My truck is an 04 4.7 extended cab with four wheel drive and the towing package. I had a small coolant leak last November and replaced the upper and lower radiator hoses as well as the thermostat and housing.


About a month ago it started running hot on me when pulling a trailer that's 3,000 pounds at most when loaded. I was having to pull over when I saw the heat hand creeping up and let it cool off enough to add more coolant. When I finally got it to a local shop the mechanic told me the head was cracked and I needed a new motor.


Took it for a second opinion elsewhere and was told they could find nothing wrong with the truck. Put in a 180 degree thermostat after flushing the radiator. Radiator was filthy so it needed doing but didn't fix the problem.


I then replaced the radiator and took it to another shop that said the head was fine and there was just a lot of air in the system. Pulled my trailer which was about 3500 total for 42 miles before it got to running hot again. The motor sounds and runs great. No power lost at all. Pulls like a champ. No milky oil or smoke in exhaust.


Has anyone had any kind of trouble like this or know what I should try next? I've had it in three mechanic's shops and still don't know what's going on. Any help will be greatly appreciated.

 

Basically, there's three tests at play:

1) Test for exhaust gasses in the coolant

2a) Perform compression test with engine cold

3a) Pressurize cooling system when cold and see if system bleeds down

2b) Get engine hot with radiator cap removed and pressurize cooling system and see if system bleeds down

3b) With the pressure gauge still mounted and coolant hot, run compression test again.

Note if values have changed, or if the gauge on the cooling system changes as the engine spins over for the compression test.

 

1. Get your front end high up on ramp/jack and run with the radiator cap off to get rid of the air.

2. Tow package radiator is far superior to anything you'll find at the auto parts store. You'll probably want to get the CSF I mention in this thread. https://dodgeforum.com/forum/2nd-gen...-radiator.html

3. Rent a head gasket test kit like Magnethead mentions. Plenty of vids on youtube on how to use it. It sniffs the coolant for exhaust gases. It's free when you take it back and the blue solution only costs like five bucks. Clear your mind of the suspicions.

4. Once you get the cooling issue worked out, get rid of the 180 stat and go back to 195, especially if you run conventional oil. If your engine runs too cool, you risk sludging because water condensation in the oil will not evaporate like it should.

 

Have you checked out your fans? Mechanical fan and electric fan? When the motor builds up some heat the mechanical fan clutch should engage more and you should be able to hear it throwing tons of air. Or if you try and spin it with the engine off it should only make like 1/2-1 revolutions or something like that and stop. Just as long as it's not spinning round and round. and the electric fan should come on when the temp needle gets to about half way up (at least on mine) or when you turn the AC on.
I had a similar problem to you once and my radiator ended up being heavily restricted with junk despite clean looking coolant. But being as you just changed it that's not likely.

 

Had the same problem as you. Ended up replacing the radiator. havent had a problem since.