This is my first post so bear with me, please. About a month ago I was given a 2006 Toyota Sienna. The first two weeks it was driving like a dream and very quiet. It has about 350,000 miles. The engine is a VVT-i V6 3.3. All of a sudden it would start randomly overheating. To be clear it was never driven but immediately pulled over and shut off. The overheating was not all the time. I started by doing the simple changes such as a new thermostat, new cap, new hoses, new belts, and a new heat sensor. When done I flushed the radiator. Some dirt came out and the pressure was pretty forceful coming out. The whole time I couldn't find any leaks before or after the changes. It drove amazing again with zero problems for about a week. One day driving the temp shot up smoke started rolling and oil light came on. The van shut off and I was able to coast it to a safe area. After letting it set, I checked oil and it was almost non-existent. Two days prior I had checked the fluids and everything was good. I had put oil in and filled the antifreeze. Since then I have barely driven it but I am a mom with no other transportation so I still had to run a few miles for necessities. The van now overheats but never shows hot on the gage. The oil light stays on regardless. I do make sure that there is water at all times. A knocking has started a couple days ago. Does not happen at startup. Just happens when I accelerate. Once I get going the knocking stops. Its only at lower RPM. I had it looked at yesterday and was told the radiator was very bad but then told the engine is too. That I need a new engine. He never really said specifics on why the engine is bad. I can't afford to replace an engine and can't afford a new vehicle. I do all my own work unless it's something major then my friend helps. Can anyone please give me ideas or where I should start to look. Please.
Well this is unfortunate. 350k miles is impressive though.
I want to start by saying that at 350k your engine/trans were probably already on their last leg. That is very impressive, even for a honda/toyota (unless hybrid). There are exceptions but not many.
If your engine is knocking, it is most likely coming from the bottom, which would require a rebuild/motor swap. It could possibly be coming from the valvetrain, at which point I would suggest replacing the motor anyway with that mileage.
Oil light is probably on due to no/low oil pressure (assuming you enough oil in the motor).
As for why the car is overheating, it would be difficult to say. Radiator might bad as someone suggest or it could be the head gasket.
In all honestly, your motor is practically finished. You can try to drive it until dies completely and then scrap it or you can swap the drive train.