So I have had no issues with my disco overheating during my ownership, has always stayed dead middle with no movement.

Today I was towing a boat to test out before I buy it and on the way home after dropping it off the temp gauge started steadily rising. It got nearly to the end of the "normal" range of the bracket. I've read that anything past middle at all is overheating so I shut it off while I was idling. I had to get home and it was only a few miles away so I drove there and when it got moving it slowly dropped down to the middle and stayed there.

Any idea what happened, did the extra load from the boat just tax it heavily, keep in mind it has been 100-105 here all week. The boat is probably on the end range of towing capacity coming in ~3000-3500.

 

Towing capacity is 5500lbs in the US.
Most likely your fan clutch is bad.
Over heating is not past the middle of the gauge, overheating is outside of the "normal" range.
Scare tactic's have gotten you scared, no it should not have gotten that hot, but it was hot out, you were working it hard and I assume you had the a/c on.
Next time it happens turn the a/c off, leave it running, shutting off a engine that is running hot only makes it worse because the coolant cant circulate with the engine off, the coolant is what carries away the heat remember.

 

In all fairness, your towing simply brought the performance of the cooling system beyound the edge it could handle. Not be design, but by a combination of factors. Could be mud and leaves blocking the radiator fins. Electric fan not working. Main fan viscous clutch not working 100%. Radiator sludged up with calcium or Dexcool mud, reducing the heat transfer it can handle. The truck can handle towing and certainly should you purchase that hole in the water to toss money into you would want to go over your cooling system.

Your truck was showing symtoms when it was not hooked up to the boat trailer, so it is more likely that you have modest cooling system issues. These problems will likely continue boat or not.

Overheat at idle points at electric fan, fan clutch, radiator somewhat blocked; since it did come back down when speed increased (load on engine increased, but air flow really increased).

 

Also, I'd differ with Spike on the gauge position for overheating. Guess that depends on your definition. Rover decides that it is too hot for normal operation when you hit 212 F, so it turns on the electric fan even if AC is off. 50:50 coolant mix has a boiling point around 223 F, add the 15 PSI coolant pressure cap and that increases to about 270F. But Rover has no warning light on a D1, and on a D2 it turns on when your are certainly toasted.

From the RAVE shop manual:

2. Under normal engine operating temperatures the engine coolant temperature gauge will display in the centre of the gauge.

3. When the engine is cold e.g. from first start-up, the coolant temperature gauge will display in the cold band.


4. When the engine is over heating the temperature gauge will display in the high temperature band. [Note: Does not say where in that band, just above center]


Long term operation at elevated temperature can't be good. Certainly at idle you will increase. But 230, 240, where do you draw the line? Take a peek at this gauge and scanner on my D1 - would you think it is running too hot at idle?

As for scare tactics, hell yes, I'm guilty - I want people to be scared of overheating their truck, and do something about it. On dad's Ford, the temp gauge moved up slowly each day if something wasn't correct. On a D2, it is held with digital precision at the mid-point, from temp "X" to temp "Y", then goes up. So by the time you notice it overheating has already begun. Are slipped sleeves and leaky head gaskets related? Could be. That's why a lot of guys took Spikes's advice and got an Ultra Gauge, so they could see exactly what is going on.

 

thanks for the info guys, i was fearing the worst.

i will hook up the Launch we have at work to it on monday to check the idle temps

 

I would also have your transmission filter changed and flush the transmission to get all the old spent fluid out.

Towing - is "severe service".

Personally, I think you'll have transmission problems down the road if you tow too much.

When you say your engine coolant temps have risen as they have -
Imagine what is happening in the transmission.

You overtemp the transmission fluid and it loses it ability to lubricate and then it is a down hill spiral.

The torque convertor alone is struggling to move that boat.

If you are intent on towing - get a piece of crap Dodge Ram truck for a few thousand.

You'll soon be spending that money to fix your transmission on the D2.

For whatever reason, those will tow and tow and not break a sweat.

Well, OK the D2 transmission does have an over temp light.
But, why tempt fate...

Level 10 PTS Land Rover Bulletproof Transmission 4HP22,4HP24,5HP24,JR506E

 

You can check your fan clutch (Spike and I agree on that possibility) in the morning when truck is cold. Spin fan and release, should not go more than part of a revolution. Warm up truck, turn off, repeat test. Still should not go more than 1 revolution. Fans that have lost the internal silicone liquid will freewheel. This shows up as OK temp on roadway, but overheat when parked or in slow trafice.

 

would also go with the fan clutch. If towing regulaly then you might think about changing to a 180 thermostat. I have had much lower temps with my 03 after doing this change. For relability I went with the moto rad one rather than the S##t Part. I regulaly tow with mine, boat and a fully loaded ATV on a trailer.

 

I tow a 2500lb boat all the time with my DI and I'm yet to have any issues. Yes towing is more work for the engine and transmission but a few thousand here to buy a new crappy truck that could have worse issues or just be prepared to replace something for a few thousand (max). You tell me what would be cheaper.
I over heated my truck a while back on accident (before ultra gauge) it makes a little bit of a ticking now. Probably slipped a sleeve but its not too loud nor do I loose coolant/ over heat so its going to stay in there for now!

 

Or it could me being paranoid and its actually an exhaust leak!