I have a 2006 Chrysler 300 v6 3.5 liter engine, I had to replace the water pump and thermostat and heat censor and the coolant reservoir. It still overheat forcing the coolant out of the reservoir through the side of the reservoir coolant tank. I let it cool replaced the coolant and drove it across town, no problem stayed cool then halfway back started overheating again. What can cause this to work for a while then overheat again. No coolant in my oil. The whole in the new reservoir is smaller than the old one.

 

I forgot to add! ( the coolant is forced out of the reservoir tank through the side of the reservoir cap, yes the cap is new as well. Has anyone experienced anything like this with their Chrysler 300 2006 vehicle?? Any help would be greatly appreciated.
thank you

 

Be sure the seal on the cap is good, it sounds like it's not sealing. Make sure there are no chips or chunks out of the sealing surface of the coolant reservoir. Be certain the cooling system is "burped" properly. Get all the air out. Good luck, let us know what you find.

 

over heat while driving or sitting still still in traffic?