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Hi All! I'm new here, and could use some advice/diagnosis.
I bought a 2001 Civic with 190k miles for a junkyard price--$400. It was burning/smoking a ton, almost no power, etc. With my teenage son, we did the following:
--pulled the head
--got the head, pistons, and rods thoroughly cleaned
--got the head surfaced and the valves reground
--replaced most of the the seals and gaskets (including the head gasket, valve guide seals, intake and exhaust gaskets, etc)
--replaced the piston rings (thoroughly gunked up)
Despite the neglect from a previous owner, there was still just a bit of crosshatching visible in the cylinders. After reassembly, it ran great...
... for ~10k miles. Then, over the course of about 1500 miles, it started burning oil, then burning oil faster, then burning about 2 quarts per tank of fuel, while misfiring like crazy. Pulling the plugs showed #1 totally caked with burned oil
So we're tearing it down for a second time. The head is now off, and some things are immediately apparent:
--Cylinder #1's exhaust valves are...in poor shape
--The tops of all four pistons are coated with black, burned residue. However, cyl #1 seems to have a whole lot less than the others
Here are a few other notes:
--Unfortunately, we didn't do a leakdown or compression test after the first reassembly, so I can't say for sure that it was good at that point. Before we opened up the engine this time, however, we did a leakdown test. #3 and #4 were great, #2 was acceptable but not as good, and #1 was toast, as you might expect.
--My son really wanted to learn to drive a manual, which is one of the reasons we tackled this project in the first place. This one is quite stock, which makes it somewhat of a rarity--an unmolested 25-year-old manual civic is not common!
--There wasn't any notable consumption of coolant, and we never really noticed a cloud trailing behind the car, although it has a coating of soot on the rear bumper
--We're willing to throw a bunch of man-hours at this car, but not a ton of money. We're happy to replace lots of parts, as they tend to be cheap. And this isn't a super-urgent repair, either.
--Please ignore the oil in the coolant passages here--the coolant appeared nice and clean until I pulled the head and oil dripped.
So, a few questions:
1) What could have caused the slowly-for-a-long-time, then all-at-once oil burning?
2) If no obvious cause, how would you suggest we go about tracking down the cause?
3) What suggestions do you have to ensure this engine is fine for a long, long time? This has been a great father/son project, but we'd rather have it fixed for the long haul.
Well, I think I figured out the rapid decline. That exhaust valve is burned something bad. Almost certainly caused by carbon build up.
But where would that burning oil have come from? For what it's worth, the intake valve stems on that cylinder are much darker than their counterparts in the other cylinders. The PCV valve vents to that end of the intake, and didn't get replaced the first time around. Could a bad PCV valve cause that kind of oil burn?
That cylinder might be out of round, or just more worn than the rest. I would just dump another motor in it for a couple hundred.
Swapping the motor is certainly an option, if that's what's required. Other than the local pick-and-pull, where do you recommend we look for an engine?
Aside from the bad valves in cyl 1, the head appears to be fine. We also ran a leak down test on the cylinders themselves, and found no leakage. Yay! Unfortunately, that also means that it's still a mystery how oil got into the cylinders to be burned in the first place...
