Hello

I installed one of those nifty Ultra-Gauge devices on my 2003 LR Discovery 2 SE7 and one of the gauges I've started monitoring is the coolant temperature.

It's interesting - the analog coolant temp gauge stays smack in the middle between High and Low, while the coolant temperature fluctuates between 0 to 208 F.

What is the normal coolant operating temperature? I read somewhere it should be between 199-202? I drove up to the mountains last night where the ambient temperature was about 37 degrees and I saw the Ultra-gauge coolant temp reading go up 204, 206 and 208 and was freaking me out a little, since i've had the car just for several months.

So what is the normal coolant temperatures for these vehicles?
Are my readings normal?
Does the cold outside temperature have anything to do with the higher readings?
There is a default alarm on the Ultra-gauge for 240 F - I changed mine to 220 - should I go back to the default or have a different alarm value?

Cheers

Al
'03 D2 SE7

 

Yes the Rover gauge is not trust worthy, it hits the neutral spot at 150 degrees and won't move till around 230.
A clean/well functioning cooling system should run around 202 to 206 in town, 208 to 210 at a 10 minute and 185ish on the highway.
These numbers can be lowered some with a 180 degree soft spring t/stat.
Your highway temps are high. How many miles on your Disco, has the radiator, viscus cluth, t/stat and pressure cap ever been changed

 

You are responding to the new data in typical worry-wart fashion. That is why Rover designed the dash gauge to be "broad". The stock thermostat is designed to start to open at 180F, and be fuly open at 204F, this would be measured inside the stat, not available to ultra gauge. The UG sees the temp from the coolant sensor in the top of the engine. Might be a few degrees ahead of the stat. The stat will also take longer to cycle the first few operations in the day, it is just a ball of wax that melts and re-hardens inside the guts of the stat. You are in fact monitoring this mechanical process with digital precision. There is no "adjustable" digital thermostat like you might have on your home HVAC system.

The truck is fine in the temp range you observed. At 212F, it is designed to turn on the electric fan to boost cooling, which is normal for idle or slow traffic or working hard (trailer or uphill long grades).

Now when you get past 217 - 220 and stay there, you would wonder why your cooling system can't keep up with the load. Maybe fan clutch, low coolant, radiator blocked with mud, radiator blocked with gunk on the inside.

I have a 180F stat in my D1 and it makes 178-183 on side roads and 187 on freeway, in moderate weather, may touch 200 in summer. You can get a 180F stat for a D2, which would drop your temps about 10F from oem.

Your temps are good,, the truck is performing well. Having the Ultra Gauge can let you know when things start to drift higher, because the dash gauge is not gonna move off the fence until it gets way too hot for too long. Like the same politicians we elected to fix things. 220 sounds like a better point to start asking questions than 240.

The UG helps an owner keep an eye on things that not only are "hidden" by the dash gauge, but actually "lied about". Think about it, would you buy a truck if the gauge read 230F at idle? By knowing your long term values and changes, you can spot things before they start to be a problem.

As for temp values, on any engine you would want to be within the range of "start to open" to "fully open" on the stat. Otherwise the stat has no control. I like being under the fully open value so there is a little room for when you need it. If running 205 on level ground at 50 mph now in winter (where I am) - what will you be in summer when temps are a good bit higher?

But the temps really do go up and down normally, and very wide swings are a cause to investigate as well.

 

Mike

The vehicle has 89K miles. Don't know if the radiator, viscus clutch, thermostat and pressure cap have been serviced. What should be done to the above items?

Thanks

 

Cap is a u-buy and screw on.

Thermostat is next easiest. The 180F soft spring verion which DM mentioned is a good way to cool things down, but it will only mask problems if fan clutch (next hardest) or radiator are slack.

Test for fan clutch determines if there is any visocous fluid left inside to do the job. When cold, spin and release fan. Should feel like peanut butter inside, and stop in 1/4 turn or so. Warm up truck, engine off, repeat. Should still spin, maybe a little more, but not more than 1 revolution. Freewheeling indicates clutch fluid lost. Clutch and fan don't make any big difference at 50 mph.

Warm at highway speed makes you think radiator is slightly sludged up outside with mud or inside with Dexcool sludge or calcium from well water or tap water. The radiator has horizontal rows, sludge, extra stopz leakz fluid, and calcium build up and block off the lower rows. That reduced flow makes them cooler than upper rows. Eventually you have half a radiatior. One test is engine warmed up, engine off. Measure temps on fins with IR thermometer or a well calibrated Mark 1 Palm Reader (left or right, but it could be very hot). Measure low and high on the fins in a vertical line. More than 10F spread makes you think something may be a bit clogged up.

On a D2 the radiator is so slim inside that flushing seldom works for clogs. It should be done as preventative maintenance, as a repair it is not usually successful.

 

Pressure cap - is that the one on top of the coolant reservoir? Why will replacing the pressure cap lower the coolant temperature?

Thermostat - do you mean replacing the thermostat? Because it thermostat turns the fan on sooner than later?

Fan clutch - thanks for the explanation I understand now.

Radiator - are you saying radiator eventually needs replacement?

Thank again

 

Pressue cap is atop the reservoir. When it starts to go bad, it does not hold pressure and vents coolant thru an overflow hose. This leads to over heating because of coolant loss. The cap gasket could be degraded by the Dexcool coolant. The cooling system is pressurized when it warms up. The pressure reduces the boiling point of water, back in the 50's people did not have coolant, and they ran anti-freeze in the winter months. Edit - I made a high school goof - it really increases the boiling point of water.

There are two fans under the hood. The electric one at the front should spin freely at all times, if it is going bad it will get stiff or sieze, blow fuses. Driven by logic from the Engine Computer. The fan behind the radiator spins with the water pump and has a viscous clutch, it always has some power (20% to 80% coupling). When fluid is lost it can just freewheel. The thermostat constrols the water flow into the engine block. See attached plumbing plan. The thermostat does not turn on either fan directly, it is not like the HVAC stat in your house that clicks on the system.

Radiator, if system not maintained (flushed and new coolant and never well water (minerals) or tap water) will have buildup. Worse with Dexcool coolant. Eventually the radiator is not transferring enough heat. Older D1 and Range Rovers had a copper / brass radiator that could be partially dismantled and the calcium pushed out by a rod. Not practical on the D2, and a replacement radiator is $200 ish. Versus $600 ish for a D1, unless you go aluminum.

 

Thanks very much!

1. Pressure cap - buy from Atlantic British and install.

2. Thermostat - can I order that from AB also? What is it called? Is this a DIY job? On a scale of 1 to 10, what is the difficulty level?

3. I will check the two fans first, if they behave normally as you describe I will consider myself lucky.

4. Radiator - I don't want to undertake this if I don't need to.

To summarize, my readings are a little high, which warrants investigation of the above items, correct?

Thanks

Al

 

Your temps are fine, they are not on the high side at all, run the engine to cold and your oil wont get hot enough to evaporate all the water and blow by gases that collect in it.
The thermostat is called...a thermostat.
Yes all radiators need to be replaced eventually.
ALL cars that have temp gauges on the dash are programmed to not move at the slightest change in engine temp, if they did everyone would be at the dealer complaining their car was running to hot while at stop lights and to cold while going down the highway.
Each engine runs at a slightly different temp, just find out what is normal for YOUR truck and if it gets out of range you know that you have a potential problem.
If you just bought the truck then first things first, have the cooling system flushed.

 

I just went all thru this.

I had temps around 212 when I was idling in a parking lot.
AUX fan always came on.
That was unacceptable to me.

I replaced in this order:

1) Fan clutch - no affect. But, made the nice cool roar sound of the fan after replaced.

2) Radiator. Took me a long long time to replace it. Make maybe a 2 degree drop in temps.

3) Put in the 180 degree "soft spring" thermostat. This made a HUGE difference.
At idle now I only get to 203 or so.

Put in the soft spring 180 degree thermostat first.
If it solves your problem, then you are set.