8.1 Low Oil Pressure

[Tacoma290]

I wanted to close the loop on this. Below is what I found on the starboard side of the starboard engine when we removed the head. I did not think to get a picture of the head gasket, but it showed signs of failure.
The only good news is that I had an explanation: Blown head gasket. During the overheat, the head gasket was compromised, and the opening grew with time and use. This was the source of the water (coolant) in the oil.
Fortunately the rust was on the surface and was not pitted.

 

[Tacoma290]

Here is what I did:

• Pulled the heads and inspected them. I then had the heads resurfaced. They each has about 6 thousandths removed as part of resurfacing. Then they were tank cleaned.
• Spent a day cleaning the block and cylinders. I did have to resort to using Naval Jelly to rid the cylinders of all deposits. You have wipe that stuff right away after using it.
• Drained the oil and coolant.
• Coated everything with PBlaster and covered with shop blankets while I sourced parts.
• Purchased new parts: Head gaskets, head gasket bolts, intake manifold gaskets, new plugs, new alternator (was splashed with sea water during the over heat, then had engine coolant spilled on it; it was not worth re-using), and oil filter. The head gaskets were a pain to obtain since port and starboard are different for the 8.1, and I was not confident with an automotive equivalent; I had to get the gaskets from different supply sources based on availability.
• I had previously purchased exhaust manifold kits more than a year ago. The kit included the exhaust gaskets. So that portion of parts was already on hand. And my wife was happy to see the four big boxes of exhaust manifolds finally leave the garage closet...
• With the super capable hands of a friend, installed all the new parts. We were super finicky about how clean the block surfaces were, and also super finicky about following the proper torqueing sequence for the heads and intake. We used a MAC digital torque wrench so that we could accurately track the degrees of torque (first part of the head sequence is to ft-lbs of torque, then two rounds of turning to specific degrees of tightening. For one round we needed to go to 120 degrees of turn. At a few locations we only had had 90; the torque wrench added and tracked it perfectly). With all the time effort tied up in it, there was no point in short-cuts.
• Reconnected all the parts we pulled from the engine to get at the heads.
• Filled with oil and coolant.
• Fire up was successful. Checked for leaks. Ran the engine in idle to warm then ran it up in rpm. Seems solid. I will feel better when I have it on plane for a few miles.

The plan is to drain and replace the oil after 10 hours of use, since there is no way I was able to remove all of the water from the bottom of the pan.