engine cooling system questions

[Mark Price 2]

Hey all, I am trying to fully understand how/why the ST cooling system works the way it does.('03) Anyone willing to take a few moments to clarify/correct these questions/statements for me would be greatly appreciated.

1)Coolant is always flowing through the heater hoses. From top of engine(thermostat area)->heater core->heater control valve->back to water pump UNLESS a/c is on max.?

2)if max a/c closes the HCV completely, I assume the coolant just sits there stagnant all the way back to the therm housing area.?

3)and stagnant the foot of hose between hcv and water pump?

4)Was there any (good)reason Ford moved the HCV up closer to the firewall after '03? (mine is further down the hose basically under the air box just a foot before water pump)

5)when the temperature dial in the cab is adjusted..does this adjust a blend door or the HCV? 6)if it controls how much coolant flows through the hcv...how does that work??

7) or is the hcv either always fully open or fully closed?

8)when back flushing the system..from a prestone tee lets say. wouldn't it be wise to use hot water from the laundry machine faucet? running cold water through the engine while it is coming to temp doesn't sound good to me.

9)when back flushing(engine on)..the flow is going against the water pump "fins" this does not cause damage? the pressure from the faucet hose just goes right past the water pump "fins" like its not even there? even though the fins are going the opposite way

-- I hope this makes sense. Thanks for reading. I am going to be doing some work on the cooling system soon and I always like to understand the why while I am doing the how.

 

[JR Neuzil 2]

I don't think Max closes the valve like that. It was always my understanding that the difference between max and normal air is where the air to be cooled comes from. Regular draws outside air to cool while max recirculates the air already cooled from inside the car.



But , I could be wrong.



JR

 

[Jim Upton]

 

[Mark Price 2]

JR- True. But, the role I believe of the HCV fully closed when a/c max and temp at full cool is so that there is no hot coolant flowing through the heater core. Thus making the cold air coming from the vents very cold. Much appreciated here in Texas. If there is hot coolant flowing through the core while you are trying to get the cab cold, it would take a bit longer as the hot heater core would make the cold air coming out a few degrees warmer. But, I could be wrong

 

[Mark Price 2]

I have been thinking long and hard all day. I taught myself a few things(I think)

1)coolant always flows through heater hoses unless max a/c or OFF is selected. Then it completely closes flow.

2)yep, coolant just sits there in the hoses from the hcv, back through the core and back to the top of the engine when the hcv shuts off flow

3)not sure. the pump may "suck" some of the coolant between the hcv and water pump. Wouldn't matter anyway.

4)I think Ford moved the HCV closer to the firewall after '03 for easier access. Hard to believe I know

5)temp dial only affects blend door, not hcv

6)N/A

7)already answered this in 1)

8)people have been back flushing forever with the garden hose. it doesn't seem to hurt as long as you don't do it too long. But using hot water wouldn't hurt either. It may even do a better job and put my mind at ease about possibly cracking a block

9)back flushing with the engine on wont hurt the impellers (fins) on the water pump. (i guess?) as folks have been doing this for years as well.



To add, seems a lot of vehicles hcv shuts off flow to the core BEFORE the core. Gen 1 ST's(well my 03 anyway) HCV stops flow after the core. Thus, stopping flow all the way back to the top of the engine. But, allows coolant to stay in the hoses and core . I believe this is to prevent sudden surges when flow is released to the core. possibly helps prevent ruined cores. the sudden surge affect may be too much for the somewhat empty core to handle. idk? makes sense to me.



Also, Iv'e seen the tee flush attachment put on the "wrong" heater hose. It doesn't really matter i suppose. It's just that if you have crap in your core your pushing(back flushing) that stuff toward your thermostat(if you left it in) and into your block. I don't like the idea of that.(bypass the core altogether when flushing and flush the core separately) I think folks have mistaken the location of the heater inlet hose because of where the hcv is located on the ST.



Thank you to my brain for still being able to think somewhat logically after starring at a machine/appliance/whatever for awhile.



If anyone has anything to add or correct. Please do so. Thanks

Just trying to learn and possibly help others. Keep on Trac'in