Coyote’s cooling system focuses close attention to exhaust valve cooling as well as other high-heat areas of the engine. Ford calls this “cross-flow” cooling, which is different from the conventional cooling for which the 4.6L and 5.4L Modular engines are known. Cross-flow cooling routes coolant up through the block, where it enters cylinder heads at the exhaust valves for excellent heat transfer and reduced operating temperatures. Coolant runs through a long manifold cast into the cylinder head at the exhaust valveseats. It then flows toward spark plugs, intake manifold, and block before heading back to the radiator. This keeps detonation issues to a minimum and durability high. Gone is the mid-valley coolant tube that consumes so much space in the 4.6L and 5.4L engines.
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When you examine the Coyote’s cooling system it can get confusing. There is what looks like two thermostat housings: one on top of the intake manifold on the left-hand (driver) side and another at the left-hand (driver) cylinder head in front. There’s only one thermostat, which is located at the left-hand (driver) cylinder head where coolant flows from the radiator into the block. In a conventional cooling system, coolant flows into the block from the radiator. The thermostat controls flow out of the engine. With the Coyote, coolant flow remains from the radiator through the bottom hose. However, the thermostat controls flow into the engine instead of out of it.
Although the Coyote cooling system appears complex with its cluster of hoses and plumbing, it really is a simple system with clear priorities. The focus is the hottest segments of the engine and heat transfer to the radiator and atmosphere. Moreover, this is a system designed to prevent hot spots that come from coolant cavitation (trapped air) in the system. All air pockets are vented via the “Y”-shaped hose package at the front of the engine.
How do you improve on an already great cooling system? Modular Motorsports Racing offers the head cooling kit, which improves coolant flow at the rear of Coyote engines. One weak link in the Coyote has been excessive cylinder pressures and temperatures from boost and nitrous, resulting in extraordinarily high engine temperatures at the back of the engine. The Modular Motorsports Racing head cooling kit reduces the risk of engine failure. Under more normal operating conditions, the Coyote enjoys more than adequate cooling and doesn’t need the head cooling kit.
Another improvement for the cooling system is the Meziere electric water pump, if you’re searching for hair-splitting increases in power. Engine-driven water pumps consume a certain amount of power, especially at high RPM. On the street or for weekend racing, the benefit of an electric water pump is debatable. For all-out racing, where every second counts, it’s a measurable improvement. A high-flow coolant pump for the Coyote engine is not available at press time, although I expect that to change in time.
When you are servicing your Coyote with coolant you must ensure that all water jackets are filled with coolant. I have heard from engine builders and tuners that the Coyote engine’s water jackets are challenging to fill due to the engine’s cooling system design. Some builders say they fill the Coyote’s cooling system via the heater hose tubes to ensure both sides of the engine are filled with coolant. Then, they add remaining coolant at the radiator/expansion tank. Coyote engines are known for hot spots, even after the initial coolant fill, which tends to yield fluctuating coolant temperatures until coolant occupies all cooling passages throughout the engine.
Written by Jim Smart and Posted with Permission of CarTechBooks