Sometimes the "low coolant" light REALLY means LOW COOLANT!
 

The W124 used to get false readings from the "low coolant" indicator last year. Coolant level was fine, so I cleaned the sensor and the problem went away.

Last night, the light came back on. When everything cooled down, I check the level and it was indeed, low. So I topped it off and things are fine. Appeared to be about a pint or so low.

Here's my question. Should I be concerned about having to top off the coolant? Engine temps remain at around 87C, even in the hot Texas stop-and-go traffic situations! No sign of any fluid on the ground, either.

Does this stuff evaporate over time?:confused:

Note: practically every cooling system component has been replaced in the last three years...but the head gasket is still original...

Pressure test the coolant system when engine cold & hot you should able to find the leaks........also check the heating coil inside windshield washer tank for leaks.

Thanks for the quick response! ;)

I'll do just that!

Uh...spoke too soon...how does one "pressure test"? :confused:

Interesting. Pulled the connector off last night and saw that it was slightly damp. Maybe a slow leak has manifested itself?

Could you please explain how to remove the circular clip surrounding the coolant tank sensor. I am stumped. Thanks.

Source to get a pressure tester
 

If there is an AutoZone store in your area, go there and rent one. I rented one two days ago. I paid $75 and will get my money back when I return it. Pressure test the cap. Mine caused the car to overheat. I personally suggests replacing the one you got and the sensor along with a new mounting kit that inclues an O-ring, snap ring, and the male part connector.All parts are about $35. A 100 miles after I put the head back on the car (3 days ago), the car lost antifreeze/water and got mixed with oil. My sensor was dead and it was ordered before I even test drive the car, however, it was late. The head came back from the shop today and it was fine. The first machine shop that had it did not machine the surface right per the second machine shop and water/antifreeze fluid leaked into the cylinders. You will need a snap ring plier to get the ring out.
Good luck
Meza

I would like to suggest that you check the radiator cap itself. Make sure the rubber is still in good shape, and that the spring is still in good shape. I had to replace the cap on my W124 after only getting 89k mi. out of it. (I also noticed corrosion on the cap, and on the brass neck on the tank)

-Larry