Join Date: Jan 2006
Location: Northern California
Thanked 2,306 Times in 1,836 Posts
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Blowby is normal. Especially in the ISB which is an open loop emission system engine. But in saying that, excessive blowby is either 1) worn out rings, 2) unseated rings, or 3) a vacuum leak. Since 1 would only be a problem if oil changes were performed rarely, or if the engine has many many hundreds of thousands of miles on it, I would say this is probably not the problem. And 2 being only an issue if there's less than 100k miles on the engine, which may have also been babied on nothing but high dollar synthetics at 3000 miles change intervals, I again, wouldn't think thats the problem. But 3 being a vacuum leak is more common when someone thinks they have more blowby than they're used to since any leak in vacuum is simply pumped into the crankcase and exited out the blowby vent hose.
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