The 1999 Mercury Mystique with the 2.5L Duratec V6 is Ford's rebadged Contour sibling—a competent mid-size sedan undermined by catastrophic head gasket failures and chronic transmission cooler leaks that often destroy the automatic before owners realize there's a problem.
Head Gasket Failure (Both Banks)
Common · high severityTypical onset: 60,000-100,000 mi
Symptoms: White smoke from exhaust, especially on cold start, Coolant loss with no visible external leaks, Overheating or fluctuating temperature gauge, Milky oil on dipstick or oil cap, Rough idle and misfire codes after warmup
Fix: Both heads must come off on the V6—it's not a one-side issue. Expect machine shop resurfacing, new bolts, timing components inspection, and 12-16 hours labor. Many shops recommend doing timing chains/guides while you're in there since access is already open.
Estimated cost: $2,200-3,800
Transmission Oil Cooler Line Leak Into Radiator
Common · high severityTypical onset: 70,000-120,000 mi
Symptoms: Pink milkshake appearance in coolant overflow tank, Transmission slipping or delayed engagement, Overheating transmission even in normal driving, Sudden transmission failure after coolant contamination
Fix: The internal cooler in the radiator fails and allows coolant into ATF, destroying clutches and valve body. Requires radiator replacement, complete transmission flush (or rebuild if contamination sat too long), and all cooler lines. If caught early: 4-6 hours. If trans is damaged: add 12-18 hours for rebuild.
Estimated cost: $800-1,200 if caught early; $2,500-4,000 with transmission rebuild
Lower Engine Assembly Wear (Bearings, Rings)
Occasional · high severityTypical onset: 120,000-180,000 mi
Symptoms: Heavy knocking from crankcase, especially on cold start, Excessive oil consumption (quart per 500-1,000 miles), Low oil pressure at idle when warm, Blue smoke on deceleration, Metal debris in oil filter during changes
Fix: The Duratec V6 develops rod bearing and main bearing wear, sometimes accompanied by ring land failure. Most shops recommend short-block replacement or full rebuild rather than piecing it together. Figure 18-24 hours labor plus machine work if going the rebuild route.
Estimated cost: $3,500-5,500
Ignition Switch Failure (NHTSA Recalled)
Occasional · medium severitySymptoms: Key won't turn or gets stuck in ignition, No crank, no start intermittently, Accessories stay on after key removed, Dash lights flicker or stay on with key out
Fix: Ford recalled this (00S14), but many vehicles were never serviced. Replacement involves steering column disassembly and new lock cylinder assembly. About 2-3 hours labor. Check if recall was completed before buying.
Estimated cost: $250-450 if not covered under recall
Front Suspension Strut Mount Failure
Common · medium severityTypical onset: 80,000-130,000 mi
Symptoms: Clunking over bumps from front corners, Steering feels loose or vague on center, Tire wear on inside edge, Visible separation of rubber in strut tower
Fix: The top strut mounts deteriorate and allow excessive movement. Plan on doing both sides with new mount bearings and alignment afterward. Good time to do struts if they're original. 3-4 hours for mounts alone, 5-6 if including struts.
Estimated cost: $400-650 mounts only; $800-1,200 with struts
Transmission Mount Collapse
Common · low severityTypical onset: 90,000-140,000 mi
Symptoms: Harsh clunk when shifting from park to drive or reverse, Excessive engine movement visible from driver seat during acceleration, Vibration at idle in gear, Banging noise over bumps from engine bay
Fix: The hydraulic transmission mount wears out and allows the powertrain to shift excessively. Straightforward replacement, about 1.5-2 hours labor. Do it before it tears other mounts or damages axles.
Estimated cost: $200-350
Hard pass unless you find one with documented head gasket and transmission cooler replacement under 100k miles—otherwise you're buying someone else's ticking time bomb at a bargain price that won't stay a bargain.
AI-assisted summary drawn from NHTSA recall data, our labor-times database, and platform knowledge. Not a substitute for a pre-purchase inspection on a specific vehicle.