Have a 2005 Freightliner with a C7 that is having foamy coolant. All I know so far is that she starts it up in the morning and has no coolant in the sight glass on the tank, she brought it to the door this morning to have it topped off, and after only running for just a few minutes (from her parking spot to the garage door), I took the cap off and lots of foamy coolant came out. I haven't seen this before. Any ideas?
We had this happen to a few of our Cummins 5.9L engines. It ended up being a bad head gasket...the foam was greenish brown. We initially thought it was because we switched our shop coolant, but it wasn't happening to our other buses. There was no visible coolant leaks, but we were topping off the coolant every couple of days. Good luck, I'd start with putting a pressure tester on the coolant system and run the engine, see if the needle jumps up and down.
What type of coolant? Is the correct type called for by the engine manufacture? ( Cummins?) When is the last time it was tested? When is the last time it was changed?
It is Mobil CATEC1 coolant. This should be a suitable coolant for the engine. I don't know the last time it was tested or changed, but will dig further for that information.