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Smoking, Oil Consumption and Oil leaks

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Cars prone to these symptoms:

  • 318 E46 (2001 – 2005) – N42 engine – facelift
  • 320 E90 (2005 – 2009) – N46 engine
  • X5 4.4 , 4.6, 4.8 (2000 – 2006)
  • 735, 745, 750 E65 E66 (2002 – 2008)

Oil leaks:

The seals, gaskets and o’rings all become hard due to age and heat. The most common areas is the

  • sump,
  • vacuum pump
  • oil filter housing
  • dipstick tube
  • tappet cover gasket
  • Oil separator (breather valve)
  • Oil filler cap
  • The list goes on

The 318 E46 Facelift and 320 E90 have the over sensitive engines and do have serious oil leaks.

The good thing about oil leaks is that they can be repaired. The changing of most seals, gaskets and o’rings will resolve this. It can be costly to do it all at once so it’s best to do it in stages as the leaks occur.

Most mechanics will quote you for a new vacuum pump. If the pump is functional and just leaking then replacing it is not necessary; replacing the o’rings on it works perfectly fine.

With the E90 if your engine has suffered from sludge (see previous article) I would suggest you change the oil level sensor as your car has no dipstick and these sensors do fail.

Note that replacing all the seals and gasket etc will stop an oil leak but not fix an engine that’s consuming oil.

Smoking and Oil consumption:

1lt of oil per 1000km is normal as per Be-Em.

Customers complaints:

  • Oil consumption is high (1lt per 600km) and smoking – 318 E46 and 320 E90
  • Light puffs of smoke from exhaust on idle and pull off -smoke just increases – 7 Series and X5 mentioned above

The Problem:

  • The valve stem seals harden and swell in the head due to age and heat. Valve stem seals allow for small amounts of oil to lubricate the valve guides. The seal has a lip (oil- metre) on it. When the seals age or harden there is no resistance and the high intake vacuum sucks oil into the combustion chamber. The oil burns in the chamber and this will make the car smoke. The longer the car goes on with this problem the bigger the coke build up on the valve guide and this could cause a loss of power.

The solution:

  • Remove the head and replace the valve stem seals. Depending on the model it is advisable to recon the head and while you there replace the timing chain. Diagram below shows the valve and seal

1) Valve Guide
2) Lower plate spring
3) Valve-stem seal
4) Outer spring
5) Inner spring
6) Top spring plate
7) Valve tapers

The first thing most clients notice (other than the initial problem being solved) is that the car is a lot more responsive and powerful. Once the engine is de-coked there is no build of residue on the guides and your car is generally like new. Because there is no oil contamination in the combustion chamber the combustion process is stronger hence the car feeling more powerful.