Troubleshooting BMW E46 Common Problem Areas

We explore everything you need to know about the popular E46 320d and its common problem areas

Troubleshooting BMW E46 Common Problem AreasOne of BMW’s biggest selling models is now a shade over 20-years-old. Wounded by the success of the Audi A4 1.9 TDI, BMW tried the M41-engined E36 318tds stopgap but despite modest sales and an on paper 90hp, it was never very good with the 1665cc M41 being woefully short of lowand mid-range grunt. No, the 1999 E46 320d was the real deal with its new 16-valve 2-litre turbodiesel knocking out 136hp and 206lb ft of torque. An 84mm bore and 88mm stroke gave 1951cc. It was an immediate success and the new M47 also found its way into the E39 as the 2000 model year 520d (LHD only).

BMW were not standing still though and in late 2001, the revised facelift 320d arrived with a new M47N engine. Now with common rail and refinements such as intake swirl flaps, and a mass airflow sensor (MAF), the 320d put out an impressive 150hp and 243lb ft of torque with the stroke lengthened to 90mm to give 1995cc. The 320d was now available as an automatic. Late 2003 saw the introduction of a standard six-speed manual gearbox and a detuned 318d for the UK with 115hp and 195lb ft – these had been available in Europe since 2001.

A 320td Compact was also launched in 2001 with its UK introduction a bit later, although we never had the 318td. A 320cd Coupé was launched here for late 2003. Production ended with the Saloons going in 1996, the final Tourings and Coupés in 2006

1. The original 136hp cars are getting rare now – as you’d expect with a 19/20-year-old car. The engines were very reliable but injection pump failure was the bugbear in old age, along with inevitable injector and turbo trouble. Used parts are quite scarce now and new stuff probably outstrips the value of the car itself. Tuning boxes such as the HOPA unit were quite popular back in the day. The136hp 320d was mainly sold in pretty basic SE trim but air-con was standard.

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2. The 150hp 320d was faster but they are more troublesome unless you take some basic precautions. Those swirl flaps have just got to come out. No, they don’t all fail and most are still okay after 15-years but if one comes loose, it’s goodbye engine, and probably a financial write-off. Blanking plates are cheap but it’s quite a fiddly job to remove and replace the manifold. It’s not the two-hours of work most internet mechanics say it is unless you’ve done loads before.

3. There are a plethora of braided vacuum pipes under the manifold. These all plug into a plastic vacuum tube that runs under the inlet manifold. These are for the vacuum capsules, the radiator blind and the swirl flap actuator as well as the turbo actuator on pre- 2003 cars, mainly five-speed ones. The pipes deteriorate over time and one vacuum leak will cause trouble. With the manifold off, it’s essential to replace every pipe. Buy a reel of proper stuff and replace each pipe one by one.

4. The 318d cars don’t have swirl flaps so that’s one less thing to worry about. They still have those pesky vacuum pipes though and it’s worth replacing them. Post-2003 318d and 320d cars had a new type of turbo with an electronic waste gate actuator control as opposed to a vacuum operation, introduced at around the time the six-speed manual box was phased-in. These are no less awful to replace than any other E46 diesel turbo, an absolutely delightful task…

5. The turbo is bolted to the exhaust manifold with three hardened steel spline bolts best removed with a multi-point 12mm socket. They’re accessed through holes in the base of the air cleaner housing once the steel plate is unclipped. These are easy enough as is the oil feed pipe, but the two turbo-to-exhaust downpipe nuts are an absolute swine. A good lead light, various wobbly socket extensions, and a lot of patience, are the key. You can fit a decat downpipe (ideal when the original flexy joint fails) that makes reassembly a whole lot easier.

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6. The dual mass flywheel on six-speed cars is known to be a weak point. Rattling or a strange vibration when the clutch is depressed is a sign that the flywheel centre bearing is on the way out, rattling at idle means it’s really grim. Good used ones are rare, new ones are £300+. Solid flywheel conversions are an unknown quantity – we’ve heard of them breaking the crank on Ford units and really, they’re not cheap enough to be worth the risk. Five-speed flywheels don’t last forever but they were generally much better.

7. Other engine issues centre around the front crank pulley and the crankcase breather. The pulley is two piece with a rubber damper sleeve and over time this delaminates and the outer pulley can come loose. Good used ones are cheap enough and shared with the later E90, E60 and 1 Series 2.0 units. The crankcase breather on top of the cam cover was changed from the original ‘loo roll’ unit to the later Vortex breather so long ago that you’re unlikely to find an original – these could block up causing excess pressure and turbo failure. They are quick and easy to replace.

8. Injector problems come and go and these days, decent reconditioned units aren’t expensive. The design changed from the 136 to 150hp cars, and then again around 2003 when the E60 arrived with different connectors and feed pipe angle. They are best replaced with the engine hot. Intercooler to EGR boost pipes can split around the upper rubber section but these are easily replaced with new rubber curved pipes from eBay. Split hoses cause loss of boost and clouds of black smoke. Glow plugs can fail as can the module, requiring manifold removal.

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9. The E46 has it’s own little peccadillos, of course. Rusty arches are a given on any age example (they’re all at least 14-years old now) and broken window regulators are common but not too bad to replace. The airbag light can be sorted with a cheap eBay resistor under the front seat to bypass a broken seat occupancy sensor that fools the car into thinking the seat is always occupied and deploying both front airbags in a crash. Faulty central locking will be a GM5 module, hiding behind the glovebox. A used one can be fitted and coded to the car in about an hour. E46 handbrakes are notoriously terrible unless rebuilt with genuine OE parts.

10. Maintenance is key. Keeping the arches clean slows down rust and spraying WD40, spray grease or silicon spray into the window channels gives the windows regulators an easier time. Change the oil and filter every 8000-miles. On Tourings, spray a good penetrating fluid like PlusGas into the tailgate hinges for the tailgate and the glass hatch as they seize and snap. The E46 has two fuel pumps, one in the tank and other under the front passenger floor. A failing one can hum noisily as do cheap aftermarket replacements. An E90 in-tank pump is much more powerful and can apparently be modified and fitted to get rid of the under floor pump.

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