Initial Inspection and Diagnostic Overview

COOLING SYSTEM INSPECTION
1. Allow the engine to cool and remove the coolant recovery reservoir cap.
2. Inspect the coolant condition:
^ Vehicles with Mazda Premium Gold Engine Coolant VC-7-A (in Oregon VC-7-B), have a clear or pale yellow color, this indicates higher water content than required.

Note:
^ The addition of stop leak pellets, darkens Mazda Premium Gold Engine Coolant VC-7-A from yellow to golden tan. Dark brown could indicate unauthorized stop leak may have been used. Use Cooling System Stop Leak Pellets VC-6 or equivalent.

^ A light or reddish brown color indicates that rust may be present in the cooling system. Flush the system and refill with the correct mixture of water and Premium Engine Coolant.
^ An iridescent sheen on top of the coolant could indicate a trace of oil is entering the system.
^ A milky brown color may indicate that either engine oil or transmission fluid is entering the cooling system. If transmission fluid is suspected, the cause may be a leaky radiator; test the cooling system. If engine oil is suspected, the cause of the leak may be internal to the engine.
^ If transmission fluid is contaminated with engine coolant, the cause may be a leaky radiator; test the system.

3. If the engine coolant appearance is acceptable, test the engine coolant freezing point range with a suitable coolant tester. The freezing point should be in the range -50°F to -10°F. If the vehicle is driven in cold climates less than -34°F, it may be necessary to increase the coolant concentration to get adequate freeze protector.
^ Maximum coolant concentration is 60/40.
^ Minimum coolant concentration is 40/60.
4. Adjust coolant range and level if necessary:
^ If coolant is low, add specified coolant mixture only.
^ If the engine coolant tests weak, add straight engine coolant until the readings are within acceptable levels.
^ If the engine coolant tests strong, remove some of the engine coolant and add water until the readings are within acceptable levels.