I agree with others that 208°F is not "way too hot". The electric auxiliary fan doesn't even start operating until the temp is 212°F.

As for the slow leak, you can "rent" a cooling system pressure tester from any of the big box parts stores. They're easy to use, and you can pump up the system pressure to 18 psi and look for leaks in the comfort of your driveway or garage with the engine cool. You pay for the test kit when you pick it up, and then get a full refund when you return it. I think you have 30 days to return it. With the kit I got from AutoZone, the correct adapter was the orange one, I recall (adapter number 5).

I also agree with Richard that the throttle body heater is a likely source of the leak. The TBH is a notorious failure point on the DII. Another common failure is the white translucent plastic coolant reservoir. They can develop leaks at the seam or where the small nipple attaches at the bottom.

But, I'll add too that so long as the reservoir didn't run dry, the small leak probably isn't the cause of the higher temps.

 

A little pro tip for the throttle body heater plate... I went through a few of them before doing this... I took a piece of 220 sand paper, put it on a table saw top (the key is a flat top), and then passed the throttle body plate across it a few times before installing. Haven't had a leak since.

 

Yes, this is good advice. But, a great many of us also simply bypass (or block off) the TBH circuit. Foolproof.

 

Update: I replaced the thermostat this weekend. Bled the system. Then started up to check for leaks. Within 5-8 min, temps were up to 200 and climbing. I let it cool, bled it again, started it, and again it was up to nearly 200 in no time. I removed the battery box for better access to the thermostat and hoses, after feeling around, I found the bottom hose coming out of the thermostat was cold, and the bottom of the radiator was cold with a few drops of coolant. I started it back up again and gave it a few revs to 2000-2200 rpms and found coolant spraying out of the radiator. So, my radiator is shot.

More info: Ambient temps were 55-60 degrees, original head gaskets, original water pump, hoses changed a few months ago. Should it be a surprise that the radiator let go? When changing the radiator, are there other components that should be changed too?

Thanks,

 

Was the leak on the top right corner of the radiator as you face the engine?

 

The leak was in the lower center. With the engine at normal operating temps, the lower 1/4th was cool to the touch. When reving the engine, fresh fluid would spray out towards the engine.

 

Check the condition of the power steering cooling loop and the A/C hard lines (and the transmission cooler, if you have one) while you have the radiator out. Much easier to do something about them at that stage rather than have to remove the radiator again if any of them have a problem down the line.

 

I'd seriously put in an inline thermostat instead while it's all out. A carrs4x4 or allisport aluminum coolant reservoir, or just a new coolant reservoir is a great idea. I'd also bypass the throttle body heater plate and then renew the plastic coolant Y at the bottom hose if you didn't do that. there is an aluminum one carrs4x4 makes that I plan to get when I switch out my hoses in the future. otherwise, just make sure to bleed it properly. Nissens radiators are good.

 

Thanks tnrangerover. I sent you a message on instagram as well. I ordered a radiator from Rovers North. I read about Nissens radiators after ordering from RN. I may return the RN one and seek out a Nissens and your other recommendations. I am repairing with another 100k miles in mind so I want to do it right.

 

Unless going to a full aluminum rad getting a 100K out of the plastic end tanks are a toss up...I have a nissen in both of my d2s with no complaints thus far, replaced both a year ago and maybe 10-15k miles on each disco. The inline mod is a must as well imo.