2004 HUMMER H2

Typical onset: 80,000-150,000 mi

Symptoms: Cold-start knocking/slapping that fades after warmup, Sudden loss of power and metallic rattling under load, Excessive oil consumption (1 qt per 500-1,000 miles), Milky oil or coolant loss if piston skirt breaks and scores cylinder

Fix: Early piston slap (just noise) doesn't require immediate repair, but once oil consumption starts or a piston skirt fractures, you're looking at either a full engine rebuild with upgraded pistons or a reman/used long block swap. Labor runs 18-24 hours for removal/install plus machine work. Many shops recommend replacing rings, bearings, and head gaskets during rebuild.

Estimated cost: $4,500-8,500

Typical onset: 70,000-120,000 mi

Symptoms: Transmission fluid puddles under front of vehicle near radiator, Burnt transmission smell or slipping shifts if fluid runs low, Pink or red fluid visible at radiator connection points, Check engine light for transmission temp if leak progresses

Fix: The steel cooler lines rust through where they attach to the radiator or at frame mounting points. You must replace both lines as a pair — they're pre-formed and run the length of the frame. Job takes 3-4 hours and requires lifting the vehicle. Always check transmission fluid level immediately if you spot a leak; running low will cook the 4L65E in under 50 miles.

Estimated cost: $600-1,200

Typical onset: 60,000-100,000 mi

Symptoms: Clunk or bang when shifting into drive or reverse, Vibration at highway speeds that feels like driveline shudder, Visible sag or torn rubber on crossmember mount, Exhaust may contact floor if mount collapses completely

Fix: The rubber mount separates or tears, allowing excessive drivetrain movement. Replacement is straightforward — support transmission with jack, unbolt crossmember, swap mount. Takes 1.5-2 hours. Inspect front engine mounts at the same time; if rear is gone, fronts are usually stressed.

Estimated cost: $250-450

Typical onset: 50,000-80,000 mi

Symptoms: Hard starting or extended cranking when hot, Loss of power under acceleration or uphill grades, Surging or stumbling at steady cruise, Check engine light with fuel trim codes (P0171/P0174)

Fix: The inline fuel filter clogs with sediment and rust from the tank, starving the engine. Filter is frame-mounted and takes 0.5 hours to replace — but GM didn't specify a service interval, so many owners never change it. If pump is failing (often due to running on clogged filter), add 8-10 hours labor to drop tank and swap pump assembly.

Estimated cost: $80-150 filter only; $800-1,400 with pump

Typical onset: 90,000-140,000 mi

Symptoms: White residue or crusty buildup at head/block mating surface, Slow coolant loss with no visible external leaks, Sweet smell from exhaust or steam at startup, Occasional misfire codes or rough idle if combustion gases enter coolant

Fix: The 6.0L Vortec can weep coolant externally at head gaskets or develop internal leaks that pressurize the cooling system. Requires removing both heads, resurfacing if warped, and installing updated MLS gaskets with ARP studs recommended. Labor is 12-16 hours. Often done in conjunction with piston work if engine is already apart.

Estimated cost: $2,200-3,800

Typical onset: 80,000-130,000 mi

Symptoms: Power steering fluid leaking from gearbox input shaft seal, Steering wheel must be constantly corrected to maintain straight line, Clunking or looseness felt through wheel over bumps, Low fluid causes whining or groaning when turning

Fix: The Delphi-style steering gearbox develops input seal leaks and internal wear. While seals can be replaced, most techs recommend a reman gearbox if wander is present — internal tolerances are shot. Replacement takes 3-4 hours with front end lifted. Also inspect pitman and idler arms; if gearbox is worn, they usually are too.

Estimated cost: $650-1,400

Symptoms: Brake pedal sinks slowly to floor when holding steady pressure, Soft or spongy pedal feel with increased stopping distance, Brake fluid leaks at master cylinder or ABS module connections, Amber ABS light or red brake warning light illuminated

Fix: Two NHTSA recalls addressed brake issues: one for corroded brake lines (especially in salt-belt states) and another for defective brake line fittings at the ABS module. Inspect all hardlines for rust perforation and flare fittings for cracks. If corrosion is advanced, plan on replacing all steel lines — labor-intensive, 6-8 hours. Master cylinder or ABS module replacement adds significant cost.

Estimated cost: $800-2,500