Hey I have a 06 is350 and I’ve been having overheating issues I’ve changed the water pump radiator to an oem one radiator cap and thermostat and I don’t think it is a blown head gasket there is no white smoke coming out of the exhaust or milky oil, when I drive it for more or close too an hour and it comes to a stop it spits the coolant out through the overflow tank I bled the cooling system properly incase there was any air in it. Any ideas or guesses on what it could be ?

 

Out of curiosity. Which way is the overflow tank lid tab facing? To radiator, or to the engine?

 

It’s facing towards the engine

 

It needs to face the radiator. Have a look here swap the dip hose to correct side if it's not already. You want the dip side to be connected to the engine. So when on cool down it's replenishing with fluid, and not introducing air into the system. The small one is the vent which just let's the coolant overflow when either the overflow tank is over filled, or too much pressure coming from coolant system. As you can probably see now. You'll want to purge all the air out of the coolant system after this fix.

https://www.carcarekiosk.com/video/2...ze/add_coolant

 

In addition to Mike's advice, the vent hole cannot be plugged either. As the block cools off, coolant displaces less area and a vacuum is formed inside the block. This vacuum needs to overcome the spring of the most most inner flap of the pressure cap and any crust formed around the vent hole.

Also, the radiator cap has 3 sealing components.
Outer one keeps fluid from leaking out of the cap.
Pressure seal to set pressure of cap.
Pressure/Vacuum seal to allow the system to pressure up and opens when a vacuum is applied.

Any seal in the cap with debris in its path making a leak can cause the whole system to not refill the block as it cools off. Make sure all sealing surfaces are clean!

 

Our factory radiator caps over time degrade and will fall apart within the housing (happened to me). So first thing I'd check is whether when you replaced the old cap, that you had left behind any components of the previous within the housing. Secondly, how exactly did you blurp the cooling system? These vehicles can be difficult to bleed all the air from the system.

Good luck!