1984 CADILLAC ELDORADO

Typical onset: 50,000-90,000 mi

Symptoms: white smoke from exhaust, coolant loss with no visible leaks, overheating despite thermostat replacement, milky oil, external coolant weeping between head and block, loss of compression in multiple cylinders

Fix: The aluminum block expands differently than iron heads, causing head gasket failure and often pulling threads from the block. Proper repair requires time-serts or helicoils in all head bolt holes, deck surfacing, and new gaskets. 16-22 hours labor. Many engines are too far gone and need replacement — used HT-4100s run $800-1,500, plus 18-24 hours swap time.

Estimated cost: $2,800-5,500

Typical onset: 80,000-130,000 mi

Symptoms: knocking from lower engine, oil pressure drop, visible cracks near freeze plugs or main bearing caps, coolant in oil, catastrophic oil loss, engine seizure

Fix: GM's 350 diesel used a converted gasoline block that couldn't handle compression loads. Blocks crack between cylinders or at main caps. Requires complete engine replacement — no rebuild saves a cracked block. Replacement diesels are scarce; many owners convert to Olds 307 gas V8. 20-28 hours labor for swap.

Estimated cost: $3,500-6,500

Typical onset: 70,000-110,000 mi

Symptoms: no overdrive/4th gear, harsh 3-4 shift or slipping in 4th, torque converter won't lock, causing highway RPM flutter, transmission overheating, burnt transmission fluid smell, check engine light with transmission codes

Fix: The 4-speed overdrive unit was undertested and the 4th gear clutches burn out, along with torque converter clutch failure. Requires full rebuild with updated clutch packs and converter. 12-16 hours labor. Some shops won't touch these—parts availability is declining.

Estimated cost: $2,200-3,800

Symptoms: gauges flickering or completely dark, intermittent display segments missing, fuel gauge reading empty when full, speedometer/odometer not working, climate control display blank

Fix: Cold solder joints on circuit boards fail over time. Cluster requires removal and either professional circuit board repair or replacement. Replacement clusters are getting rare. 3-4 hours labor for removal and reinstall, plus 2-6 hours for board repair or $300-800 for rebuilt unit.

Estimated cost: $500-1,200

Typical onset: 60,000-100,000 mi

Symptoms: rough idle, stalling when warm, hesitation on acceleration, hard starting, black smoke, poor fuel economy

Fix: The TBI system on the 4.1L carbons up badly, and the injectors clog or fail. Requires throttle body removal, ultrasonic cleaning, new injectors (often NLA—used units required), and fuel pressure regulator check. 4-6 hours labor. Injector availability is becoming a real problem.

Estimated cost: $600-1,100

Typical onset: all mileages—age-related

Symptoms: oil spots under car near front, transmission fluid puddles, low oil pressure after sitting, transmission overheating, coolant contaminated with oil or ATF

Fix: Steel lines rust through or rubber sections crack. Lines run along frame rails and are exposed to road salt. Requires replacement of affected lines—some require subframe work for access. 2-5 hours labor depending on which lines. Transmission cooler in radiator can also fail internally, mixing coolant and ATF (catastrophic).

Estimated cost: $350-900