Fluids and intervals

Running it

The GM 6.5L V8 diesel engine has its roots in the late 1970s and early 1980s. It is an old design by today’s standards and needs more routine attention than a modern engine. Every engine sounds and reacts differently; you will get to know exactly how yours runs, feels, drives and sounds.

Keep an eye on oil pressure and engine temperature while driving. Both are critical to knowing everything is operating correctly. These gauges are rarely accurate; they are reference gauges. They are very consistent, though, so you will learn the normal operating range for yours and can read it against that.

The ECV and prior series Humvees use a hydraulically actuated fan clutch. In normal operation the engine temperature should cycle between 200 and 220 °F, and the fan may cycle on and off as often as every 60 seconds. That may not read accurately on your temperature gauge, so cross-check the maximum with an IR temperature gun pointed at the thermostat housing. Above 220 °F the truck is running too hot.

Check the engine oil level from time to time and keep it in the cross-hatch on the dipstick, ideally just under the full mark. These engines are an old design, and light oil burn over several thousand miles is normal and expected.

At every oil change

• Check around all wheels and geared hubs for evidence of leaks. A minor leak shows as a damp, oily surface; a major one leaves large splatter patterns on the wheels and surrounding components.
• Spot-check every component in the fluid list above. Minor damp areas are not uncommon, but once a leak develops into a consistent drip it should be investigated and repaired.
• With a pair of gloves on, check the brake rotors, calipers, tie rods, driveshafts and any other moving parts for excessive play. Nothing should rattle noticeably when you try to shake it. Inspect the brake caliper mounts attached to the differential housings: these should never be loose. If they move, the brake and differential output flange assemblies have to come apart to tighten them.
• Inspect the serpentine belt and the pulleys. The belt should show no excessive wear and the pulleys should all be tight and rattle-free. If you hear squeaking from the engine bay, spray water on the belt while it is running: if the squeak goes away the belt likely needs replacing, and if it stays a pulley bearing may be at fault.

Wear items and part numbers

Brake Pads

57K3565

Wiper Blades (unarmored)

11″, match the old blade hook mount

Engine Air Filter

12342870

Engine CDR Valve

12340256 (every 15,000 miles)

Batteries

Group 65EXT 900CCA 150RC or similar

Engine Oil Filter

Wix 51060

Power Steering Filter

5716372

Fuel Filter

5589161

Fuel Filter Water Separator

5741059

Transmission Filter

5714971

Fluids and intervals

Running it

The GM 6.5L V8 diesel engine has its roots in the late 1970s and early 1980s. It is an old design by today’s standards and needs more routine attention than a modern engine. Every engine sounds and reacts differently; you will get to know exactly how yours runs, feels, drives and sounds.

Keep an eye on oil pressure and engine temperature while driving. Both are critical to knowing everything is operating correctly. These gauges are rarely accurate; they are reference gauges. They are very consistent, though, so you will learn the normal operating range for yours and can read it against that.

The REV series uses a geared fan drive extending from the front of the engine crankshaft assembly. It sets the fan at roughly 45° to match the radiator stack, which improves cooling and airflow.

The fan clutch itself is a standard viscous clutch attached to that geared fan drive. It changes fan speed with the temperature of the air flowing across it, so unlike an ECV the temperature gauge should not cycle. Once at operating temperature it should sit steady with only minor variation. Do not let it exceed 220 °F, and cross-check the gauge with an IR temperature gun pointed at the thermostat housing.

Check the engine oil level from time to time and keep it in the cross-hatch on the dipstick, ideally just under the full mark. These engines are an old design, and light oil burn over several thousand miles is normal and expected.

The REV series also uses the engine cooling system to cool the transfer case and the rear differential. Inspect the condition of the coolant from time to time: if one of those cooling loops cracks or fails, oil and coolant can cross-contaminate.

At every oil change

• Check around all wheels and geared hubs for evidence of leaks. A minor leak shows as a damp, oily surface; a major one leaves large splatter patterns on the wheels and surrounding components.
• Spot-check every component in the fluid list above. Minor damp areas are not uncommon, but once a leak develops into a consistent drip it should be investigated and repaired.
• With a pair of gloves on, check the brake rotors, calipers, tie rods, driveshafts and any other moving parts for excessive play. Nothing should rattle noticeably when you try to shake it. Inspect the brake caliper mounts attached to the differential housings: these should never be loose. If they move, the brake and differential output flange assemblies have to come apart to tighten them.
• Inspect the serpentine belt and the pulleys. The belt should show no excessive wear and the pulleys should all be tight and rattle-free. If you hear squeaking from the engine bay, spray water on the belt while it is running: if the squeak goes away the belt likely needs replacing, and if it stays a pulley bearing may be at fault.

Wear items and part numbers

Service Brake Pads

5717285

Parking Brake Pads

5717265

Wiper Blades (unarmored)

11″, match the old blade hook mount

Engine Air Filter

12342870

Engine CDR Valve

12340256 (every 15,000 miles)

Batteries

Group 65EXT 900CCA 150RC or similar

Engine Oil Filter

Wix 51060

Power Steering Filter

5716372

Fuel Filter

5589161

Fuel Filter Water Separator

5741059

Transmission Filter

5714971