The BMW E46 320d with the M47 engine is one of the most popular base diesel combinations in the 3 Series. The M47 four-cylinder diesel has a reputation for longevity: well-maintained cars routinely pass 186,000 miles. The main running concerns are the DPF and EGR (late post-facelift models), crankcase ventilation, and front axle bushings.
The M47 Engine
The M47 is a 2.0-liter four-cylinder diesel produced from 1998 to 2007. It’s the reliable predecessor to the N47, free of the problematic timing chain arrangement — the chain sits up front. Output depends on the version: 136 hp for the pre-facelift M47 and 150 hp for the LCI M47TÜ, with peak torque of 243 lb-ft.
The diesel particulate filter (DPF) was factory-fitted only on late LCI models from around 2004. On earlier build years it can be retrofitted.
Maintenance Schedule
| Service | Interval |
|---|---|
| Oil change (5W-30 LL-04) | every 12,400 miles / 1 year |
| Fuel filter | every 37,000 miles |
| Air filter / cabin air filter | every 25,000 miles |
| Brake fluid | every 2 years |
| Front brake rotors and pads | 37,000–62,000 miles |
| EGR cleaning | as needed |
| DPF cleaning (LCI only) | 93,000–124,000 miles |
The oil change interval is defined as Longlife — 12,400 miles or one year. Real-world wear depends heavily on conditions: short trips and high loads call for more frequent servicing than the schedule formally requires.
Typical Weak Spots
Crankcase Ventilation (KGE, Cyclone Separator)
This is one of the most common issues to address. The diaphragm in the intake manifold tears, and the engine starts pulling in unmetered air. The result is a rough idle and increased oil consumption. Repair with the genuine kit is usually inexpensive.
Intake Manifold Swirl Flaps (LCI M47TÜ)
The swirl flaps in the intake manifold break off and can be sucked into the engine. The telltale code is 493B. In practice, the fix is either blanking plates in place of the flaps or a used intake manifold.
EGR Valve: Carbon Buildup
The valve cakes up with soot, primarily on short trips. Symptoms are power loss, limp mode, and code 490A. Most of the time a cleaning is enough. Related codes for the same assembly: 4905 — EGR position sensor, 490D — EGR stuck open.
Front Axle Control Arms and Bushings
The lower control arms and tension struts wear out early. Symptoms are vague steering and a clunk over bumps.
Hydraulic Engine Mounts
It comes up periodically: a mount starts leaking oil and vibration appears at idle. Replacement is an independent-shop job and falls into the moderate-cost category.
What Shops See in Practice
The most common reason owners bring these cars in is crankcase ventilation: a torn diaphragm causes an unstable idle that owners sometimes mistake for an injector or EGR fault. The second most common complaint is a carboned-up EGR on cars used mostly for short trips.
A separate group is the LCI swirl flaps. Blanking plates or a used manifold are the standard solution here, not the exception. On the suspension side, front axle control arms come through regularly: their service life is noticeably shorter than the engine’s.
Diagnostics
- Check DPF regeneration.
- Clean the EGR system and recalibrate the actuator.
- Test the injectors.
- Run a glow plug diagnostic.
- Check the vacuum system.
- Visually inspect the front axle bushings and control arms, plus the condition of the engine mounts.
- Pull the codes; for the EGR circuit, watch for 490A, 4905, and 490D, and for the flaps, 493B.
Buying Advice
The E46 320d ranks among the most reliable BMW diesels built before 2010. During an inspection, check the crankcase ventilation, the swirl flaps (on LCI cars), the EGR, and the front axle bushings. A well-kept post-facelift car with up to 155,000 miles and a documented service history is a very solid everyday diesel.
Related Systems
BMW water pumps differ by drive type: the N52/N54/N55 use an electric pump, the diesels use a mechanical one, and the B47/B48/B58 get their own dedicated units. A pump failure leads to overheating, with consequences comparable to an engine rebuild.
For the intake manifold, the practice looks like this: cleaning (including walnut blasting), full replacement of the assembly, or a repair that restores the swirl flaps. For diesels this work becomes relevant from roughly 75,000 miles; for the direct-injection N53/N54 engines, from 50,000 miles.
On the exhaust side, there are OEM-spec diesel particulate filter replacements for four- and six-cylinder engines, plus aftermarket alternatives. After replacement, DPF adaptation is mandatory.
FAQ
How much horsepower does the BMW E46 320d have?
Depending on the model year — 136 hp (pre-facelift M47) or 150 hp (LCI M47TÜ), with up to 243 lb-ft of torque.
Does the E46 320d have a diesel particulate filter?
From the factory, the DPF was fitted only to late LCI models from around 2004. Earlier cars can be retrofitted.
Is the E46 320d worth buying?
Yes. With a solid service history, a working crankcase ventilation system, and blanked or replaced swirl flaps, it’s a very economical highway diesel.
Disputed Points in the Source
- The M47 is described as reliable and durable, free of chain problems, while its successor the N47 is portrayed as problematic. This is an evaluative contrast, and no supporting data is given for it.
- The oil change interval — 12,400 miles / 1 year (Longlife) — sits alongside a general recommendation covering long periods of inactivity and heavy load, but the source never explains how the two relate.
Bottom Line
The key takeaway: the E46 320d’s reliability rests not on the engine itself but on the condition of the ancillaries and the recirculation circuit. Crankcase ventilation, EGR, swirl flaps, and front axle control arms determine whether the car will be trouble-free. Check the crankcase ventilation first during an inspection, along with blanked or replaced swirl flaps — more often than not, they decide the outcome of the purchase.