BMW Z4 2.5si (E85) engine: which one, problems and replacement

The BMW Z4 2.5si in the first Z4 roadster generation (E85, built 2002–2008) was built with one engine, the N52B25: a 2.5 L petrol inline-6 with 218 hp.

This guide tells you which engine your Z4 2.5si has, what goes wrong with it, what a replacement costs from our stock and what else to plan for when you fit one.

• Generation: first Z4 roadster, 2002–2008
• Body styles: E85 (roadster)
• Engines: N52B25
• Output: 218 hp
• Replacement engines in stock: 128 from 1.421,00 €

Which engine is in your Z4 2.5si?

N52B25 in the Z4 2.5si

The N52B25 was used in the E85 Z4 2.5si, built 2004–2011. It is a 2.5 L naturally aspirated petrol inline-6 with 218 hp and 250 Nm.

Reading the code: N marks an N-series code, the generation of BMW engines introduced from 2001; 52 is the family number; B stands for petrol (from the German Benzin); 25 is the capacity in decilitres, so 2.5 litres.

Z4 2.5si engines by model year

The Z4 2.5si kept the same engine for the whole E85 run, which makes ordering simple: any unit with the same code fits, subject to the gearbox, drive type and sump.

Other cars with the same engine as the Z4 2.5si

A replacement engine does not have to come from another Z4 2.5si. These models left the factory with the same engine code, so a unit from any of them is a candidate donor once the sump, mounts and ancillaries are matched to your car.

N52B25: BMW E90 325i, BMW E60 525i, BMW E83 X3 2.5si.

How to confirm your engine code

The Z4 2.5si only used the N52B25, but the exact version can still change with the build date, gearbox and market. Send us the last seven characters of the VIN and we read the engine code from BMW's records, or look for the code stamped on the block. How to find your BMW engine code.

Known Z4 2.5si engine problems

The N52B25 in the Z4 2.5si shares the known weak points of the N52 family. Full N52 guide.

Hydraulic lifter tick. Some engines tick on cold start because lifters drain down.

Electric water pump and thermostat. The pump fails around 100,000 km with little warning.

Valve cover gasket and eccentric shaft sensor. The plastic valve cover leaks and its sensor gasket fails.

Oil filter housing gasket. Leaks oil down the block and onto belts.

VANOS solenoids. Dirty solenoids cause rough idle and codes.

Symptoms to watch for on the Z4 2.5si

Rattle for a few seconds after a cold start. The classic sign of a weak timing chain tensioner or stretched chain. It must be checked quickly: a chain that jumps a tooth can bend valves.

Poor low-down torque and uneven idle. VANOS seals or solenoids. The engine may run well at high revs but feel flat and lumpy at low speed.

Limp mode with a Valvetronic fault. The Valvetronic motor, its eccentric shaft sensor or the wiring. The engine runs on a reduced throttle until it is repaired.

Looking after the Z4 2.5si engine

• Oil: 5W-30 BMW Longlife-01 or 04, about 6.5 litres.
• Service interval: Oil every 10,000 to 15,000 km.
• Timing drive: Timing chain at the front.
• Workshop notes: Fit a new water pump and thermostat with any used N52; they are on the outside and cheap compared with labour later.

Buying a used engine for the Z4 2.5si: checklist

1. Gearbox and flywheel match. Manual and automatic engines differ at the flywheel or flexplate, and sometimes at the crankshaft spigot. Make sure the engine you buy matches your gearbox or that you transfer the right parts.
2. Look at the oil and coolant. Clean oil without metal particles and coolant without oil are good signs. Milky oil, oily coolant or a burnt smell mean the engine needs further checks before it is fitted.
3. Ask how the donor car was damaged. Most good used engines come from cars with body damage. A front-end impact can crack sensors, the timing cover or the sump; a rear or side impact usually leaves the engine untouched. The yard records the damage on each unit.
4. Why your old engine failed. Before fitting a replacement, find out why the original failed. An overheating radiator, a blocked intercooler or a failed turbo can destroy a second engine if they are not fixed.
5. Confirm the exact engine code. Read the code stamped on the block and compare it with the code for your car. Send us the last seven characters of the VIN and we confirm the match before anything is paid.
6. Timing chain noise. Listen for a rattle at the front of the engine for the first seconds after a cold start. On an engine that cannot be run, look at the chain guides through the oil filler or with the valve cover off.
7. VANOS operation. Rough idle, a rattle from the front of the head and a loss of torque at low revs point to VANOS seals or solenoids. These are serviceable parts and are easier to renew with the engine out.
8. Double VANOS units and solenoids. Ask for the adaptation values or fault history if the engine was running. Solenoids are inexpensive and are often replaced as a matter of course on a used engine.
9. Valvetronic motor and eccentric shaft sensor. The Valvetronic motor and its sensor cause limp-mode faults when they fail. Inspect the connector and the seal around the motor for oil.
10. Electric water pump. This engine uses an electric water pump. It fails without warning and needs a diagnostic bleeding routine when it is replaced or the system is refilled.

BMW Z4 2.5si replacement engine cost

Across 128 Z4 2.5si engine units in our stock today, prices start at 1.421,00 € and reach 2.300,00 €. The median — the price in the middle of the range — is 1.841,00 €.

Prices depend on the exact version, the donor's mileage, how complete the engine is and the demand for that code. Higher-output versions, low mileage and dressed engines with turbo, injectors and ancillaries cost more; long blocks and higher mileage cost less.

Z4 2.5si engine prices by model year

Engines from 2005–2009 have a median of 1.801,00 €, while units from 2010–2014 sit at 1.890,00 €. Newer engines usually cost more because they come from younger donor cars with lower mileage and later updates.

Z4 2.5si engine prices by mileage

Mileage matters less than history on a well-maintained BMW engine, but it is a useful guide. A low-mileage unit from a younger car gives you more life for a modest premium.

On top of the engine, budget for the workshop's labour and the parts that are best replaced while the engine is out: engine mounts, the rear main seal, cooling parts, a clutch or converter seal, fluids and filters.

Replacement engines in stock for the Z4 2.5si

Here is a selection of Z4 2.5si engines currently on our shelves, photographed in the yard. Click any of them for the full photographs, mileage and specification.

BMW E91 325i N52B25 Engine 2007, 40,100 km1.695,00 €BMW E91 325i N52B25 Engine 2006, 110,900 km1.817,00 €BMW E91 325i N52B25 Engine 2008, 95,800 km1.883,00 €BMW E60 525i N52B25 Engine 2007, 156,600 km1.649,00 €BMW E90 325i N52B25 Engine 2006, 194,300 km2.014,00 €BMW E90 325i N52B25 Engine 2006, 182,900 km1.665,00 €BMW E90 325i N52B25 Engine 2008, 193,400 km1.757,00 €BMW E91 325i N52B25 Engine 2010, 203,800 km1.642,00 €BMW E60 525i N52B25 Engine 2010, 32,300 km1.510,00 €BMW E60 525i N52B25 Engine 2011, 58,400 km2.143,00 €BMW E90 325i N52B25 Engine 2005, 164,700 km2.139,00 €BMW E90 325i N52B25 Engine 2010, 181,900 km2.116,00 €

BMW E91 325i N52B25 Engine 2007, 40,100 km — 1.695,00 €, reduced from 2.800,00 €. It comes from a 2007 donor car with 40,100 km, and 29 units are available. The listing shows every side of the engine and the fitted parts.

BMW E91 325i N52B25 Engine 2006, 110,900 km — 1.817,00 €, reduced from 2.950,00 €. It comes from a 2006 donor car with 110,900 km, and 17 units are available. The listing shows every side of the engine and the fitted parts.

BMW E91 325i N52B25 Engine 2008, 95,800 km — 1.883,00 €, reduced from 3.300,00 €. It comes from a 2008 donor car with 95,800 km, and 21 units are available. Ask the desk for compression figures or extra photographs before you order.

BMW E60 525i N52B25 Engine 2007, 156,600 km — 1.649,00 €, reduced from 2.950,00 €. It comes from a 2007 donor car with 156,600 km, and 23 units are available. The listing shows every side of the engine and the fitted parts.

BMW E90 325i N52B25 Engine 2006, 194,300 km — 2.014,00 €, reduced from 3.150,00 €. It comes from a 2006 donor car with 194,300 km, and 24 units are available. Ask the desk for compression figures or extra photographs before you order.

BMW E90 325i N52B25 Engine 2006, 182,900 km — 1.665,00 €, reduced from 2.350,00 €. It comes from a 2006 donor car with 182,900 km, and 25 units are available. The listing shows every side of the engine and the fitted parts.

BMW E90 325i N52B25 Engine 2008, 193,400 km — 1.757,00 €, reduced from 2.750,00 €. It comes from a 2008 donor car with 193,400 km, and 11 units are available. Ask the desk for compression figures or extra photographs before you order.

BMW E91 325i N52B25 Engine 2010, 203,800 km — 1.642,00 €, reduced from 2.900,00 €. It comes from a 2010 donor car with 203,800 km, and 10 units are available. Ask the desk for compression figures or extra photographs before you order.

BMW E60 525i N52B25 Engine 2010, 32,300 km — 1.510,00 €, reduced from 2.850,00 €. It comes from a 2010 donor car with 32,300 km, and 23 units are available. Ask the desk for compression figures or extra photographs before you order.

BMW E60 525i N52B25 Engine 2011, 58,400 km — 2.143,00 €, reduced from 3.500,00 €. It comes from a 2011 donor car with 58,400 km, and 6 units are available. Ask the desk for compression figures or extra photographs before you order.

BMW E90 325i N52B25 Engine 2005, 164,700 km — 2.139,00 €, reduced from 3.100,00 €. It comes from a 2005 donor car with 164,700 km, and 17 units are available. The listing shows every side of the engine and the fitted parts.

BMW E90 325i N52B25 Engine 2010, 181,900 km — 2.116,00 €, reduced from 3.350,00 €. It comes from a 2010 donor car with 181,900 km, and 13 units are available. The listing shows every side of the engine and the fitted parts.

Will it fit my Z4 2.5si?

Will the N52B25 fit my BMW E85 Z4 2.5si?

The N52B25 is the original engine for the BMW E85 Z4 2.5si, which makes it the straightforward choice. The first Z4 roadster was built 2002–2008, and the N52B25 was produced 2004–2011, so check that your car's build date falls inside that window. Confirm the drive type (rear-drive or xDrive), the gearbox (manual or automatic) and the emissions standard, because these can change the sump, the flywheel and the software. Send us the VIN and we check all of it for you.

How much is a replacement engine for a BMW E85 Z4 2.5si?

We have 128 N52B25 engines in stock, priced from 1.421,00 € to 2.300,00 €. Delivery to your door is included, and the engine carries a 12-month warranty when fitted by a qualified workshop. Add fitting labour and the parts you replace at the same time — seals, cooling parts and mounts — to estimate the total.

Engine swaps and upgrades for the Z4 2.5si

These engines were fitted to other versions of the E85 at the factory, which makes them the most practical upgrades: the body was designed around them and many parts are shared.

Can I fit the M54B30 in my Z4 2.5si?

Yes, it is one of the more common upgrades. Both are petrol inline-6 engines, so the mounting points are similar, but the M54B30 needs its own wiring and engine control unit, the matching gearbox or clutch, and often a different sump, cooling and exhaust. The gain is 13 hp and 50 Nm. In Germany and most of Europe an engine swap must be inspected and registered.

Can I fit the S54B32 in my Z4 2.5si?

Yes, it is one of the more common upgrades. Both are petrol inline-6 engines, so the mounting points are similar, but the S54B32 needs its own wiring and engine control unit, the matching gearbox or clutch, and often a different sump, cooling and exhaust. The gain is 125 hp and 115 Nm. In Germany and most of Europe an engine swap must be inspected and registered.

Fitting a replacement engine in the Z4 2.5si

1. Inspect or replace the timing chain parts. Look at the guides and tensioner. On high-mileage engines, replacing them now costs far less than doing it later.
2. Reset VANOS adaptations. Clear the VANOS adaptations so the ECU learns the camshaft positions of the new engine.
3. Teach the Valvetronic limit stops. Run the Valvetronic learning routine so the ECU knows the eccentric shaft limits.
4. Fill with the right oil and prime it. Fill with new oil of the correct specification and a new filter. Crank with the fuel and ignition disabled until oil pressure builds.
5. Coding and adaptations. On modern BMWs, the engine ECU must be matched to the car's immobiliser (CAS, FEM or BDC). Reset adaptations, register the battery and clear faults with diagnostic software.
6. First start and leak check. Start the engine, let it idle and watch oil pressure, temperature and fault codes. Check for leaks and bleed the cooling system.
7. First 1,000 km. Drive gently for the first few hundred kilometres, vary the engine speed and avoid full load. Change the oil and filter after about 1,000 km to remove any assembly debris.

The full fitting and first-start procedure.

Z4 2.5si engine questions

How much power and torque does the BMW N52B25 have?

From the factory the BMW N52B25 makes 160 kW (218 HP) and 250 Nm of torque. It is a 2.5 liter (2,497 cc) inline 6, DOHC, 24 valve petrol engine with no turbo (naturally aspirated).

Without a turbo, the power builds smoothly with the revs. A clean air intake, healthy ignition and the correct fuel are key to getting the full figure.

A used engine reaches its factory numbers when it is fitted with the matching engine computer and software, and serviced with the right oil and filters. If the engine computer from your car is a different version, a specialist may need to code it.

Every N52B25 on our site lists its year and mileage. You can ask for extra photos, a close-up of the code stamp or a short video before you order.

See all N52 Engines · Search N52B25 in the shop

What is the BMW N52B25 engine?

The BMW N52B25 is a 2.5 liter (2,497 cc) petrol engine from the N52 family. It has an inline 6, DOHC, 24 valve layout with no turbo (naturally aspirated), and makes 160 kW (218 HP) with 250 Nm of torque. BMW built it from 2005 to 2011 and it meets the Euro 4 emission standard.

You find the N52B25 in the BMW E90 325i, BMW E91 325i, BMW E60 525i and BMW E87 125i. What we list: BMW N52 naturally aspirated petrol engines for E90, E60 and Z4.

At Autowerke Engines every N52B25 is a real used engine from our yard in Hamburg. Before a unit is listed, the yard checks the engine code against the listing, writes down the parts fitted to it, seals every opening and photographs the real engine you will receive. Each listing shows the year, the mileage and the price, so you can compare units side by side.

Not sure? Send us your VIN and your gearbox code. We match the engine family, the year window and the parts on the engine before anything is reserved, and the check is free.

See all N52 Engines · Search N52B25 in the shop

Can you check if an N52B25 fits my car with my VIN?

Yes, and it is free. Send the 17-character VIN of your car and, if you have it, the gearbox code. We check the engine family, the build year window and the parts your car needs.

For the N52B25, we confirm that your car was built with this code or with a version that can take it. BMW used it in the BMW E90 325i, BMW E91 325i, BMW E60 525i and BMW E87 125i.

We only reserve an engine once the match is confirmed, so you never pay for the wrong unit. You can reach the Hamburg desk by email at autowerkeengines@gmail.com, or by phone and WhatsApp on +49 15510 030835, Monday to Friday, 9:00 to 16:00 CET.

You can also use the VIN check on our site. It reads the year, the make, the model and the engine from the public vehicle register.

See all N52 Engines · Search N52B25 in the shop

How do I know a used N52B25 engine is in good shape?

Each engine in the yard is inspected in Hamburg. The code is matched to the listing, the parts on the engine are recorded, the openings are sealed and the real unit is photographed. An inspection certificate for the unit can travel with the order when you ask for it.

When you look at a listing, check the recorded mileage, the year and the photos of the ports and the stamp. Ask for photos of anything you want to see closer. You can ask for extra photos, a close-up of the code stamp or a short video before you order.

On a petrol engine like the N52B25, a careful fitter will also look at the spark plugs, the coils and the timing side before the engine goes in.

If the engine fails inside under normal use, the warranty covers you. Eligible engines come with a 12 months warranty from the delivery date. It covers internal mechanical failure under normal use and correct fitting by a qualified mechanic or workshop.

See all N52 Engines · Search N52B25 in the shop

How much is a replacement N52B25 engine for a BMW E87 125i?

A used N52B25 for the BMW E87 125i costs from about 1.400 € to 2.350 € in our yard. The price depends on the year, the mileage and the parts that come with the engine.

Shipping is a flat 249 € per order. It is added once at checkout and printed on the invoice, so there is no extra fee later. Inside the EU there is no import duty. Outside the EU, the receiver pays local duty and VAT.

A replacement engine is often much cheaper than rebuilding a damaged one, and much faster. The N52B25 you buy is photographed and checked in Hamburg before it is listed.

Eligible engines come with a 12 months warranty from the delivery date. It covers internal mechanical failure under normal use and correct fitting by a qualified mechanic or workshop. Not sure? Send us your VIN and your gearbox code. We match the engine family, the year window and the parts on the engine before anything is reserved, and the check is free.

See all N52 Engines · Search N52B25 in the shop

How much does a used BMW N52B25 engine cost?

A used BMW N52B25 engine in our yard usually costs between 1.400 € and 2.350 €. The exact price depends on the year, the mileage and the parts that come with the engine.

Our units show recorded mileage from about 22,000 km up to around 200,000 km. Lower mileage and more ancillaries mean a higher price. Each listing shows its own price, and the price you see is the price you pay. Prices include VAT for private buyers.

Shipping is a flat 249 € per order. It is added once at checkout and printed on the invoice, so there is no extra fee later. If you order a gearbox or a second engine on the same order, the fee is still charged once.

Inside the EU there is no import duty. For the UK and other non-EU countries, import duty and local VAT are paid by the receiver, and we supply a commercial invoice.

See all N52 Engines · Search N52B25 in the shop

Which cars use the BMW N52B25 engine?

BMW fitted the N52B25 to the BMW E90 325i, BMW E91 325i, BMW E60 525i and BMW E87 125i. These cars were built with this engine from about 2005 to 2011.

The badge on the boot is not enough to be sure. The same model name can hide two different engines, for example after a facelift or a change in emission rules. Always read the engine code stamped on the block, or look it up with your VIN.

Other engines in the same N52 family are the N52B30 (258 HP). They look alike but differ in power, parts and electronics, so they are not always a direct swap.

Not sure? Send us your VIN and your gearbox code. We match the engine family, the year window and the parts on the engine before anything is reserved, and the check is free.

See all N52 Engines · Search N52B25 in the shop

Will the N52B25 engine fit my BMW E87 125i?

Yes, if your BMW E87 125i was built with the N52B25. BMW used this 2.5 liter (2,497 cc) petrol engine with 160 kW (218 HP) in the E87 125i from about 2005 to 2011.

In our records the N52B25 is the engine for the E87 125i, which makes the match simple. Still, check the code on your old engine or send us your VIN.

Also tell us if your E87 has a manual or an automatic gearbox. The flywheel or the flex plate and some sensors depend on it.

Not sure? Send us your VIN and your gearbox code. We match the engine family, the year window and the parts on the engine before anything is reserved, and the check is free.

See all N52 Engines · Search N52B25 in the shop

Delivery, warranty and payment

Before a Z4 2.5si engine leaves our Hamburg yard it is drained of oil and coolant, every opening is sealed, and it is strapped to a pallet and wrapped. We send photographs of the packed unit and the tracking details.

Delivery is door to door and included in the price. Most European addresses receive the engine within five to ten working days; Germany and its neighbours are usually faster.

Every engine carries a 12-month warranty on eligible internal failure when a qualified workshop fits it with new fluids and filters. Payment is by card, bank transfer or crypto; your invoice is emailed as soon as you order.

All E85 engines · N52 engine guide · Send us your VIN