2013~2016 CX-5 Radiator drain and fill questions

[ticker]

What’s the expectation for how much coolant drains from radiator. I drained mine and only got 1/2 gallon. Everything to read/watched said to expect a gallon. Refilled with a gallon of fluid.

Would the expansion tank still have fluid in it if the radiator was that low. It was right on the l line.

 

[Jmaz]

First thing I'd suggest is a new radiator cap. Yours is 9 years old if original. If for no other reason it's good insurance. You didn't mention any leaks but I could see that a leaking radiator cap can allow coolant to slowly "boil away" causing a low level in the radiator. When cooling down, the coolant contracts and shrinks in volume causing a vacuum that pulls coolant from the overflow bottle back into the radiator.

Too much "headspace" (low level) above the coolant level wouldn't allow enough vacuum to develop to pull coolant back in from the overflow bottle. So the overflow bottle level doesn't change. The low level also doesn't cause enough expansion when hot to push coolant into the bottle as well.

So again the bottle level doesn't change. That's my best guess. I'd start with a full system and a new radiator cap and monitor it. A half gallon is a lot of coolant loss. Beyond glancing at the overflow bottle level it's good to periodically remove the radiator cap and check the level at the filler neck.

 

[ticker]

Thanks. Thats a good suggestion. How full should it look at the filler neck?

 

[Jmaz]

Thanks. Thats a good suggestion. How full should it look at the filler neck?

I've always gone with servicing the coolant to the bottom of the filler neck on level ground after any air is worked out of the system. Which means checking the level cold for the next few days as operation works the air out and adding more if needed. The constant cycling of coolant back and forth to the bottle will establish a level. If the level is checked on a cold winter morning the radiator level (not the bottle) will probably be down a bit just from normal contraction.