Hello, in need of some advice for some heater issues I'm having. My heater is blowing cold at idle and then when I get up to around 1500 RPM it starts blowing hot. It stays hot until I idle back down at a stop and then it blows cold again only to blow hot when I get back up and going. I have verified my coolant is all the way full. My actuators are working as expected. I'm running out of ideas at this point and hopeful someone has encountered this and has a solution. I'm sitting at 104,000 miles on the odometer.

Thanks in advance

 

Sounds like the thermostat is constantly open.

 

I thought about that, but didn't consider it much because the engine temp gauge is running normal. Nothing bouncing around or overheating. I'll have to look more into that. Thanks!

 

Air bubble in heather core? Have you changed your water pump recently?

 

Yes, changed the water pump as part of the timing belt replacement. I didn't get done at the stealer, but a really good local mechanic. Took back to them and had them look at it. They even raised the front up and did everything possible to try to eliminate that possibility. I guess that could be the issue.

I just went out and looked at the radiator hoses. They are on the right below the air intake. Not sure if I'm able to do the thermostat myself. Not much in the way of videos for that for the 13 RDX.

 

If the temperature gauge is ok, then 100% you have air in the heater core. Did your really good local mechanic fully vacuum the system before adding new antifreeze?

 

They certainly should have taken air out of system but apparently they were lazy and didn't do it. You may want to go back to them and let them properly take the air out of it (if they know how to do it though!)

It is highly recommended to replace the thermostat with TB and WP replacement after 100K miles. Changing the thermostat is principle is supposed to be easy. The only problem is that one of the bolts is hidden under wires and it is very tough to reach. You need assistance from another person who should hold those wires down with a prybar while you are removing that infamous bolt. The rest is pretty much easy. Also you need to remove the air filter housing to have enough space to work in that area.

Here's a video that shows how to do it:

 

Got it. Thanks! I know what I'm going to do this weekend. I found a video in another thread about bleeding the system, so going to see if that's something I can do with a funnel, etc. Hopeful that's the solution. I've not gotten any warning lights or error messages, so hoping for the easiest solution here

 

Kits like these are cheap and easy to use when it comes to properly bleeding the coolant system

 

I followed the bleeding process to a t and ran the car for about 30 minutes and the only burps I got were when I squeezed the radiator hoses. I can say confidently that there is no air in the system. I did not observe any improvement in the performance with the heater at idle.

Is there anything that I can do to diagnose if the heater core is the issue?

 

It sounds like you're on the right track, this def isn't the best video in the world lol but my next steps would be flushing the heater core to ensure there isn't anything stuck in there.

 

To help diagnose the problem get yourself an infrared thermometer and check the temperature at the inlet (bottom) and outlet(top) heater hoses near the firewall at idle and a higher rpm and also at different blower motor speeds. This can tell you a lot about any difference in coolant temperature at the different rpms and if there's a coolant flow problem through the heater core. When I get a chance I'll get temp readings on my car at idle for both heater hoses for reference.

When did the problem start, any difference when the water pump was replaced?

 

Great question on the timing. I noticed it after the timing belt service, but that was right when the weather started turning colder and I hadn't run the heat any before then. Could have well been an issue before and just didn't know it.

 

It could very well be a stuck open t-stat.. and really its not an expensive part if you wanna throw the parts cannon at it! . if you have an good obd 2 scanner what does the temp tell you. whatever you do just get an OEM honda part. Do as DCS stated by checking the hoses. The rad hose is the hot and the bottom the cold. if your Top hose isn't getting hot and then staying hot its the T-Stat. This all being said.. did your mechanic replace the water pump? and if so did they use an OEM pump? Chinese pumps and the like can have issues!

 

They didn't replace the thermostat at the time. I observed that the heater hose was hot going in and warm going out. I looked at trying to flush myself, but ended up taking to the stealer and they flushed the heater core and treated with CLR. Now it's blowing hot like a furnace.

I appreciate all of the help and advice. I was able to provide them with all of the steps I took and helped isolate the issue. Now I have to go sell an organ to pay for it

 

I'm actually looking for a pair of kidneys to buy. what is your asking price? I'm sure we can strike a deal.

 

After my trip to the stealer, I'm about ready to make a deal! LOL