Overheating after swapping 5sfe head, need some guidance! Options

[Mattattack]

So after finding a valve seat in my cat, me and a friend who is a mechanic swapped my 5sfe head, torqued all headbolts down to specification, resurfaced everything before putting new headgasket on, etc. after finishing it ran great for all of 10 minutes then started overheating and when we stopped and pulled the radiator cap off coolant was volcanoing. I'm still a noob/learning a lot of this stuff and I know it is a broad question but does anyone know where we may have went wrong? from what I've been told it is probably the new headgasket being blown but I want to know if anyone else has experienced this before i waste money/time sending the head in to get milled. Any help is greatly appreciated

[Box]

We'll start with the easy stuff first, did you let the coolant burp? Did you replace the thermostat? If it were the head gasket you should have oil/coolant contamination or white smoke out of the exhaust.

[Mattattack]

We'll start with the easy stuff first, did you let the coolant burp? Did you replace the thermostat? If it were the head gasket you should have oil/coolant contamination or white smoke out of the exhaust.

Tstat is relatively new, changed less than 2 months ago. I haven't checked to see if it's bad or not though so I will tonight. We did burp the cooling system when it happened but not for long so there may be a decent amount of air still in. right now its sitting in my friends shop parking lot and i had him start it up over the phone since I'm not there to which he said no white smoke or coolant volcanoing so maybe there is just more air needing to be burped out, at least that's what I'm hoping. Going back to look at it tonight, anything else i should look out for?

[Box]

Next time let it run without the radiator cap off and see what it does. An actual thermometer would tell you for sure what's going on, as what's in the car isn't really any good and any air bubbles can make it read high. Not really much else to look for.

[Smaay]

you found a valve seat in the CAT? what did the piston look like?

[Box]

I thought it said valve seal, so I went right over it. Indeed, how was the piston and cylinder wall?

[Mattattack]

Problem seems to be solved, just ended up needing to be burped some more thankfully. as for the cylinder walls and pistons they were worn but nothing too bad. Thanks so much for re-mentioning the burping thing I would have completely forgot about that

[Box]

Glad to hear it was something easy afterall.