Hi guys, I was looking to buy a 1995 NAS Defender 90 that had the engine rebuilt about 2,000 miles ago. I asked the owner how the engine was cooling since the rebuild. He responded by saying that the engine operated within normal temperatures and gave examples, such as driving it for several hours between 60 and 70 on highway with AC on and it was at 50% temperature. When left idling with AC on, it moved to 60% temp.

My disco II when left idling would never creep past 50% (it's never had a rebuild).

Is the temperature moving around like that on a D90 typical?

Thanks guys

 

First, never use the factory gauge to determine how hot the engine is, they are not accurate at all. In the case of your D2, plug in a good scanner in and read the real time temps while driving.
Driving in town should be 201 to 206
on the road, 195 to 198
at a 10 minute idle 206 to 210.
As for the defender I would install a good gauge, for the most part, they rarely had an over heat issue.

 

Adding to what Mike said:
This is because the temp gauge in your Defender is operating like a temp gauge should. The temp gauge in your Discovery, on the other hand, isn't really a temp gauge, it was designed so that the drivers who know nothing about cars wouldn't see it move like a normal temp gauge will. The gauge in the DII rises at a rate set by the ECU and then stays at 50% until it's too hot then it jumps to overheat. I have an independent gauge and the coolant temp is only 140 degrees when the factory gauge reads halfway, the factory gauge stays there on mine up to 205 degrees (which is the hottest mine has ever gotten). So that's a 65 degree swing that the factory gauge doesn't reflect. I've heard that it stays in the middle for even higher temps but I can't verify that.

 

X2 on the D2 keeping the owner calm about temps with computer programming. And a D1 is designed in similar fashion but uses different circuitry to obtain the same.

Important point about thermostats - from the Defender pages of the RAVE shop manual (attached) you'll see that the spec for the thermostat is to be "fully open" at number stamped on stat (shows 82 C). That's 180 fully open . American stats, like Stant, are rated to "start to open" at the nameplate rating, and be full open in 15-20 degrees more.

Most engines are designed to not force thermostat to be wide open all the time (otherwise why have one?). So a Defender with that 82C stat would be running at 160 - 170F, and that has a lot to do with it not over heating (as Mike mentioned). Putting in a replacement American stat can shift your running temp higher.

You can remove stat and test in a pan of water on the stove. You can also replace the stat with a 160 or 180F American style stat. IMHO running a 195F American stat is too warm for these engines, except in the frozen north, where having your fanny frozen to the seat is a real possibility. I do not support the tree huggers and the pollution abatement folks that want ever smaller emmissions, but that is just me, I live in a county that does not require annual testing.

I run a 180F American stat, and make 178 - 180 to 183 at roadway speeds, maybe get up to 187 on 95 degree day. In a D1.

 

Thanks so much guys for all of the information. This makes total sense. It didn't occur to me to check OBD temps while driving the D2.

and yes, I have noticed once when my D2 thermostat blew (because it did not stay wide open) that the temp gauge was just fine humming along in the middle and then wham-o, a quick jump to the right (followed by me making a quick jump to the right of the road).