[Willygbr66]

Hi,

My 335i 2007 plate with 113k started smoking in the engine bay recently. Having spent much time researching I decided to replace the gasket and also the plastic valve cover with new BMW genuine ones.
With the use of online videos and the excellent ECS Tuning step by step guide, myself and a neighbour undertook the task. Two problems occurred however. Firstly my neighbour dropped an extension bar into the engine bay (which after much deliberation/discussion and 2 hours of our time we managed to retrieve). Secondly we also made the mistake of not checking the O2 sensor cables were clear of the cover and one of them ended up being pinched in the NW corner as we torqued done the bolts. This has led to 2C9C, 2C9D, 2C9E and 2C9F codes (I appreciate I may need to swap this out for a new one as after deleting the codes using MHD they still come back). In total it took us 8 hours to complete the job and to be honest was pretty straightforward.
The issue however that I have is that the smoke in the engine bay is still happening. Not when the engine is started up and idling but when I take her for a drive and return and park back home.
Could this just be residual oil still burning off or is it possibly somewhat more sinister.
Any comments/thoughts etc would be gratefully appreciated.

[mweisdorfer]

Originally Posted by Willygbr66

Hi,

My 335i 2007 plate with 113k started smoking in the engine bay recently. Having spent much time researching I decided to replace the gasket and also the plastic valve cover with new BMW genuine ones.
With the use of online videos and the excellent ECS Tuning step by step guide, myself and a neighbour undertook the task. Two problems occurred however. Firstly my neighbour dropped an extension bar into the engine bay (which after much deliberation/discussion and 2 hours of our time we managed to retrieve). Secondly we also made the mistake of not checking the O2 sensor cables were clear of the cover and one of them ended up being pinched in the NW corner as we torqued done the bolts. This has led to 2C9C, 2C9D, 2C9E and 2C9F codes (I appreciate I may need to swap this out for a new one as after deleting the codes using MHD they still come back). In total it took us 8 hours to complete the job and to be honest was pretty straightforward.
The issue however that I have is that the smoke in the engine bay is still happening. Not when the engine is started up and idling but when I take her for a drive and return and park back home.
Could this just be residual oil still burning off or is it possibly somewhat more sinister.
Any comments/thoughts etc would be gratefully appreciated.

A few questions....

Are you still getting o2 codes. Did you replace the o2 sensor you think that the wires were damaged?

Oil could be residual. Why did you replace the VC? Was it cracked?

Did you sandwich the OEM gasket in between two beads of Ultra Black?

Did you replace the PCV valve with an upgraded one & cap?

Does the car have a catch can?

Last, did you replace the PCV breather hose/ valve?

[Emilime75]

The smoking could be residual oil dripping on the exhaust...or, since you pinched the O2 sensor wires, you may have damaged or dislodged the valve cover gasket and it's still leaking. Taking it one step further, if you tightened(hopefully used the right torque wrench on the right setting) you may have even cracked the valve cover when the cables were trapped underneath it. By "right torque wrench" I mean one that goes a minimum of 20% lower/higher than the setting you need, as they get out of spec the closer you get to the min/max range.

You can try degreasing/washing the passenger side(assuming LHD) of the engine to remove all residual oil from the original leak, then drive the car and see if oil and/or smoke return. If no, you should be good. If yes, I'd be replacing the valve cover again. Keep in mind you will still have some smoke as the residual degreaser burns off, but it shouldn't last very long and should smell different than oil burning.

As for your O2 sensor wiring, you'll need to replace it. The O2 cables that come up on top of the engine are the 2 front bank 1 and bank 2 sensors, and I don't believe there is another plug that can be disconnected and cables replaced. I believe they are part of the actual O2 sensor, and it's typically not advised to try and splice them. I would fix this before driving the car too much.

[Soden82]

It could very well be residual oil from the original valve cover leak.

Did you clean the inside of the block after removing the valve cover to make sure the surface was clear of debris and oil before putting the new one on?

If you don't torque it properly or do it in a specific pattern then it can cause the new cover to crack

[Willygbr66]

Thanks to all for your prompt replies.
1) valve gasket and cover replaced as it was obvious there was oil leakage. On taking the old one off it was so brittle.
2) took a methodical approach to cleaning the surfaces of all debris and oil so everything was clean and smooth.
3) we decided not to use gasket sealant (researching this there are differing ideas on this one)
4) Pcv valve is stock as it came with the cover. Hard to get the RB upgrade in the UK.
5) breather hose was replaced with genuine BMW. We decided to just cut the clips of the old one at both ends as it’s a PITA to do that without possibly breaking the hose anyway.
6) as to torquing the bolts followed the recommenced sequence. I was very cautious here and possibly I may need to redo this after a few drives. (I bought a very specific wrench for this which is brand new with excellent calibration on the torques)
7) my plan is to get the entire bay steam clean from above and below to assist in any possible further leaks
8) O2 sensor is yet to be replaced which I will do however. Engine runs fine with no misfires.

Again thank you for all your advice/suggestions etc. It is very much appreciated.

[Bimmer_Engineer]

Mine did the same thing and I did the gasket again because I thought it was still leaking. After the second vcg it was still smoking so I just drove it for a few days and it quit...