Hi, I'm looking for a bit of advice... I have a 2013 Mazda CX5 2.2 diesel. My OH does the maintenance generally, but we're searching for some advice. He says that the coolant seems to move from the radiator into the expansion tank, so he moves it back again, but it moves again over the course of a day or 2? Any ideas? Also, when checking the coolant this morning - car hasn't been driven or started for 16hrs and it was 2oC overnight, so cold engine - he said there was pressure in the radiator when taking the cap off?
He's thinking replace the thermostat? We recently replaced the radiator cap in case it was that but it's had no effect.
Any ideas what to do next please?!

 

Where in the world are you?

These engines are known to have head gasket issues.

 

Cambridgeshire, England.
There aren't any other signs of head gasket problems, oil is fine, no exhaust smoke tinge. The coolant level doesn't drop, it just moves about in the system?

 

Excuse me for making assumptions on your knowledge of cooling systems but since the thermostat is the only "valve" in the continuous flow of coolant propelled by the water pump why not suspect it of being stuck closed? After the engine comes to temperature, is the upper radiator hose hard with excess pressure? This condition is what will compress the pressure rated spring in the radiator cap to expel coolant into the bottle. Does the engine overheat? Does the heater core warm the cabin or is it getting starved for coolant? Just remove the thermostat and go "wide open" with just a gasket installed. That would eliminate a lot of the puzzle. Could be something as simple as a defective radiator cap. A pressure tester would tell you that. Cheers,

 

Brilliant, thank you. I have very limited knowledge of the coolant system (or any system!).
The temperature in the cabin is always spot on, so no issues there. But I have considered the thermostat, it's just that googling says it often affects the inside temperature so I wssnt sure. They're pretty cheap to buy though so I think it'll be my next try to see if its that. Thank you.

 

The head gasket issues on Mazda Diesel engines is compression gasses entering the cooling system, pushing coolant out of the radiator & into the overflow bottle, usually more than the capacity of the overflow bottle, also exbating the issue is these vehicle also have known issues with radiator caps failing, which can prevent the coolant being drawn back into the radiator as the cooling system cools down.

 

mine having same issue apps head gasket, but was told this is a known issue with Mazda

 

Hello Grim,
I have just signed up today to this forum as I'm trying to help out my father in law with a Mazda CX-5 that has an overheating problem.
His car is overheating & leaking from the overflow bottle, spraying coolant all over the engine.
Which cap did you use as a replacement and if he does get one if he should carry a spare with him just in case?
The cap was changed by his mechanic with a Tridon CB 16110, which is the correct cap for his car.
The same mechanic recently changed his radiator as well and has most recently said that he thinks it could be a piston problem & he advises we sell it off...
Since then, a good friend, who is also a licensed mechanic, have a look over the car. He did a pressure test and checked the coolant for gases and he said that it appears to be okay but he would suggest changing the cap, just like you. also do you think the car would run fine cold if there was some internal engine problem?
Thank you
Jason

 

Book it in with Mazda, if it has a good service history there is a good chance you may receive a free engine.

 

Did you or anyone else solve this because my son has exactly the same vehicle and exactly the same faults? Thanks in advance.