Chrysler Repair: Why does the car keep overheating ?, intake manifold gasket, head gaskets

Question
QUESTION: I bought this car second hand and they were troubleshooting an overheating problem. They had already replaced the radiator, thermostat, pressure cap and starter. They claimed the water pump needed replacing. I have since replaced the water pump and head gaskets along with taking the heads to the machine shop and having then tested and machined in hopes of solving this problem. Yet even after all this it can only drive 5-10 minutes before boiling the 1/2 & 1/2 coolant inside the overflow. A mechanic noticed that the cap and right side of the radiator are cool and the left and hose are hot and tight with pressurized fluid. After overheating, it can take up to 20 minutes for the coolant to flow naturally back through the radiator. I have had it flow checked and pressure tested. Finally, I took the thermostat out completely and the gauge continues to rise and fall at it's own pace and seems to be unaffected by turning the heat on or off. Also without change in driving or traffic it seems to reach the red and fall back with a mind of it's own, yet I know when it will overheat by the temperature of the heat in the car, the inside heater throws cold air just before overheating again...the fan seems fine but may be turning on late...what else can be done ? after reading many forum Q&A I am wondering what to do next...another pressure cap ? a freeze plug ? a temperature sensor ? a radiator chemical flush ? intake manifold gasket ? another pressure test for a leak that has not been found ? I really want to drive this car with a thermostat before winter...HELP

ANSWER: Hi Wendi,
A couple of ideas. Was the radiator replaced in the past year or so? If not, then it might be plugged up because of the mechanic's observation that one manifold is hot and the other cold. That could mean that the tubes that flow across the radiator are plugged. But if it is a new radiator then that should not be the problem. Another explanation is that there is a bubble of air trapped in the system which is causing the flow to be inefficient. You didn't mention the year, model or engine size so I can't give you the specific procedure for how to refill the system so as to eliminate that possibility. So do a follow-up question with that information and then I may be able to tell you about how to get rid of that if it were the cause.
Finally, is there a chance that the brakes are dragging? After you have driven it for 5-10 minutes stop and see if any of the wheels feel hot to the touch which would be a sign of that problem.
Do the fans ever come on when the temp rises to hot? Do the fans come on when you ask for AC? Have you done a fault code readout on the powertrain controller? An Autozone parts store may do that for free, or around $40 at an independent shop.
Everything so far sounds like it was appropriate but tell me answers to my questions, please.
Roland

---------- FOLLOW-UP ----------

QUESTION: I am not sure when they replaced the radiator [but it was replaced due to the current oveheating problem] I did find sealant in the new radiator, they must have tried to seal it again after replacing it but by then it was the head gasket [and I replaced that] a mechanic said the waterways inside would not likely be plugged in a new radiator, due to sealant. plus another mechanic said he did a 'flow test' and the water flowed through fine [I have not done a chemical flush yet] I thought I got the air bubble out but if there is a specific way for different models then i guess I haven't. it is a 1994 Chrysler LeBaron, 3.0. yet the system has been drained and filled from scratch several times...most recently the water pump was replaced. I had the brakes checked twice and replaced one they found no issues but I will check for a hot wheel [as you suggested] the fan comes on but only after it has reached 2/3 hot on the gauge. I did a diagnostics on it but the only code was about the transmission and the guy said it must be a ghost in the system since the transmission was shifting fine. he told me the code would mean the transmission was not shifting at all.

Answer
Hi Wendi,
I don't have anything to offer about refilling the system on the 3.0L engine, but other engines have some specific techiniques.
Other than that, I would suspect the radiator if one side remains cold while the system overheats. A radiator shop is probably equipped to do a reverse flush on the engine which may be the next step. Do check for a dragging brake.
The only other thing I can conjecture about is the timing belt tensioner spring which may, if too weak, allow the belt to slip on the water pump pulley. I don't know if this is common but that would be a reason for poor circulation if the pump weren't rotating at full speed.
Roland