Hi.
After running for about an hour, the thermometer pointer on the dash steady at the center of scale, stopping, popping the hood open, turning engine off, getting out of the car, opening the hood, touching the radiator core with my hand in front of the fan, (less than 10 seconds after turning the engine off), it is cold, I mean cold top and bottom areas !

The radiator inlet tank is hot, the outlet tank is warm, but the core is cold. Can you please try with yours, confirm and post ? What is going on ? Never expected that, cannot understand...

 

1. On a D2, the coolant temp sensor is monitord by the ECU, which computes the signal to send to the idiot light with a pointer. The gauge is not to be trusted. It is designed to stay at the 50% mark until the slow roasting over hickory coals is complete. A scanner or Ultra Gauge can show a much better picture of what is happening.

2. This is a horizontal tube radiator. The entire tank on one side feeds all tubes, and they are collected by a tank on the far side which sends that coolant toward the themostat. If some tubes (usually lower ones) are clogged, they will be cooler than others. My indy rad shop guy said he looks for no more than 10F difference top to bottom on the fins. I suspect you would have to read with an IR thermometer. The collection tank will normally be hotter than the fins, which are doing the heat transfer over a very large surface area.

 

Thanks again for your permanent assistance.

Unreliability of the dash thermometer ? Another detail to add to the overheating-prone design of the Disco2.

Understand clearly the workings of the horizontal tubed type of radiator, the tanks temperatures, but the core being cold is out of sense.

Guessing... If the entire core has a buildup of whatever internally, insulating the heat transfer capability; it would show that symptom, right ?

The radiator was washed with detergents, peeked at the tubes as was possible trough the openings and looks very clean, no deposits.
Is there another logic explanation ?