Coolant - disappears like a Ghost

[volvogal8]

2006 XC90
Hello,
I am needing to fill my coolant about every 7-10 days. I always keep it topped off so the low coolant light doesn’t come on. There is no leakage onto the ground. I’ve checked the line and don’t see any leaks. It has to be going somewhere. The idle is rough. If I keep
The gas filled over half the idle is much better. Any suggestion or experience with this issue?
I really need to keep this car going.
Thanks, Kate

[MoVolvos]

2006 XC90
Hello,
I am needing to fill my coolant about every 7-10 days. I always keep it topped off so the low coolant light doesn’t come on. There is no leakage onto the ground. I’ve checked the line and don’t see any leaks. It has to be going somewhere. The idle is rough. If I keep
The gas filled over half the idle is much better. Any suggestion or experience with this issue?
I really need to keep this car going.
Thanks, Kate

.
No coolant on the ground, out of the expansion tank cap nor in the cabin but have rough idle?
.

.

[BlackBart]

It could be a small external leak and evaporates on the hot engine right away. Don't go to worst case scenario first, check the basics.

[abscate]

Hello , Kate.

First, run the heater on a cool day with all the windows up for 10 minutes then go in and smell for sweet coolant. Usually you can pick that up. That’s a leaky heater core which isn’t too serious for damage but it’s messy.

Connect up with someone who can help guide you through removing you spark plugs and inspecting. We can help you here , too. What you are looking for is evidence of very clean plugs that are getting coolant on them. That’s more serious. You can also sometimes detect this at the exhaust pipe , smelling for coolant smell there. Don’t breathe it in, just go back there for a minute and see if it smells “ sweet”

Finally, look around all the hoses for white residue, that’s coolant leaks which rapidly dry, so you might not see wetness

Check back after all that

[dikidera]

Could be heater core.
Could be the transmission cooler.
Can be a small leak from the coolant tank on the lower hose underneath it.
Can be the engine oil cooler (but you will see milkshake on the dip stick).

Could be getting burned in the cylinder.