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Join Date: Apr 2006
Location: Minneapolis, MN
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Well it has been a long time since my last post. I have news that may be helpful to others as well. The crankshaft pulley is not the problem. The original user who started the thread was probably on the right track thinking carbon build-up could be the problem. My corolla was actually burning more oil than normal, about 1 quart per 500-1000 miles depending on city/highway miles and ambient temperature. Bluish exhaust is only visible under start-up after the car has been sitting for awhile. A compression test by the Toyota dealer revealed good compression on all cylinders dry and wet test, between 190-195psi if I remember correctly. I will have to find the original receipt for exact specs. I talked to a number of mechanics and did some research to conclude that the oil burning is most likely related to leaky valve stem seals and maybe to some extent piston rings (yes, even with good compression numbers).
Therefore, I pulled the cylinder head to replace the valve stem seals and check overall engine condition. The camshafts were in near perfect condition, with no visible wear! There was normal carbon buildup on the valves. I sent the head to a machine shop to be inspected and have valve stem seals installed. I just got the cylinder head back from the machine shop, which inspected the head, installed the valve stem seals, removed carbon from valves, and machined the surface true (even though the head was not warped).
I am also replacing piston rings to make sure the oil consumption is loweredl and bring compression up. It is not much more work and money to do this at this stage since the bores are in almost perfect condition with no signs of wear. Original cross hatching is still visible and a ridge is almost non-existent. Therefore, I can do this without taking the engine out and do not even need to hone the cylinder. A ridge reamer will not be used (not needed and will damage the bore). The Toyota mechanic viewed pictures I took of the pistons and could tell from the carbon wear pattern where oil was "leaking through" and preventing carbon buildup. A moly ring set from the dealer is about $100, which is comparable to aftermarket rings. Rings are on order right now. I will pull the oil pan tommorow, check condition of the engine bearings, and prep for piston ring install.
While new valve seals and piston rings may help with oil consumption, I am hoping the biggest improvement will come from cleaning carbon build-up from the intake air plenum and intake manifold. The air plenum was almost completely blocked on a few small but important passages. The EGR valve was completely blocked as well! This seemed excessive and I will try to determine the original cause. I was told that this blockage may be a contributing factor for the carbon build-up, rough idle when cold (when warm the engine still runs great though), and oil consumption. As such, the machine shop also cleaned these parts. I cleaned the throttle body and squirted throttle body cleaner through all the vacuum hoses and emissions sensors. Hopefully, my EGR system will now function correctly. EGR problems are difficult to diagnose, so I will need to vaccuum test it when it is all put back together.
I will try to upload some pictures over the next few days and give progress updates. Even though the engine is not being removed, this is proving to be a challenging project. Fortunately, I have an official Toyota service manual (downloaded from Toyota/Lexus technical website, not free), which is much more detailed than a Haynes Manual.