I own a 98 4runner with 190k miles on the original engine. I took it to my mechanic to get a full tune up. He called me to his shop to show me a serious issue with the truck. A noticeable amount of coolant debris has built up between the head and the block. He also pointed out 2 of the pistons were leaking. He says he wouldn't expect the truck to last too much longer driving it the way it is. He recommends resurfacing the heads and rebuilding the engine. The engine doesn't leak and there's no noticeable signs of a cracked head, but he recommended having the head resurfaced while it's already pulled out to be on the safe side. However, I've read online numerous times that these cylinder heads are only expected to last between 200-300k miles before they fail. I've also read that the cylinder head bolts must be replaced. Can anyone chip in on this?

(NOTE: The truck runs great. But recently it started to idle high on start ups. The engine never overheats, no rough driving or anything else out of the ordinary.)

 

There isn't really any set "time" for when the heads expire. With excellent maintenance, they can last a very long time. So what you have to do is look at the signs that he pointed out, and decide if you want to do the work now while you can save the parts, or wait until it overheats and potentially destroys other parts.

IF you choose to have the work done, make SURE they use OEM parts. Otherwise you are taking a good running engine and stacking china junk in there. That's a sure formula for a failure.

Cylinder head bolts on a 5VZ are Torque to Yield so they must be replaced.

Good info here: http://www.tacomaworld.com/forum/tec...cement-v6.html

I agree with most of that thread, but I would stay away from FelPro junk. OEM is the way to go, and costs about the same as aftermarket.

 

If you are thinking of not rebuilding and the heads are already off, I would send the heads in and have them serviced. A good head shop will resurface as needed. Replace valves (and reseat), springs, guides, seals and keepers as needed. Hot tank/bead blast it. magnaflux and or vacuum test it. It is relatively inexpensive to have done.