I have a 00 dodge caravan. Has always been a good van. Recently when I start it up first thing in the morning there is a puff of blue smoke come out of the exhaust. This will not show up again if you start the van up wth in an hour or so. If you leave it for 3 or more hours you will get a puff of blue smoke but not as much as the one after it has sat all night. Any ideas what this might be??? Thanks Silvia
Generally bad valve seals or the possibility of oil pooling in the cylinder heads caused by oil sludging.
Sounds like a 3.0 liter Mitsubishi engine with worn/hard valve seals.
agreed, bad valve stem seals.
As long as oil consumption is moderate, repairing this problem is generally not worth the effort. It won’t hurt anything…If the amount of smoke on start-up disturbs you, try switching to synthetic oil as it smokes a lot less when burned…
Worn valve guide seals.
Your valve train assembly lubrication in the “head” of your engine runs back down to the crankcase via return paths in the head and block. Your valve stems have seals that prevent it from going into the cylinder. Should these valve stem seals become worn, oil can seep down past them when you stop the engine and onto the back of the valves. When you then start the engine, it gets drawn into the cylinders and burns.
As long as you keep the oil level from dropping too low you should be fine. It does not portend the end of the engine. You may find you’ll need to replace the upstream oxygen sensor and perhaps even the cat converter sooner than you would have, because the residue from the burning oil can coat the surfaces and render them nonfunctional, but then engine itself can run forever like this.
Sounds like valve seals. My '88 Ford Escort has been doing this for 10+ years and probably 200K miles. To me it’s just not worth the effort to repair them.