The problem started after a crack in the radiator caused all the coolant to leak out while my 16 year old was driving the car on the interstate. Unfortunately he continued to drive for several miles with the engine hot, before deciding to pull over. Luckily it was a cool night so the engine was at least getting some cold air flow. When I arrived the engine was extremely hot. We got the car home, replaced the radiator, cooling fans, fan switch, and thermostat. Refilled with coolant and bled the air. When we finally started the car I was shocked it cranked right up and the engine sounds great, runs smooth and has power. No white smoke from exhaust and the oil is clean. However, as the car reaches normal operating temperature the top radiator hose gets really hot, but the bottom hose never warms up and the interior air flow never blows warm. My first thought was a bad thermostat even though it was brand new. So I replaced it with another brand new one. Same result. I noticed when I start the car both the top and bottom hose get really tight and firm. The top hose feels hot like it’s trying to push water into the radiator but it has no where to go. The bottom hose is tight, but never warms up and doesn’t feel like there is any flow inside. Could this be a sign of internal engine damage stopping the coolant flow? I took the thermostat out and drove the car for a week without it, again it drives and sounds perfect, just stays below normal operating temperature due to constant water flow and colder temps outside. Reinstalled the thermostat and got the exact same results as before. Again no white smoke, no milky oil. Any thoughts?
2004 Accord LX 2.4

 

You mentioned taking out the thermostat and driving for a week. Are you using an OEM thermostat? The OEM thermostat is a housing/thermostat assembly.

 

I took the original thermostat out of the housing and reinstalled the empty housing to drive it. The two new thermostats I installed were both aftermarket, different brands.

 

Air in the cooling system perhaps.....

 

Did the op ever find the results or an answer to this? Because I have the exact same car with the exact same problem. And it happened the exact same way with the cracked radiator.. if anybody has any answers, please let me know. Thanks for everyone's time for even reading this

 

I eventually sold it to a mechanic to give to his grandson. Last time I talked to him he was still driving it without a thermostat. Runs good just not much heat during the winter. He thought it had a slight head gasket leak on the exhaust side. But without the thermostat there wasn’t enough pressure in the system to cause any issues. Good luck.