I wonder how much is limited by the water pump design. Too bad there is not a high performance option. Mone is fine during the 90+ deg weather here in the midwest. But 100+ and a long grade who knows.
Has anyone heard of the theory that the piston drops below the water jacket on the downstroke creating a hot area that can't be efficiently cooled? I read it on a different forum somewhere is a rant. no idea if it is true or not.

 

By the way I apologize for hijacking your post. I’m truly jealous of your temps.

 

The same guys that designed the plastic thermostat that gives so much trouble are the ones that designed the system to run 20psi. They were not concerned with the potential for splitting hoses or coolant bottles or tanks because they were selling new D2's with components made in Europe. Today you are driving a vehicle that it is almost impossible to get a plastic component for that is not made in China with questionable quality when new, never mind after several years of heat cycling. As an engineering professional who has managed engineers for 3+ decades, the enthusiast community gives the "it was designed for" way too much credibility.

 

I seem to remember your rig having a winch bumper, winch, and large spots in front of the grille. Based on experiences from other inline users that seems to increase operating temps at highway speeds around 10-15 degrees. Still your temps seem a bit high compared to other users. You might want to pull the thermostat element and give it a go for a while to validate proper radiator function. Had a guy in Florida with a brand new radiator that could not get below 200 until he changed it AGAIN, first new one he had was half plugged.

 

Lived out in Bakersfield a couple years in the mid-90's, kinda liked it actually. Was a big dirt biker at that time, went down to a major Jeep trail near Tehachapi which was cool, out in the high desert a couple times, but mostly preferred Kennedy meadows and the Giant Sequoia trails west of Tulare. We would go up to elevation above Kernville on the weekends to escape the summer heat.

As someone mentioned low range will help keep the revs up. As you get up in elevation you will lose power obviously requiring more fuel input but also the ambients drop. You might want to consider dual electrics (I have them on my off road rig) as a way to keep the airflow up at low speeds, doesn't help with water pump speed but again low range).

Doesn't get very hot in England or Germany in the summer, they weren't really keen on the Desert testing way back when these were designed.

Sidebar - one of the guys I went to school with in the late 80's was from Sweden, summer job was at Volvo inc. After graduation he got a job at their Phoenix proving ground where they were doing high temperature testing of turbos, brakes, cooling systems etc.. This was late 80's, not sure if LR was their yet. I think they all do it now though.

 

Not so much limited by water pump design as by pulley size, and even that limitation is only at idle. You can test that by shifting to third which speeds up the engine and water pump with minimal increased load. Have not heard the water jacket theory but can confirm it is incorrect in both details and theory. Piston skirt is the only part that comes below the jacket that section of the block is cooled quite well by both the motor oil and the conduction of heat through the aluminum block. Our biggest limitation is radiator size vs horsepower required to move 5000 lbs of brick up a grade at 70 mph. Its a BTU in vs BTU out problem.

 

Is that a down grade, cause I only reach 70 on the way to terminal velocity after driving off a cliff.
At least keeps me from getting speeding tickets.
Joking aside, I rarely go past 55 even when not pulling a trailer as my fuel mileage greatly decreases

 

A little information from my run this weekend I ran 183 -186 low speed off road, 3rd gear under 40 KPH (24 mph) hitting 188 - 194 occasionally on uphill stretches depending on the length of the grade ambients were 28C / 82 F no heat or air
Hi way speeds 183 -194 (50 and 65 mph), higher on the uphills average was 186, except on long 8% + grades usually hit 196. 199 once but I was already at 188 from a long slow traffic line and running hard to pass said line of traffic, dropped to 171 on the downhill on the other side

On way the home I hit 3 very slow sets of traffic ambient 29C about 84F - no heat or air

1. 30 minutes at about 3 to 5 mph uphill etc in 2nd gear never broke 194
2. Sitting for 30 minutes hit 199 put her in park rev's the throttle dropped to 190 in side of 2 minute
3. 30 minutes of serious 0 to 3 miles an hour 194 to 197 same as number 2 dropped to park rev'd the engine to drop the temp

My fan clutch works although I am not sure of the engagement temp but she roars pretty good when engaged it seems mostly when the engine temps hits the 197+ range. Normal idling I would hit 186 - 188, depending on how long and how warm at the stop.

 

What is the dual electric mod? Two A/C fans run in series? I’m not opposed to a Single electric fan to replace the vicious fan, but I don’t really want to mess around with finding and modifying a shroud that doesn’t wok as efficiently. I just ordered the 2991/Dorman fan upgrade, and a new reservoir cap. I think the fan will help with another degree or two the cap is just a precaution.

 

Good to know.It sounded fishy to me. If the below diagram of a rover V8 is accurate there is no way the piston rings drop below the coolant passages.