So since doing the head gaskets and new oil pump on my Disco II,it has been running great and a joy to drive.
Outside temp has been cold lately low 20-30s,truck has been running at 195f on average, which was after reading other posts was what I expected.
Today the outside temp was around 68f,truck was running aound 195f for six miles then the ultra gauge started to move up.200f,then 206f,pulled over and all seemed fine under the hood.
Drove back home with the temp on the ultagauge aound 205f.
Is this just the outside temp passing over the radiator causing the problem or am I running slightly hot.
Am I being paranoid over heating issues and not wanting to do headgaskets again!!
Truck has new 180f Stat,fan working well,heater good, and no leaks.
Only thing I can think of is maybe the rad.
I had flushed the rad and heater matrix after doing the heads, the water coming out was crystal clear and a good flow.
It's a 2001 with 97000 miles

 

Be sure all air bled out of cooling system. An air bubble at top of intake water jacket can have the coolant not touching the tip of the sensor that tells the ECU the temperature.

If this is a real Land Rover 180F stat that would indicate a problem. If a Motobad knockoff, it could be quality control.

You can eval your radiator by checking temp on lower fins vs upper. If 10F or more cooler, could easily be a blockage.

Not sure why a 180F stat would be giving you those kind of numbers. Here's a pix of one at speed in warm weather.

The Ultra Gauge is a great tool, but can be distracting.

 

so the differance in temps could be the fact that on a 30 degree day your using the heater. On a 60 degree day you are not.

 

But the same volume of water is passing thru the heater. It would be true that heat is being extracted from that water by the fan blowing thru the heater core. There is no on/off valve on the heater core water. I'm wondering why you are running 15-20F above opening point of the thermostat on a cool day. If it is a 180F stat you are running it wide open (15-20 above open point). What will happen in summer when temps are much hotter?

 

So if you want to hunt around and see if their is an issue get a infrared thermometer and test the cooling system. Below is a clip from a article that can explain how to go about doing that. You can get a infrared thermometer for 25 bucks at harbor freight

While the need for testing here is obvious, there are a few guidelines that may help you avoid misdiagnoses. First off, remember that the outside temperature of a block or thermostat housing is generally 10� to 15� cooler than the coolant itself. That makes sense in light of the cooling of the external surface from convection. So, when you measure the external temperature of an engine with an IR thermometer and want to compare that to, say, scan data, be sure to account for this effect.

The best location for temperature measurement on a warmed-up engine (thermostat open) is at the top radiator hose connection, where the radiator offers little mass to insulate the internal temperature.

Radiators are made of great heat-conducting material, so to find internal blockage, you must test it with good airflow. Given adequate airflow, a radiator should be able to drop the coolant temperature about 40�. If you suspect a blockage problem, run the cooling fan and/or drive the vehicle at highway speed, then stop and quickly test for cool spots and/or insufficient temperature drop from inlet to outlet. Remember, without airflow (convection), the entire radiator can equalize to an even temperature rather quickly from conduction.


Perhaps an IR examination of the entire engine (under load or immediately after) might have revealed the problem. It's hard to say, though, because of the equalizing effect of the mass of the block and coolant; the external measurement difference may have been very subtle. The point is, be suspicious of sudden but subtle temperature differences in an object because of its mass and conductivity. Also, always check an engine from front to rear and top to bottom.

When diagnosing cooling system problems, don't forget to check the fan clutch engagement temperature, as it can shift upwards with age. While in the area, check belt and pulley temperatures, too. A loose belt will get hot and slip. Another common but overlooked problem is worn or polished pulleys that slip even with a good belt. Before I began IR testing, I used to touch all pulleys and belts with my hand (engine off); a burn mark or blister indicated a problem. I think I found a better way!

 

entire radiator should equalize -

which points to a common cooling problem, old rad with crud or DexMud inside. Lower rows block off first, making them cooler than the top by more than 10F. If head-gaskit-fix-in-a-jug was used (stopz leakz) before the HG job, rad could have suffered. Don't bother trying to flush it, too small in the vein department. $200 and a new Nissens from Rock Auto.

But eval rad first. At freeway speed, fan is not an issue on/off/ or removed. 5280 feet per minute of air flow from forward motion is a lot more than the 800-1000 feet per minute at idle (from the fans).

I had my rad in a D1 rodded out, was getting about 5F variation top to bottom. But then I did not leave radiator moist and sealed up when I did the worlds's worst HG job, so my temps suffered and I'll end up getting a new rad to replace the one that has dried up gunk inside it. That'll wait until summer.

 

As far as the heater core only dispenses heat when you run the fan over it, thus cooling down the coolant. It isn't as efficient as the radiator but it does have some effect on the coolant temp. However, I would check my system if i felt it was running hot or a little hot.

Now, with that said. just because you have a soft stat doesn't mean you will run at 180. it means the coolant to your heater and radiator will flow at 180 degrees. it is the job of the radiator to despense the heat.

normal operating temp is between 195 and 215. My disco runs fairly consistent at 201 degrees with a standard thermostat. It doesn't leak any coolant and runs a little cooler in the winter, which it should, heater and colder air through the radiator. If your concerned Ir test it, but more than likely your fine, over 215 starts to become a issue.

 

re: just because you have a soft stat doesn't mean you will run at 180. it means the coolant to your heater and radiator will flow at 180 degrees.

Seems like there is more to it. The soft spring allows the port to the heater to open at less pressure. There is only one thermostat element, and when the main opens it shoves the bypass element with the soft spring closed. Truck should not run with a working 180F Rover thermostat in cool weather with a good radiator at 195 - 205 F. The job of the thermostat is to set the lower temperature the engine is maintained at. As engine heat increases, thermostat opens more. At 20F over base temp, most stats are fully open, and no longer control the situation. The radiator, water pump, rpm, fan, fan clutch then become limit factors. I think radiator in this case is suspect. Or there is a lot of trash in the holes of the top disk of the stat, which will make it open late.

Because of the remote nature of the D2 stat (hanging in mid air instead of inside the block) there will be some "delta" between temp displayed (top of engine) and temp inside the stat. But not 20F.

Would agree that you are not in a danger hot zone. But if truck is running this temp (which for the state thermostat is wide open (205F) then what will be left to cool the truck on a hot day? And why do others have lower temps with the 180F stat? Seems to me thermostat is at the end of the range it is designed to work in, it is not normal to run wide open under moderate loads and temps.

 

Firstly thanks to Savannah Buzz and xxDoylrxx for the input.
I had tried an IR over the rad after bleeding the system of air,I found it hard to get steady readings what with the fan in the way etc(obviously with the engine stopped)When I first bled the system all was good,then after about 100 miles I lost the heater,purged the system again for air and all seemed good again.
I will bleed the system again,maybe there is a sneaky pocket of air in there,although not in the heater matrix as the heater was blowing warm,
I just don't want to buy a new rad and find it makes no difference,and the old one is ok.
That ultragauge is hypnotic,but sure gives some peace of mind.
My main thoughts were just the much outside warmer temp passing over the rad not having the same effect as cold chilly air,but like you say, what will happen on a hot summer day!
Will check for air today and take her for a spin and report back later.
Oh! stat was from Atlantic British,and also a new water pump.

 

If tinkering with rad be careful about the plastic lines, they will snap off just to spite you. Not much on the back side of them.

Rad can have calcium buildup (those chips go all the way across).