Q. Why should I be concerned if my water pump has a plastic impeller?
A. Model year 1995, most, if not all, 1996, and even some very early 1997 M3s were equipped with the plastic impeller water pump. The unofficial build date cut off for the plastic impeller is 10/96 (check driver side door jamb to verify build date). If you have a 1996 or early build 1997 M3 and are unsure if the improved metal impeller water pump has been installed, consult your dealership as the water pump needs to be removed to determine the impeller type (there is no other way of verifying). Plastic impeller water pumps have commonly failed without warning at around 60K miles and up. The result is sometimes a badly overheated engine that can cost thousands of dollars to repair if your warranty has expired. Note that in 2001, BMW has reintroduced an improved durability plastic impeller water pump for all vehicles.
BMW Water Pump (metal impeller; remanufactured)
Q. How long should I wait for the engine to warm up?
A. Because an oil temperature gauge is not provided with the vehicle, it is not possible to determine the precise engine temperature. However, it is possible to approximate a safe operating temperature. As a general rule, engine oil is most efficient above 180° F. Using an ambient temperature of 32° F, begin by allowing the vehicle to idle for no more than one minute. Begin driving, using as little throttle as possible (no more than half throttle), while keeping the engine speed below 3000 RPM and above 1500 RPM between shifts. The coolant temperature will slowly creep up and level off at the midpoint. At this point your engine oil should be above 100° F, however it will still be relatively cold so stay below 4000 RPM with no more than ¾ throttle usage. Depending on your driving and environmental conditions, an additional five to ten minutes may be required to reach the magic 180° F mark. After that, full throttle and limited high RPM visits are acceptable, but it would be a good idea to wait a few additional minutes to ensure you are at optimum engine operating temperature.
Q. What is the firing order of the M3 engine?
A. The cylinders fire in the following order: 1 & 5, 3 & 6, 2 & 4.
Q. What OEM spark plugs are used in the M3 engine?
A. Depending on the engine type, the two OEM brands are Bosch and NGK. For the proper spark plug part number, refer to the spark plug application chart at Unofficial BMW at http://www.unofficialbmw.com/images/sparkplugchart.jpg.
Q. What is the oxygen sensor fault code?
A. One of the more common causes of the check engine light is a failing or failed oxygen sensor (also referred to as a lambda probe). The 1995 M3s had only one oxygen sensor (located before the catalytic converter) due to OBD I standards and the 1996-1999 M3s had four oxygen sensors (two before and two located after the catalytic converter) due to more stringent OBD II standards. In short, the oxygen sensor measures the air/fuel mixture and transmits the signal to the DME which attempts to achieve the stoichiometric air:fuel ratio of 14.7:1 (or a Lambda of one). Running the vehicle with a failed oxygen sensor is not overly harmful, but efficiency is reduced because the vehicle will be running excessively rich; a default setting of the DME to reduce any probability of damage when no signal is present.
Q. What is the tapping noise near the top of my engine?
A. The tapping noise is often attributed to the hydraulic lifters in a low oil condition. Oil starvation also occurs during prolonged hard turns and is pronounced with an initial low oil state. Detailed oil starvation occurrences and solutions have been outlined below thanks to Edgar Bernard who spoke with Gregg Forde, chief mechanic of PTG (edited).
The US M3 engine will have oil starvation problems on left handed, high G corners at limited duration (roughly 10 seconds). It is a combination of oil starvation and oil foaming. A temporary remedy is to put 1 to 1-1/2 quarts of extra oil in the crankcase during track events. The E36 M3 engine does not experience the same problems as the E30 M3 engine when the oil is over filled. (The E30 M3 engine will blow or leak oil out of the rear engine seal if too much oil is used.) A low cost fix to the problem is to install the M3 Lightweight oil pan/pump kit. The kit has two pickup points in the oil pan and is indeed tricked. PTG has the kit for around $1600 with the gasket (should be under $100). The US M3 engine produces approximately four bars of oil pressure in the block and one bar in the head.
Q. What is the grinding noise when I start my M3 in cold weather?
A. The noise is most likely a delayed actuation of the starter gear causing it to remain in partial mesh and consequently grind with the ring gear for a longer period than normal. This problem is exacerbated in cold weather and is often solved by replacing the starter provided the dealer can confirm the noise. If replacement of the starter is not possible, simply release the key sooner on startup, perhaps after one or two engine revolutions.
Q. What is the ticking noise after I turn off my M3?
A. The ticking noise is due to the rapid cooling of the various metals in your exhaust system and is completely normal.
Q. How can I check my engine’s fault codes without a special tool? (1995 M3 only)
A. The procedure only works on 1995 (OBD I only; OBD II vehicles require a special scan tool) M3s and will not work on later models. Instructions on how to retrieve and interpret the fault codes can be found at Unofficial BMW at http://www.unofficialbmw.com/repair_faqs/motronic.html.