kiransr1992

Hi!!
I have a Honda Accord 2004 Lx 4 cyl with 140k miles on it, recently the heater stopped working and the car overheated.

I took it to a mechanic he said the Thermostat needs to be changed, I changed the thermostat (It was a Honda genuine part), the overheating problem got solved but since then the heater doesn't work when idling.

It works fine when driving or when the engine revved up to 2000 rpm, but as soon as I stop at a signal it blows cold air.

I tried accelerating up to 6000 to 7000 rpm for some time and it seemed working good after that for some time (heater worked fine when idling), and after that the same thing happens,
can someone please tell me where could be the problem is, I do not know much about the cars...

Thanks in advance...
Sai
.

poorman212

Re-check the coolant level in the rad. Many times when an issue like your are describing happens, the coolant in the rad/engine is low so only at higher RPMs is there enough flow to get the coolant into the heater core to produce heat.

There are other things that can cause this but lets start with the simple ones before we get too far into things.

kiransr1992

Thanks a lot for the reply..
I opened the radiator cap and I can see there is no coolant in it or its very less to be visible,
but in the coolant reservoir (white plastic tank) the coolant is more than the max level does this indicate anything??.
at the time of thermostat replacement the mechanic filled up the coolant I don't know where it has gone...
I'll fill up the coolant and check if the heater is working..

thank you...

prodjay10

Take some coolant out of the reservoir so it's within the min and max. Make a note of the level. Top off the coolant in the radiator. Drive it and monitor the level of coolant in the reservoir.

poorman212

Getting the air out of the cooling system can take a bit of time.

Not sure if you want to get into this or not - don't take that the wrong way. I'd top off the coolant in the rad, ok leave it a bit below the very top where the cap seals - leave the rad cap off. Turn the key to on - like the car engine was running - set the heat to max, a/c off and then turn the blower to "low" or off. Then start the engine and let it run, yes some coolant might push out the top of the rad - don't worry this is normal. Let the car idle for 20~30 minutes, keep an eye on the temp gauge and if at any point it starts to overheat shut it off. As the car is running check the level of the coolant in the rad, if it drops really low - like you can see the silver fins of the rad, add a small amount to get it back towards the top. At some point while running the cooling fans to the radiator should cycle - even if they do not after ~30 minutes of engine run time you should have pushed almost all air out of the system. Shut the engine off.

Top off the coolant in the rad if needed and replace the cap all the way......drive the car and see what you have.

WARNING - hot engine coolant can burn so you must be aware of that and take caution.