1972 MERCURY MARQUIS

Typical onset: 80,000-150,000 mi

Symptoms: Rough idle and hard starting when engine is hot, Metallic rattle from front of engine on cold start, Backfiring through carburetor, Loss of power and poor fuel economy, Check timing with light — if it jumps around 5+ degrees, chain is stretched

Fix: Replace timing chain, gears, and tensioner. On 351/390 this is 4-5 hours; 429/460 requires 6-7 hours due to tighter clearances and accessories in the way. Always replace the nylon-toothed cam gear while you're in there — they disintegrate. Use double-roller chain set, not OE single-row.

Estimated cost: $650-1,200

Symptoms: Hesitation or stumble on acceleration, Black smoke from exhaust, fuel smell, Flooding and hard starting, Rough idle that improves when warm, Fuel leaking from base gasket or accelerator pump

Fix: Most need a full rebuild kit with new gaskets, needle/seat, accelerator pump, and float adjustment. Ethanol fuel rots the old cork gaskets and damages plastic components. DIY rebuild takes 3-4 hours for experienced hands; most shops charge 2.5-3.5 hours plus kit. If venturi cluster is damaged, replace carburetor with reman unit.

Estimated cost: $350-750

Typical onset: 60,000-120,000 mi

Symptoms: Overheating in traffic or on grades, Radiator leaking at seams or from core rot, Sweet coolant smell in cabin, fogged windshield, Passenger floor soaked with coolant (heater core), Rusty or muddy coolant when drained

Fix: Radiator re-core or replacement runs 2-3 hours. Heater core on Marquis requires full dash removal — absolute nightmare job at 8-10 hours book time. Shops often bypass heater core if owner can live without cabin heat. Replace all hoses, thermostat, and flush system while you're in there.

Estimated cost: $400-800 radiator; $900-1,800 heater core

Typical onset: 70,000-130,000 mi

Symptoms: Whining or groaning when turning at low speed, Fluid puddles under front of engine, Hard steering or wandering, Low fluid level despite topping off regularly

Fix: Usually starts with high-pressure hose failure at crimp or fitting. Hose replacement is 0.8-1.2 hours. If pump itself is leaking at shaft seal or making noise, rebuild or replace — 2-3 hours. Ford pumps are cheap and plentiful. Check steering gearbox for leaks at same time; sector shaft seal is common weeper.

Estimated cost: $180-450

Symptoms: Transmission refuses to downshift for passing, Delayed or harsh upshifts, Slipping between 1st and 2nd gear, Hangs in gear at stoplights

Fix: The carburetor-to-transmission kickdown rod and bellcrank wear at pivot points and rod ends. Inspect and lube every 30k; replace worn bushings and clips. Common to find linkage disconnected or bent after carb work. Adjustment is critical — 1.0 hour to diagnose and set properly. If ignored, causes internal clutch damage.

Estimated cost: $120-280

Typical onset: 80,000-140,000 mi

Symptoms: Clunking over bumps from front end, Wandering or loose steering feel, Uneven tire wear on inside edges, Grease weeping from ball joint boots, Front end shimmy at highway speed

Fix: Upper and lower ball joints wear, especially lowers which carry weight. These are riveted from factory; replacement requires drilling out rivets and bolting in new joints. Plan 3-4 hours per side for both uppers and lowers, plus alignment. Do both sides at once. Inspect tie rod ends and idler arm at same time.

Estimated cost: $600-1,100

Symptoms: Loud ticking or popping from engine bay on cold start, Exhaust smell in cabin, Loss of back pressure affecting idle quality, Visible cracks in cast iron manifolds

Fix: Cast iron manifolds crack from heat cycling, especially on 429/460 engines. Studs break off in heads when manifolds are removed. If you're lucky, studs extract with ease-out; if not, head removal for machine work adds 6-8 hours. Budget 4-5 hours per side for manifold replacement with good studs. Aftermarket headers eliminate the problem but require custom exhaust work.

Estimated cost: $500-950 per side