Car says its overheating then after a few seconds goes back to normal

[Shockalocka]

Hi there i habe a 2015 3.8 awd 145000 miles. I have a issue where the car will run fine for a few hours of driving then All of a sudden start spitting coolant out of the reservoir and the temp will rise but fall down immediately after, as if air is in the system. We have replaced every component on car at this point except heater core. Pressure check was good, also checked for head gasket leak and found none.
We have bleed according to the genesis dealer specs and got a vacuum kit to pull vacuum and fill. Anyone ever had a issue like this or know someone to ask. Thanks for any help

 

[joegr]

Does the actual moment of overheating start while driving over 30 MPH, or under 30 MPH or stopped?

 

[Shockalocka]

Does the actual moment of overheating start while driving over 30 MPH, or under 30 MPH or stopped?

Its random, very random.

 

[joegr]

If it overheats while you are moving more than 30 MPH, then it's not the fan. If it overheats will you are stopped or barely moving, then it could be the fan.

 

[EdP]

Hi there i habe a 2015 3.8 awd 145000 miles. I have a issue where the car will run fine for a few hours of driving then All of a sudden start spitting coolant out of the reservoir and the temp will rise but fall down immediately after, as if air is in the system. We have replaced every component on car at this point except heater core. Pressure check was good, also checked for head gasket leak and found none.
We have bleed according to the genesis dealer specs and got a vacuum kit to pull vacuum and fill. Anyone ever had a issue like this or know someone to ask. Thanks for any help

I can only think of two things but you said all components were changed.
Bad thermostat that closes when it should not
Bad hose that either collapses or has a delamination inside the hose that sometimes blocks the flow.

It sounds like the flow is stopped for a bit and then blows open when it overheats. My two suggestions could cause that, so could a golf ball in the system but that seems unlikely.

 

[joegr]

Did "all the components" include the radiator cap (not the overflow cap)?

 

[G-666551]

We are having the exact same issue. Did you ever find out what was causing this?