I've got a 2000 4Runner with about 108K on the original engine (3.4L V6). Recently a dealer tech. pointed out that there was a coolant leak on the lower part of the engine on the drivers side of things (pretty much several inches above and in line with the oil filter, but on the engine block), but left it as that. Anyway, I took it in and had the dealer do a closer look...pretty much the dealer confirmed (visually) that it is, indeed, a minor external head gasket leak Doh!

The engine runs great, there's no smoke on startup, and I haven't been losing any noticeable amount of coolant (marked on the overflow reservoir). The dealer recommended that I wait until things get worse before getting the head gasket replaced (~$2,300 total, as labor isn't cheap in Alaska).

Any suggestions on whether to just leave it and let it continue to leak, or to just get it replaced?

 

Get it fixed before it gets worse!! You don't want coolant mixing with the oil, that will trash your bearings!