UrS4boy

Our C4 AAN cooling system is obviously connected to the heating system. It is also part of a system that is used to protect the turbo after the engine is shut off. The intent of this post is to consolidate the links to info about the various components of this system. It won't be perfect but it will be a start. Updates (and bumps) to follow, as needed.



Once you start a 20VT (or any) engine, the coolant is circulated by the water pump. For the 20VT engines (RR, 3B, AAN, ABY and ADU) coolant immediately starts circulating to the turbo to help cool the turbo bearings, even before the thermostat opens.

With the exception of this turbo-coolant circuit, coolant generally remains in the block until the thermostat warm enough to open. However, depending on the coolant temperatures and the HVAC heating requirements, coolant might start to circulate to the heater core before the thermostat is open because the connection from the engine to the heater core is at the back of the engine, independent of the thermostat that is located near the front of the engine.

Once the thermostat is open, flow to the radiator begins.

So coolant leaves the 20VT inline-5 block to:

a) cool the turbo bearings
b) supply heat to the HVAC system
a) be cooled in the radiator

As discussed below (underlined text = hyperlinks to more detailed information):

Turbo Coolant Feed and Return Lines<click here for more info>

Feed:



Return (under intake manifold):



Heater and Radiator coolant systems

The overall coolant system with PNs (Info Links under diagram:



General HVAC info

C4 HVAC Ducting and Stepper Motors

Heater Core DIY

HVAC Bleeder Valve

Heater Control Valve

Climate Control "Tee"

Expansion Tank/Reservoir

After-run pump and control module

Radiator

Water Pump

Thermostat, details, replacement, etc

Coolant Flange

20VT Water Manifolds

Hope this helps someone somewhere sometime.

Or Not. It was fun putting it together, regardless.

tonycosta1984

Thanks Dave. This is awesome!