Engine oil sludge / cam follower wear (1.8T)
high- Typically appears
- 60–120k mi
- Estimated repair
- $800 – $3,500
2004 Audi
A4Convertible
Convertible
The 2004 Audi A4 Cabriolet is a four-seat, soft-top convertible built on the B6 platform — Audi's stylish answer to the BMW 3 Series convertible. It pairs European driving refinement with a fully-automatic folding roof that operates in about 30 seconds. In the U.S., it came primarily with the turbocharged 1.8T four-cylinder or the 3.0L V6, though the 1.8T was the higher-volume seller. The B6 Cabriolet is generally regarded as one of the better-looking Audis of the era, and the interior quality was a noticeable step above most competitors at the time. However, it is now 20+ years old, and the complexity of the convertible top mechanism, the known weaknesses of the 1.8T engine when neglected, and the cost of European-brand parts make it a vehicle that rewards attentive owners and punishes neglectful ones. For buyers in the Lake Geneva area, the open-top appeal is real during Wisconsin summers, but this is not an ideal year-round daily driver. Salt exposure attacks the undercarriage aggressively, the soft top needs extra winter care, and sub-zero cold starts are harder on the 1.8T's turbo and cooling system than on a typical naturally aspirated engine. Buy one only if you're willing to keep up with it.
Reliability
2/5
Verified data
Specs shown for A4 Cabriolet — the most common configuration.
Other trims may vary in engine, drivetrain, or fuel economy. Sign in to see your vehicle's exact specs.
Engine
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Drivetrain
FWD
Fuel
Premium gasoline
MPG
20 city / 28 hwy / 23 combined
Seats
—
Doors
—
Body
Subcompact Cars
Overview
AI-curatedThe 2004 Audi A4 Cabriolet is a four-seat, soft-top convertible built on the B6 platform — Audi's stylish answer to the BMW 3 Series convertible. It pairs European driving refinement with a fully-automatic folding roof that operates in about 30 seconds. In the U.S., it came primarily with the turbocharged 1.8T four-cylinder or the 3.0L V6, though the 1.8T was the higher-volume seller. The B6 Cabriolet is generally regarded as one of the better-looking Audis of the era, and the interior quality was a noticeable step above most competitors at the time. However, it is now 20+ years old, and the complexity of the convertible top mechanism, the known weaknesses of the 1.8T engine when neglected, and the cost of European-brand parts make it a vehicle that rewards attentive owners and punishes neglectful ones. For buyers in the Lake Geneva area, the open-top appeal is real during Wisconsin summers, but this is not an ideal year-round daily driver. Salt exposure attacks the undercarriage aggressively, the soft top needs extra winter care, and sub-zero cold starts are harder on the 1.8T's turbo and cooling system than on a typical naturally aspirated engine. Buy one only if you're willing to keep up with it.
Known for
- Stylish B6-generation styling with a well-built soft-top convertible roof
- Turbocharged 1.8T engine — responsive when maintained, trouble-prone when not
- Upscale, driver-focused interior with quality materials for the era
- European sport-sedan handling in a drop-top package
- Higher-than-average ownership costs for an entry-level luxury convertible
Best for
- Enthusiasts who enjoy European driving character and want a convertible
- Buyers who can perform or closely monitor regular maintenance
- Warm-season/weekend use rather than harsh-winter daily driving
- Owners with access to a trusted independent European-specialty shop
Watch for
- Neglected oil change history — the 1.8T sludges quickly on extended intervals
- Convertible top hydraulic leaks and worn seals adding significant repair costs
- Cooling system failures (water pump, thermostat) common on the 1.8T
- High cost of parts and labor relative to the car's current market value
- Rust and undercarriage corrosion on cars from salt-belt states
Common issues by mileage
6 knownCooling system failure — water pump, thermostat, expansion tank
high- Typically appears
- 70–110k mi
- Estimated repair
- $400 – $1,100
Convertible top hydraulic system leaks / pump failure
high- Typically appears
- 80–150k mi
- Estimated repair
- $500 – $2,500
Turbocharger bypass (diverter) valve failure
medium- Typically appears
- 60–100k mi
- Estimated repair
- $100 – $350
Oxygen sensor / heated O2 sensor failure
medium- Typically appears
- 80–130k mi
- Estimated repair
- $150 – $450
Soft-top seal deterioration and weatherstripping leaks
high- Typically appears
- Any age/mileage on 20-year-old top
- Estimated repair
- $200 – $900
Maintenance schedule
- 1 Every 5,000 miles — do NOT stretch to OEM long-life intervals on a used example Engine oil and filter change (use VW/Audi-spec full synthetic, 5W-40)
The 1.8T is notorious for sludge buildup when oil changes are skipped or extended. At 20 years old, assume the engine needs the shorter interval regardless of the dash reminder.
- 2 Every 40,000 miles or at first sign of temperature fluctuation Coolant system inspection — water pump, thermostat, hoses, expansion tank
Plastic components in the cooling system become brittle with age. A sudden coolant loss on a turbocharged engine can cause rapid, expensive damage.
- 3 Every 75,000 miles or 5 years — whichever comes first Timing belt and water pump replacement
The 1.8T is an interference engine. A snapped timing belt destroys the engine. If history is unknown, do it now.
- 4 Annually, before convertible season Convertible top hydraulic fluid check and seal inspection
Hydraulic leaks are slow at first and become a major repair if the pump runs dry. Catching a seeping cylinder early is a $200 fix vs. a $1,500+ pump replacement.
- 5 Every spring and fall Convertible top fabric/vinyl inspection and treatment
Wisconsin UV in summer and freeze-thaw cycles degrade the top material and seams. A conditioned top stays pliable; a neglected one cracks and leaks.
- 6 Every 40,000 miles Spark plugs and ignition coil packs
B6 1.8T coil packs fail without much warning, causing misfires. Replacing plugs and inspecting coils together is cost-efficient at the same service interval.
- 7 Every 2 years Brake fluid flush
Audi specifies this interval because DOT 4 fluid absorbs moisture over time, lowering boiling point and accelerating internal caliper corrosion — worse in a salty-road environment.
- 8 After every significant salting event during winter Undercarriage wash and inspection
The B6 chassis is susceptible to subframe and control-arm mount corrosion in salt-belt climates. Washing underneath and catching early rust buys years of extra life.
Always defer to the manufacturer's service manual for warranty-mandated intervals.
Cost of ownership
Annual maintenance
$900 – $2,500
Fuel
Premium fuel required. At 23 MPG combined and ~15,000 miles/year, expect $2,000–$2,600/year depending on local premium prices.
Insurance
Expect moderate-to-high premiums for a European luxury convertible — typically $1,200–$1,900/year for a driver with a clean record in the Lake Geneva area. Verify with your insurer as collector/seasonal policies may reduce cost if not driven year-round.
This is not a cheap car to own even though the purchase price is now modest. Parts carry a European premium, labor hours are higher than on domestic vehicles, and the convertible top system adds cost that sedan owners never see. A well-maintained example in the $3,000–$8,000 purchase range can still cost $1,500–$2,500/year to keep right. Budget accordingly and don't let deferred maintenance stack up — on a 1.8T, it compounds fast.
Seasonal care
Lake Geneva, WI Winter
- Store or minimize winter driving — road salt attacks the B6 undercarriage, subframe mounts, and brake lines aggressively. If driven in winter, wash the undercarriage weekly.
- Do NOT operate the convertible top below 40°F. Cold hydraulic fluid is sluggish and the top fabric becomes brittle; forcing it risks torn seals and a broken hydraulic cylinder.
- Use a full synthetic 5W-40 oil rated for cold starts — the turbo needs immediate oil flow at startup in sub-zero temps. Let the engine idle 30–60 seconds before moving.
- Test the battery before first freeze. Cold temperatures hit European vehicles with higher electrical loads hard; the OEM battery size is marginal for Wisconsin winters.
- Switch to a winter washer fluid rated to at least -30°F. The windshield is large on the Cabriolet and freezing fluid on a wiper mid-drive is a real hazard.
- If storing for winter, clean and condition the convertible top fabric, support the top in the closed position, and use a breathable car cover to prevent mold inside the cabin.
Summer
- Check tire pressure monthly — Wisconsin summer heat causes pressure to rise 4–6 PSI above cold readings. The 1.8T's front-heavy FWD layout makes proper pressure critical for handling.
- Inspect the A/C system each spring before convertible season. The condenser on the B6 is exposed and prone to stone damage; a weak A/C on a hot day with the top up is miserable.
- Watch coolant temperature closely during stop-and-go traffic — the aging cooling system on a 20-year-old 1.8T struggles in heat. If the gauge climbs toward hot, pull over immediately.
- UV-treat the convertible top fabric every spring. Wisconsin sun is strong June–August and breaks down unprotected soft-top material quickly.
- Check and top off power steering fluid and brake fluid before the warm season — heat accelerates fluid degradation and any small leaks become bigger problems in summer.
Comparable vehicles
2004 BMW
3 Series Convertible
The direct class rival. The E46 330Ci offers similar European driving character with a more robust inline-6 engine and slightly better long-term reliability, though parts costs are comparable.
2004 Volvo
C70
Turbocharged European convertible at a similar price point. Safer crash ratings and often simpler top mechanism, though slower and less sporty than the A4.
2004 Saab
9-3 Convertible
Another turbo European soft-top from the same era. Generally lower parts costs than Audi, good top quality, and a similar fun-to-drive character.
2005 Chrysler
Sebring Convertible
A much cheaper-to-own domestic alternative if the convertible experience is the priority over European driving dynamics. Lower performance but dramatically lower parts and labor costs.