Andrew,
Are these the facts?
* You bought the truck at 67k miles about a year ago.
* At the time of purchase the dealer put in:
....1-New radiator
....2-New valve cover gasket (due to oil leaks)
....3- New timing chain cover gasket (due to oil leaks)
* In July, you used Seafoam in 2 tanks to address the pinging issue.
...The Seafoam was at the advice of your mechanic.
* In July, you reported sludge in the valve cover and were advised by C-Dan that the
...leaks (valve cover & timing chain cover) were probably positive pressure in the
...crankcase; possibly due to a clogged PCV.
* Somewhere in the July-August time frame you replaced the knock sensor
* On numerous occassions you have checked the overflow at 3k RPM and you have no bubbles
* On numerous ocassions you report the engine has good power, runs strong & very smooth.
* At some time in the past few months you changed the timing to 2 degrees BTDC
* In July you reported that your mechanic did a complete tuneup
....Plugs, cap, rotor, wires. You implied they used all Toyota parts.
* In July you replaced the PCV, EGR valve, EGR modulator, and the VSV for EGR.
....This corrected the P0401 and reduced the pinging by 90%
* Over the past 3 months, Robbie, Lars, and Beowulf all suggested you have
....a cylinder leak-down test.
....To date, you have not had a cylinder leak-down test.
* In July, Mike (clownmidget) advised that you have a fuel delivery problem.
* In July, you had the engine wiring harness repaired due to missing (?)
* In July, you reported the intake manifold was cracked.
....You were advised by Landtank on how to test if this leak was creating a lean condition.
....You were also advised by Christo that a lean condition could be causing the pinging.
* In August, Doug and Tom (Scamper) both suggested you use a fuel additive (e.g. Redline)
* In August (79k miles) you also reported that you have warped rotors. [Unrelated]
* In August, your mechanic did a compression check and found all 6 cylinders normal.
* Somewhere in the June-August time frame, your mechanic added
.... powdered ginger-root to the radiator to address coolant leaks. [added after post #42]
* Up to 18-Aug you were reporting high oil consumption (1qt/2k)
....and that consumption was back to normal after switching to 15w-40 Delo in mid-Aug.
* In late August you detected an oil leak at the head/block junction.
* Sept 1, you have your mechanic (reluctantly) remove the head
* Sept 2, mechanic reports head gasket had not failed.
Would you please add to the list or clarify any of the above facts and please put them in chronological sequence.
In trying to figure out whether you're a hypochondriac or not, I am really getting confused on what's transpired with your truck.
As of right now (pre-chronological sequence) it seems like your problem with pinging may still be
related to the wiring harness. I suspect you've got an injector that isn't supplying enough fuel
or some other fuel delivery problem as suggested by clownmidget many months ago.
It also sounds like you've still got the positive pressure in the crankcase as suggested by
C-Dan 3 months ago. Is the PCV valve installed correctly and is it OEM? That could explain the oil leak at the head/block junction. Did you take pictures of the head/block oil leak? If so, please post.
In summary, it seems like you had your mechanic pull the head for the wrong reasons.
-B-