As I mentioned in my post about having the turbos replaced, I wasn't happy with the cold start performance of the car. I felt it wasn't as smooth as I imagined a straight 6 engine, showing a shade over 40k miles on the clock, should be.
Several hours of investigation later, I concluded that carbon build up on the intake valves could be the culprit, the Achilles heel of direct injection engines. Basically, the byproduct of the combustion process leaves a carbon deposit on the intake valves and intake manifold, gumming them up and reducing airflow.
Most of the discussions on N54 engine carbon build up revolve around walnut blasting as the cure, a process similar to shot blasting, except the media doing the work is ground up walnut. The thinking behind walnut is that if any of it gets in the engine, it's not going to do any harm. The process is so effective that BMW have even made a special tool for the job (P/N: 81292208037). Trouble is, I couldn't find any one in the UK offering the service, only US and Australia.
Unfortunately, I was going to have to roll up my sleeves and get stuck in, polishing and cleaning manually with wire brushes.
Whilst researching, I looked up any possible preventative actions I could take. I'd rather not have to clean the engine out every few thousand miles. One suggestion was to use an oil catch can, but they are pretty expensive, the Burger Motorsports catch can is $179, a bit too much having just shelled out £3000 on turbos. Happily though, the other suggestion that came up was to swap the standard PCV valve (Positive Crankcase Ventilation valve) for a Rob Beck PCV valve. These come in at a much more wallet friendly $40 plus $10 shipping to the UK.
I ordered one of those, then called the ever helpful BMW Hereford (who are now on my speed dial list) and ordered the following genuine BMW parts (full OEM part numbers in brackets).
- Throttle Body Seal (P/N: 13547522361)
- Intake Manifold Seal (P/N: 11617547242)
- Hex Bolt + Washer (P/N: 07119903918)
- Hex Nut with Plate (P/N: 07129905541)
- Vent Hose (P/N: 11157553949)
Total for all that posted? £63.01.
Finally, I ordered some new Bosch ZGR6STE2 spark plugs, as the car was over due a change. The spark plug service interval is 45k miles for the N54B30 engine, as stated in SI B 00 02 06.
To get to the intakes a fair amount of the engine bay needs to be removed, the air filter housing, throttle body, charge pipe and intake manifold to name but a few.
The job was the perfect opportunity to use my new Laser panel protector though. Leaning over the fenders in zip up overalls is a recipe for scuffs, happily the Laser mat is large and thick enough to avoid that completely. I'd definitely recommend the home mechanic having one in their tool kit, whether it's Laser or not.
Whilst the throttle body was out I gave it a good clean and fitted the new seal.
Next up was removing the electrical connector box from the tangs on the bottom of the intake manifold. This was an absolute pain in the backbox, in the end wedging some feeler gauges under the tabs and wiggling managed to free it.
About 2 hours into the job, there were only the bolts securing the intake manifold left to remove.
To avoid any tears I taped off the cylinders next to the one I'd be working on.
Now the real hard work could begin. After hand cranking the engine to ensure cylinder 1's valves were firmly closed I filled the intake with Wynn's Air Intake & Carburettor Cleaner. This is some real good stuff, I was high as a kite on the fumes by the end of the job, make sure you've got good ventilation if you use it.
Using a combination of wire brush drill bits and Dremel bits purchased on eBay, each intake was cleaned as thoroughly as possible.
The condition of the intakes after just over 45k miles was quite shocking, you can see just how gunked up they had become, and in stark contrast how well they came up after cleaning.
The difficulty was getting to the inboard side of the valve, obscured by the stem, they are also a lot deeper into the block than they appear in the image, making accessing the job as well as being able to see what you're doing mutually exclusive, as you can see below.
Many hours later, all six intakes had been cleaned, some requiring higher levels of contortion to access than others.
Time to replace the spark plugs and fit the new Rob Beck PCV valve.
Replacing the PCV valve was fairly simple, it just requires unscrewing the retainer and switching out the PCV valve.
Last but not least, the spark plugs. I chose to replace with OEM spec plugs, having read that 'upgrading' really wouldn't make any difference and would likely lead to a shorter life plug being installed. All was going well until I got to the third plug which, when removed, was coated in oil. You can see the colour difference compared to the new one.
This is an indication of another common N54 problem, a leaking valve cover gasket, which was also the likely culprit of the gunk on the front of the engine.
Feeling rather deflated at finding another problem, I got the engine back together using all the new seals and bolts, then got started researching the next job.
Staying positive though, the car did feel better, the starting characteristics were much improved and preventative measures had been taken to avoid carbon build up in future, so not a total loss.
Let me know what you think in the comments below, have you attempted a DIY carbon clean? Was your engine's carbon build up even worse than mine?
Don't forget to subscribe using the Follow by Email widget in the top right for plenty more content to come.
Post a Comment
Let me know what you think by leaving a comment below.