
>Unfortunately, this flow is directly counter to the normal "thermo-syphon"
>flow, and makes it harder to eliminate air bubbles, so I hear. For now we
>are stuck with conventional flow as described above, at least in our engines
>and most others.
> HTH.
>
>Rick Staples
>'75 Eleganza
>Louisville, CO
>
>
