The following information concerns the loss of coolant on some 2002-2006 Toyota 2.4L, 2AZFE engines. The location of this condition has been noted at the rear of the engine where the cylinder head bolts to the cylinder block.
It has been reported that stripped head bolt threads have been found on some of these engines during tear down. When the two rear head bolts lose their clamping ability they allow coolant to seep out at the rear of the cylinder head.
To repair this condition, engine builders report using thread repair tooling used for various GM engines. Specifically, Cadillac 4.6L engines use the same threaded head bolts (Figure 1). The head bolts for this Toyota engine may be reused if they are not damaged and meet the following length specification.
Using a vernier caliper, measure the length of the head bolts from the seat to the end.
Specified bolt length: 6.350? to 6.465? (161.3 mm to 164.2 mm). If the length is greater than the maximum, replace the bolt.
This information was provided by the Engine Builders Association (AERA). 
