2. Coolant temperature "Spikes" in cold weather:  During periods of extreme cold weather, some engines at idle have a tendency to run at elevated temperatures, 250°F to 260°F, then return to normal levels when vehicle is underway. In most cases the problem is due to an inherently large thermostat bypass circuit allowing the coolant (more viscous in extreme cold) to bypass the radiator through the open circuit at slow pump speeds. Although not detrimental to the engine, the situation can usually be corrected by blocking the thermostat bypass (usually located at the pump), removing the OE thermostat and installing the EVANS Total Flow Thermostat (see page 11). Alternately an EVANS NPG pump may be installed, if available for your engine, which incorporates a blocked by-pass.

CAUTION

After blocking the bypass circuit, only the specially designed EVANS Total Flow Thermostat should be used or engine damage may occur. When ordering state vehicle make, year, model and engine. (see Page 11 for more information).

Coolant temperature "Spikes" in extremely cold weather (10°F or below) have also been found to be caused by a restriction in the radiator and/or a very inefficient coolant pump, both of which result in reduced coolant flow when the coolant becomes more viscous in extremely cold weather.

Generally, the problem is found to be the pump and is usually corrected by installing an EVANS NPG Pump (refer to catalog listing), or EVANS NPG Pump Backing Plate and then adding an EVANS Total Flow Thermostat (with blocked bypass), and pump bleed, as described on page 11.

3. Expansion tank does not return coolant to engine:  The cause is usually traced to a vacuum leak somewhere in the system, or that the system was opened (radiator cap removed while coolant was hot and not closed again during "cool down"). Since vacuum draw on the coolant in the expansion tank is the only way coolant is drawn back into the system, any air leak, no matter how small, will cause the engine to draw back in air rather than coolant and the coolant to remain in the expansion tank. If you find a need to add coolant to the radiator after each "cool down" and the expansion tank level keeps rising, then a leak exists and must be found. Check all clamps and tighten as necessary, or apply a vacuum tester to the vent line where it attaches to the tank to locate the leak.

4. Engine runs hot at all speeds and loads:  The most common cause is an air locked pump (see Page 9, SPECIAL PUMP MODIFICATIONS). If the system being used is a Stage I Basic System and the system is installed properly, according to this instruction manual, with the proper pump pulley ratios as recommended on Page 20, and the engine still runs hot, the cause is usually an air locked or inefficient pump or a restricted flow radiator. A Stage II system would then be required.

5. EVANS NPG Coolant gradually changes to a darker color during use due to organic aging. This change has no effect on the performance of the coolant which normally will operate for at least 100,000 miles before requiring replacement.

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