How Does Coolant Get Into The Block The "First" Time?

[peejay]

Greetings, all!

 

Let's say you have drained all the coolant from your radiator and the engine block. When you add new coolant to the radiator, and start the engine, how does the coolant get sucked in by the water pump, past the closed thermostat, and into the block?

 

I understand how it works on vehicles where the thermostat is located in the water outlet, but i'm getting lost on systems with the thermostat located in the water inlet!

 

Thanks for any help!

[Nefarious]

That is the outlet.. you just crack the coolant bleeder and fill it up from the rad...its one of the easiest coolant systems I've ever filled. I'm appalled when I work on vehicles and there's no coolant bleed bolt!

[peejay]

Ah, so the top hose draws coolant, from the radiator, to the engine, and the bottom hose returns the coolant to the radiator (once the thermostat opens)? Totally makes sense if that's the case!

Edited July 30, 2013 by peejay

[k9sar]

not only when the thermostat is open. There is a small air-bleed in the thermostat that allows coolant to flow into the block while the air is vented through the small hole in the thermostat until the block fills. When filling a completely drained system, you will notice that the coolant level drops slowly after the initial fill. This is the block filling and the slow flow of air to the highest point through the thermo.

[peejay]

Sorry, one "last" question...so does this mean coolant is forced from the bottom of the radiator [circulates, is cooled, and then goes] to the top of the radiator?

[Nefarious]

No, when I said the top is the outlet I mean the top line is the outlet from the engine. the engine coolant temp is measured as it leaves the block . That's why your coolant temp sensor is in the top pipe. Coolant flows down the rad.

[peejay]

I read somewhere that the thermostat is always the outlet...hot coolant hits it, and causes it to open, allowing the hot coolant to enter the radiator, get cooled, and then flow back into the engine via the return hose.

 

Since the lower radiator hose has the thermostat, this must be the outlet...which means that the upper hose is the inlet/return.

 

So when i fill the radiator up the "first time", the engine will draw in coolant from the upper hose.

 

Seems backwards, but I guess there's a method to the madness!

 

Thanks, all!

[k9sar]

I think there's a picture in the FSM or the coolant flow but I can't access it through my work's firewall right now

[peejay]

I was able to pull it up, it shows that when the thermostat is open:

 

Water outlet-->Radiator-->Thermostat-->Thermostat housing (Front cover)-->Water pump-->Cylinder block and Heater-->Cylinder head-->Intake manifold-->Water outlet

 

(Heater-->Intake manifold and Thermostat housing (Front cover)-->Throttle body-->Water outlet)

 

I'm used to engines with the thermostat housing serving as the water outlet, i think that's where my confusion came from!

 

When/if I ever get this thing runnin, i'll take the radiator cap off and view the flow, and see if indeed the coolant is exiting the radiator through that top hose!

Edited July 31, 2013 by peejay