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To overheat, or not to overheat

I have a 2001 Nissan Frontier Crew Cab XE with a V6 (without the supercharger). I bought it on Halloween night (no comments, please) with only 42,000 miles. It now has 112,000 miles on it. I moved from Georgia to Kentucky and heard that I needed to have the cooling system flushed/filled to prevent it from freezing in the winter time. I then noticed that it would periodically “overheat.” The temperature gauge would climb up to the line just below the “H” and then I would turn on the heater. I read online about a “bleeder valve” on top of the intake manifold. I loosened it, squeezed the radiator hoses to get all of the air out and then tightened the bleeder valve. I then let it run until the thermostat opened, revved it up to 3,000 to let all of the coolant flow. Now, at various time with no specific reason, it will run fine and then just “decide” to overheat. I can drive it on the interstate for fifteen minutes, park it in front of my house and then have to “tack it up to 3,000” just to get it cool. I’ve changed the thermostat and had the water pump tested. Neither of them are faulty. My mechanic vacuumed out all of the air from the system with a special tool the dealer recommends using and it still does the same thing. What’s going on with this vehicle?

The coolant system should have a pressure check done, but I would throw a new radiator cap at it just for kicks.

Sitting still and revving the engine makes it cool down? Sounds like it isn’t circulating well enough. A blocked radiator, maybe? Did this start when the system was flushed, then?
Are the fans turning on high when it overheats?

Barkydog…I thought about the cap as well but it seems like a band-aid.

RemcoW… it actually did start after the cooling system was flushed and filled. Some research I’ve found leads me in the same direction as you’d advice. I will try that next.

Thanks guys.

The possibility of a bad radiator cap isn’t something that should be so easily disregarded. If it opens too soon because of low spring tension the system cannot pressurize and the boiling temp will be lower, if I remember that correctly. If it is sticking the system will over pressurize and cause a new place to escape off the pressure. Either condition could cause erratic behavior on the temperature gauge. Are you sure it is over heating and not just an air bubble at the temp sensor. Bringing the RPMs up would indicate you are moving water around to either cover the sensor or just actually move the water around in the block.
I have seen new water pumps with a stamped impeller not move as much water as a cast impeller cause similar issues you are talking about if all the air is truely gone from the system.

Well, I had the radiator replaced and so far it seems to be working fine. I am now going to be more cautious about having my cooling system flushed from now on. Thanks for all of the advice. I appreciate it.

Glad to see that the problem is fixed, but if it comes back, I’d have the fan clutch checked.

+1 Glad you got it licked.
Also thanks for the update. We don’t always hear what the outcome is.