radiator light on every now and again on 2000 Mercedes-Benz ML430

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I have a 2000 ml430 and just replaced the radiator and 2 hoses. Since the change the radiator light on the dashboard comes on every now and again. The last time it went on the coolant was bubbling but the temperature was fine. The light just turned on again but the coolant is not bubbling.

What can be causing this problem?
(1) Answer
(2) Comments
Did you change the radiator cap when you replaced the radiator? But only change this when the vehicle is cold and at the same time you can check the coolant level
If it didn't come with the new radiator then probably no. Do you know if new radiators from the dealer come with the cap. I don't even think it has a radiator cap. Do you know for sure if they have caps. I thought that was for older models.
I see Gates and Stant have caps available and they have a 20 psi rating and it might be mounted on the reserve tank, Available at any auto parts store