Hello,
I am a new owner of a Mazda CX-5 (2,5 petrol AWD, 2019, from USA) and need advice / help from experienced users

For the second time (2 weeks apart), the "engine check" icon and a fault in the engine control system appeared.
After connecting to the computer, the error "coolant temperature too low" appeared.
After erasing the error, everything was fine for 2 weeks and it reappeared yesterday.

I wonder what the problem may be.
When I start a cold engine in the morning, within 1-2 minutes the engine heats up to approx. 140-160 degrees F (American version), i.e. to approx. 65-75 degrees C. and the air supply warms up nicely. This temperature holds, unless I push a little harder, then the temperature briefly rises to around 170 degrees F (almost 80 degrees C) and drops back to around 150 degrees F. Outside it's around 3 degrees.

This error appeared to me in the morning with a cold engine 2 weeks ago, and yesterday during the day (earlier it had traveled several dozen km).

Generally, nothing is happening to the car, the power is ok, the engine speed is ok, only this message.
Have any of you had a similar situation?

Next week I am leaving the car to the mechanic so that the computer can measure the temperature, but out of curiosity I asked the Dealership about the prices of the parts (temperature sensor and thermostat).
What was my surprise when I read that the thermostat costs EUR 570.
Are there any cheaper alternatives? This price scared me, because thermostats for other brands cost not more than half of this price.

Thank you in advance for the help of forum members.

 

Are you saying that the engine temp never exceeds 170f? Never? How are you measuring this?

Normal operating temps should be near 200f and if your engine isn't reaching that temp then you have an issue. My guess would be that the thermostat is in need of replacement.

This is why you're seeing an error message from your car.

 

Yes, I also think that this is thermostat failure, that's why I asked for the price and got the suprise
I tried to find some cheaper one (not original or used) but without luck

 

That's a crazy price for a thermostat! Is that including installation?

 

In this model, according to the Dealership, thermostat is together with with cooling control valve (it's in drawing no. 15-16Z).
Thermostat separetely cannot be replaced (according to what they claim ).
Very strange...

I don't know if it's worth to do it if I don't see any negative symptoms (besides icon of "engine fault")...

 

I'd get a second opinion on those parts if I were you. If it was mine I'd do the work myself.

If your car is not ever reaching proper operating temps it would be very bad for your engine, for multiple reasons. This needs to be fixed.

 

Looks to me like the thermostat is a separate item:



PE0115171.html

 

...but I have CX-5 KF (2017-), the new model. The part you sent is for the older model.

 

What they told you is correct - the actuator, sensor, and mechanical thermostat are all packaged up inside of the part called the coolant control valve, and none of those individual components are replaceable. This is a known issue at Mazda, and they have issued a TSB stating that replacement of the valve is their only resolution to the problem - not what you want to hear, but it is what it is. They don't provide any method or specs in their service manual for testing this valve, and so far there has been no information on what the actual problem with the valve is, or what they've done to fix it (but who knows if they even have fixed the problem). A dismal effort so far from Mazda on this problem IMO.

The price of the valve in the USA is around EUR 260, however I have no idea how much international shipping would cost you, assuming you could find a seller here who would be willing to do that.

Just an FYI that my CX-5 has a target operating setpoint around 195F, and the coolant valve (and fan when necessary) consistently maintains the coolant at that temp. As Conrad 16.5 already posted, it's really bad to run an engine significantly colder than the design temp for an extended period of time, so you really should get that valve replaced as soon as possible.

 

Ok, I understand. Thanks guys for all your help.