The other day my ultra gauge alarm sounded for high coolant temps while it was idling after a 5 mile drive. My alarm is set to go off at 215f, it went up to 224f until I started driving home and it dropped to 186 then settled into its normal range of 190-205 stop and go traffic. All was normal from that point until today after a short drive my range became 205-221, so essentially same swing but added 15f to my temps. There is no overheating issues. I changed the coolant temp sensor and thermostat today after this and it did not change the problem at all, what might be some other causes of this sudden spike in my temp range.
Only asking because this of course happens the day before I'm heading up to NH to go hit the slopes and I'm not 100% comfortable taking the truck on a long run now.

If you can't see my signature my Rover is a 2004 Discovery HSE with 117k

 

It could be some air in the line, don't know why it spikes here and there like that. Not trying to sound whatever but did you make sure to bleed all the air out of the line after you changed the thermostat? What temp thermostat are you running for normal range to be around 190-205.

 

I also have an 04 and this is an issue I've seen a few folks with 03's and 04's bring up. In my case I replaced the entire cooling system and am using the genuine 180degree tstat. I still see occasional high spikes, although mine only go to 216.

 

What all is different from the 2001 discovery 2 to the 03-04 version far as the cooling system. I run around 188.6 thinking that is high but I guess not.

 

mine is 2003 with 120K plus milage and a little bit modified from when it left the factory. Couple of questions....

1/ have you fitted the genuine grey 180 T/stat from a L/R parts box

2/ did you change the coolant to get rid of the orange dex col and use water wetter

3/ how did you bleed the system...

This is the best way that I have found to bleed these coolant, its not how the RAVE says to do it but over 20 years as a L/R tech this is by far the best:

https://landroverforums.com/forum/di...9-180-a-68428/

 

So the first time this occurred the other day nothing had been touched on my coolant system since I put new hoses, water pump and thermostat in some time ago. Never had any dashboard water fall sounds or ever saw temps above 207. I'm using OE LR 190f thermostat and replaced with the same today. I do now have a trickling water sound under dash while revving engine so I know I need to bleed it again but the symptoms are still the same before and after I did t-stat and coolant temp sensor. Just honestly baffled at why it started out of the blue like this but doesnt really cause any problems. if it wasn't for the ultra gauge I'd be non the wiser. Just wondering if this is a precursor to a more serious underlying problem.

 

I bleed the system by raising the reservoir and filling it until coolant flows from bleeder. Then reseat resevoir and top off, run engine to temp.

T-stat is a 190 OE LR. I opted against the 180 because some noted a drop in MPG.

Coolant is 50/50 prediluted Prestone green coolant which I first switched over to at 60k after head gasket job. No water wetter.

Symptoms occurred prior to any bleeds or fixes. The system had been intact for at least a year with no problems.

 

The 03's and 04's have the 4.6 engine and no oil cooler.(not sure if the 01's have an oil cooler?)

 

Yep the 01 has both oil and transmission cooler found out the hard way when I blew the lines off driving down the road. Does the 4.6 offer any real increase in power or just an extra .6?

 

Heh DiscoDubs, the scenario you described is also when i'll see my occasional high spikes. It's always after a longer drive running at freeway speeds (60ish) followed by slowing either to a stoplight or extended idle. The fan kicks on and temperatures do start to drop as soon as I start to drive again. It's quite perplexing! My freeway temps are high 180's and around town 180's through 203. It's almost as if sometimes the thermostat doesn't open properly, except I've changed the thermostat to no effect.