Archives

Hi All

Many FEH/MMH owners thought the primary engine coolant pump was electrical, but this doesn’t appear to be the case. The primary coolant pump is a mechanical pump with a pulley and is driven by the accessory drive belt above the A/C compressor (Vol 1 Engine Cooling - Escape Hybrid page 303-03B-21). There is a diagram on that page also.

The Aux. Coolant Pump (heater pump) can be seen through some vent holes near the bottom of the radiator shroud (drivers side). The larger coolant pump for the electronics is just to the right (passenger side). Another diagram of the aux. pump is on the next page (22) in the repair manual above. This pump is only activated while in EV mode with the climate control switch in any other position but OFF. Coolant still circulates through the heater core while the engine is running and I got that wrong. Someone at GH was thinking about adding an ON and OFF button for the Aux pump, but that would not do much more than stop circulation of coolant while in EV. You can do that by turning the climate control switch to the OFF position.

It appears there is a by-pass hose from the mechanical coolant pump to allow circulation of coolant through the engine until the thermostat opens to allow radiator flow. This all means that the volume of coolant will not heat any quicker with the heater pump OFF. However, if the climate control switch is in any position but OFF while in EV going down a mountain, you could cool down the engine for a restart of the ICE in cold weather. The most that could be gained with this information is how to save energy (electric motor running) and engine heat while in EV. This will improve MPG and further explains my increase in mileage since I stopped leaving the climate control switch in the vent position and just turn the thing off.

Haven’t found anything that states the PCM would kick on the Aux. Electric Pump if the primary mechanical pump failed or the drive belt broke. It may mean the Aux Pump is to small for cooling the engine.

Gary

The Prius is similar. Even with the fan on low and
demanding relatively little in the way of cabin heating,
I can sit there with the ICE off and *watch* the block
temp fall when stopped at an intersection. The cabin
heater can account for a fair amount of heat loss from
the engine.. it's about a quarter of the main radiator
area and has a fan blowing over it, so it's not an
insignificant transfer capacity.
.
_H*

The Prius is similar. Even with the fan on low and
demanding relatively little in the way of cabin heating,
I can sit there with the ICE off and *watch* the block
temp fall when stopped at an intersection. The cabin
heater can account for a fair amount of heat loss from
the engine.. it's about a quarter of the main radiator
area and has a fan blowing over it, so it's not an
insignificant transfer capacity.
.
_H*

Hobbit or anyone here know if there would be a problem piping in a bypass where the inlet and outlet heater hoses connect to the heater core? The reason is two fold which is to stop hot coolant from circulating through the heater core heating the cabin air duct system during vent or A/C use during the summer heat. The second reason would reduce the volume of coolant needed to be heated for engine warm-up, therefore reducing the time to go EV.

The inlet and outlet connections in the FEH are connected inside the engine compartment at the firewall, but I maybe able to just take the inlet hose lose and connect it to the source of the return and just plug the ends of the heater core.

My thinking is that the recirculated cabin A/C air would last longer during EV when the compressor is off during the normal recirculation position. That heater core has got to be heating the cooled air and even the vented air, any thought?

GaryG

I'm not sure about the FEH, but in the Prius you don't need
to do that. If the system is turned to "max cold" and then
turned OFF, coolant basically doesn't go through the heater
loop and the pump doesn't run. There may be a tiny dribble
of it left going through there, but it's not enough to make
any cabin heat and the bulk of it either stays in the block
or goes to the radiator loop [depending on engine t-stat].
.
If you can access anywhere near where the heater core in
your cabin is and play with settings and get your hand in
there to feel how much waste heat it's throwing off, you
might come up with a setting that does what you need..
.
_H*