B58 Turbo Swap Guide

This guide follows BMW's own repair instructions for the 2019 and newer G20 M340i xDrive (B58, second generation). The same turbo comes out the same way on most B58 cars. We list where the F-series cars (340i, 440i, M240i) differ. Upgrading? The swap is the same job as a stock replacement. The tune, the fuel and the parts around it are what change.

Engine stays inThe turbo comes out from below. Plan on unbolting the passenger engine mount for room.

7 new nutsM7 flange nuts, tightened in five passes: 10, 10, 16, 16, 16 Nm.

Prime itFill the new turbo with BMW's turbo additive (17 ml) and fresh oil before it ever spins.

IA EURO illustration of the BMW B58 turbo and exhaust manifold, numbered: expansion bellows, exhaust manifold rail, electric wastegate actuator, clean air inlet, charge air outlet, turbine housing — The B58 turbo and the exhaust manifold for cylinders 3 and 4 are one cast part. 1 expansion bellows (never bend them), 2 exhaust manifold rail, 3 electric wastegate actuator (never pull on it), 4 clean air inlet, 5 charge air outlet, 6 turbine housing (lift it here).

Read this before you start

Order the right manifold gasket. The G20 M340i uses 11658669733. Earlier F-series B58 cars use a different gasket (11657643149). Check your car before you order.
Bigger turbo means a tune first. A bigger turbo on the stock software gains nothing. Have your tune (MHD or similar) ready before the car leaves the stands. Newer G-series DMEs can be locked and may need a bench unlock before any flash tool can write to them, so check yours before you buy the turbo.
Catted downpipes only. Remove the catalytic converter and you have an illegal car and a failed inspection.
Plan for coolant and oil. The turbo's coolant lines drain a lot. You will drain the high-temperature cooling circuit and refill and bleed it after. Do an oil change with the job. A fresh turbo should never see old oil.

Tools and parts

Jack stands or a lift. This is an underbody job on the G20.
22 mm oxygen sensor socket, torque wrench that reads down to 5 Nm, plastic trim tools.
Coolant drain pan, fresh BMW coolant, a vacuum coolant filler if you have one.
BMW turbo additive, 17 ml (BMW 83195B305D6), and fresh engine oil to prime the turbo.
All the one-time seals, nuts and bolts below. Never reuse them.

Gen 2 kit (G20 M340i, Z4, 2020 X3/X4 M40i) Gen 1 kit (340i, 440i, M240i, 540i, 740i)

The passenger engine mount

BMW's own turbo procedure for the G20 leaves the engine mounts alone. On the shop floor, the passenger (right) engine mount usually has to come off so the engine can be raised a little and the turbo has room to come out. If you do it:

Support the engine from above with an engine support bar before you touch the mount. BMW raises the engine only 10 mm for its mount job.
Lower the engine fully onto the mounts before you tighten anything, so nothing is preloaded.
Engine mount to front axle support: M8, 19 Nm. Mount bracket to engine: M10, 38 Nm. Mount to bracket: new M12 bolt, 110 Nm.
Replacing the mount while you're there? The passenger side is BMW 22116860472 on the G20 M340i.

IA EURO illustration of the BMW B58 engine mounts with the passenger side mount highlighted — The passenger (right) engine mount is the one highlighted, BMW 22116860472 on the G20 M340i. New M12 bolt, 110 Nm.

Removing the turbo: the short version

Engine cold. Hood to the service position. Remove the engine covers, the front-end struts and the top cross braces.
Remove the fan cowl, the intake silencer housing, the engine ventilation line and the clean air pipe.

Remove the charge air line from the turbo outlet. Set the auxiliary coolant pump aside on its bracket.
Remove the heated vent adapter from the turbo inlet (two screws). Move the positive battery cable holder aside.
Unplug and remove both oxygen sensors. The grey cable is the rear (monitoring) sensor, the black cable is the front one.
Underneath: remove the underbody panels, the stiffening plate (xDrive has its own plate) and the steering gear cover.
Remove the turbo oil return line (two screws, have rags ready).
Remove the tunnel brace, the rear braces and the complete exhaust system with a helper. Then remove the catalytic converter: pressure hose off, V-band clamp loose, holder nuts off.

IA EURO illustration of the BMW B58 catalytic converter, numbered: V-band clamp at the turbo, front oxygen sensor, rear monitoring sensor, converter holder, connection to the rest of the exhaust — The stock catalytic converter, the part a catted downpipe replaces. 1 V-band clamp at the turbo (new, 19 Nm), 2 front oxygen sensor, 3 rear monitoring sensor (both 50 Nm), 4 converter holder (new M8 nut, 19 Nm), 5 to the rest of the exhaust.

IA EURO illustration of the BMW B58 catalytic converter exploded: V-band clamp, gasket ring, converter, holder brackets and the muffler clamp, with the gasket ring highlighted — The converter taken apart: V-band clamp, gasket ring (new every time), the converter, its holder brackets and the clamp to the rest of the exhaust. A catted downpipe replaces the converter and reuses this layout.

Drain the high-temperature coolant circuit at the bottom right radiator hose.
Remove both turbo heat shields. Unclip the coolant return line at the turbo's coolant pump. Remove the oil feed line, the coolant feed line and the turbo support bracket.
BMW clamps the manifold with a special tool so the expansion bellows cannot flex. If you don't have it, support the turbo by the turbine housing the whole time and never let it hang on the bellows.
Remove the 7 flange nuts in order, 7 to 1. The bottom of the manifold is clamped by a slide rail, not bolted. Support the turbo, slide the rail out and lower the turbo out.

Don't pull on the electric wastegate actuator or its rod. If the turbo is stuck, push and pry on the turbine housing and the manifold only. A bent actuator is a new turbo.

The oil feed line: the one that kills engines

The oil feed line carries pressurized engine oil to the turbo's bearings. A tired seal here leaks oil fast, and a leak that drops the oil level can starve the whole engine, not just the turbo.

IA EURO illustration of the BMW B58 turbo oil feed line, numbered: seal at each end, the steel line and the flexible section, with a failure mark at the seals — The turbo oil feed line. 1 and 2: the seals at each end, new every time the line comes off. 3 the steel line. 4 the flexible section: check it for cracks and seepage. The black ! marks the seals: tired seals leak here, and a leak here can starve the engine of oil (our shop-floor call).

IA EURO illustration of the BMW B58 turbo oil feed and return lines with their four O-rings highlighted — Both turbo oil lines. Feed line O-ring 11427590576 at each end, return line O-ring 11427590577 at each end. All four are new every time a line comes off.

IA EURO illustration of the BMW B58 turbo coolant lines with the line from the auxiliary coolant pump highlighted — The turbo's coolant lines. Highlighted: the line from the electric auxiliary coolant pump to the turbo. New O-rings on every coolant line you open.

Never reuse the oil feed seals. BMW renews them every time the line comes off. Our call: if the line has 60,000 miles or more on it, replace the line too, not just the seals. It's cheap next to an engine.

Just replacing the lines? On the G20, BMW's jobs for the oil feed line, the coolant feed line and the coolant return line all take the turbo out. If one of those is leaking, it's a turbo-out job, so do every seal while you're in there. The oil return line is the easy one: stiffening plate off, two bolts.

Installing the turbo

IA EURO illustration of the BMW B58 turbo exploded from the cylinder head with the manifold gasket, clamping strip and outlet gasket ring highlighted — Everything between the turbo and the head. The manifold gasket, the clamping strip and the gasket ring at the outlet are new every time the turbo comes off.

Check the upper manifold studs: they stick out 30 mm from the head. Screw them in or out to match.
Clean both sealing faces with plastic scrapers only. No sandpaper or abrasive pads, they cause leaks.
New turbo: move the oil feed line, coolant feed line and coolant return line over with new seals. Pour the 17 ml of turbo additive into the oil feed bore, then fill it with fresh engine oil.
New manifold gasket. Fit the turbo, slide the rail back in with its part number facing out, then run 7 new flange nuts down.
Tighten the nuts in order 1 to 7, five passes: 10, 10, 16, 16, 16 Nm.
Coolant feed line, support bracket (new bolts), oil feed line (new sealing ring), coolant return line (click it into the pump), both heat shields (new bolts).
Oil return line with new sealing rings. If you replaced the return line, clean the pipe it plugs into on the oil pan first. It cokes up.
Catalytic converter with a new seal, a new V-band clamp and a new holder nut. New pressure hose.
Exhaust back in with no strain on it, tightened from the rear muffler forward. Oxygen sensors with a light coat of BMW sensor paste on the threads only.
Refill and bleed the high-temperature cooling circuit. Change the oil. Check the oil level hot.

Torque specs (G20 M340i xDrive)

Joint	Size	Torque
Manifold to cylinder head, new flange nuts, order 1 to 7	M7	10, 10, 16, 16, 16 Nm
Turbo support to block, new bolts	M8x20	19 Nm
Turbo to support, new bolt	M8x25	19 Nm
Oil feed line to block (new sealing ring)	M6x12	8 Nm
Oil and coolant lines to turbo	M6x12	8 Nm
Coolant feed line to block	M6x12	8 Nm
Coolant return line bracket to block	M6x12	8 Nm
Oil return line, turbo end and block end	M6x12	8 Nm
Heat shields to head, new bolts	M8x12	19 Nm
Heat shield to clamping strip, new bolt	M6x16	8 Nm
Heated vent adapter to turbo	M6x26	8 Nm
Charge air line to throttle body	M6x30	8 Nm
Catalytic converter to turbo, new V-band clamp	V-band	19 Nm
Catalytic converter to holder, new nut	M8	19 Nm
Oxygen sensors	M18x1.5	50 Nm
Exhaust V-clip at the converter	V-clip	25 Nm
Exhaust ribbon clamp	M8 / M10	26 / 55 Nm
Front stiffening plate, xDrive, new bolts	M8	25 Nm + 70°
Rear Y-strut, new bolts	M10x25	56 Nm + 90°
Front-end struts	bolt	56 Nm

One-time parts to have on the bench (G20 M340i)

Part	BMW number	Qty
Exhaust manifold/turbo gasket	11658669733	1
Flange nut with spring washer, M7	11658670587	7
Oil feed line O-ring	11427590576	2
Oil return line O-ring	11427590577	2
Coolant line O-ring	11537590575	1
Turbo to converter gasket ring	18328612538	1
Turbo to converter V-band clamp	18328612537	1
Manifold stud (spare, in case one snaps)	11127647711	2

F-series 340i, 440i and M240i: same O-rings and nuts, but the manifold gasket is 11657643149.

What breaks, and what to do about it

A manifold stud snaps or comes out with the nut. Have spare studs on hand. Set the new ones to 30 mm out of the head.
The turbo is stuck on the studs. Pry on the turbine housing and manifold only. Never on the actuator, the compressor housing or the bellows.
Coolant everywhere. Drain the circuit first, and keep the open ports covered so nothing falls in.
Coked oil return pipe. If you replace the return line, clean the pipe it plugs into on the oil pan.
Plastic clips and connectors. Coolant and vent lines lock with an audible click. No click means it isn't locked. Never pull a connector by its wires.
Seized oxygen sensors. Use the 22 mm sensor socket. Grease new threads with sensor paste only, never the tip.

Catch can: where it goes

A catch can is a small can that collects the oil mist in the engine's crankcase vent gas before it reaches the turbo and intake. On the B58, the engine ventilation line runs from the valve cover to a heated adapter on the turbo inlet. The catch can goes in that line: valve cover to the can, can to the turbo inlet.

Catch can routing on the B58: valve cover vent, then the can, then the heated adapter on the turbo inlet. The fuel tank vent line stays on its own port.

Leave the fuel tank vent line alone. On the G20 it clips into the same area. It carries fuel vapor and must never run through the catch can.
Keep the heated adapter. It stops the vent gas from freezing at the turbo inlet in winter.
A cheap can works. A basic baffled plastic can does the same job as a billet one. Just mount it away from the exhaust and use hose rated for oil and heat.
Empty it at every oil change, more often in winter. Some states don't allow changes to the crankcase vent system on a street car, so check yours.

Top mount or bottom mount

Bottom mount (stock location, upgraded turbo): bolts in exactly like this guide. No fabrication, and the car looks stock with the hood open.
Top mount: a new tubular manifold puts a big turbo up top where you can see it. Expect a full kit with its own downpipe, wastegates, charge pipes and oil and coolant lines, and more labor. Follow the kit maker's instructions for anything this guide doesn't cover.

After the job

Change the oil with the new turbo. Our B58 oil change kit for the G20 M340i has everything (F-series cars: this kit).
Bleed the cooling system fully before you drive.
Flash the tune for your turbo before you push it. Then idle, check for oil and coolant leaks, and drive gently while you log boost and temperatures.

Steps and torque values follow BMW's repair instructions for the G20 M340i xDrive. Always check the instructions for your exact car and for your turbo kit.