I am new to the forum and jeep world. I just got a 1992 Jeep Wrangler YJ 2.5L. When i was driving home after picking it up all the guages worked good. The drive is about 45 min. About 15 minutes from my house the temperature started to rise i turned on the heat in the jeep and it keep going back in forth. By time I got home and parked the jeep the needle was right above 260. The jeep didn't overheat.
I have searched the forum and read over a couple of items to replace. I have replaced the thermostat and the temp sensor. when I start it up and it starts to get warm the temp guage automatically goes to about 250. I am not sure what to check next.
Check the level and condition of your fluids.... any coolant loss? You said that temp gauge read high, but Jeep didn't over heat... I ssume you mean it didn't boil over? Did you feel hood to get an idea of how hot this Jeep got? Any other issues?
The first thing you need to determine is do you have an overheating issue, or just a faulty guage. Infrared will tell you this pretty quickly. I'm not a 2.5L guy, but when the radiator cap is removed (cold engine), can you see directly into the radiator to see the coolant? If yes, leave cap off, start engine and allow it to run until your thermostat opens...... watch for good coolant flow, you should be able to see movement in the coolant. If not, you may have a bad thermostat or the fins on the rear of the water pump maybe worn off. You stated that you just purchased this Jeep... then you stated it has a new radiator, this makes me wonder if prior owner wasn't having this issue and just never found the cause, or didn't like the cause he found.
I changes the thermostat and temp sensor. I started the jeep and within 5 minutes the temp guage was already reading 260. I let it idle for about 20 minutes then i took it for a 10 minute drive didn't not boil over and no steam like it was over heating. I have come to the conclusion that the guage is broken.
If you really think your temp gauge is not working, try attaching an after market one. You can buy them Harbor Freight for about $10 and they are very easy to install. That would let you know for sure if it is a gauge problem.