I have a 2002 dakota 4.7, last January I overheated crossing the Sierra summit on a ski trip. It overheated pretty bad before I could get off the freeway. I filled it back up with coolant and nursed it home. I drained the system replaced the stat and cap (the cap seal was split) and filled it up again.
Over the last 5 months I have continued to keep an eye on it and have had to add a little (maybe 2-3 times). My normal driving is to and from work 34 miles round trip flat ground 2/3 highway. Last weekend I took a 100 mile trip again through some mountains (not as much climb though) and was getting hot towards the end of the drive (didn't overheat but got up to about 3/4 on the gauge). The overflow was boiling. Filled the radiator and drove home the next night. I did not ever get past 1/2 gauge on the way home but again the overflow was bubbling.
So I have been watching real close and everytime I top it off it transfers over to the overflow, but will not transfer back.

O.K. so now what I have done this weekend so far.
1. Replaced the after market cap (20 lb) with dealer cap (21 lb).
2. compression test, 3 cylinders 180, 4 175 and 1 168.
3. I installed a pressure gauge in the coolant bleed port to keep an eye on the pressure. It does not build any pressure until warm (5-6 minutes) then creeps up to 10-11 pounds idle 13-15 pounds revved up. It holds the pressure quite a while after shut down. When I open the radiator cap it is always a pint or so low and it has moved to the overflow.

Sorry this was so long I wanted to give all the info I could think of. Any ideas would be great. Thank you for taking the time to read this.

 

have you checked your oil to make sure theres no antifreeze in it

 

Yes, Sorry I forgot to mention I drained the oil (even though I changed it right before last weekends trip) still looked brand new. No trace of water.

 

radiator

 

I have not checked the radiator. I have been focusing on a head gasket. The reason for this is when I tried to burp the system I was getting a never ending supply of small bubbles. I figured exaust in the cooling system, However the pressure gauge I installed does not increase in pressure until warm and doesn't go past 15 lb.

I should also mention even though the coolant is always low the temp gauge never (except the two mountain trips) goes past 12 o'clock.


Do you still think it could be the radiator?

 

well they do crack cause they are plastic and aluminum my first one had cracked even thou it had never overheated

 

Well I ran a pressure test through the fill port (test kit on loan from autozone) pumped it up to 15 lb. Over the coarse of ten minutes it dropped to 9 lb. then seemed to halt. I put my cap back on and ran the pressure up to 13 lb (on the gauge installed in bleed port) and it holds for quite a while (slowly drops as it cools) so I figured the autozone tester wasn't sealing right. What should I do to test the radiator heat scan or removal?

 

autozone has a uv leak detector kit that you could use to locate your leak this would probley be the easiest at this point on trying to find it i dont think they cost all that much either

 

Did you ever check your Frostplugs? I had to replace my frost plugs as i would drive it for 3-4 mouths and i would have to top off my coolent.