I've read about the 2AZ-FE engine (our engine) and how the head bolts can loosen out of the block. Some have had to have their engines replaced because of it. Toyota even released a service bulletin about it.

My question is, what are the symptoms BEFORE the head bolts really separate from the block? What would we look for to happen?

 

Oil leaking at the headgasket

 

it's not necessary a "loose bolts" problem. IMO the 2az water pumps are known to leak rather regularly, which causes higher engine temps from the lower coolant levels. with the higher engine temps the aluminum block has a problem where the threads in the block for the headbolts will become softer causing the headbolts to actually "pull the threads out of the block". Gutling is correct though, you will see either oil or coolant from a headgasket failure.

 

thanks that makes sense of what I would see. I've also heard "weeping from the water pump weep hole" is the sign the water pump is dying, since the water pump looks like it plays a role in this overheating, is a water pump that is weeping from the weep hole about to die?

 

leakage from the weep hole is a sign that the waterpump is failing. when exactly it will totally fail isn't sure but that's the indication to change it before it totally fails and not pump the water through the engine at all. if that happens engine will overheat and most likely will have head gasket issues.

 

it's rare that a water pump completely fails. I have heard of them leaking heavily where they will spray that pink "flaky" residue everywhere or where they will make a metalic rattling noise, and those have been the worst cases that I know. The weeping of the water pump is just the start of your leak and things don't get better after that.