2004 sonata air pressure at oil cap


Asked by Dec 02, 2017 at 03:02 PM about the 2004 Hyundai Sonata FWD

Question type: Maintenance & Repair

blue smoke only after hot

4 Answers


If the engine is making pressure and the PCV system is fully operational then you have worn out piston rings or badly worn cylinder walls, maybe even a cracked cylinder head leaking compression into the engines internals. Run a cylinder compression and a leak down test too see where the compression it going. Doesn't sound good for your pocket book.


Time to get a new car.


I drive 2.5 miles to work and then back at night. At 10 am there is no traffic and my motor doesn't ever get up to temperature and there is never any smoke in the morning, even gunning at work when I arrive. At night there IS traffic and about 1/2 mile from home it will smoke if I idle at a stop light. By that time it IS up to running temperature. Could this be the PCV that only kicks in when hot? BTW the idle is down to 750 rpm when warmed up but over 1000 rpm in the morning when cold. Spark plugs are perfect too, light tan.


The PCV system operates the second the engine fires up, it is not a turn turn of type of unit, it has to have engine manifold vacuum and a clean air supply, older cars with some blowby will plug up the vacuum supply so you need to make sure both the vacuum tube and air supply from the air filter box is free and clear. If this type of running is all this rig has ever known it could have carbon fouled the rigs, you might rent a bore scope and see what the pistons and cylinder walls look like, if you see any cylinder scoring then it time for a new, rebuilt or used engine.

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