1993 GMC SIERRA 3500

Typical onset: 80,000-150,000 mi

Symptoms: No-start when hot, restarts after cooling, Stalling at operating temperature, Intermittent loss of power, Check engine light with fuel system codes

Fix: The Pump Mounted Driver (PMD/FSD) module overheats and fails. Replacement involves relocating the module to a cooler location with remote mount kit (2-3 hours labor). Full injection pump replacement if internal damage occurred (8-10 hours).

Estimated cost: $400-800 for PMD relocation; $1,800-3,200 for complete injection pump

Typical onset: 120,000-180,000 mi

Symptoms: Heavy knocking from crankcase under load, Oil pressure drop, Metallic debris in oil filter, Catastrophic failure if ignored

Fix: Rod bearings and main bearings wear excessively on trucks used for heavy towing or sustained high load. Requires complete bottom-end rebuild with crankshaft polishing or replacement (20-28 hours labor). Often combined with piston ring work if doing teardown.

Estimated cost: $3,500-6,500 depending on machine work and parts replacement depth

Typical onset: 100,000-160,000 mi

Symptoms: Transmission fluid in radiator or coolant in trans, Pink milkshake in coolant reservoir, Transmission slipping or delayed engagement, Overheating transmission

Fix: The internal transmission cooler inside the radiator fails, mixing coolant and ATF. Requires radiator replacement, transmission flush, and often full transmission rebuild if contamination circulated (12-18 hours total). External line corrosion also common (2 hours).

Estimated cost: $800-1,200 for radiator and lines; $2,500-4,000 if transmission rebuild needed

Typical onset: 100,000-180,000 mi

Symptoms: White smoke from exhaust, Coolant loss with no visible leak, Overheating, Bubbles in coolant reservoir, Milky oil

Fix: Head gaskets fail due to cylinder pressure and heat cycling. Both heads should be done simultaneously with machine shop resurfacing (16-20 hours labor). Often reveals cracked heads requiring replacement.

Estimated cost: $2,200-3,800 with gaskets; $3,500-5,500 if heads need replacement

Symptoms: Hard starting, Loss of power under load, Surging or hesitation, Excessive smoke

Fix: The mechanical lift pump fails or tank sediment clogs the fuel filter housing. Requires fuel filter replacement every 10,000-15,000 mi (0.5 hours). Lift pump replacement (2-3 hours). Water-in-fuel is common if fuel quality is poor.

Estimated cost: $80-150 for filter service; $300-500 for lift pump replacement

Typical onset: 80,000-140,000 mi

Symptoms: Clunking when shifting into gear, Excessive vibration at idle, Driveline shudder under acceleration

Fix: Rubber mounts crack and collapse under the weight of the heavy-duty transmission and driveline stress. Replacement requires supporting the transmission (1.5-2 hours labor).

Estimated cost: $200-400

Typical onset: 140,000-200,000 mi

Symptoms: Blue smoke on startup or acceleration, Excessive oil consumption (1 qt per 500-800 mi), Fouled spark plugs, Loss of compression

Fix: Piston rings wear in the bores, especially in engines used for towing. Requires complete teardown with bore honing or re-boring and oversized pistons (24-30 hours). Often bundled with bearing work at this point.

Estimated cost: $3,000-5,500 for full ring job and machine work