I want to chime in again. First the fan should be harder to spin when hot then cold, by a factor of 2.
Second, you can not replace just the clutch on an 03 or 04, you have to replace the whole assembly or buy a used 4.0 fan that can be rebuilt with a new clutch.
How much Dexcool did you put in your truck, be specific. By your last reply you said you installed a 50/50 mix of Dexcool and distilled water which you shouldn't do.
As for rust in the coolant, it is an aluminum engine, they don't rust but your radiator will plug up with calcium do to the very narrow veins of the radiator.
Lastly, don't make the mistake of doing the inline t/stat conversion, it is not what it is made out to be, go read the 2 pages in the Rave regarding how the Disco t/stat is routed and you will see what I mean.

 

Here is my bullet point for our Disco as best as I can remember:

- Bought the Disco w/4k miles and serviced at Dealership for first few years (wife's vehicle)

- Took over and started reading various forums to educate myself mostly for aftermarket stuff (lift kit, tires, etc.)

- Discovered that the coolant was not flushed ever by myself and did the oil changes, diff and transfer case fluid changes myself over the past few years. Read about the Dexcool situation after having it flushed at a local place that insisted on Dexcool. They installed the new t-stat and expansion tank cover flushing the Dexcool ( I never saw the condition of the Dexcool). Decided after our trip to reflush the system myself with Peak Flush kit and go green. I used 50/50 distilled and Peak Global green and (1) bottle of Water Wetter. Learned how to bleed air out of the system since it was gurgling on two occasions
- Purchased Ultra Gauge to monitor water temp etc. In addition installed an oil pressure gauge around same time. Over the past two months I noticed a slight elevation of my water temp at idle. Was not sure what might cause this: ( no leak, dip stick clear, no air in system, no smell of coolant from exhaust, level in expansion tank green and at full).

- Thought maybe the fan clutch was going bad. Tested at cold and hot. Yes, it's harder to turn after engine at normal running temp when parked.

- This is where I'm at for now. Just want to make sure I do everything possible to keep it running as best as possible before head gaskets do have to be replaced. I'm just over 50k miles. I noticed that my idle water temp averaged around 204- 206 F after the Peak flush. A month later it averages 206- 212 F when the outside temperature has gone down at least 15-20 F.

 

[/quote]I noticed that my idle water temp averaged around 204- 206 F after the Peak flush. A month later it averages 206- 212 F when the outside temperature has gone down at least 15-20 F.[/quote]


RAVE state the following regarding driving in colder climates:

"In cold ambient temperatures, the engine temperature is raised by approximately 10°C (50°F) to compensate for the
heat loss of 10% exposure to the cold coolant returning from the bottom hose"

I believe your temperature increase is by design, but out of curiosity does your condenser fan come on when the temperature is at 212 F?

2003 Discovery 124K with high miles service complete

 

You are in Wilmington, just up the coast from me. Not exactly sub zero these days. Would not expect any compensation for external temperature has kicked in. BTW, wondering just how they change engine temp 50 degrees, when fan clutch and water pump and thermostat have no sensors or other controls. Perhaps they increase idle speed?

Mike is correct , if you mixed 50/50 premix coolant with distilled water, it is diluted below percentage it should be. Perhaps you mant to say 50/50 mix of distilled water and straight coolant, which would be OK. If any question in your mind, one of those elcheapo coolant testers with little ***** that float will test specific gravity and tell you if it is way off.

As far as flushing, draining and a two minute squirt are not enough, takes a while, best done in reverse direction. 20 - 30 minutes, not on full blast.

As for clutch - if stiffer when warm, great. How stiff is subjective, as temperature determines percentage of re-coupling. But main thing is firm, not spinning three or four revolutions when flipped by hand. No cartwhels under the hood, please.

Don't experiment with cooling system design unless you have a disposable Rover, or are really ready for it. Get the basic working before you enchance.

I'm thinking that since you don't get down in the under 200 F region your cooling system is running at 80 - 90% capacity. Now you have an oil gauge, would you be comfortable at 2500 rpm running low oil pressure? But it is not doom and gloom.

If coolant formula off, simple test shows that.

If radiator now marginal from old dexcool sludge still inside, that dexcool will react poorly with new coolant. Dexcool can only be mixed with dexcool. If radiator is marginal, a test by hand (Mark 1 Palm Reader) or infrared thermostat should show something. If sludged, would expect bottom area of radiator to be much colder, as coolant can't pass or can't pass quickly through that area. In some cases, the cold area of the radiator is up even with the fan clutch. When that happens, the face of the clutch receives cooler air, and delays activating the re-coupling, keeping any coling at the low power range normally used for freeway driving. On many fan clutch units you would expect to see 170 F on the face of the fan (which equals about 200 F coolant) to start the re-coupling process. Again, a place for an IR thermometer. See pix for what dexcool can leave behind, may not all flush out.

The fan and fan clutch don't do much at 40 - 50 mph. Try holding a pizza box out the window at 50 mph, you'll see what kind of air flow there is. So if at 50 mph, if your temp doesn't drop down, you are left with fewer things to consider.

One we have not talked about is the accuracy of the engine coolant temp sensor, which could be off. Not suggesting you change this $25 sensor, but use your ultra gauge to look at coolant temp and Incoming air temp. Would think on cold start both should be close. There is some thought that scale can build up on the business end of a sensor in the water jacket, would think that would act as insulation.

I just cranked my truck and let it idle while I searched for radio antenna wires. After 20 minutes I was up to 187F, with a 195 stat installed yesterday. It is mid 60's here.

If water pump not leaking, not wobbling, and belt in good condition, correct route, and not loose - that's all good. WP failure may be around the corner, but erosion of vanes, etc. is not standard for this miles or this vehicle.

 

Today averaging 206- 210F taking son to dentist. Drove a fair stretch of highway.

Added notes:

- Peak Flush kit- I did as instructed on directions. I ran the mix w/water for 50 minutes of driving. I took a trip to a designated site using highway for the majority of mileage before flushing.

- 50/50 mix- I remember opting for the Peak Global straight mix due to cost. The pre-mix was substantially more per gallon. I will buy on of the testing kits to see the concentration per Savannah Buzz just to eliminate this variable.

- Belt when replaced at shop is tight and I will have to compare to Rave for proper install.

- Water pump- I'll check to see if it's wobbling as I see no leaking but never say never.

- Ultra Gauge vs. temp sensor- I'll check this too. It seemed to be accurate watching needle rise w/ temp increase

- Fan- I'll check to see if Aux. fan turns off at 202F and comes on at 212F

 

here is a link to a GM TSB on dexcool flush technique, takes like 3 hours.... GM Service Informatio - Dexcool System FLush

If radiator is suspect, feeling by hand or with IR thermometer, it would be much warmer at top, and much colder at bottom. Coolant can't move through the remaining sludge. GM believes sludge is prone to form when coolant low (there would be an air space), there are posts about dexcool exposed to air being an issue, and Rovers are famous for air in cooling system. Might be something to all that. But "solventing" the sludge will take strong chemicals and some time.

Over time the sludge "grows" as more of it, when mixed with another coolant, turns thicker in the bottom rows of the radiator. So if there was sludge there, what did not come out in initial flush is certainly not happy that you have sent green stuff to mix with it.

But don't buy a radiator today. Test it for hot/cold spots, talk to an indy radiator shop about "boil out", etc. Truck is not in danger zone, and winter temps will be cooler, you have a reasonable time to keep an eye on this and resolve.

 

You might also consider that the heater core could be restricted (not blocked). If it was, coolant would flow very slowly when main thermostat is closed. The external stat requires a flow of water to keep fresh hot coolant coming thru metering holes of stat. The flow is through the heater core, which has no on/off valve. Heat is done by dampers in the dash. Delay in heating stat lets it open, just later than normal.

If you were to remove heater hoses and back flush, probably all kind of junk would come out, and running temps could easily improve. If water did not seem to come out of core as fast as going in, you could splice hoses together with a fitting and couple of hose clamps, for testing.

And sure, if Dexcool or gunk affects that big radiator, imagine what it can do in a little one. A little one that is very important when stat is closed off. On a D1, not so much, they have a valve that bypasses coolant flow through heater.

 

As I continue to diagnose I wanted to say thanks for all of the information and more importantly continuing to chime in on topic. I'm sure readers receive all of this valuable information and take what they want for it.

Regards-

 

More important is what you report back, as it is well documented and using accurate instruments, helps everyone. Thank you!

 

I believe my serpentine belt was installed correctly at a local shop before moving to N.C. I found a picture of a belt installed on a 4.6 liter from a different website. The picture is of a 4.6 liter being disassembled.

How can this affect my motor. I've put over 1000 miles on it since this belt replacement.

Thanks-