warp2diesel wrote:
Your delta T is too much from the water outlet and the head that is close to the cooling jacket. A delta T of 5 f-10 f would be more in line. Since pulling the thermostat is a pain, I would hope for a bad hose of other large debris flapping in front of the radiator inlet that would be quick to pull out. Thermostats can be intermittent on failures by not fully opening. If you can go with out the CRD for a couple days.
I would yank the thermostat and put it into a pan of water on the stove and test it. If it behaves per the specifications in the service manual, it is not the problem. If you see wax leaking out of the wax element actuator that opens the flap, you have a junk thermostat that will not fully open and produce the symptoms you describe.
Smell your coolant in both of your CRDs, if yours has a sour or burned smell that your Wife's CRD does not have, replace it with the kind used in the CRD. Wet sleeved engines can have serious problems (Holes through the cylinder wales) with poor quality antifreeze. A PH test would put any concerns to rest if both smell the same.
I know that Cat, Navistar, Cummins and Detroit Diesel produce wet sleeved engines and should have suitable coolant if you don't want to do business with your local stealer. Other members with ORT experience may want to advise on the specific trade names of coolants that are suitable.
Since you have two CRDs investing in a thermostat may be a good move, just in case you find out you need it.
Thank you!
I checked the two CRDs side by side. The coolants look the same and smell the same. I squeezed the top radiator hose and was able to get them both to gurgle the same amount of water with the same amount of resistance into the overflow tank.
I did find one odd difference: The the section of the T-stat housing that connects to the hose on hers is rock solid. On mine, it rocks slightly. Since it doesn't leak I figured maybe it was just a press-fit wobble on a soft gasket....but it prompted me to take the T-stat out for a closer look.
So....
I thought I would be clever and take out the darn T-stat using a special sidewinder wrench I got years ago. The hope was to get the thing out without removing the airbox and inlet hose to the turbo etc.. etc.... I did manage to take off the two bolts on either side of it and the one on the bracket on the top but it still won't budge...... I hope I don't have to take the manifold off. :
Still, I have a gut feeling it isn't the T-stat. If I can get it off, I'll replace it anyway (I can only imagine how many hundreds $ it will cost) but from what I see looking into it with a flashlight I don't see any goop or debris.