Check Coolant Light

lrh032146

2005 C230 Kompressor 155,000 miles
I get the "check coolant light", add a gallon of coolant, light goes off, within half tank of gas light comes back on...can see no leak on the ground under the car...where is this coolant going? Thanks

lrh032146

where is coolant going?

ray80

After adding coolant and running it a bit did you check to ensure it was completely full? . Any white smoke from exhaust (except when starting cold)?

Mr_Shiftright

Coolant is either leaking or its burning. There's no other way to lose it.

Given that, ray80 is on the right track here.

First thing I'd do is have the cooling system properly "bled" to remove all the air.

If that doesn't solve it, then have the cooling system pressurized and have it examined carefully for leaks under pressure.

If that doesn't reveal anything, keep the system pressurized and then remove the spark plugs one by one. If any of them have coolant on their tips, then you have a bad head gasket---and given the age and mileage of the car, a big decision to make.