1991 CHEVROLET S-10

Typical onset: 100,000-150,000 mi

Symptoms: Deep knocking at idle that worsens with RPM, Metal shavings in oil, Sudden loss of oil pressure, Catastrophic failure without warning in neglected engines

Fix: Complete lower-end rebuild or short block replacement required. Expect 18-24 hours labor for in-chassis rebuild, 14-18 hours for short block swap. The 2.8L has inadequate oiling to the #4 main bearing and rod bearings under sustained load—design flaw that oil changes alone won't prevent.

Estimated cost: $2,800-4,500

Typical onset: 80,000-130,000 mi

Symptoms: External coolant leaks at head/block interface, White smoke from exhaust, Coolant loss with no visible leaks, Overheating under load, Oil contamination in coolant reservoir

Fix: Both head gaskets typically fail due to inadequate torque spec and head bolt stretch. Requires head removal, resurfacing, and proper torque sequence. Budget 12-16 hours labor. Always replace both sides—if one failed, the other is close behind.

Estimated cost: $1,400-2,200

Typical onset: 70,000-120,000 mi

Symptoms: ATF leaking near radiator, Transmission overheating, Low fluid warnings, Slipping in gear after highway driving, Pink milkshake in radiator if cooler ruptures internally

Fix: Steel cooler lines rust through at radiator connections or where they pass frame rails. External line failure: 1-2 hours to replace lines. Internal cooler rupture (coolant mixes with ATF): requires radiator replacement, transmission flush, and often transmission rebuild if contamination circulated. Catch it early.

Estimated cost: $150-300 (lines only), $2,500-3,800 (if trans contaminated)

Typical onset: 60,000-100,000 mi

Symptoms: Clunk when shifting from Park to Drive/Reverse, Excessive driveline vibration, Visible sag of transmission tailshaft, Harsh engagement into gear

Fix: Rubber mount deteriorates from heat and age, allowing transmission to drop and creating driveline angle issues. Simple fix: 1-1.5 hours to replace. Always inspect while underneath for other issues—don't ignore this, as it accelerates U-joint and yoke wear.

Estimated cost: $120-220

Typical onset: 150,000-200,000 mi

Symptoms: Blue smoke on startup, Increasing oil consumption (1 qt per 500-800 miles), Loss of compression in one or more cylinders, Fouled spark plugs

Fix: The Iron Duke is significantly more durable than the 2.8L but eventually wears rings due to inadequate lubrication on cylinder walls. Requires in-frame rebuild with new rings, hone, and valve job. Budget 14-18 hours labor. Often combined with timing gear replacement while it's apart.

Estimated cost: $1,800-2,800

Symptoms: Hard starting when tank is low, Stalling under acceleration, Loss of power uphill, Surging at highway speed

Fix: Steel fuel tanks rust internally, especially if left sitting with less than half-tank for extended periods. Particulates clog the inline filter. Replace filter every 15,000-20,000 miles on these trucks regardless of service interval spec. If filter clogs repeatedly, tank replacement needed. Filter change: 0.5 hour.

Estimated cost: $35-75 (filter), $600-900 (tank replacement if rusted)