2004 Honda Accord Ex

Did you buy a Honda thermostat? Did you install with burp nipple up? If yes on these 2, pressure test system and cap to see where your leak is. If you lose pressure but not externally, then you have an internal leak most likely head gasket.

Is all the air out of system? Test coolant temperature sensor also.

Guru9FSV8- thermostat was bought at autozone, when I installed it i made sure the burp nipple was facing up.

Do you have heat in cabin? Thinking maybe you have a clogged heater core not letting fluid circulate. Pressure test next.

I have A/C Blowing cold but no heater not at all? The heater hasn't been working over 5 years. The Overheating problem barely started. Thats when I started to change everything I have mentioned.

Do you have to fill antifreeze from time to time? If so you have a leak. Antifreeze should never have to be filled. It circulates but is not used by vehicle. Only fill should be when changing it out

Find your heater core lines on the firewall in the engine bay and touch these hoses and see if they are warm or hot. Thinking you have a clogged heater core. One line is in and one is out.

No since 5 years I havent touched the A/C and it works great with no problem just no heater whats so every. At first i was thinking water pump but its not leaking or no other noise is coming from water pump. The last thing I can think of could be the head gaskets, but theres no radiator fluid in the motor. I also did the oil change and the oil and motor cap seems normal.

Antifreeze NOT Freon. Talking heating not air conditioning. Do you have to fill the antifreeze from time to time? Fluid that is in the radiator.

When I check it do I check it with the car and heater on? If the heater core is clogged and this cause the car to overheat? I would also have to see if the sensor on the heater core works. Alot of these accords the heater core sensor go bad located passanger behind the glob box

Yes on the question about adding antifreeze/ coolant from time to time. I checked and replaced all radiator wholes. As well I checked for any leaks on wholes and no leaks or spot.

Check the white reservoir. What I do is fill it to the fill line or slightly above it and take a black sharpie marker and make an exact line as to the level. Then I know if I come back in a few days or a week, wether the car is using antifreeze or not. If it is using...the car has a leak. Check it cold. Mark it cold and check it cold in the reservoir. This level should never go down unless you change it out then you have to refill. Antifreeze does expand when you turn car off so the expansion goes back into reservoir until cold again.

You have a leak. The engine cooling system relies on pressure to work. You are adding so you have a leak. It could be internal. Blowing it out tailpipe.

Can the leak be on the head gasket I would need to check the pressure on the block if its blowing it out by the tailpipe. First im going to try to see if the heating core is clogged or leaking. Ill keep up those the updates thanks.

Yes internal leaks are primarily due to the head gasket

Pressure testing is easy. I bought a mighty vac on amazon for like $40. Instructions are on package. I also watched a few YouTube videos.

There are videos also on YouTube how to clean out a heater core. It is easy also. Garden hose and some clear hose and hose clamps.

This may or may not help but try bleeding air from system like this remove cap from overflow tank fill with antifreeze to full mark leave cap off and start vehicle and let idle you will notice level in tank start to rise this is normal once thermostat starts to open level in tank will drop add more antifreeze to full mark then put cap back on.