Problem with Overheating and Warning Lights

[aileron37]

2015 CX 5 2.5L Had an issue with the temp sensors (po11 a) replaced them, now have the check engine and the engine overheat light on (starts blue but turns to red quickly). Pretty sure we have no air trapped in the system. Drove it about 6 miles heater was very really hot and overheat light stayed on.

Now even with a cold engine the overheat light (and service engine light are on) and the fans runs for about 5minutes afterward even if you only move the car a few feet. Thinking I may change the thermostat and give that a try.

Any thoughts?

 

[Jmaz]

Lights and codes aside, overheat in 6 miles would lead me to believe that there is still air in the system. Have you checked the radiator level each time on a cold engine before startup. May need to add more coolant. Is the overflow bottle reasonably full or is it empty and the radiator level down. It can take a few times for the air to work out.

Were the temp sensors really bad or possibly the symptoms were present first and caused a mis-diagnosis.

The OBD code you show looks incomplete. Is it still present and does it return after erasing it. What is the code?

Possibly the new sensors be faulty/incorrect and the cause of the overheat light with a cold engine that would not be overheating. Exactly what sensors were changed and what led you to believe they were bad.

Changing the thermostat is a PITA and I doubt it suddenly went bad. I would not touch it at this stage of the game. Interesting that this occurred after changing the sensors but it was OK before.

 

[aileron37]

Changed out both ECT sensors (PO11A via code reader as the check engine light came on). after the sensor change I checked the coolant level several times when cold as I drained it and refilled it. My first thought was air too. Had it on ramps and added coolant while idling and heater on. Only had a few air bubbles. The overflow bottle is at the full mark. I can squeeze the larger radiator hose and get coolant to come out an open cap. If there is air I don`t know why I cannot work it out!!

 

[HyFlyer]

How is your water pump belt? (It's a separate belt than the serpentine belt sits closer to the engine and only drives the water pump)

 

[Jmaz]

Changed out both ECT sensors (PO11A via code reader as the check engine light came on). after the sensor change I checked the coolant level several times when cold as I drained it and refilled it. My first thought was air too. Had it on ramps and added coolant while idling and heater on. Only had a few air bubbles. The overflow bottle is at the full mark. I can squeeze the larger radiator hose and get coolant to come out an open cap. If there is air I don`t know why I cannot work it out!!

You want to burp the air out on the level not raised on ramps. With radiator filled to the top of the neck for starters, level should drop when thermostat opens at full operating temp (or close) and rev engine and maintain at 2500-3000 for a couple minutes. You should see the level drop as someone revs the engine while you observe. Check radiator level and let rest at idle for a minute. Repeat and add coolant until no more coolant can be added. Check the next morning before starting cold engine . Top off coolant again if needed. If coolant is needing top off on the first morning, check it again the next day.

I still think air is the culprit here. Lots of heat is a good indication the heater core isn't clogged. In the heater mode with fan running there will be a difference between sensor 1 and sensor 2 readings. Sensor 1 is the hot (engine temp) coolant going into the heater core. The fan blows heat from the heater core into the compartment thus removing heat and results in lower temperature at sensor 2 which is after the heater core outlet. At an idle with fan off both temperatures will be close and maybe even identical.

There are youtube videos about this but don't go jumping right away into changing the thermostat. And if you do, use a OEM Mazda thermostat. Mine cost `$25 from a dealer. Cheap insurance against a cheaper aftermarket failing and causing possible expensive overheat engine damage and requiring a tow. They typically don't overheat in the driveway at home.

A bad radiator cap can also cause overheating. Your factory cap is now 10 years old. Replace it with a high quality one like OEM Mazda (expensive but it protects a much more expensive engine-- think of it that way). NOT a Stant brand or chain store cap. And skip the caps with the release lever on the top. OR going a less expensive route, I replaced mine with a Sankei KH-C17 for about $13.( Sankei supplies them to auto manufacturers.)

That's all for now. Try burping it again and let us know what you find.

 

[Lazy2.5]

I'm really hoping you are not continuing to drive with the red coolant light solid.

 

[aileron37]

Forgot to reply Looks like the coolant was fine, no trapped air. Issue was one of the replaced ECT Sensor caps had a bad connection. Like I said, it would show overheating even with a cold engine and now a PCM code. Once warmed up in the driveway all coolant hoses (and heater) got warm. All seemed like a normal running engine. Still thinking its something electric or computer. So I took off both sensor caps and put them back on; NO GO. So removed them and cleaned them out with an electronic contact cleaner and boom all if fine !!!!!!! No warning lights, no codes and runs great again. Thanks for all the troubleshooting advice.

 

[madar]

As an FYI, Harbor Freight sells these funnels that prevents air entering the system while changing coolant.

https://www.harborfreight.com/no-spill-radiator-funnel-kit-58423.html

 

[madar]

A bad radiator cap can also cause overheating. Your factory cap is now 10 years old. Replace it with a high quality one like OEM Mazda (expensive but it protects a much more expensive engine-- think of it that way). NOT a Stant brand or chain store cap. And skip the caps with the release lever on the top. OR going a less expensive route, I replaced mine with a Sankei KH-C17 for about $13.( Sankei supplies them to auto manufacturers.)

That's all for now. Try burping it again and let us know what you find.

Thanks for the reminder. Usually what happens here is the rubber gasket swells over time increasing pressure on the system which will eventually cause a leak, usually in the radiator somewhere.

 

[Jmaz]

Thanks for the reminder. Usually what happens here is the rubber gasket swells over time increasing pressure on the system which will eventually cause a leak, usually in the radiator somewhere.

Haven't heard of that failure mode. I would think the spring would still compress and allow the pressure to release. I've seen where the gasket compresses and hardens and starts to leak and allows the coolant to slowly "boil" away. Slow enough while driving not to see any steam escape. Followed by overheat. Could develop on a long trip in hot weather. How often do people check their coolant level anyway and could catch it early. You know how that goes. Some people never raise the hood assuming the oil level is fine because they get it changed. That and many other things keep the repair shops in business. So it goes.

 

[madar]

Haven't heard of that failure mode. I would think the spring would still compress and allow the pressure to release. I've seen where the gasket compresses and hardens and starts to leak and allows the coolant to slowly "boil" away. Slow enough while driving not to see any steam escape. Followed by overheat. Could develop on a long trip in hot weather. How often do people check their coolant level anyway and could catch it early. You know how that goes. Some people never raise the hood assuming the oil level is fine because they get it changed. That and many other things keep the repair shops in business. So it goes.

The swelling of the gasket prevents pressure release. Actually a common problem.