Got an 04 disco. I can idle for over an hour and stay at 185 to 189. As soon as I start driving it (35 to 45 mph) will begin to overheat. I'm not leaking coolant into oil. I'm not leaking coolant anywhere, but air is getting in and I'm assuming exaust gas but I haven't done a chemical test.
I made an inline cooling mod and deleted the thermostat all together, heater core aswell, just to see if it would change anything and it hasn't.
coolant level pretty much stays the same just appears to have more due to the air getting in.
I've left it alone for about a month and today the top radiator hose was still pressurized with air so im assuming it's still air tight but I really have no idea what could be happening.
water pump, radiator, reservoir, and head gaskets were just replaced.
so I'm just trying to get some opinions on what could be happening.

 

How are you defining "overheat"? Please be specific.

 

If it will idle forever and not overheat but overheats when driving you have a plugged radiator. I have had clients with new radiators that were bad.

 

I'll let it get to 230 before I shut it off. It will continually rise if I dont.

 

it might be, I'm doing a chemical test right now but it's testing negative. The coolant hose where the bleed screw would go is filling with air and stays pressurized so I assumed it might be exaust gasses entering the system. Could a clogged radiator cause that too?

 

Recently got a truck in that did this, it was blown hg and failed chemical test as well as pressure test. Suggest you do both. Oreilly and Advance have the kits for free.

 

did the chemical test. No combustion gasses are in the coolant. Not sure if this is related but just noticed reving the engine in neutral will cool the car with no coolant leaking from the reservoir. While in drive and reving to about 1500 to 2000rpm coolant shoots out from the reservoir

 

Pretty sure you have a blown hg, suggest pressure test.