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Engine Smoke - Valve Seal ?


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I bought my 1995 Lexus ES300 at 165,500 miles and replaced the oil with Mobil Clean 5000 petroleum base oil. After 3000 miles, I changed the oil to Mobil 1 High mileage and the engine became a lot smoother during about 150 miles of driving.

Recently, i started seeing blue smoke from the exhaust after an overnight cold startup for a few seconds or so.

There is no oil in the coolant, and no coolant in the engine oil. The engine oil level appears to be the same.

I just want to know if changing over to fully synthetic can cause the valve stem seals to leak? Or is it possible for the high mileage additives to cause this?

I have read all other posts on engine smoke and i will run Bardahl No Smoke additive later.

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It may be that neither is the cause, but rather that the valve oil seals have just gotten too old to do the job any more. Years ago my wife had a high mileage Cressida that developed the same problem almost over night. The local dealership replaced all of the valve stem seals by pumping air into each cylinder (to hold the valves in place during the replacement procedure) and cured the problem. The cost was about $300 and I'm sure it would be at least twice that now, if not more.

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That's definitely indicative of valve stem seals losing their sealing power. It's a progressive thing, but it's also known that fully synthetic oils penetrate seals better than dyno oils, and if there's a pathway to leak, the synthetic will find it.

There are a few things you can do, first being stepping up oil weight. The 5W-30 is a generic factory all purpose spec. At 165K on the ticker, clearances have definitely opened up some and a heavier weight oil will work fine, plus it's less likely to creep past the seals (and that's what happens, when you shut off the vehicle for an extended period of time, the oil in the engine settles and the oil creeps down the valve stem, pools over the seal, and seeps past the seal; the oil sitting on the valve is what burns off on initial start up; when the engine heats up, things expand, and usually runs with no signs of smoke unless the seals are really old/worn/bad). You can also throw in the Bardahl's, which will definitely fix the problem seeing as how your amount of smoke is so minor... but that's just a temporary fix and Bardahl's will need to be added at every oil change to keep the smoke from coming back. Eventually (could be another 20K-40K miles), the seals will wear down to the point even Bardahl's won't prevent the smoking, but Bardahl's will bide you some time.

By the way, this happened on our '95 ES300, and the repair to remove the cams and get to where they can replace the valve stem seals was $1350. In our case, the mechanic didn't quite put the keepers back on correctly on two of the valve stems, and when they started the engine, the keepers shot out and dropped the valves into the engine... promptly punching holes in the pistons and trashing the engine completely. We went to a good shop and they stepped up and sourced us a good used engine, but still...

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