Same thing happened to mine. I had a coolant leak, and found it to be the "little blue hose" to the EGR Cooler. Found out the only real way to replace that hose is to pull the cooler, replace the hose and reinstall the cooler. I don't have emissions testing in my state, so I made the decision, if it came off, it wasn't going back on. Before I had the EGR removed, the heat in my Excursion was a warm as any gasser I've ever owned. It was winter when the EGR was deleted, and I picked it up, and found if the air temp is below 20 degrees Frankenstein, the engine just doesn't really warm up. I had "warm", not heat. I found even if the temp was in the teens, and I drove home from work, which is a 30 mile mixed, city, interstate, county roads route, that wne I would stop at the fuel station near my house, the truck would kick up to hi idle because the coolant temp was so low. If it was closer to 30 and up... heat was fine, but when it was really cold out, no real heat. Even the factory "gauge" showed the heat was low. I still want to buy a winter front for that truck, but haven't....