Coolant temperature sensor

Just put in the new thermostat. It's a Mazda brand thermostat. Put coolant back in and burped the cooling system with a lisle spill free funnel kit. I ran the car for at least 20 minutes. No more bubbles came from the funnel. Car still doesn't get heat. It will feel warm for a few seconds then go cold. ObdII scanner still shows at least a 30 degree difference between the two ECTs. Running out of ideas.
 
Blender door actuator might get stuck on cold, thus you have no heat. This may or may not be the same issue with CEL.
 
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Just put in the new thermostat. It's a Mazda brand thermostat. Put coolant back in and burped the cooling system with a lisle spill free funnel kit. I ran the car for at least 20 minutes. No more bubbles came from the funnel. Car still doesn't get heat. It will feel warm for a few seconds then go cold. ObdII scanner still shows at least a 30 degree difference between the two ECTs. Running out of ideas.

http://nema.club/2014wsm/workshop%20manual/n6w01/html/id0102s6381500.html

http://nema.club/2014wsm/workshop%20manual/n6w01/html/id0140g0802400.html
 
I called the dealership shop this morning. They said they were going to call the mazda techs to see what they say. I will try to check the connections with the blend door, but I was wondering something else. Does anyone know of the cx-5 has a heater control valve? I tried fining it in the shop manual but no luck. I also asked the guy at the dealership and he said he would have to ask the mazda techs.
 
Does anyone know of the cx-5 has a heater control valve?
I was wondering about the same thing, and it doesn't look like it has one. Your manual HVAC blender control is purely mechanical, no electrical actuator. This doesn't eliminate the possibility of the cable slipping off though.
I wonder if they really have disconnected the heater core to test for a good water flow, or just felt the hoses' temperatures and called it a day...
 
yeah, they told me they ran water through it and had no signs of blockage, but who knows. I did slip off part of the panel under the glove box and I can see the heater core. the lower pipe gets really hot, while the upper pipe takes a while to get warm but does not feel as hot as the lower. I'm not that familiar with heater cores to know if this is normal. I know its basically a small radiator and the coolant flows through to heat the air. But, should the lower pipe be hotter than the upper one?
 
So the dealership wont get to my car until next week. I'm going to try to troubleshoot some things this weekend. I'm not sure if the issue with the heat is related to the engine code. Especially since I just replaced the thermostat. Why didn't mazda put in a temperature gauge? Anyway, Sometimes the heat will be kind of warm but not much and then soon it just goes normal temp. there are two vents in the center console below the radio. The one on the right towards the passenger is the one that gets warm sometimes, while the one on the left is noticeably colder than the vent right next to it. I'll try to get behind the dash and make sure there or no loose connections on the actuators and see if i the air mix door is functioning correctly. Running out of ideas. I wish mazda would trade in a car with the check engine light on.
 
See if you can take a look at the blend door movement when you change temperature settings. Yours is manual, so should be obvious.
There shouldn't be very significant temperature difference between inlet and outlet heater core hoses. Air bubble still trapped after the core?
 
Is it possible you have a water pump problem? Low or intermittent flow. These days the pump may have it's own sensor.
 
Some cars have a electrically controlled valve that shuts off the heater water flow to keep heat out of the passenger area when running max air conditioning. My C5 Corvette does this if the auto ac is set at 60 degrees and I think my infiniti G35 also did this. Not sure if the CX5 has this valve or if yours is stuck/not functioning...
 
I took out the glove box and got a good look at the connections. The actuator seems to function correctly. When I switch between A/C and heat the actuator moves and for what I hear it seems that the blend door is working. However it is possible the its moving, but not all the way. I've looked at a few different diagrams and can't figure out wear the blend door is. FYI the shop manual refers to it as the Air Mix Door but same thing. I tried burping the system again this weekend but it didn't seem to help. I might be trying to do my heater core flush today to make sure it was done. It does seem that there is slight heat on both passenger side vents, but none on the driver side. When looking at all the connections under the dash everything looks to react the way it should when turning the knobs. But again, the heater core seems to be the problem because the inlet pipe get very hot while the outlet pipe has a major temp. difference. The dealership did confirm that this CX-5 does not have a heater control valve to control the flow of coolant to the core.
 
The dealership did confirm that this CX-5 does not have a heater control valve to control the flow of coolant to the core.

All the info here points to debris caught in the heater core. But I'm thinking there must be a heater control valve to control the flow of coolant to the heater core and maybe the dealership meant it was not controlled electrically. In this case the linkage to the valve would be suspect (but this doesn't explain the check engine light).
 
That's what I'm thinking also, so I will have to do my own flush. They told me that this car doesnt have a heater control valve at all. I even checked through the hoses and done see anything extra on them that looks like that. The check engine trouble code is saying engine coolant temp sensor. There is an ECT sensor where the coolant hoses go into the fire wall to flow through the heater core. From the looks of it, it seams that the outlet hose feeds into the connection where the ECT sensor is. If I'm right, and there is a blockage in the heater, it would explain why the sensor is getting such a different temp reading after the heater core, compared to the engines ECT sensor.
 
I flushed the heater core last night. Water seemed to flow with no problem. I did a reverse flush and a little debris came out but nothing that seems like it could have clogged the core. I burped the system this morning. but the heat still isn't working. I'm at a loss. With a brand new thermostat I'm not sure what else it could be. No leaks. I called the dealership to confirm taking my car in tomorrow and they said one of the Mazda techs is out so they are down to one guy and I can't be seen till Tuesday. So I have a week to mess with this thing an figure out what is going on. I am going to drive it around this evening to get the coolant flowing through and try to burp the system again after it cools down. I was looking at the radiator hoses. When I replaced the thermostat I only removed the thermostat housing and left it attached to the hose. So I know I put it back in the right place. I'm confused because the hose attached to the thermostat housing goes to the bottom of the radiator, while the top hose (the one that gets hot after a while) goes directly into the engine. I know the hot coolant is supposed to flow down the radiator to get cooled and go back into the engine. From diagrams I have looked at the thermostat should open to let hot coolant flow to the radiator to get cooled. But that doesn't look to be the case here. I am positive I did not revers any hoses because I only removed the the thermostat housing and left the hose attached then put it right back. Does anyone know about this?
 
Thanks. I have so many diagrams printed out Its probably the whole repair manual by now. The diagrams shows its right. I'm about to give up until the dealer can see it, but I will try to burp the system a few more times to make sure the heater core doesn't have air trapped. I wish I had a steeper driveway so i wouldn't have to jack it up to burp it.
 
Thanks. I have so many diagrams printed out Its probably the whole repair manual by now. The diagrams shows its right. I'm about to give up until the dealer can see it, but I will try to burp the system a few more times to make sure the heater core doesn't have air trapped. I wish I had a steeper driveway so i wouldn't have to jack it up to burp it.

The manual does not mention having to jack up or angle it? http://nema.club/2014wsm/workshop%20manual/n6w01/html/id0112h5800600.html
 
I tried that way before. Im just wondering how that lets any trapped air escape from the system. For other cars, I have seen the best way to burp the system is to use the lisle spill free funnel kit. it locks onto the radiator cap spot and you fill it about halfway with coolant and then run the engine for a while. When i did this a few times i saw bubbles coming from the funnel so i know it was working. Jacking it up is suggested on cars because the cooling system has so many ups and downs. Jacking the front up helps the air rise towards the from of the system where it can escape through the funnel. I searched through the repair manual for a bleeder valve of some kind to make things easy, but there wasn't anything. unless they call it something complettely different. I search for air valve, bleeder, bleed valve, coolant valve. Nothing.
 
I've been looking at this on Identifix, not too much of a progress. I know you've got quite some skills at coolant replacement by now, but I noticed a couple of steps that I don't think you mentioned before. Have you given the motor some gas as per the manual?

A. Refill the coolant from the cooling system filler neck until it is close to the top of thecooling system filler neck.
Refill the coolant into the coolant reserve tank up to the F mark on the tank.
Install the cooling system cap.
B. Start the engine and warm up the engine by idling.
C. After the engine warms up, perform the following steps. At this time, be careful of the coolanttemperature to prevent overheating. Run the engine at approx. 2,500 rpm for 5 minutes.
D. Run the engine at approx. 3,000 rpm for 5 seconds, then idle.
Repeat step (2) several times.
E. Stop the engine, and inspect the coolant level after the coolant temperature decreases. If it is LOW, REPEAT STEPS A-D.
 
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