The coolant level in my 2003 4Runner (V8) expansion tank consistently drops down to the bottom after a few days or week. It doesn't disappear entirely, however, goes down to maybe about an inch showing at the bottom. It then seems to just stay there. If I top it up to Max line, after a few days it goes back to that low level. Meanwhile the level in the radiator appears to remain at the top.

I am unable to see/find any noticable leaks anywhere. Any suggestions on this one. Is there anything specific to this engine that u should look for?

 

Well, it's going somewhere! Could you have a bad head gasket, allowing it to get out of the cooling jacket and into a cylinder, and getting burned off? Do you have a plug cleaner than all the others? That's a good indicator of coolant leaking into a cylinder.

Are the tubes going to, and out of, the recovery tank hooked up correctly? The one going to the radiator attached to the fitting that feeds the tube going to the bottom of the tank, and the other allowing air in and out of the top of the recovery tank.

Me, I think the head gasket, personally. Just my opinion, though.
Good luck!
Pat☺

 

Did a little more checking. I saw one drop hanging off the bottom of radiator (passenger side). Removed skid plate and cannot see anything too obvious - radiator hoses are dry at connections. However, I do see a little seepage along the bottom edge of radiator where it meets bottom of shrowd. So I would assume this would mean the radiator itself would be leaking from some point. The vehicle has 333,800 km (207,000 mi). Would this be typical lifespan for this radiator? Actually, let me see if I can get a picture to add here... not a great picture but you can see along the bottom edge of the black (shrowd) where coolant is evident.