The 2007 DTS with the 4.6L Northstar V8 is a comfortable highway cruiser plagued by catastrophic engine failures and transmission cooling issues that can strand owners unexpectedly. The Northstar's head bolt design and head gasket failures are legendary for ending these cars prematurely.
Northstar Head Gasket Failure / Head Bolt Pull-Out
Common · high severityTypical onset: 80,000-130,000 mi
Symptoms: White smoke from exhaust on cold start, Coolant loss with no visible leaks, Overheating despite proper coolant level, Milky oil on dipstick or oil cap, External coolant seepage at head-to-block junction
Fix: Northstar engines use torque-to-yield head bolts threaded into aluminum block — bolts pull threads out under thermal cycling. Proper repair requires time-sert thread inserts in all 20 holes per side, new head gaskets, resurfacing heads. 18-24 hours labor. Many shops won't tackle it; owners often opt for used engine swap instead.
Estimated cost: $3,500-6,000
Transmission Oil Cooler Line Failure at Radiator
Common · high severityTypical onset: 70,000-110,000 mi
Symptoms: Pink or strawberry milkshake appearance in coolant reservoir, Transmission slipping or erratic shifting after coolant contamination, Coolant in transmission pan during fluid service, Sudden transmission failure after mixing fluids
Fix: Internal transmission cooler in radiator fails, allowing coolant into ATF (or vice versa). Requires radiator replacement, transmission flush, often complete transmission overhaul if contamination progressed. 6-10 hours for radiator and flush; add 12-18 hours if transmission rebuild needed.
Estimated cost: $800-1,200 (cooler/flush only); $2,800-4,500 (if transmission damaged)
Engine Oil Consumption / Piston Ring Failure
Common · medium severityTypical onset: 90,000-150,000 mi
Symptoms: Using 1+ quart of oil every 500-1,000 miles, Blue smoke on acceleration, Carbon buildup on spark plugs, Oil fouling on rear cylinders more common, No external leaks but constant low oil level
Fix: Northstar rings wear or carbon-lock in grooves due to heat and design. Proper fix is engine-out teardown, hone cylinders, new rings on all pistons. 20-28 hours labor. Most owners just add oil until something else fails.
Estimated cost: $4,000-6,500
Ignition Control Module / Coil Cassette Failure
Occasional · medium severityTypical onset: 60,000-120,000 mi
Symptoms: Random misfires on multiple cylinders, No-start when hot, starts fine cold, Check engine light with P0300-P0308 codes, Stumbling or hesitation under load
Fix: Northstar uses two ignition cassettes (four coils each) that fail from heat exposure. Replace both cassettes preventively. 2.5-3.5 hours labor, must remove upper intake plenum.
Estimated cost: $800-1,400
Front Strut Mount Bearing Failure
Occasional · low severityTypical onset: 80,000-130,000 mi
Symptoms: Clunking over bumps at low speed, Steering wheel not returning to center smoothly, Grinding or popping when turning at standstill, Uneven tire wear on front
Fix: Upper strut mount bearings wear out, especially in northern climates. Replace mounts and bearings with struts during suspension work. 3-4 hours labor for both sides with alignment.
Estimated cost: $600-1,000
Transmission Mount Collapse
Common · low severityTypical onset: 70,000-120,000 mi
Symptoms: Clunk when shifting from Park to Drive/Reverse, Excessive vibration at idle in gear, Visible engine/trans movement when revving in Park
Fix: Hydraulic transmission mount fails, allowing excessive drivetrain movement. Simple replacement, 1.5-2 hours labor.
Estimated cost: $250-450
Buy only if you find a pampered low-mileage example under $5k and budget for a Northstar grenade — otherwise, the Town Car is a better V8 luxury sedan bet.
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.