1994 MERCEDES-BENZ SL

Typical onset: any mileage, age-related (25+ years)

Symptoms: Random electrical gremlins: windows, locks, gauges acting erratically, Check engine lights with multiple implausible codes, Engine stalling or no-start conditions, Harness insulation crumbling to dust when touched

Fix: Complete engine and chassis harness replacement required. Mercedes used soy-based insulation that degrades regardless of mileage. Expect 20-30 hours labor for full harness swap, more if corrosion has damaged connectors. This is THE common issue on any R129 that hasn't been addressed.

Estimated cost: $3,500-6,000

Typical onset: 60,000-120,000 mi

Symptoms: Top moves slowly or stops mid-cycle, Hydraulic fluid leaking from cylinders or pump, Top won't latch or unlatch properly, Pump runs continuously or makes grinding noise

Fix: The hydraulic cylinders develop internal seal leaks, and the pump wears out. Often needs cylinders rebuilt or replaced plus pump, along with fresh fluid and bleeding. Microswitch failures also common. 8-12 hours labor depending on what's failed. DIY-friendly if mechanically inclined, but parts are expensive.

Estimated cost: $1,800-3,500

Typical onset: 120,000-180,000 mi

Symptoms: Heavy oil consumption (quart every 500-1000 miles), Blue smoke on startup or acceleration, Loss of compression and power, Metallic knocking from lower end if bearing wear present

Fix: The M119 develops worn piston rings and cylinder bore glazing at higher miles, especially if oil changes were extended. Repair means full engine-out teardown: new pistons, rings, bearings, machine work, head gaskets. 40-60 hours labor for complete rebuild. Some opt for short block replacement instead. This is the reason you see so many high-mile SLs needing engine work.

Estimated cost: $8,000-15,000

Typical onset: 80,000-130,000 mi

Symptoms: Coolant loss with no visible leaks, White smoke from exhaust, Overheating or temperature fluctuations, Coolant in oil or oil in coolant (severe cases)

Fix: The V12's head gaskets fail between the cylinder banks and coolant passages. Both heads must come off, surfaces machined flat, and new gaskets installed. Extremely labor-intensive in the tight SL engine bay. 35-45 hours labor. While you're in there, replace all coolant hoses and consider valve stem seals. Parts aren't terrible; labor kills you.

Estimated cost: $7,000-11,000

Typical onset: 70,000-140,000 mi

Symptoms: Transmission fluid spots under vehicle, Fluid dripping near radiator area, Low transmission fluid level, Harsh shifting if fluid level drops significantly

Fix: The hard lines and rubber sections to the external cooler corrode and crack. Lines run along subframe and are exposed to road salt. Replace all cooler lines and inspect radiator-mounted cooler for internal leaks. 3-5 hours labor. Preventive replacement at 100k recommended in rust belt.

Estimated cost: $600-1,200

Typical onset: 60,000-100,000 mi

Symptoms: Clunking on acceleration or deceleration, Excessive driveline vibration, Visible sagging of transmission tailshaft, Harsh engagement into drive or reverse

Fix: The rubber mounts deteriorate and allow excessive movement. Replace transmission mount and often the engine mounts at the same time since they're the same age. 2-4 hours labor for trans mount alone. Cheap insurance and dramatically improves drivability.

Estimated cost: $400-800

Typical onset: 80,000-150,000 mi

Symptoms: Hard starting, especially when hot, Stumbling or hesitation under acceleration, Stalling at idle after driving, Whining noise from fuel tank area

Fix: In-tank fuel pump fails from age and contamination. Mercedes spec'd frequent fuel filter changes (every 30k) that most owners skip. Pump replacement requires tank drop. Do both pumps (main and pre-pump) and filter at once. 4-6 hours labor. Use OE-quality pumps or you'll be back in there.

Estimated cost: $1,200-2,000