The entry-level G29 Z4 pairs the proven B48 2.0-litre turbo four with a ZF 8-speed automatic in a lightweight rear-drive roadster. Built at Magna Steyr in Austria on a platform shared with the Toyota Supra, the sDrive20i produces 197 hp and handles with genuine sports car agility. Production ran from 2019 to early 2026, with an LCI facelift in late 2022 bringing mild styling updates and revised infotainment.· more· less
Proven B48 engine, well-documentedLower running costs than 6-cylinder Z4s
Oil filter housing prone to crackingSoft-top drain blockage causes leaks
Buy if: You want an engaging rear-drive roadster with manageable running costs and can maintain the soft top and cooling system proactively.
Avoid if: You plan to leave the car parked outdoors for weeks at a time or want a completely carefree ownership experience.
Price & maintenance
Used price
€37,000
median asking price, typically 25,000 km
Typical range€33,500 – €44,300
Kilometres drivenAll
Maintenance cost
€900 – €1,600/year
at 15,000 km/year
Fixed costsservice, tyres, brakes€550 – €900 /yr
Risk bufferunplanned repairs€350 – €700 /yr
Price estimates are based on German asking prices. Prices and costs vary by vehicle condition and location.
Ownership costs
Maintenance assumes 15,000 km a year. Price estimates are based on German asking prices. Prices and costs vary by vehicle condition and location.
Plastic oil filter housing warps or cracks, causing oil or coolant leak typically after 80,000-100,000 km · more· less
The B48 engine uses a plastic oil filter housing that also serves as a heat exchanger (oil cooler). Over time, the plastic warps from repeated heat cycles, causing the gasket to fail or the housing itself to crack. Symptoms include oil spots under the car, low coolant warnings, or in severe cases oil mixing with coolant. This is a well-documented issue across all B48-equipped BMWs. Gasket-only replacement at an independent shop costs around €800-1,200, while a full housing replacement (if cracked) runs €1,500-2,500. The coolant vent hose connected to the housing is also brittle and should be replaced at the same time. Most specialists now recommend replacing gasket, housing, and vent hose together as a package to avoid repeat repairs.
Electric water pump failure
€700 - 1,2002 of 8
Electric water pump typically fails between 80,000-120,000 km, causing overheating warnings · more· less
The B48 uses an electric water pump integrated with the thermostat housing. Failures are common between 80,000 and 120,000 km, although some cars see pump issues as early as 60,000 km. Symptoms include a coolant temperature warning, poor cabin heating, or the heater blowing maximum heat unexpectedly. Most specialists recommend replacing the water pump and thermostat together since they share the same cooling circuit and often fail in a similar timeframe. Parts cost approximately €300-500, with 3-5 hours of labor needed due to the tight engine bay in the Z4.
Valve cover gasket oil leak
€600 - 1,0003 of 8
Valve cover gasket degrades with heat, causing oil seep typically after 80,000-120,000 km · more· less
As the rubber gasket around the valve cover hardens with age and heat cycles, oil begins to seep down the side of the engine. On the B48, this repair is more involved than on older BMWs because the fuel injectors and high-pressure fuel line must be removed first, requiring special tools. The gasket itself costs around €30, but labor is the main expense. Independent shops typically charge €600-800, while BMW dealers may charge €800-1,000. If left unaddressed, oil can drip onto hot exhaust components, creating a burning smell and potential fire risk.
Soft-top drain blockage and water ingress
€150 - 8004 of 8
Roof drainage channels clog with debris, causing water to enter the cabin or boot · more· less
The Z4's soft-top drainage system relies on channels that run from the roof frame, through the A-pillars, and exit near the rear wheel arches. Leaves, dirt, and general debris gradually block these drains. When blocked, water overflows into the cabin, footwells, or boot during heavy rain. If caught early, cleaning the drains with a pipe cleaner costs essentially nothing but time. However, if water has been sitting in the boot or under carpets for an extended period, electrical damage to wiring harnesses, amplifier, or boot-mounted modules can result in repairs costing €500-800. Checking and clearing drains every 6 months is recommended, especially if the car is parked under trees.
Convertible roof mechanism fault
€500 - 2,5005 of 8
Roof latch, microswitch, or motor can fail, causing the top to stop mid-cycle · more· less
The G29's fabric soft top is mechanically simpler than the E89's retractable hardtop, but still relies on electric motors, microswitches, and latch mechanisms that can fail over time. Reported issues include the roof stopping mid-cycle, latches not engaging properly, and the roof ECU throwing errors. Minor fixes like microswitch replacement or ECU recoding cost €500-800. More serious issues involving motor replacement or frame realignment can reach €1,500-2,500. This is less common on the G29 than on previous Z4 generations, and many cars reach high mileage without any roof mechanism problems.
Harman Kardon amplifier failure
€300 - 1,2006 of 8
Audio amplifier cuts out intermittently, especially bass channels, common across 2019-2021 G29 models · more· less
Several G29 owners report the Harman Kardon audio system developing intermittent dropouts, particularly affecting the bass frequencies. The amplifier is located in a position exposed to heat and moisture. BMW dealer replacement costs €1,000-1,200, but specialist amplifier repair services can fix the unit for €200-400 by resoldering failed components. This issue affects multiple BMW models from the same era and appears linked to a supplier batch problem. Cars without the HK system use a simpler HiFi amplifier that is less failure-prone.
Engine mount degradation
€400 - 7007 of 8
Fluid-filled engine mounts soften and sag, causing increased vibration from around 60,000-80,000 km · more· less
BMW uses fluid-filled engine mounts that gradually lose their damping properties as the fluid leaks out internally. Forum reports indicate some G29 owners have needed engine mount replacement as early as 30,000 km, though 60,000-80,000 km is more typical. Symptoms include increased vibration felt through the steering wheel and gear lever at idle, and a slight clunk when blipping the throttle in neutral. Parts cost approximately €150-200 per mount, with 2-3 hours of labor. This is a relatively straightforward repair at any BMW specialist.
Starter motor relay corrosion (recall-related)
€0 - 5008 of 8
Manufacturing defect in starter relay can cause hard starts or, rarely, localized overheating · more· less
BMW issued a global recall in early 2026 affecting Z4 models built between July 2020 and July 2022. The magnetic switch in the starter can develop excessive wear, leading to hard starting or, in rare cases, a short circuit and localized overheating. This is a free recall repair (starter replacement) if the car is affected. However, if you are buying a used car where the recall has not been completed, factor in the need to have this done promptly. Always verify recall status with BMW using the VIN before purchase.
Reliable for a roadster, but cooling system needs attention
The B48 engine in the Z4 sDrive20i is well-proven across the BMW range and generally reliable. The main ownership concerns are the plastic cooling system components (oil filter housing, water pump, thermostat) that degrade between 80,000-120,000 km, and the soft-top drainage system that requires periodic maintenance. The convertible mechanism itself is simpler than the previous E89's hardtop and less prone to expensive failures. With proactive maintenance of the cooling system and regular drain cleaning, the sDrive20i can provide dependable ownership at moderate cost for a premium roadster.
Service history
Complete BMW dealer or specialist records essential. Verify oil changes every 15,000 km or 12 months.
Tire condition
Check tread depth on all four tires. Staggered setup means rears wear faster. Check for uneven wear indicating alignment or suspension issues.
Cold start
Start engine completely cold. Listen for any unusual rattling, ticking, or roughness in the first 30 seconds.
Test drive
Minimum 30 minutes including motorway speeds. Test roof operation multiple times. Feel for vibrations at idle that could indicate worn engine mounts.
Specific for this vehicle
Inspect under the engine for oil leaks
Look around the oil filter housing area and valve cover gasket. Any fresh oil residue or dripping indicates impending repair needs.
Check coolant level and condition
Low coolant or discolored coolant can indicate oil filter housing crack or water pump issues. BMW coolant should be blue-green.
Operate the soft top at least three times
Open and close the roof fully each time. Listen for grinding, hesitation, or error messages. Verify it latches cleanly at front and rear.
+ 4 more checksShow less
Inspect boot and footwells for moisture
Lift boot floor carpet and press door sill carpets. Any dampness suggests blocked roof drains causing water ingress.
Test all audio system functions
Play music at moderate volume for 10+ minutes. Listen for bass cutting out or crackling, especially if equipped with Harman Kardon system.
Verify starter motor recall status
Cars built July 2020 to July 2022 may be affected. Contact BMW with the VIN to confirm the recall has been completed.
Check steering tie rod recall completion
Early 2019 models may be affected by the steering tie rod recall. Verify with BMW using the VIN.
Recalls and Technical Service Bulletins
Starter motor relay corrosion — risk of hard start or overheating (July 2020 - July 2022 production)Verify completed
Steering gear tie rod — earlier design may fracture under stress (Oct 2018 - July 2019 production)Verify completed
Fuel tank weld — insufficient weld may allow fuel leak (June 2019 - July 2020 production, approx. 14 vehicles)Verify completed
Power window/sunroof ECU software — windows may close after digital key removal (2022-2023 models)Verify if applicable
Contact BMW with the VIN to verify all recalls have been completed. The starter motor recall is the most broadly relevant for 2020-2022 models. The steering tie rod recall mainly affects very early 2019 production cars.
Warranty Status
Factory warranty (2 years, 3 years from Nov 2016)Expired on most used examples
BMW extended warrantyAvailable through BMW dealers, typically 1-2 years additional
Rust perforation warranty (12 years)May still apply on 2019+ models
All pre-2024 Z4 models are outside their original 3-year factory warranty. BMW offers extended warranty packages through dealers. The 12-year rust perforation warranty still covers 2019+ models against bodywork corrosion from the inside out.
Sources: Research draws on model-specific owner forums and owner communities, recall information from official authorities, German automotive press, and multiple workshop cost references cross-checked against each other.
This report is for informational purposes only and does not constitute professional advice. Estimates may be inaccurate. Always have a qualified specialist inspect the vehicle before purchase. We accept no liability for decisions made based on this information.
