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Old 06-14-2013, 04:26 PM
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A B Able Truck A B Able Truck is offline
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Location: San Diego
Join Date: Jun 2013
Posts: 1,627
Mein Auto: 2006 550I (N62TU) V8
**The valve stem diameter was increase at a production point to remedy the guide problem. I can not believe BMW would continue to use inferior stem seals after this change. I have attached my post related to this carbon buildup issue. My vehicle has passed smog test & no longer smokes. I did have to run the proceedure twice before it lowerd the HC levels within specs. And I will probably do it 1 more time for good measure. It cost me $200 to fix compared to the $4000 > $5000 I was told it would take for a guide/seal replacement **

2006 BMW 550I 92,000 miles V8 (N62TU)
Smokes (white/gray ) failed visual Smog Report (15 mph HC ppm Measured 91 Max. 49)

It used oil (approx. 1 qt. per 2-3 tanks) and I read the history of V8 valve stem problems (internet & local shop research), I was about to have the valve guide/stem seals replaced or drive the car off a cliff. But it didn't have the classic symptoms of defective valve stem seals/guides. It also ran like a rapped ape (old school for ran great). I'm a heavy truck mechanic with old school car experience (35 years). The plugs were clean and the exhaust smelled funny, also the exhaust dripped clean water no matter how hot or long it ran. I pulled the intake throttle housing and noticed excessive oil. Replaced the (ccv) diaphragms in the valve covers (torn) & read up on the cyclone oil separator (like a Dyson vacuum). Because I wasn't happy with the oil consumption & residue in the intake, I fabricated a sponge with screen for each valve cover vent outlet. This cleaned out the oil residue and I assume it will reduce oil consumption while allowing crankcase recirculation, but it did not solve the smoke problem. I pulled the spark plugs and stuck a camera down a couple plug holes. Yes, the top of the pistons were loaded with carbon. So I sprayed Sea Foam in each plug hole, followed by a shot of low pressure shop air to help spread it around the piston. I let it sit for an hour or so, then reinstalled the plugs. I topped off the fuel tank with high octane and added 12 oz. of CRC Fuel System Cleaner (part #05063) to the tank. 100 miles later and what a difference no smoke or water dipping out the exhaust after warm up. I'm in love with the car again
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