N55 Turbo Oil and Coolant Line Leaks

1. Oil feed, oil return and coolant line seals
2. 15 flange nuts and 6 gaskets at the head
3. Downpipe gasket and V-band clamp
4. Charge pipe joint, leak-test it after

N55 wet with oil or coolant around the turbo lines? BMW's N55 turbo job says the oil feed line can only be replaced with the turbo off. Pulling the turbo, for a leak or a bigger one? Here is every seal BMW renews.

Feed line

BMW: the oil feed line can only be replaced with the turbo out. BMW's N55 text says no such thing about the oil return or coolant lines.

33 lb

The turbo and exhaust manifold are one piece, about 15 kg. It comes out from below, toward the gearbox.

15 nuts

hold it to the head. New nuts, 8 Nm in order 1 to 15, then 13 Nm in the same order.

Before you pull it

• Check the easy stuff first. BMW's general turbo troubleshooting says a leak at the oil feed or return is often a loose bolt or a bad seal at that joint, so check the line bolts and seals first.
• Not every oily turbo is the turbo. The same BMW note says oil from a clogged return or high crankcase pressure is not the turbo's fault. A worn PCV valve can push oil out of joints that were fine.
• Return or coolant line only? BMW's N55 turbo job does not say the turbo has to come off for those. Procedures differ by version, so get the steps for your car by VIN from a BMW dealer or shop.
• Going big turbo anyway? The turbo is coming off regardless. Use the seal list below so you only do it once.

What you need

When the turbo comes off, BMW renews every seal it touches. Nothing gets reused.

Part	BMW number	Qty
Oil line O-ring	11 42 7 590 576	2
Oil line O-ring	11 42 7 590 577	2 (1 on some cars)
Coolant line O-ring	11 53 7 590 575	3 (1 on some cars)
Turbo flange nut (M7)	18 40 7 502 196	15
Manifold gasket ring	11 65 7 593 303	6
Downpipe V-band clamp, earlier cars	11 65 7 620 508	1
Downpipe gasket, earlier cars	18 30 7 553 601	1
Downpipe V-band clamp, later cars	18 30 7 606 136	1
Downpipe gasket ring, later cars	18 30 7 581 970	1

Earlier cars: E-series (135i, 335i, X1, X5, X6), F30 335i sedan, F25 X3, F10 535i to 2013, 740i. Later cars: F22 and F23 M235i, F32, F33 and F36 435i, F34 335i GT, F15 X5, F16 X6, F87 M2, F10 535i from 2014. The 640i and X4 can be either. Your VIN decides. Also: new turbo holder screws (BMW says replace them) and fresh BMW coolant, since BMW says never reuse it.

We stock this whole list as one kit, in two versions: earlier cars or later cars, matched to the downpipe gasket and clamp your car takes.

Earlier cars kit Later cars kit

How BMW does it with the turbo off

The prep work depends on the car: usually the charge air cooler or its duct, the downpipe, and the right engine mount and support arm, and on some cars the coolant pump and thermostat. xDrive cars also lose a brace underneath.

1. Cold engine, coolant drained. BMW: only work on a cooled-down engine.
2. Coolant lines off. At the block, then the single bolt at the turbo that holds both the supply and return line. New seals.
3. Oil return line off, at the turbo and at the bottom of the block. Expect oil to run out.
4. Oil feed line loose at the block, and unplug the blow-off valve.
5. Turbo holder: one bolt out, the others loosened but left in.
6. 15 flange nuts off. Nuts 1 to 5 from above, 6 to 15 from below. Lower the 33 lb module out toward the gearbox.
7. Now the oil feed line comes off the turbo. BMW: it can only be replaced with the turbo out.
8. Back in with all new seals, nuts and clamp. Fit the module without stress, nuts to 8 Nm in order 1 to 15, then 13 Nm in order 1 to 15. Then the holder, lines and downpipe to the torques below.
9. Refill and bleed the coolant. Ignition on, engine off, heat on max, blower on low, floor the gas pedal for 10 seconds. The electric pump runs about 12 minutes. Top up to 100 ml (about 6 mm) above MAX.
10. Leak test. BMW finishes with a leak test of the intake side. At home: check every charge pipe joint you touched before you send boost through it.

Torque specs

Joint	Torque
Turbo flange nuts (new, M7)	8 Nm, then 13 Nm (115 in-lb)
Turbo holder (new screws, M8)	20 Nm (15 ft-lb)
Oil feed line, oil return line (each end)	8 Nm (71 in-lb)
Coolant lines at the turbo	8 Nm (71 in-lb)
Coolant feed line at the block	8.5 Nm (75 in-lb)
Heat shield	8 Nm (71 in-lb)
Downpipe V-band clamp (new)	13 Nm (115 in-lb)

Sources: BMW's repair instructions for the N55 engine (turbocharger removal and installation, 11 65 020, and the N55 cooling system bleed), BMW's torque tables for the N55, and BMW's parts catalog. Prep work differs by model and drive type. This guide is our own summary. If you are not comfortable doing the work, have a shop do it.