Questionpurchased a turn key engine, and we are having problems with the cooling system, it has a reverse flow pump a diagram or answer on how to hook this up correctly, this engine has been a nightmare. We are completely stuck. Thank you
AnswerClifford,
I'm assuming you bought an LT1, so I will use that as the example here. The incoming coolant first encounters the thermostat, which now acts both on the inlet and outlet sides of the system. Depending on the engine coolant temperature, cold coolant from the radiator is carefully metered into the engine. This allows a more controlled amount of cold coolant to enter, which immediately mixes with the bypass coolant already flowing. This virtually eliminates the thermal shock present in the old system.
After entering through one side of the 2-way thermostat (at the appropriate temperature), the cold coolant is routed directly to the cylinder heads first, where the combustion chambers, spark plugs and exhaust ports are cooled. Then the heated coolant returns to the engine block and circulates around the cylinder barrels. The hot coolant from the block re-enters the water pump, and hits the other side of the 2-way thermostat, where it is either re-circulated back through the engine or directed to the radiator, depending on temperature.
All of this means that the thermostat housing is the INLET (opposite of most engines), while the water pump is the OUTLET. The water pump (outlet) on the engine runs to the top left (inlet) of the radiator. The lower right (outlet) of the radiator runs to the thermostat housing (inlet) on the engine. This also means that the "upper" hose on the radiator would be connected to the water pump (mid/lower part of the engine) and is the outlet of the engine, so it should be hot with the thermostat open. The lower hose on the radiator is connected to the thermostat housing (upper part of the engine) and is the inlet to the engine.
The main concept behind reverse flow cooling is to cool the heads first, which greatly reduces the tendency for detonation, and is the primary reason that the LT1 can run 10.5 to 1 compression and fairly significant ignition advance on today's lead-free gasoline. Reverse flow cooling is the key to the LT1's increased power, durability, and reliability over the first generation small block engine. There are three main circulation systems for the LT1, while most engines only have two systems. As with most cars there is circulation through the heater core and the radiator, but there is a third system on the LT1 which includes steam vents in the head, along with a pressurized reservoir. Coolant to the heater core comes from the water pump. The lower hose on the water pump is the heater core inlet, and should have a flow restrictor mounted in the hose. This is to prevent over-stressing the core at high engine rpm. The heater core outlet hose returns to the water pump at the upper hose connection, and also has a T-connector to the pressurized reservoir to bleed off any air. Hope this helps... if you have any more problems with it, let me know. Good Luck!
