Thursday

BMW 318i N42 Timing chain and tension problems

This blazing black BMW 318i , 2003 year vintage  fitted with a N42 Valvetronic engine presents itself at the workshop.


The engine would not idle , then it would , would rev up and then suddenly loose the plot.
A visual inspection revealed many oil leaks, mostly from all the sensors and around the rocker cover.
A strange slapping and rattling noise came from the front of the engine.

After removing the rocker cover we were greeted with this - see photos below.





What caused all these problems?

1  Was it just wear and tear?
2  Was it poor maintenance
3  Was it poor quality oil?
4  Was it poor design?

You be the judge.

Look carefully at the photo and compare it with the parts drawing below. What is missing? Oh yes there is no top plastic timing guide rail, all broken and floating around in the engine.



Look at part number 16 closely.




What caused all this contamination to happen??
What caused the top of the guide rail to snap off??

Well the slapping noise in the timing tunnel was a result of the chain not being tensioned enough.
That is for two reasons on this engine.
1)  Timing chain was worn or as some folks would say stretched.
      The cause, wear and tear and the use of a cheap and nasty engine oil.
2)  The original factory timing chain tentioner does not have enough throw or length.
      The cause, faulty design, and a up-dated tentioner. This is pictured in the photo below
      The old tentioner has a larger and fatter hex head, also has a shorter stubby on the other end.
      The fastest way to determine which tentioner your engine has is to compare the size of the hex head.
3)  With the chain worn and the tentioner not doing there job, when this engine back-fires the sudden slap of       the chain breaks off the top guide rail. More on back-fire a little further on.
4)  Badly contaminated engine oil and engine. This would most probably be the root of all the evil.
      These are electronically controlled engines with all fuel , ignition, timing , valve timing and valve opening          controlled by on-board ECU or computer. When any of the many sensors or control valves do not get             the right signal the system goes south causing a heap of problems.
     Cause for contaminated engine and sensors? One cheap non synthetic engine oil , two to long a distance          between oil changes.

Read the comments of other BMW technicians around the world, they have mostly found the same problem.

Here is one just for your entertainment.
http://www.tunetech.co.za/n42-timing-chains-318i-e46-and-318ti-facelift-engines/






Replacing the timing chain and tentioner is not rocket science, but does require with out a doubt special tools to align the camshafts and the balance shaft at the bottom of the engine.
In the picture below is a outline of the chains and the balance shafts that need the be aligned.
The vanos timing gears also need to be reset back to the home position. Also make sure that the Valvetronic system is parked in the right spot, other wise there will be a loud crunch and the next best option is to locate a used engine from a wrecker.


The complete online workshop manual in available with a step by step instruction on how to carry out the above work. Please click on the link below

http://bmw.workshop-manuals.com/3_Series_E91/318i_N46_TOUR/index.php?id=406






This is what the special tools look like. Some places hire them out for 5 days. Mostly you have to purchase them for around $ 550-00 , just make sure that the balance shaft aligning tool is also included. You cannot complete this job without aligning the balance shaft. By the way enjoy removing the sump while the engine is still in the car, challenging but fun.





Enquiries regarding this type of repair are welcome.

Call or text Charlie on 0403 861 597

You are also welcome to contact us on the form below.                           












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