My 2000 disco has been running with idle temps hovering around 206 with running temps at 194. I install a motorad 180 thermostat a few days ago and now the idle temps are 204 and running temps 201. It seems like everyone else that has installed these has had bigger temp drops. Should I keep it in, go back to the stock thermostat or should I step up to the genuine grey rover one? I'm in California btw. It has been in the 80s.

 

step it up with the genuine 180 stat, its likely that you have a faulty motobad stat.

 

I have seen the same as you with the cooler thermostat. Keep it, I saw 206 climbing a big hill with a trailer at 90deg ambient, running cooler without a "check engine light" is a good thing in the Rover.

 

I will have to see if I can get the genuine one in less than 3 days. I have a trip coming in 4. I was really hoping to see all the magical low numbers everyone talks about. I have to pull a small u-haul trailer and I just want to play it safe.

 

better safe than sorry. You might also have air in your system that's not bled out.

 

True. Well I will give it a couple days and see what happens.

 

I can only speak from my own experience. I have a motorad and it's great. I went from 205-215 down to 188-195. since installing my temp has never gone higher than 197 and that sitting in traffic for long periods. I also did a coolant flush and added purple-ice coolant additive.

 

If you have idle temperatures higher than running temperatures I would get the fan clutch checked. It could well be that it has got a bit old and is not driving the fan properly. You may also have a faulty water pump - the one on my V8 had been damaged by the previous owner not using anti-freeze.

Here in the 120F+ temperatures of Abu Dhabi, my 2003 model was getting too warm when left idling but would cool down when driving. A new fan clutch took away almost all of the problem but I decided to do a pre-emptive change of the water pump and thermostat along with a VERY thorough flush of the radiator and now the temp stays rock solid at the right point regardless of what I do with the car. You would not believe the amount of crap tha came out of the radiator.

 

Did a pretty good flush when I did the thermostat. Would the pump fail with less that 40k miles. New motor was installed a few years ago. This engine has has long life green coolant since it was first started. Clutch seems fine. I will check it again. I think I will overnight a grey thermo and see what happens.

 

201 is well with in the OK range for your Discovery. Secondly, what a 180 degree thermostat does is open the valve to your heater when the coolant temp hits 180 degrees. If your heater is on, your temp will not drop. Now I may be dumb here but it is summer and the odds of your heater on are small.

Thus in a nut shell a 180 thermostat does not and will not affect the running temp of your Discovery.