Hi , 

i have SMAX 09 2.3L MK1 and i have slow collant leak , it's unvisible after 2 different garages check this issue with pressure test .

recently i replaced : coolant tank + original cap and it's 2 pipes , radiator + radiator hose and the water level is still dropping slowly every trip without it being visible to the eye.
I also checked the heating radiator and there are no signs of leakage on the piping . 

I must mention that occasionally (not regularly) I see drops coming out of the exhausts (no signs of smoke), I also checked the gauge and the oil cap and there are no signs of sludge on them (even though the coolant tank has a little black on the side and one of the garages told me that because the tank is new it is his silicone Although the coolant was replaced several times it returned), a reverse pressure test was also performed on the engine and the pressure was maintained.

I'm quite at a loss and discouraged about this issue considering the fact that I bought this vehicle less than a year ago (all in all I'm satisfied with the vehicle and the comfort it offers 🙂 ).

I would appreciate tips and ideas for a solution.

Have you tested the coolant for signs of Hydrocarbons ?

It's possible to have a very slight head gasket leak that only occurs when either the engine is very hot, or when under heavy load like accelerating hard.

A hydrocarbon test kit can be bought cheaply from the likes of Amazon. Test the coolant to see if there are any exhaust gasses present.

EXAMPLE of test kit: https://www.amazon.co.uk/RELD-Cylinder-Combusion-Universal-Motorcycles/dp/B07RS3N98V/ref=sr_1_6?crid=1MKSXYYJ2NJHC&keywords=hydrocarbon+test+kit&qid=1681984700&sprefix=hydrocarbon+test+kit%2Caps%2C217&sr=8-6

Hi , 

thanks for your update , i thought about this option : slight head gasket leak and still hope that this is not the problem .

i'll try to check and tesr coolant signs of Hydrocarbons  , just wanted to check if someone had similar problem or any other idea for the leaking source .