Mercedes-Benz A-Klasse W168
Weaknesses, engine ratings and buying advice
The W168 was Mercedes' entry into the compact segment — and it started rough. The infamous 1997 "moose test" rollover led to a recall of all delivered vehicles and ESP becoming standard equipment. Buying a W168 today means getting a car with history, but also some quirks.
The M166 petrol engine ranges from 60 to 103 kW. The smaller A 140 and A 160 are reliable daily drivers, while the A 190 and A 210 offer noticeably more punch. All M166 variants develop oil leaks at the valve cover gasket and crankshaft seal beyond 75,000 miles. The OM668 1.7L diesel is frugal but rough — injector issues past 90,000 miles and a fragile turbocharger are typical problems. Blue smoke on cold starts is a red flag on CDI models.
The sandwich floor concept with the engine mounted under the front axle was technically innovative but makes repairs expensive — even a timing belt change becomes a major job. Rust is a serious concern: wheel arches, sills, and rear axle mounting points are the critical areas. After 15 years, virtually no example is rust-free.
The automatic transmission (CVT) was a weak point in early model years — jerky starts and slip at higher mileage. The manual 5-speed is significantly more durable. Suspension is decent for the class, but front axle bearings wear past 50,000 miles and tie rod ends are a consumable.
Test-drive checklist: Start the engine cold and listen for rattling from the engine bay. Shift the automatic slowly from P through R to D — delays or harsh shifts indicate CVT wear. Turn the steering at standstill and check for clicking.
2026 market: Between $1,600 and $5,000 for well-maintained examples under 90,000 miles. A 190 and A 210 are slowly gaining collector interest.
Insider pick: A 160 with manual gearbox and documented rust prevention — the most hassle-free W168.
Generations
Engine Overview
The Mercedes-Benz A-Klasse W168 is available with 6 engine variants — from 60 to 140 hp.
The first common rail diesel in a Mercedes passenger car — a small four-cylinder for the first A-Class with modest power but reasonable economy. The injectors are the critical weakness: copper sealing rings harden and allow leaks which, if untreated, lead to the injectors burning into the cylinder head. Seized injectors are a complex and expensive repair. The timing chain stretches with age. Check the glow plug system regularly, especially on cold-start issues. DPF regeneration is incomplete on short journeys — occasional motorway runs are recommended. Not a performance engine, but a workable city diesel with proper maintenance.
- !! Injectors Leaking — Copper Sealing Ring Failed from 120,000 km
The copper sealing ring between injector and cylinder head fails and allows combustion gases to escape. A tarry black sludge forms around the injectors. If ignored the injector will break on removal.
Symptoms: Diesel smell inside the vehicle, rough idle, black tar-like deposits on the engine block around the injectors, three-cylinder running - !! Seized Injectors on Removal from 150,000 km
Corrosion and tar deposits can cause injectors to seize in the cylinder head. If an injector breaks during removal, extensive cylinder head work is required. Special tools and experience are essential.
Symptoms: Seized injectors discovered during workshop inspection — no driver indication beforehand, only apparent during repair - !! Timing Chain Stretches — Engine Damage Possible from 150,000 km
The K9K-based OM668 in the Citan is prone to premature timing chain stretch. Multiple cases of chain failure and total engine loss documented. Clicking on cold start is an early warning signal.
Symptoms: Clicking or rattling on cold start, noise from front of engine, CEL, in extreme cases engine stall
+ 3 more engine weaknesses + vehicle weaknesses
The first common rail diesel in a Mercedes passenger car — a small four-cylinder for the first A-Class with modest power but reasonable economy. The injectors are the critical weakness: copper sealing rings harden and allow leaks which, if untreated, lead to the injectors burning into the cylinder head. Seized injectors are a complex and expensive repair. The timing chain stretches with age. Check the glow plug system regularly, especially on cold-start issues. DPF regeneration is incomplete on short journeys — occasional motorway runs are recommended. Not a performance engine, but a workable city diesel with proper maintenance.
- !! Injectors Leaking — Copper Sealing Ring Failed from 120,000 km
The copper sealing ring between injector and cylinder head fails and allows combustion gases to escape. A tarry black sludge forms around the injectors. If ignored the injector will break on removal.
Symptoms: Diesel smell inside the vehicle, rough idle, black tar-like deposits on the engine block around the injectors, three-cylinder running - !! Seized Injectors on Removal from 150,000 km
Corrosion and tar deposits can cause injectors to seize in the cylinder head. If an injector breaks during removal, extensive cylinder head work is required. Special tools and experience are essential.
Symptoms: Seized injectors discovered during workshop inspection — no driver indication beforehand, only apparent during repair - !! Timing Chain Stretches — Engine Damage Possible from 150,000 km
The K9K-based OM668 in the Citan is prone to premature timing chain stretch. Multiple cases of chain failure and total engine loss documented. Clicking on cold start is an early warning signal.
Symptoms: Clicking or rattling on cold start, noise from front of engine, CEL, in extreme cases engine stall
+ 3 more engine weaknesses + vehicle weaknesses
Compact four-cylinder in the unique sandwich construction of the first A-Class — the engine lies transversely below the vehicle floor. Robust with consistent maintenance, but with one critical Achilles heel: the timing chain can stretch even at relatively low mileage and destroy the engine in a complete failure. Oil change intervals below 15,000 km are essential. The camshaft adjuster tends to leak oil which can travel through the wiring into the ECU — an expensive consequential failure. Check glow plugs regularly; the tight engine bay makes access difficult. No successor engine — spare parts are increasingly hard to find.
- !! Timing Chain Wears Prematurely from 90,000 km
The single-row roller chain on the M166 can stretch from as early as 80,000–100,000 km. In the worst case the chain breaks and causes severe engine damage. Rattling on cold start is the first warning sign.
Symptoms: Rattling on cold start, rough engine running from altered timing, in extreme cases chain break with total engine damage - !! Oil Creeping in Wiring Harness Damages ECU from 150,000 km
Oil migrates by capillary action into the wiring harness and reaches the engine control unit over years. The ECU corrodes and eventually fails — a typical late failure on high-mileage W168.
Symptoms: Engine misfires, starting problems, fault codes without clear cause, ECU no longer responds to diagnosis - !! Crankshaft Sensor Fails — Engine Dies Suddenly from 130,000 km
The crankshaft position sensor on the M166 in the W168 fails due to oil crust and ageing. Without a signal from the sensor, engine start is impossible. Failure often occurs suddenly.
Symptoms: Engine dies suddenly while driving, starts briefly and dies again, crankshaft sensor fault code, CEL
+ 4 more engine weaknesses + vehicle weaknesses
Compact four-cylinder in the unique sandwich construction of the first A-Class — the engine lies transversely below the vehicle floor. Robust with consistent maintenance, but with one critical Achilles heel: the timing chain can stretch even at relatively low mileage and destroy the engine in a complete failure. Oil change intervals below 15,000 km are essential. The camshaft adjuster tends to leak oil which can travel through the wiring into the ECU — an expensive consequential failure. Check glow plugs regularly; the tight engine bay makes access difficult. No successor engine — spare parts are increasingly hard to find.
- !! Timing Chain Wears Prematurely from 90,000 km
The single-row roller chain on the M166 can stretch from as early as 80,000–100,000 km. In the worst case the chain breaks and causes severe engine damage. Rattling on cold start is the first warning sign.
Symptoms: Rattling on cold start, rough engine running from altered timing, in extreme cases chain break with total engine damage - !! Oil Creeping in Wiring Harness Damages ECU from 150,000 km
Oil migrates by capillary action into the wiring harness and reaches the engine control unit over years. The ECU corrodes and eventually fails — a typical late failure on high-mileage W168.
Symptoms: Engine misfires, starting problems, fault codes without clear cause, ECU no longer responds to diagnosis - !! Crankshaft Sensor Fails — Engine Dies Suddenly from 130,000 km
The crankshaft position sensor on the M166 in the W168 fails due to oil crust and ageing. Without a signal from the sensor, engine start is impossible. Failure often occurs suddenly.
Symptoms: Engine dies suddenly while driving, starts briefly and dies again, crankshaft sensor fault code, CEL
+ 4 more engine weaknesses + vehicle weaknesses
Compact four-cylinder in the unique sandwich construction of the first A-Class — the engine lies transversely below the vehicle floor. Robust with consistent maintenance, but with one critical Achilles heel: the timing chain can stretch even at relatively low mileage and destroy the engine in a complete failure. Oil change intervals below 15,000 km are essential. The camshaft adjuster tends to leak oil which can travel through the wiring into the ECU — an expensive consequential failure. Check glow plugs regularly; the tight engine bay makes access difficult. No successor engine — spare parts are increasingly hard to find.
- !! Timing Chain Wears Prematurely from 90,000 km
The single-row roller chain on the M166 can stretch from as early as 80,000–100,000 km. In the worst case the chain breaks and causes severe engine damage. Rattling on cold start is the first warning sign.
Symptoms: Rattling on cold start, rough engine running from altered timing, in extreme cases chain break with total engine damage - !! Oil Creeping in Wiring Harness Damages ECU from 150,000 km
Oil migrates by capillary action into the wiring harness and reaches the engine control unit over years. The ECU corrodes and eventually fails — a typical late failure on high-mileage W168.
Symptoms: Engine misfires, starting problems, fault codes without clear cause, ECU no longer responds to diagnosis - !! Crankshaft Sensor Fails — Engine Dies Suddenly from 130,000 km
The crankshaft position sensor on the M166 in the W168 fails due to oil crust and ageing. Without a signal from the sensor, engine start is impossible. Failure often occurs suddenly.
Symptoms: Engine dies suddenly while driving, starts briefly and dies again, crankshaft sensor fault code, CEL
+ 4 more engine weaknesses + vehicle weaknesses
Compact four-cylinder in the unique sandwich construction of the first A-Class — the engine lies transversely below the vehicle floor. Robust with consistent maintenance, but with one critical Achilles heel: the timing chain can stretch even at relatively low mileage and destroy the engine in a complete failure. Oil change intervals below 15,000 km are essential. The camshaft adjuster tends to leak oil which can travel through the wiring into the ECU — an expensive consequential failure. Check glow plugs regularly; the tight engine bay makes access difficult. No successor engine — spare parts are increasingly hard to find.
- !! Timing Chain Wears Prematurely from 90,000 km
The single-row roller chain on the M166 can stretch from as early as 80,000–100,000 km. In the worst case the chain breaks and causes severe engine damage. Rattling on cold start is the first warning sign.
Symptoms: Rattling on cold start, rough engine running from altered timing, in extreme cases chain break with total engine damage - !! Oil Creeping in Wiring Harness Damages ECU from 150,000 km
Oil migrates by capillary action into the wiring harness and reaches the engine control unit over years. The ECU corrodes and eventually fails — a typical late failure on high-mileage W168.
Symptoms: Engine misfires, starting problems, fault codes without clear cause, ECU no longer responds to diagnosis - !! Crankshaft Sensor Fails — Engine Dies Suddenly from 130,000 km
The crankshaft position sensor on the M166 in the W168 fails due to oil crust and ageing. Without a signal from the sensor, engine start is impossible. Failure often occurs suddenly.
Symptoms: Engine dies suddenly while driving, starts briefly and dies again, crankshaft sensor fault code, CEL
+ 4 more engine weaknesses + vehicle weaknesses
Vehicle Weaknesses
| Weakness | Cost | |
|---|---|---|
| Sills and Underbody Perforated by Rust Water collects between wheel arch liner and sill, keeping it permanently damp. Extensive through-rusting of side sills including structural damage. Older examples regularly severely affected. Symptoms: Rust bubbles on outer sill surface, creaking when getting in, visible rust under rear doors from 100,000 km | Medium | |
| Rust on Rear Wheel Arches Rear wheel arches rust extensively, sometimes with risk of perforation. Door sills and tailgate also frequently affected. Vehicles over approximately 8 years without regular care are severely at risk. Symptoms: Rust bubbles at inner wheel arch edge, visible rust at door sill from 110,000 km | Medium | |
| Rust damage to door hinges Door hinges rust from the inside out and can break, causing the door to sag and requiring lifting to close properly. Particularly on vehicles without regular underbody maintenance. Symptoms: Door hangs out of alignment, can only be closed properly by lifting, visible rust on hinge from 120,000 km | Low |
Test Reports
TÜV Report 2024
The first A-Class generation shows clearly elevated fault rates in old age, above the class average.
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Known Problems and Issues +
A total of 21 weaknesses have been documented for the Mercedes-Benz A-Klasse W168 (1997–2004) — 13 engine-related and 8 vehicle-related. 2 problem engines: M166 (1.4-2.1L NA), OM668 (1.7L Diesel). Typical issues affect Rust, Gearbox, Suspension, Electronics.
A-Klasse (OM668, 1998–2001) — Stay Away!: Injectors Leaking — Copper Sealing Ring Failed, Seized Injectors on Removal, Timing Chain Stretches — Engine Damage Possible. Power: 60 PS.
A-Klasse (OM668, 1998–2001) — Stay Away!: Injectors Leaking — Copper Sealing Ring Failed, Seized Injectors on Removal, Timing Chain Stretches — Engine Damage Possible. Power: 90–95 PS.
A-Klasse (OM668, 2001–2004) — Stay Away!: Injectors Leaking — Copper Sealing Ring Failed, Seized Injectors on Removal, Timing Chain Stretches — Engine Damage Possible. Power: 75 PS.
A-Klasse (M166, 1997–2004) — Stay Away!: Timing Chain Wears Prematurely, Oil Creeping in Wiring Harness Damages ECU, Crankshaft Sensor Fails — Engine Dies Suddenly. Power: 82 PS.
A-Klasse (M166, 1997–2004) — Stay Away!: Timing Chain Wears Prematurely, Oil Creeping in Wiring Harness Damages ECU, Crankshaft Sensor Fails — Engine Dies Suddenly. Power: 102 PS.
A-Klasse (M166, 1999–2004) — Stay Away!: Timing Chain Wears Prematurely, Oil Creeping in Wiring Harness Damages ECU, Crankshaft Sensor Fails — Engine Dies Suddenly. Power: 125 PS.
A-Klasse (M166, 2001–2004) — Stay Away!: Timing Chain Wears Prematurely, Oil Creeping in Wiring Harness Damages ECU, Crankshaft Sensor Fails — Engine Dies Suddenly. Power: 136–140 PS.
What to watch out for with the Mercedes-Benz A-Klasse? See the detailed listing of all engine and vehicle weaknesses in the sections above.
Frequently Asked Questions
What problems and weaknesses does the Mercedes-Benz A-Klasse W168 have? +
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Which Mercedes-Benz A-Klasse W168 engine is the most fun? +
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Last updated: February 2026 · All information without guarantee