This method may require a bit more time to add through bleed screw but doesn't require removal and raising of reservoir. You can use a small funnel to add via the t-fitting, won't waste as much coolant as LR's method, get maximum amount of coolant in with minimum air left in system.
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I just did this Saturday when I replaced my water pump. After a full gallon of bleeding using the approved LR technique, I still had an significant air pocket and was getting large temp jumps.

I used jfall's engine running bleed technique, and it cleared the problem up. I had to add at least a quart more coolant.

That said, if the temp gauge had moved at all I'd shut it down instantly. My temps was jumping between 185 and 205. The gauge starts to move when the temp hits 230deg F, That's very high, and that's why people are saying you need another way to measure coolant temp. I personally use a cheap bluetooth OBDII interface and the android app Torque on my phone. Others use an ultragauge. My way is cheaper, but the ultragauge is probly more reliable.

 

So I used LR technique and number9. I drove the car around for about 10 minutes up and down hills and the temperature gauge started to rise. I immediately pulled over and let the engine cool down. I managed to drive it home and I heard this hissing sound coming from the driver side by the steering pump. Here's YouTube video:
Is this a blown head gasket? I did not see any leaks under the car. I went under with a flashlight and could locate the source of the hissing sound. The hissing sound went away as the engine cooled down.

 

Well, that's a definite thing that's happening that doesn't happen on mine.

If you are absolutely certain it isn't fluid, and it sounds like you would know about it if it was, then pressurized air is escaping from somewhere.

I'm not certain what could do that for such a prolonged period of time. But the far superior collective hive mind will be along shortly with suggestions.

Goes without saying, don't run it for extended periods until you have this sorted.

Do you have any lights illuminated on the dash? How long have you had the truck, and have you ever had any fault codes read?

Edit, just read your sig.

 

Almost sounds like a radiator bubbling internally from being to hot. If you have any leak externally like the radiator, it'll leave a drip trail.

Very funky sound for sure! I wouldn't play with that system until you could monitor the exact temps.

I've had one D2 in my lifetime up to 229F and the temp gauge never and I mean never budged above halfway, no red warning light nada zip nothing. I only knew what the exact engine temp was with my Scangauge II. I didn't do any damage to that D2 however and after I replaced a stuck closed thermostat I was back down into the 193-205F range.

I took my 99 D2 out for a drive today as it's getting warmer down here in SETX. It is running an aftermarket made in Germany OEM temp thermostat. I wanted to see what kind of temp range a good working OEM setup would do vs my 180 soft spring setup that has a very wide temp range from 184-204F.

The OEM setup range is 204F at 75-80MPH, 209F at a stoplight, but then it drops back down to 206F. Once moving again it'll do 204-206F. So the OEM setup is giving me a temp range of 204-209F. That is a much smaller temp range vs the soft spring setup on my 02.

Having a cool running engine is good, but having an engine that runs to cool isn't. Your computer is tuned/preset to run at a certain temp to give you the best HP, Emissions, and MPG. If you get an engine running cooler than it's tuned/preset config you'll have more Emissions, worse MPG, and your heater output will also not be as good.

I messed with this exact issue on my older Gen 1 Mitsubishi Montero's. People complained about them running to hot during the summer with the stock 195F thermostat so people slapped in 180's and even some people installed 160 units. Engines ran cooler up to a point, but their MPG's were horrible, they went thru cat's, and 02 sensors more due to the engine not running at the optimal temp. 190F thermostats ended up being available eventually and it was good enough to keep em running cool and optimal.

I myself am liking the way the 204-209F range is performing so far. I am not seeing any giant temp spikes or drops, and it's more of a constant temp. MPG is good, engine runs smooth, plenty of power, and my heater actually produces heat. I agree we need to keep our LR's cooling systems performing great, but my H3 Alpha with an aluminum block and small radiator is a comparable setup and it runs up to 237F without exploding (as I found out on that crazy trip after a 400.00 efan conversion that was pathetic..).

With that said I am fairly certain a LR V8 should be able to handle the 210-215F range as a max temp on a good condition cooling system and efan. Anything and I mean anything past that like the 229F I had at idle on that one D2 is cause for alarm and is not good. Most people that own and drive LR's that aren't working on their own vehicles, or are mechanically inclined are driving around without monitoring the engine temps, and they only know something is wrong when the pathetic gauge moves past the halfway point and the red light comes on which means it's well past 230F. I'm not upset at LR's temp gauge as almost any modern car's temp gauge does the same exact thing Off/Normal/Toast... That's why so many D2's end up on CL with blown head gaskets, or dead motors.

Since getting back into LR's I've been using Scangauge II's to monitor it's vital signs. However I owned 4 LR's back in the day 2 97's (RR 4.6L HSE & D1), then two 03 D2's. I never worried about their temps (scangauge II's weren't around then), I had em idling during summer months at the beach, sitting in traffic, and I never had a single one of them blow a head gasket, or destroy an engine. All of them I got when they were fairly new, and I kept them all until they were well into the 125-150K mileage range, and that was with Dexcool!!! I never had a single set of head gaskets installed on any of them. I of coarse kept up with their maintenance. I saw some roll into the LR Dealership or ones towed in with cooling issues, needing head gaskets, but once again those were people that turn a key, it starts, they drive it, and never listen to it or know what to listen for when something is wrong or about to happen. I am so in tune with anything I drive it's crazy. I can tell when a darn rock is stuck in a tire, to when an efan doesn't kick on, or when the idle is rough, or see when the lights dim due to a failing alternator. 90% of most people out there DO NOT and those are the LR's that just blow up....

 

What is the jfall method of bleeding?

Fyi, I've taken the rover to 251 degrees and the dash gauge read center.

The gauge is worthless.

You have to take the front end up because all the air doesn't make its way to the bleed screw or the bottle while sitting flat.

Raising the bottle is worthless.

 

I am always fascinated by these threads. I never had any problems bleeding the cooling system using the method prescribed in the RAVE. Never had to park on a steep hill. Never had to throw the winch cable over a stout tree branch and hang the truck a la The Gods Must be Crazy. (Must-see movie for Rover fanatics.) Maybe I've just been lucky.

1. Remove bleed screw from top hose.
2. Unclip the bleed hose from the battery box.
3. Remove expansion tank from its mounting bracket. Slowly fill the expansion tank with coolant, approx. 4 litres (7 pt.)
4. Raise the expansion tank approx. 20 cm (8 in) vertically, coolant will drain into the system.
5. Refill the coolant expansion tank until a steady flow of coolant is emitted from the bleed hole.
6. Fit the bleed screw then, with the expansion tank still raised, continue filling the system until the coolant level reaches the base of the expansion tank filler neck.
7. Fit expansion tank filler cap, fit the expansion tank to its mountings and clip the bleed hose to the battery box.
8. Start and run engine until normal operating temperature is reached, and check for leaks.
9. Switch off engine and allow to cool.
10. Check for leaks and top-up coolant to cold level
    mark on expansion tank.
    
    

 

Don't confuse luck with confidence over a poor procedure.

If there are multiple people coming here and posting other ways that work better I would think the poor procedure isn't the best.

I have been restoring cars since early teens, grew up in a shop that fixed radiators as well as multiple types of cars. I am in the military active duty currently as a shop foreman repairing multiple types of military rolling stock.

That procedure you might think is sufficient, but others here know their temps drop if they put the front end up. Hmmmm coincidence?

That procedure might work with new trucks or low mileage, but we have hoses being swapped for lines, coolant changes from dex to green, aftermarket pumps etc. You can come to my house, I'll drain the coolant, and you can bleed mine. Using the ultra gauge we'll see who gets lower temps.

Maybe you accept the temps you get? Not realizing you can get them lower?

 

Regarding the steep hill, "theoretically" on a level surface the water will displace the air in the system and it will bubble up and out of the bleed screw. In reality, that is not always the case, especially air trapped way in the back of the system. By raising the front of the truck, it's just like the air bubble in a level, the air "should" move from lower to higher and up and out of the system. It's just a double safeguard.

 

Wow. Just wow.