Jeep Repair: Cooling System, jeep cj 7, radiator cap

Question
I have a 1979 Jeep, CJ-7, six cylinder.
Punctured radiator and bent fan, just replaced with a rebuilt radiator, new fan and hoses.
Gauge before replacement barely moved.
Now running very hot under light conditions
Water pump seems tight.
Do I have a bad radiator, (it does circulate) or what is my next step?
Hope you can help.
Harold T  

Answer
Hello Harold,

  Occasionally a rebuilt radiator does turn up bad, but just to be sure, here are a few things to check. If the cap is old, replace it. With the Jeep running, open the hood and check to make sure the fan is turning as it should. If the fan is going, take the Jeep and drive it up an incline, so that the front is raised up, the steeper the incline the better, as long as it's safe. Now, have a bottle of coolant ready, and open the hood. When you do this, you will want the engine to have been running for no more than 10 minutes, because as you know, the radiator cap will be under some pressure. Open the cap and let off any pressure, with the engine running. Once the pressure is released, remove the cap fully. Some coolant may overflow out the cap, which is fine. Next, turn the heat on as high as it will go. Watch the radiator filler neck. If the coolant goes down, add coolant until you can't add anymore, and replace the cap. This procedure is called bleeding, and is a very common cure for Jeeps that just had the radiator out, and are overheating. Last of all, try replacing the thermostat, and checking to make sure your coolant is between 50/50 or 60 coolant 40 water. Let me know if you have any other questions. Good luck with the JEEP! --Arcticatman