This document provides a comprehensive overview of frequently asked questions regarding the purchase and maintenance of a 6.5L Diesel engine. It covers essential checks and considerations to ensure the vehicle's optimal performance and longevity.

Before finalizing your purchase, it is crucial to check for any diagnostic codes on the truck. Some codes may indicate potential costly replacements. For detailed information, refer to the thread for your truck: OBD I and OBD II.

Ensure that all battery connections are tight and free of corrosion. It is advisable to keep both batteries of the same type and age to maintain optimal performance.

Inspect the serpentine belt for any signs of cracks or fraying. Additionally, listen for abnormal noises from accessory units while the engine is running. Check the belt tensioner for any signs that it may need replacement.

Pull the dipstick to check for moisture or a white/gray slimy substance, which may indicate coolant in the oil and could require engine, head, or head gasket replacement. Black oil is normal shortly after an oil change. Also, ensure to check the levels of coolant, power steering fluid, and transmission fluid.

Always check for leaks by climbing underneath the truck, entering from under the driver's door. Ensure there are no oil leaks around the filter area, as this may indicate failing oil cooler line quick disconnects. Common leak points include crimped fittings transitioning from metal to rubber. If a skid plate is present, it may need to be removed for inspection. If leaks are found, consider a nearly leak-proof replacement kit from Leroy Diesel instead of OEM lines. Leaks down the bell housing may indicate fuel, often from the fuel filter manager (FFM). Additionally, check for leaks around the transmission and transfer case.

When starting your 6.5L Diesel, turn the key to the ON position. The "Wait to Start (WTS)" light should illuminate; wait for it to turn off before cranking the engine. After starting, it is normal for the WTS light to blink a few times (referred to as "After Glow"). During a cold start (the first start of the day or after sitting for over 8 hours), watch for excessive white smoke or rough running. If the truck smokes for 10 seconds or longer and runs roughly, it may have failing glow plugs or open wires that need replacement. After starting, squeeze the upper radiator hose; if it is hard, you may have a bad head gasket. This hose should be soft as the engine warms up.

With the engine warm, remove the oil fill cap. If no smoke or only a light haze comes out, this is normal. Excessive smoke may indicate worn piston rings or other components.

Locate the water drain valve, a brass T-valve near the oil fill cap. With the engine running, open the T-valve for about 10 seconds. If the truck stumbles or stalls, there is a fuel supply issue to the injection pump. For more information, check the Lift Pump Operation thread before replacing any parts.

While in Park and with the engine running, slowly raise the RPM to 2000 and hold for 5 seconds, then return to idle. The engine should run steadily. If it revs wildly or stalls when returning to idle, a new injection pump may be needed.

After the engine is running, check all gauges. Voltage should be above 12V. The coolant temperature gauge should rise but not exceed 210°F EVER, which is unsafe for these engines. Cold oil pressure can range from 50-80 psi, but warm oil pressure should be above 20 psi at idle and around 40-50 psi at 2000 RPM. Additionally, check if the heat and AC work (if equipped).

After reaching operating temperature (170-195°F), shut down the truck and let it sit for about 20 minutes. Then, try to start the truck without waiting for the glow plugs to finish their cycle. The engine should start with minimal cranking.

• Cruise Control (if equipped)

• The truck should shift into all gears without slipping.

• 4x4 functionality (if equipped)

• Accelerate from a stop and check for black smoke from the exhaust. It is normal for a truck to smoke briefly after initial acceleration, but it should clear up. If not, this may indicate a turbo problem.