I have a 93 4Runner. It is leaking coolant out from behind the timing cover. I have been told that it could possibly be the head gaskets. I haven't noticed any white smoke indicating that the coolant is getting into the cylinders. The part that I don't understand is that it only leaks after it has been parked for a while. I don't want to put a lot of money into it because I want to sell it. Any help would be appreciated. Thanks.