I have a 2000 Chrysler 300m 3.5liter, an for some reason it boils in the recovery tank after car runs about 25mins then temp guage shows the car is overheating. But the car seems to run fine, it doesn't shift hard or slips gear or no sound of engine issues but I don't know please help I'm hoping it's something simple I changed the thermostat, new radiator about 6mons ago What kind of signs or syntoms should I be looking for ?

First thing.......did the thermostat get put in backwards? Has it done this since changing the thermostat? Check that first. Then I would look at the head/head gaskets. Was the engine ever overheated? Did it run low on coolant? Is there any oily residue in the coolant overflow tank? When you pull the radiator cap off does it have a bunch of brown gunk on it? If you have one or more of these symptoms you could have head/head gasket issue. You have to be careful here, but with car running and not hot yet open the radiator cap if you see bubbles that seem steady most likely that is your issue. Another possibility is the water pump vanes worn down. Also could have blockage in radiator

thank you aztec626bf, that definitely got me started on the right path, so far Ive done the thermostat check an it is installed according to the Chilton Manuel, that's done. then i also replaced the water pump now with the engine off before i put every thing back i had put a garden hose into the upper radiator hose an ran that which then water comes directly out of the upper radiator hose connection im assuming that's a good sign of flow so now i have to put everything back together an start it. i was told to put blue devil into the radiator while car is running .......

Could be a head gasket leak, leaking compression and some times oil into the cooling system. Flush thoroughly and use some K & N block seal without any antifreeze in the system, run around for a day and see if problem goes away. If so run around for at least 50 miles and immediately drain radiator and disconnect lower radiator hose and leave disconnected overnight. Next morning, reconnect all, fill with proper antifreeze level and enjoy!

i was thinking a blockage, hose/radiator....

Did you bleed the coolant system? Theres a fantastic new invention on those chryslers that kicked my ass every couple years that made me think my thermostats were going out. On the top of the engine block theres a bleeder screw that releases the air from the engine block. You have to connect a tube (roughly 1/4in diam.) and let all the air out of the coolant system through that screw. You must do it with the engine running snd let it run intil there are no bubbles coming out the tube. Then tighen the screw and enjoy. Makes sure you have the right amount of fluid in the res at the end. Thank you chrysler for once again making everyones life difficult.

and autozone has no clue what the valve is for,, Haynes manual dont mention it but i be damned it right there

No, I had this happen twice. There are two pipes that run the width and length of the engine that circulate the coolant. Both might have leaks, etc. This is what happened to mine, twice!!!!

In the reservoir there is a check valve, it goes bad. Shake the resevoir, if you hear something loose. Replace the reservoir, and bleed the system, minimum twice.