I just flushed my cooling system yesterday, I used the DIY T-in the heater hose thing. That worked great, but, since then I've noticed that my truck is running warmer. It's not overheating but I can tell the needle is warmer than what it was. I can tell now when the thermo opens. Should I just change the thermostat and see if that's the fix? Thanks.

 

There may be some sludge on the thermostat, if it hasn't been changed ever or for many years I would change it. I would also change the radiator cap. There may be a leak in your system somewhere also.

If you change the thermostat you may as well change the hose that connects to it from the water pump. The stock thermostat housing has a grove that the thermostat sits in, I put a couple dabs of gasket maker in the grove and stick the thermostat in there. I let it setup so it sticks good. It is really tough to make sure that thermostat is in the correct place when you are trying to put the housing back on, it can get out of the grove and you can crack the housing when you tighten it down or have a big leak and have to do it over. Make sure you install the thermostat pointing in the right direction also.

If you see the Mr. Gasket chrome O-ring seal thermostat housing at the parts store and buy it, the stock replacement hose that goes from the water pump to the housing will no longer work. I bought the other hose that connects from the water pump to the heater hose T and cut one of the elbows out of it to go from the water pump to the Mr. Gasket thermostat housing. The Mr. Gasket housing has an O-ring seal and it very nice, really not that much money either, I think mine was 12 bucks. Great upgrade and saved me having to clean the stock one.

 

This may be a dumb question, but: have you checked the coolant level to make sure it's full? You can rarely refill a drained system to maximum capacity without running it some. Just a thought.