N62 Smoking Experiences - Fixes

[Thecastle]

So, I have the (mis?) fortune of owning a BMW X5 with the (95k miles) N62 4.8 engine, and she at least used to smoke like I'm batman smoking. I'm writing this to help others in the same boat. Living in Houston I have several good friends with Ph.D.'s in organic chemistry/petro chemicals (specifically materials/chemicals). I'm an engineer and wanted to figure out a low cost solution to this problem, so I talked with them about the causes of seal failures on BMWs.

So my car is typical of the BMW issue where it will smoke after an extended idle. I really noticed how bad it was when I backed up my travel trailer, let it idle. Then turned it off, and back on and huge clouds of smoke, and it would also smoke on extended idle. Or sitting in traffic and floor it, smoke!

1st I replaced my CCV / pipes, then changed my oil to liquid Moly. This significantly reduced my smoking but did not eliminate the I'm Batman issue. After repeated visits to my indy we determined that it was leaking valve stem seals was the cause of my cars smoking (how n62/n63 typical)

Anyway, I talked with my chemical friends and what they said is that viton/rubber oil seals come with plasticizers to increase pliability (key to sealing on oil seals). Heat/time causes these compounds to both break down and evaporate out of seal materials in a car engine. The higher the temps the faster the process of plasticizers leaching into your engine oil and the loss of flexibility and sealing properties. Once the plasticizers are lost the seals can become brittle and with the mechanical sealing stresses form cracks resulting in total failure. I suspect that BMW uses low quantities of plasticizers and bonding agents which is why they fail so frequently, along with high engine temps.

If your seals aren't cracked, but simply less pliable, it is possible to add solvent plasticizers to the oil that will restore the flexibility of the seals (you can do this to your dash too to prevent cracking). This is not the same things as seal swelling which is a bad thing (aka adding brake fluid). This is just restoring the original properties of the seal.

So for me, I added one commonly available plasticizer (there are others that will work just fine and I'm not endorsing one product). Lucas Oil Leak Stop. I have to admit that I've been very happy with the results. No smoking, no oil leaks and the car runs great, it took about 300 miles to stop smoking, but I've been running it for 5K miles with no smoke or mechanical issues. No more I'm batman, and no embarrassing smoking as I back my trailer into a campsite in pristine wilderness with folks watching... (try it in a national park and you'll get some really dirty stares)

If your seals aren't torn or cracked this will restore the seals to their original pliability and save you from spending the money to replace the seals. In my case the valve stem seals are the culprit for my smoking.

BTW I realize this MAY not be a forever fix, but neither is replacing the valve stem seals. The same gradual loss of plasticizers that caused the leaks on your 1st set of seals will re-occur with the replacement seals. That is why some folks add plasticizers as preventative on BMW vehicles. Maybe this is the long term solution?