I have a ?79' 350 C with 6 way blade and winch. My father and I purchased it mostly for firewood, helping get our sugaring operation going, a little thinning of the woods and logging. We've had it for about a year, mostly used it for clearing an area by digging up roots and pushing trees over, and skidding/winching some logs short distances. I recently had it delivered to my house where we did more of the same, but once the trees were down, skidded, blocked and chopped, it was time to move some dirt.
Since we've been using it we have found a few things that we plan to work on during the winter such as a frozen left track tensioner and a broken seal in right track tensioner. However, when i started pushing dirt, after a while I noticed that the water temperature gauge was running right on the red border. I shut the dozer off and noticed that there had been some coolant blown off on the bottom right of the front (if looking at dozer). I checked the coolant and it wasn't full. I put some more coolant in, and as i worked, later in the day noticed the same thing. the gauge went barely went into the red (gauge is 1/3 black,1/3 green, 1/3 red) , but was running hot, and blew off some more coolant.
My thoughts: The rad cap was junk. The seals were gone and wasn't tight, and when i took the cap off, there was no pressure built up. I took the cap to the auto shop, got the equivalent cap, but didnt see an improvement (same thing happening). The cap is 9 lb rated cap and didnt feel too tight when I put it on. JD has a cap i can get, but the dealers (3) that I have talked to dont know anything about what its rated for, or if its any different then what i have and there is only 1 rattling around the state... Maybe the one that was on the dozer when I bought it wasn't right? Is this what I need?
Or...I've been pushing a ton of dirt, uphill, for hours on end... Maybe I'm working it too hard....???

Any thoughts or guidance are very welcome. I'm learning about machinery as I go, but my father is a retired farmer, so hes been around dozers and other machinery and is slightly more handy we'll say.
Thanks!