My truck has started to run a little bit warmer in the last month. Oh, it's '95 F150 4x4 w/a 4.9 and 102,000 miles. I had the cooling system flushed at about 80,000 miles, and is still pretty clean. Anyhow, it used to never hardly get passed the "n" in the normal. Now it runs between the r and the m, more towards the m, and gets there fairly quickly, like w/in a couple of miles of driving if started when cold. The other day I had the air conditioner on it at a stop light it went up to the "L" so I of course cut the air off. Does it sound like my thermostat? What temperature one should I put in? I live on the east coast where it gets hot in the summer, and tow a fairly often. My radiator has a small leak, could this be contributing to it? Is one brand of thermostats better than another or are they all about the same? Any tricks to changing it? Thanks.

 

It could the rad leak...check the coolant level to be sure. Have the leak fixed, won't cost much. Pull your thermostat and hang it off the rim of a pot of water on the stove using a wire. Heat the water and use a thermometer to see what temp it opens. That's your thermo temp rating...yours is probably 180 degrees if its stock. If it don't open, replace it...just don't overtighten the two hold-down bolts on the thermo housing, it will crack if overtightened. Could also be your water pump. Sometimes they fail and don't cause a massive leak. None of these is too hard to repair/replace, just take your time and it'll go well if you have a basic set of tools.

 

My radiator has a
>small leak, could this be contributing to it?

If it is leaking, I would recomend replacing it also while you have it drained. You could try a stop leak, but I don't like them because they can clog radiators.

Is one brand
>of thermostats better than another or are they all about the
>same?

I suppose any will work, but I use Stant or Napa. My 90 f150 4.9 is supposed to have a 192 degree but Napa gave me a 195 and it works fine.

Any tricks to changing it?

When installing the new thermostat, use rtv silicone to glue the thermostat into the groove in the outlet and let it dry for an hour or so. That way, the thermostat can't come out of place when installing it and cause the outlet to leak or crack when tightend. Then use RTV on both sides of the gasket and put it together.

Your problem may be the radiator. If it leaks, replace it and the thermostat. Also check the water pump bearing for play. It is easier to get to and a small price to pay to change it if other things are apart. On my truck I replaced the radiator and thermostat at 120k and at 125(yesterday), the original water pump went. I wish I would have relplaced the pump when I had the radiator out. Those things like to go out at the worst times.

Hope this helps. Good Luck

 

If you purchase the Ford thermostat it is designed to lock into the thermostat housing by turning it once you place it in the T stat housing . No need for any other sealants other than the T stat housing gasket .

 

All the other advice is good. One other thing maybe to look into is with 102K miles maybe your radiator core is starting to get clogged up a bit. Depending on the design you might be able to look into the radiator and see if the core tubes are starting to get narrowed down with deposits. The deposits could be dirt, rust, calcium, or even normal plating effect from antifreeze. With enough miles even perfectly clean systems will start to "plate" the core tubes to the point where your flow is decreased and temperature goes up.

If your problem started suddenly though, I would suspect the Tstat or the leak, the leak may prevent the system from reaching the proper pressure and thus overheat.

Good Luck,

Jim Henderson