Have a 04 with a 4 cyl., 186,000 miles, that is leaking coolant out the back of the head and block area. Have read many threads where the only real fix is to pull the head and install the inserts, time-serts or the n3000L type system, along wiht new head gasket. I will check the head for warping but am assuming that it will need to be machined flat. Is it better to just go ahead and replace it with a rebuilt so the head components are all good? . I am wanting to know since the head will be off, what else should I go ahead and replace while doing this repair? What is typical on the water pump on replacement, mileage wise? I know with the Honda's, timing belt you go ahead and do the water pump since you have it torn apart and can very easily do the water pump. So, with 186,000, what all should I consider replacing. Thanks..

 

If pulled threads Toyota stated replacing the block was the only fix. It appears?? they may now be using an insert system.

Suggest once the head is off to inspect it. If no problems have the head warpage checked and if within fixable range resurfaced. Might have the valve stem seals replaced at this time.

An engine with this many miles must have some piston ring leakage, etc. Having a complete valve job done (or head exchange) may be over kill given the bottom end condition.

This engine has a timing chain. The link below provides info on the cam drive design. The highlander can use the same engine, 2AZ-FE.

http://highlanderclub.ru/files/manua...0e/x040001.pdf

The water pump should be driven by a belt serpentine. If access is better with the head off might change it.

If you doing the work yourself take note, valve train clearance is set with shims. Keep all valve train items for each valve together to make sure they can be replaced in the same location.

Suggest checking with the Toyotanation website, more members. If Toyota is using something new instead of block replacement, members might know what it is. Suspect it is the NS300L system, but?