The G29 Z4 is BMW's third-generation roadster, co-developed with Toyota on the platform shared with the Supra and built at Magna Steyr in Graz. The sDrive30i pairs the proven B48 2.0-litre turbo four with an 8-speed ZF automatic, giving 255 hp and brisk performance without the running-cost penalty of the M40i six-cylinder. Generally considered one of the more reliable modern BMW roadsters, though the soft top, recent starter relay fire recall, and recurring oil filter housing leaks all need attention on used examples.· more· less
B48 engine widely regarded as reliableZF 8-speed automatic proven robust
Starter relay fire recall (2019-2022)Oil filter housing gasket leaks common
Buy if: You want a refined roadster with everyday usability, lower running costs than the M40i, and verified recall completion.
Avoid if: You expect zero electrical gremlins, refuse to garage the car, or skip the starter relay recall check.
Starter relay fire risk (recall 25V-636 / 26V-056)
€0 - 5001 of 7
Valeo starter relay can corrode and overheat, risking engine bay fire on 2019-2022 cars · more· less
In September 2025 BMW issued recall 25V-636 covering nearly 200,000 vehicles in the US (and a parallel global campaign covering 575,000 cars) for a Valeo starter relay that can ingress water, corrode, and short-circuit. A follow-up recall 26V-056 in early 2026 added 87,000 more cars where the starter motor itself can wear and overheat. Both recalls affect the Z4 sDrive30i built 2019 through 2022. BMW recommended owners park outside until repaired. Remedy is a free starter or starter relay replacement at a BMW dealer. This is the single most important check on a used G29 — verify the work has been done via VIN check with BMW. If completed, no further action needed; if not, schedule it immediately and park outside in the meantime.
Oil filter housing gasket leak
€400 - 1,5002 of 7
Plastic oil filter housing warps and rubber gaskets harden, allowing oil to leak onto the engine · more· less
The B48's oil filter housing is plastic and uses rubber gaskets that harden with heat cycling. Leaks typically appear between 80,000-150,000 km and are widespread enough that a US class-action lawsuit named the B46/B48/B58 family in 2024-2025. Symptoms include oil drips on the underbody, oil smell, and visible seepage on the front of the engine. Gasket-only replacement runs €400-700 at an independent BMW specialist; if the housing itself is cracked or warped a full housing replacement is needed at €1,000-1,500. Easy to spot on a pre-purchase inspection — look under the engine for oil residue around the filter housing on the passenger side.
Steering tie rod failure (recall 20V-355)
€0 - 8003 of 7
Original tie rods can fracture in the 'kink' groove area on 2019-2020 cars · more· less
Recall 20V-355 covers 2019-2020 Z4 sDrive30i models built between October 2018 and July 2019. The factory tie rods are an earlier design and can fracture at the kink groove under high temperatures and rough roads, with sudden loss of steering control. About 4,542 Z4s were affected globally. Remedy is free replacement of both tie rods at a BMW dealer. Like the starter recall, verify completion via VIN check. If not completed, do not drive the car at speed until repaired.
Cylinder head coolant vent line failure
€300 - 9004 of 7
Thin plastic coolant vent hose from cylinder head to expansion tank becomes brittle and cracks · more· less
A documented weak point across B46/B48/B58-powered BMWs covered by service bulletin SIB 17 01 21. The vent line runs from the cylinder head to the coolant expansion tank and is a thin plastic tube that sits in a hot area. After roughly 80,000-150,000 km it becomes brittle and either cracks or splits at the connection. Coolant can dump onto the engine or evaporate inside the insulation — owners often describe a sweet syrup smell before the warning light appears. Repair is straightforward: €300-500 at a specialist, up to €900 at a BMW dealer. The bigger risk is if it fails on the highway and goes unnoticed, leading to overheating and a warped head.
Soft top operation and motor issues
€400 - 2,5005 of 7
Drain channels clog with debris causing water in the hydraulic motor housing; roof squeaks common · more· less
The G29 returned to a soft top (after the E89's folding hardtop), and it is generally well engineered. Two issues recur on owner forums: first, drain channels under the roof storage compartment clog with leaves and debris, allowing rainwater into the hydraulic motor compartment and causing corrosion. Annual cleaning of drain holes prevents this. Second, owners commonly report squeaks from behind the driver's head or at the front screen in cold weather, attributed by BMW to trim panel de-bonding. Pump motor replacement runs €1,500-2,500 if it fails; trim adjustment and lubrication of the roof mechanism is a €100-300 fix. Always cycle the roof up and down multiple times during inspection.
Valve cover gasket seepage
€350 - 7006 of 7
Minor oil seepage at the valve cover on cars past 80,000 km · more· less
A relatively benign B48 issue — the valve cover gasket can begin to seep oil after 80,000-130,000 km. It is typically a small leak that does not affect oil consumption but will leave residue visible at the top of the engine. Not urgent unless oil is dripping onto hot exhaust components, in which case it should be replaced promptly. Gasket replacement is €350-500 at a specialist, €600-700 at a BMW dealer. Often done together with the oil filter housing gasket to save labor.
iDrive freezing or rebooting
€0 - 4007 of 7
Occasional iDrive screen freezes, usually traceable to battery voltage or software · more· less
Reported by roughly 6% of G29 owners. The iDrive head unit is sensitive to voltage stability, so a weak or unregistered 12V battery is the most common cause — the system can crash during acceleration or with high electrical loads. Software updates from BMW resolve many cases. Diagnosis: have the battery load-tested and confirmed as registered to the BMS. If hardware replacement is needed it can run €1,500+, but most cases are fixed by a battery refresh (€300-400 including coding) or a free software update at a BMW dealer.
Generally reliable, but recall verification is critical
The Z4 sDrive30i is widely considered one of the more dependable modern BMW convertibles, with the B48 engine and ZF 8-speed automatic both well-proven. The biggest single risk is the open starter relay fire recall — verify completion via VIN before purchase. Oil filter housing leaks, the tie rod recall on early cars, and the coolant vent line are well-documented but predictable issues that a pre-purchase inspection will catch.
Service history
Complete BMW dealer or BMW specialist records essential. Verify oil changes every 12 months or 15,000 km.
Tires
Check tread depth, age (date codes), and brand. Run-flats wear quickly and replacement is expensive.
Cold start
Start engine completely cold. Listen for unusual rattles, especially from the timing chain area.
Test drive
Minimum 30 minutes including highway and B-roads. Test all drive modes, transmission shifts, and brakes from speed.
Bodywork and paint
Check for stone chips, kerb damage on wheels, and any signs of poorly repaired accident damage.
Specific for this vehicle
Verify starter relay recall (25V-636 / 26V-056) completed
This is the single most important check. Contact a BMW dealer with the VIN to confirm both the 2025 relay recall and 2026 starter motor recall have been completed.
Verify tie rod recall (20V-355) on 2019-2020 cars
Affects cars built Oct 2018 - Jul 2019. Confirm both tie rods have been replaced free of charge under recall.
Inspect oil filter housing for leaks
Look under the engine on the passenger side for oil residue around the plastic oil filter housing. Common failure point on B48.
+ 7 more checksShow less
Cycle the soft top multiple times
Open and close the roof 3-4 times. Listen for smooth motor operation, check fabric tension, look for any hydraulic fluid leaks at hinges.
Check soft top drain channels
Open the boot and check the drain holes under the roof storage area are clear. Blocked drains cause water damage to the hydraulic motor.
Inspect coolant reservoir and vent hose
Look for any sweet syrup smell or coolant residue around the expansion tank and the thin vent hose to the cylinder head.
Check valve cover and front of engine for oil seepage
Look at the top of the engine and around the valve cover gasket. Light seepage on cars past 80,000 km is common but not yet urgent.
Test iDrive system thoroughly
Try all menus, Bluetooth, navigation, and reversing camera. Restart the car and verify no boot delays or freezes.
Check alloy wheels for cracks
Z4 alloys, especially M Sport wheels, can crack from pothole impacts. Inspect inside the wheel rim for hairline cracks.
Verify 12V battery health and registration
Ask whether the battery has been replaced and properly registered with the BMS. Crucial for iDrive stability and start-stop function.
Steering tie rod fracture (20V-355) - 2019-2020Critical - verify completed
Fuel tank insufficient welding - 2020-2021Verify completed
Coolant vent line replacement (SIB 17 01 21)TSB
The G29 Z4 has been subject to multiple safety recalls, including two starter-related fire risk recalls in 2025-2026 and a tie rod fracture recall in 2020. Always run a VIN check with BMW before purchase to confirm all recall work has been completed.
Warranty Status
Factory warranty (2 years, BMW)Expired on all cars except 2024+
BMW Extended WarrantyAvailable through BMW dealers, ~€1,200-1,800/year
Rust perforation12 years from first registration
All Z4 G29 models built before 2024 are outside the original 2-year BMW factory warranty. The optional BMW Premium Selection or Extended Warranty may still apply on cars sold by BMW dealers — confirm with the seller. Rust perforation cover is separate and runs for 12 years.
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.
