1973 BMW 2002 TURBO

Typical onset: original turbos rarely survive beyond 100,000 mi; rebuilds fail 60,000-80,000 mi

Symptoms: blue smoke on acceleration, loss of boost pressure, rattling or whining from turbo at idle, oil consumption over 1 qt per 500 miles, sluggish throttle response above 4000 RPM

Fix: Turbo rebuild or replacement requires 8-12 hours due to manifold access and oil line routing; original KKK turbos are unobtanium so modern equivalents need custom flanges and often require oil restrictor installation to prevent oversupply that kills bearings; includes new oil feed and drain lines, gaskets, and studs

Estimated cost: $3,200-5,800

Typical onset: failure typical 70,000-120,000 mi; age is bigger factor than miles

Symptoms: hard starting when warm, rough idle with stumbling, flat spots during acceleration, fuel weeping from pump body, inconsistent throttle response

Fix: The Kugelfischer injection pump has internal plungers and seals that harden and wear; pump rebuild requires specialist knowledge (fewer than dozen shops in US can do it properly) and takes 6-8 hours labor plus 2-3 weeks turnaround for rebuild; many owners convert to Weber carbs or modern EFI instead

Estimated cost: $2,800-4,500 rebuild; $3,500-6,000 Weber conversion

Typical onset: 60,000-90,000 mi, especially if boost has been turned up

Symptoms: white smoke from exhaust, coolant loss with no visible leaks, milky oil on dipstick, overheating under boost, rough idle with misfires

Fix: M10 head gaskets fail between cylinders 2-3 most often; requires head removal, resurfacing (usually warped .005-.012 inches), new head bolts, and valve job while it's apart; 12-16 hours labor; common to find cracked exhaust valves from detonation at same time

Estimated cost: $2,200-3,800

Typical onset: 50,000-80,000 mi for mounts; guibo and center bearing 70,000-100,000 mi

Symptoms: clunking on throttle application, vibration at 45-55 MPH, shifter slop and difficult engagement, visible transmission sag when inspected from underneath

Fix: Transmission mount collapses from torque; rubber guibo (flex disc) cracks; center support bearing wears; all three typically done together; 4-6 hours labor; driveshaft must be removed for guibo and bearing replacement

Estimated cost: $800-1,400

Typical onset: 80,000-140,000 mi, accelerated by detonation or over-boost

Symptoms: excessive blow-by visible at oil cap, oil consumption over 1 qt per 300 miles, loss of compression in one or more cylinders, rattling on cold start, blue smoke under load

Fix: Mahle pistons crack ring lands from detonation; requires complete teardown, bore inspection, and typically overbore to next size (.020 or .040 over); includes new pistons, rings, bearings, and machine work; 20-28 hours labor; many shops won't tackle M10 turbo rebuilds due to parts scarcity

Estimated cost: $4,500-7,500

Symptoms: fuel smell in cabin or engine bay, hard starting after sitting overnight, visible fuel weeping near firewall, loss of prime requiring extended cranking, fuel pressure drop on gauge if equipped

Fix: Rubber diaphragm in accumulator hardens and splits; injector seals in distribution block leak; both are age-related failures; 3-5 hours labor to replace both components and pressure test system; OE parts NLA so aftermarket or used only option

Estimated cost: $600-1,200

Typical onset: 100,000-150,000 mi

Symptoms: clutch pedal pulsation, grinding noise when clutch is depressed, excessive crankshaft endplay (over .012 inches), clutch engagement point changes, metallic knocking at idle in neutral

Fix: Thrust bearing (center main) wears from clutch operation; requires complete engine teardown, crank removal, and main bearing replacement; crank may need grinding if thrust surface is scored; 18-24 hours labor; often discovered during rebuild for other issues

Estimated cost: $3,800-5,500