Today, my 1999 Durango 5.2 4x4 was heating up like normal but it easily passed the 210 degree mark and all the way up to 250 when i shut it off withought a hiccup (I did have my a/c on and there have been much hotter days this week). My tranny also reached 250 so after that it needs new fluid and im getting a b&m supercooler so i should be good there. But i have never had the slightest problem with the engine overheating before. I determined that the thermostat had stuck closed cause the lower radiator was barely luke warm but after it cooled down it drove fine. all was good until i left a relatives house and im driving down the highway it pretty heavy rain about 30 mph and i have to pull over and as soon as i stop the temp skyrocked to 230 like nothing and my a/c wasnt on. I aslo have a 2500 cfm electric fan that ive had for a few weeks but its been fine until today. im replacing the thermostat tomorrow and u dumped in a bottle of water wetter earlier. And less than 2 years ago it had a coolant flush, waterpump, a/c serviced, and a new 195 thermostat. If anybody can help it would be greatly appreciated. I completely stumped the local oreilly guys today.

 

i lied. i did have my a/c on while i was on the highway but i shut it off before i pulled over.

 

Check the coolant level first before you buy any new parts. If it's low, try to find the leak first. Top it off, put the cap back on and run it with the heat on full blast (a/c compressor OFF) til it gets up to temp and see if you see any leaks on the ground. See if you get good heat through the vents. And verify that the upper and lower rad hoses are the same temp (or both hot as hell). The lower hose will take longer to get hot, but should get as hot as the upper as soon as the t-stat starts to open. If there are no leaks, see if it overheats on a road test. Don't just throw a t-stat in there without checking it first. If the coolant level is full when you check, then the t-stat could be an issue. But it could be other things as well, but I would start with the t-stat. Also, I hope no one ever put stop leak in your radiator. That **** is the devil!

 

All has checked out good. coolant level perfect, t-stat stuck once but after cool down and restart it was fine until i pulled over on the highway, i put stop leak in before i replaced the heater core but its had 2 flushes since, never had a coolant leak,i regularly wash out the rediator and condensor fins(the fins in the condensor are a little damaged and are blocked but ill get on that and it wouldnt cause a sudden problem). ill check on it tomorrow and check the a/c to make sure it cycling properly.

 

Cool! Yeah, if the level was full, it's most likely the t-stat. But it's also *possible to be a defective water pump. Some of these newer pumps have plastic fins on them and they break apart. But if your pump has metal fins, I doubt it would be bad after only 2 years.

Also, you say u have a new electric fan. Is the fan spinning the right way? I.E. pulling air through the grill into the front of the radiator instead of pushing hot engine air into the back of it? And are you sure this fan is adequate for the vehicle?

Also, a little damage on the fins are no biggie, as long as they dont break and cause a leak. Plenty of air will still flow through. I wouldn't worry about that.

 

It was a cardone waterpump with metal fins. And the electric fan is installed right and is more than adequate. I'm leaning toward the a/c relay because I had the a/c on and the compressor might not have been cycling. And new t stats going in soon.

 

The temp senders fail too, and the readings start to get funky when that happens. Luckily they are cheap to buy and easy to replace...it sits behind the alternator in the intake manifold. I'd wager if you replace that you're issue will be solved.

 

Thats possible except for the fact that my aftermarket gauges said the same temp too.

 

it turns out my a/c relay was partially shorted out and the compressor wasnt cycling on and off.