1988 BMW 325IS

Typical onset: 120,000-180,000 mi

Symptoms: white smoke from exhaust, coolant loss with no visible leaks, milky oil on dipstick, overheating under load

Fix: Head gasket replacement requires cylinder head removal, surface inspection and possible milling (often warped), valve job while apart. Expect 12-16 labor hours. Replace timing belt, water pump, thermostat, coolant hoses at same time or you'll regret it.

Estimated cost: $2,200-3,800

Typical onset: 100,000-150,000 mi

Symptoms: oil dripping from bellhousing area, clunking on shifts or acceleration, excessive driveline movement, oil pooling under transmission tunnel

Fix: Rear main seal leaks oil into the bellhousing; collapsed transmission mount allows excessive movement that accelerates seal wear. Transmission must be dropped (6-8 hours). Always replace both the rear main seal and transmission mount together, plus throwout bearing and pilot bearing while in there.

Estimated cost: $1,400-2,200

Typical onset: 150,000+ mi

Symptoms: ticking or tapping from valve cover at idle, noise increases with RPM, worsens when cold, oil pressure light may flicker

Fix: M20 hydraulic lifters collapse from age or oil starvation; rocker arms wear grooves. Diagnosis requires valve cover removal. If caught early, sometimes oil change and flush helps temporarily, but typically needs all 12 lifters replaced plus rockers if worn (8-10 hours with head on car). If damage is severe, head removal and full valve job required.

Estimated cost: $1,200-2,400

Symptoms: hard starting when hot, intermittent stalling, rough idle, fuel smell in cabin or trunk, long crank before start

Fix: 35-year-old rubber fuel lines crack and leak, especially under-tank and in engine bay. Fuel filter clogs if tank has rust. Fuel pump and accumulator fail. Complete fuel system refresh includes in-tank pump, filter, all rubber lines, injector o-rings, and check valve (6-9 hours total if done comprehensively).

Estimated cost: $800-1,600

Symptoms: overheating in traffic, coolant loss, expansion tank cracking, heater not working, white residue around hose connections

Fix: Plastic radiator end tanks, expansion tank, thermostat housing, and all rubber hoses are time bombs past 30 years regardless of mileage. Water pump fails around 80,000-100,000 mi. Do entire system at once: radiator, expansion tank, hoses, water pump, thermostat, fan clutch (8-12 hours). Piecemeal fixes lead to repeated failures and potential engine damage.

Estimated cost: $1,500-2,400

Symptoms: ATF dripping near radiator (automatic only), low transmission fluid, transmission slipping or harsh shifts, pink fluid stains on driveway

Fix: Steel lines rust through where they connect to radiator or along frame rail. Sometimes internal radiator cooler fails and mixes ATF with coolant (catastrophic for transmission). Replace lines and external cooler or radiator (3-5 hours). If coolant is contaminated with ATF, transmission needs flush or rebuild.

Estimated cost: $400-900

Typical onset: 80,000-100,000 mi interval

Symptoms: sudden no-start, engine cranks but won't fire, no prior warning usually

Fix: M20 is non-interference so belt failure won't destroy valves, but you're stranded. Belt should be replaced every 50,000-60,000 miles or 4-5 years. Includes tensioner and idler. If it breaks, replacement is 3-4 hours plus tow. Do it on schedule (5 hours with water pump) and you'll never deal with roadside failure.

Estimated cost: $600-1,000