[Pnut]

I recently serviced the i30, changed all the fluids including the coolant. When i refilled the coolant it didnt take enough so first drive after it pushed a lot of air through and got a bit hotter than normal, i refilled again when it cooled down and temps returned to normal. It drives fine, no issues.

Now i noticed several weeks later i have to keep topping up the coolant reservoir as it has emptied out, I expected once or twice but this is starting to get me worried especially as the wife hardly looks at the gauges when she is driving it. Would this still be pushing air pockets through or have i got a leak somewhere? Oil isnt contaminated and the engine is running fine so i dont believe it has blown a head gasket (i could be wrong of course, but i doubt it is that), i cant see any leaks though at the rate it needs refilling any leak would be small. The only thing i could think of is maybe when i removed the radiator drain it damaged/unsettled the probably baked o-ring and may be leaking under pressure from there, or maybe removing the radiator cap damaged the radiator or cap seal though i would expect to see other evidence.

Any other ideas?

[CraigB]

Are you sure you're not filling to the full "hot" level while the engine is cold if so the excess coolant will be expelled when the engine is hot and once cooled again the level will look lower than where you filled it to the first time.

It could also be related to the first use of the heater as that will usually take some water after being drained, always best to have the heater running/open when refilling.

Other than that try idling the car in the driveway for 15-20 minutes and monitor for drips underneath.
 

[Pnut]

Are you sure you're not filling to the full "hot" level while the engine is cold if so the excess coolant will be expelled when the engine is hot and once cooled again the level will look lower than where you filled it to the first time.

It could also be related to the first use of the heater as that will usually take some water after being drained, always best to have the heater running/open when refilling.

Other than that try idling the car in the driveway for 15-20 minutes and monitor for drips underneath.

I wouldnt be worried if it is still had some in the reservoir, i know it pushes in and out as it heats up and cools. Last time the bottle was empty when the car was cold which is what had me concerned.  I know it had a bit of air to work through but wasnt expecting this much, from past experiance it usually pushes out after 1-2 warm up cycles but this has been a few weeks worth.

I was thinking the same thing about heating it up and looking for drips, i wonder if there are pressure testers you can use instead so im not looking around a boiling hot engine bay and radiator fluids.

[CraigB]

i wonder if there are pressure testers you can use instead so im not looking around a boiling hot engine bay and radiator fluids.

Radiator pressure test kits are quite expensive though it's rather easy to call into a local radiator or service centre and ask them to test the pressure for you.

[eye30]

Something similar hsppened on a car I had some 40 years ago.

It turned out to be the radiator cap was at fault.

[Pnut]

Something similar hsppened on a car I had some 40 years ago.

It turned out to be the radiator cap was at fault.

Ahh the 80's, it was a simpler time lol

Good call, i will give it a go it it continues. It was a bit problematic to remove, the seal looked ok though but then who knows if it is really good or not

[Pnut]

Well it looks like it was just all the bubbles working through, its been a couple of weeks and a few decent drives since the last fill and it seems to be maintaining the level now.

False alarm from a panicky new owner... rookie mistake lol