I have taken two road trips in my C-230 both trips I had the check coolant level alert come on. I replaced the sensor the first time as the engine tempature never went out of normal operating range. The second time I added coolant to the overflow tank even though the engine tempature never got to high. I have never owned a car that used coolant when there was no problem with that system?
Using the electronic gauge to monitor fluid level can have undesired results. Try to always physically check the overflow tank on level ground with a cool engine.
Is there any indication of fluid migration between the oil and coolant? Milky looking oil or globs of oil floating in the overflow tank are good indicators. This would be the worse case scenario for your problem.
There are certainly other ways you can loose the coolant on the fly without leaving a puddle.
When you run it and get it good and hot, after it cools down, sitting in one spot, are there any puddles? If not you have a running loss where the coolant is dripping directly into the air stream and not leaving any traces.
Coolant leaks can be the hardest things to find sometimes. Takes lots
of mirrors on extensions to look under hoses and in/around parts.
If you suspect a head gasket leak, you might pull the spark plugs and
see if one is burning cleaner than the others. The moisture in the
cylinder tends to clean off the plug. Compression tests will not always find a
coolant leaking past a head gasket.
If you suspect a running leak, let it idle for a long while and get it
good and hot, then shut it down and see if anything shows up.
Check the weep hole and seals around the water pump for trace moisture. Check for any staining or discoloration on the hoses and radiator. Hopefully you’ll find something that’s blowing out under pressure.
Benzman
Thank you for the info. I found stains at the back of the motor by the head gasket. I still use very little coolant, 1 quart of coolant before I started my trip home and 1 pint of water since I came back form Florida the second week of February, but you can tell it came out under pressure. I was advised to replace the head gasket. With this happening only after nine or ten hours of constant highway running will the repair be worth it or will cost a lot more if I ignore it. This is very expensive and it seems like the motor is being torn down pretty far anyway; so here is my dilemma, Should I have the motor rebuilt because it is already torn down this far already, do just the head gasket or ignore it till it gets worse?
Ignoring any cooling system related problem yields engine repair(albeit serious) to engine replacement.