"Michael Pardee" <michaeltnull@cybertrails.com> floridly penned in
news5adnWOWyKmWwSPcRVn-sw@sedona.net:


> 1) makes sense when I think about it. 2) escapes my tired brain, but
> I'll take your word.



You don't have to. Next time your car is full warm, go squeeze the rad
hoses. Sometimes they'll be firm, sometimes they'll be soft as though the
engine was cool.


>
> How does the bottom-mounted thermostat sense the temperature? Does the
> pump feed a loop that brings coolant from the head to the thermostat?
>


The thermostat is still top-mounted, at the UPPER end of the bottom hose,
since it needs to be where the heat is (heat rises).


With the old system where it's in the top hose, the sequence is this:
1) Water in block and head heats up
2) Thermostat opens and hot water flows to the rad
3) Water cools in the rad and is then pushed back into the block by the
water pump from the lower hose
4) As the cool return water comes through the block back to the thermostat
again, the thermostat closes, limiting water flow until block heats up
again.

With the new system where it's mounted in the bottom hose:
1) Water in the block heats up, with the heat backing up to where the
thermostat is
2) Thermostat opens, allowing cool water from the lower rad hose to be sent
to the water pump and pushed back into the block
3) Cool rad water makes thermostat close up again and water flow stops
4) Sequence repeats from Step #1.

Apparently this second system is better suited to cooling systems with
limited capacity. The limited capacity seems to be a response to weight-
cutting in order to help comply with government CAFE rules.



--
TeGGeR®

The Unofficial Honda/Acura FAQ
www.tegger.com/hondafaq/

 

"Michael Pardee" <michaeltnull@cybertrails.com> floridly penned in
news5adnWOWyKmWwSPcRVn-sw@sedona.net:


> 1) makes sense when I think about it. 2) escapes my tired brain, but
> I'll take your word.



You don't have to. Next time your car is full warm, go squeeze the rad
hoses. Sometimes they'll be firm, sometimes they'll be soft as though the
engine was cool.


>
> How does the bottom-mounted thermostat sense the temperature? Does the
> pump feed a loop that brings coolant from the head to the thermostat?
>


The thermostat is still top-mounted, at the UPPER end of the bottom hose,
since it needs to be where the heat is (heat rises).


With the old system where it's in the top hose, the sequence is this:
1) Water in block and head heats up
2) Thermostat opens and hot water flows to the rad
3) Water cools in the rad and is then pushed back into the block by the
water pump from the lower hose
4) As the cool return water comes through the block back to the thermostat
again, the thermostat closes, limiting water flow until block heats up
again.

With the new system where it's mounted in the bottom hose:
1) Water in the block heats up, with the heat backing up to where the
thermostat is
2) Thermostat opens, allowing cool water from the lower rad hose to be sent
to the water pump and pushed back into the block
3) Cool rad water makes thermostat close up again and water flow stops
4) Sequence repeats from Step #1.

Apparently this second system is better suited to cooling systems with
limited capacity. The limited capacity seems to be a response to weight-
cutting in order to help comply with government CAFE rules.



--
TeGGeR®

The Unofficial Honda/Acura FAQ
www.tegger.com/hondafaq/