Thanks to all for your feedback. I am on vacation this week and do not have the Disco with me. I will certainly check the additional items which you have suggested.

A few answers to your questions:

- The Disco is not a towing vehicle

- The 25-deg to 35-deg differential between top and bottom section of radiator is after the engine is warmed up, but at idle

- The aux fans are coming on when the engine is hot and A/C is turned on. Temps are going up to 210-deg when more load is put on the engine (e.g., at highway speeds or acceleration), but it does not over 210-deg. I may go for a longer run at highway speeds when I am back from vacation to confirm if it does go over 212-deg.

 

If I remember correctly, you should not have more than about 10 degrees of difference top to bottom. That could point towards a clogged radiator.

 

I would think a 20-30 degrees drop across the radiator at idle amazing, seems as if the radiator is doing it's job. if there was little temp change across the radiator then I would question it being blocked, No? (just thinking)

I would look for a blockage starting at the easiest spot the T-stat, then worry about the odd stuff like faulty water pumps.

I would also replace the pressure cap for $20 as 04dexlr had mentioned earlier If your not under pressure then your coolant is getting hotter than it should. {lower boiling point)

where are you getting your temperatures from the ecu or digital thermometer??

if digital what is the temperature entering and leaving the engine?

 

Sorry for being sporadic with my responses. I am on vacation in our motorhome and the Disco is not with me. To provide a few more comments....

I believe the radiator inlet and outlet temp differential should be greater than 10-deg. The temp differential should be as large as possible which indicates the radiator is actually doing its intended job of dissipating coolant heat from its fins. I assume my radiator is not clogged as I have a 25- to 35-degree differential. I also flushed the radiator when I am doing the water pump replacement. It appeared visually that there was as much flushed water going into the radiator as there was flushed water coming out of it.

Your various feedback in this thread made me realize the outlet temperature of the water should be below the set-point of the 180-deg thermostat. An outlet temperature below 180-degree (around 165-170?) should be observed even in the hottest weather. I do not remember the inlet and outlet temp when I was using my INFRARED thermometer to take readings (this was before I went on vacation after completing the water pump replacement). I only remember there was a 25- to 35-degree differential.

My approach when returning from vacation will be to rev the engine under constant load (around 2,000 to 2,500 rpm) and use the attached cooling diagram to:

(1) Replace the pressure cap since it is inexpensive
(2) Record the inlet and outlet temps of the radiator
(3) Record the inlet and outlet temps of the thermostat

This method may help me to nail down the specific component which is not performing to task.

Thoughts on this approach?

P/S.
I took tons of pics to detail the water pump replacement. I plan to post a write-up when I return from vacation.

 

Sorry for being sporadic with my responses. I am on vacation in our motorhome and the Disco is not with me. To provide a few more comments....

I believe the radiator inlet and outlet temp differential should be greater than 10-deg. The temp differential should be as large as possible which indicates the radiator is actually doing its intended job is dissipating coolant heat from its fins. I assume my radiator is not clogged as I have a 25- to 35-degree differential. I also flushed the radiator when I am doing the water pump replacement. It appeared visually that there was as much flushed water going into the radiator as there was flushed water coming out of it.

Your feedback in this thread made me realize the outlet temperature of the water should be below the set-point of the 180-deg thermostat. An outlet temperature below 180-degree (around 165-170?) should be observed even in the hottest weather. I do not remember the inlet and outlet temp when I was using my infrared thermometer to take readings (before I went on vacation after completing the water pump replacement). I only remember there was a 25- to 35-degree differential.

My approach when returning from vacation will be to rev the engine under constant load (around 2,000 to 2,500 rpm) and use the attached cooling diagram to:

(1) Replace the pressure cap since it is inexpensive and will help to eliminate it as one cause of problem
(2) Record the inlet and outlet temps of the radiator
(2) Record the inlet and outlet temps of the thermostat

This method may help me to nail down the specific component which is not performing to task.

Thoughts on the above approach?

P/S.
I took tons of pics of my water pump replacement project. Will post a detailed write-up to share with the forum when I return from vacation.

 

An update....

It appears the radiator is the cause of the erratic temps. You can read more about the radiator replacement project here:

https://landroverforums.com/forum/di...acement-68516/

I replaced it with a Nissens radiator, new coolant radiator and hoses from BPUtah. The temp is back to the normal 189 to 194 degree range.

Now, I am off to figuring out a high speed drive line vibration .... the wonders of Disco ownership

 

so even though you had a 20-30 degree drop across your radiator at idle, it was bad.

 

There appears to be no definitive answer for the ideal temp differential based on the tons of my own research from past posts in this forum, Discoweb and other forums. My personal logic tells me a radiator is more efficient where there is the largest possible temp differential. However, I am no thermodynamics expert in factoring the relationship between temp, flow rate and pressures. Some previous posts are indicating a 10-deg temp differential is ideal. One of them came from Savannah. I respect his experience on Discos.

The new viscous fan and new water pump was already done. In the end, I decided a radiator replacement would be worthwhile since my Disco is approaching 100K miles. It was a relatively cheap piece of mind as cooling issues are the Disco's greatest nemesis.

I will try and get temp readings for the top and bottom of the new Nissens radiator as reference points for this forum in the next few days.

 

My guess is that a higher temperature difference means you have a lower flow rate through the radiator. (clogged) With less coolant moving through and the same surface area it will cool more. The problem is your engine isn't getting the flow rate it needs.

 

Great write up, thanks for taking the time and money to figure this out and update us.