Overheating Built Evo 4

Hey Guys,

Just after some info and advice as I've been having cooling issues with my evo 4 for a bit. It runs fine when driven on the highway and cruising through suburbs, but after driving it around for a bit, the temps climb up pretty high (about 70-80% on the dash gauge) once you stop/let it idle for at least 1-2 mins. After it's overheated once from stopping, it will heat up when I'm driving slowly (traffic or through parking lots).

I have noticed that temps climb up for a bit when I accidentally bog the engine and don't give it enough RPM's (could be a hint that it's the water pump)

Parts I have replaced:

All rubber coolant lines (except the two heater core hoses)

New t bolt hose clamps for radiator hoses

Have done a cooling system pressure test that said there were no leaks

New Fenix alloy radiator

New OEM evo 4 radiator fan

New OEM coolant gauge temp sensor

New Dayco Thermostat (not sure if using an OEM stat will make a big difference)

My evo's setup:

Forged bottom end (might be using an AirTrek block since it has an AirTrek sump)

AirTrek Sump setup

Evo 7 head with GSC anti tick lifters

Stock evo 4 turbo setup

Stock evo 4 fuel pump, with evo 7 injectors

Remapped Evo 6 ECU

At this point, the only parts I haven't replaced are the head gasket (1.3mm Cometic MLS head gasket) and the water pump (used an AirTrek water pump when it was rebuilt).

The fan definitely turns on (both low and high speed), and the car drives fine, even when it heats up (not sure if there's a boost/engine cut in the OEM evo 6 ecu)

From what I've replaced and after the cooling system pressure test, it looks like a flow problem, which means it's probably the water pump, or just a bad head gasket, but I'm not sure if the AirTrek water pump is any different from the evo water pumps. I did read somewhere that some people had to use the 2.4L Mitsubishi outlander water pumps on their evo's running an AirTrek block with an evo head to make the block work.

Another point is that it's using the evo 4/5 thermostat setup with the evo 7 head. I did order the OEM parts needed to run the evo 7/9 thermostat setup, but that won't be coming in for a few more days. I'm most likely going to do the water pump and see what that does before doing anything with the head gasket.

TIA for any info

There was Airtrek water pump made my GMB with shorter blades - it always causes overheating... Hope you didn't install that one...

I honestly wouldn't be surprised if that was the case. Motor was built by the previous owner and all it says on the rebuild sheet is that it used a 4g63 airtrek water pump

Here is the picture of difference

Oh, by the way- for some reason Cometic gaskets aren't working too good specificly on 4g engines. I know a few cases when they failed.