Just got an ultraguage for my 30th birthday. Got it all set up, have been driving around for 2 days. I noticed that my engine coolant temps never get above 194 F, and thats idling in city traffic. On the highway doing 55-65 mph, temps are usually 185, but range from 183.6-188.3 F. I have read tons of posts about temp ranges, and it seems the vast majority of people run 195-205 F, with some people running lower temps after doing an inline therm mod. Are these temps a problem for my truck? I have not done the in line therm mod and have never changed the Tstat since I bought the truck at 38K miles 7 years ago, though I have flushed the coolant system every year (with prestone 50/50 OAT safe coolant, and no other additives), and maintain my truck really well. Also, my truck never leaves closed loop. Shouldn't it go to open loop when I really get on the gas? Thanks in advance.

 

185 is fine, the t-stat open at 190, so you are right where you want to be. it appears to be working better than most.
But that is a pretty old t-stat, I hate to say change it because it is working so well.
But I fear it is only a matter of time before it will fail.

 

I would point out that the D2 stat is rated to start to open at 180F, and fully open at 204F. Certainly you are in the range. The temp measured by the Engine Coolant Sensor is processed by the ECU and does appear on the OBDII port for the Ultra Gauge. Because the mechanical stat and the sensor are separated, there is a slight difference in engine temp measured vs actual temp inside the stat. Rover considers things getting warm at 212F, where they turn on the electric fan to boost cooling. You sound like you are doing much better than this Disco - Snafu / Disco Fries idling in the ATM line.



On my D1, for reference, I run a 180F in the engine block, it read 178 at 55 all they way on 30 mile commute this morning, mid 50's outside. Gets up about 185 - 187 in traffic. 180 - 183 observed today at 70 on interstate. I like an engine that does not need the thermostat wide open on moderate conditions. IMHO need some reserve capacity for those 95 - 100F+ days and stuck in traffic.

As for closed loop, if the ECU can manage things it will stay in closed loop. Mine drops out to open loop when floor boarded, just for a few moments. But mine is a different ECU.

Oh, I'd keep that stat. If it hangs open, it will throw codes. You can program an ultra gauge alarm if it heats up to much. There is also chatter on the forum about an alternate OEM stat from one of the diesels that has a softer spring and should produce similar temps to what you have.

 

Good to know I'm in range. I was panicking a bit when I thought I was 10-20 degrees cooler than everyone else. I realize that the tstat is way past due to be changed, but I'm a firm believer in "if it ain't broke, don't fix it." I'll order an OEM from AB tomorrow with some other small parts (my fuel door latch and door check broke recently, ) and just throw it in my tool box in the boot with all the other spare parts I lug around with me. I have so many spare parts back there already, I'm considering just buying a DII from a picknpull and trailering it behind me .

 

Yeah, on Saturday my disco spiked up to 221F sitting in traffic. A new thermostat was installed that day and now the highest it goes up to is 204 in traffic and 194 at around 55 miles/hr.

 

you might want to order 2 of the fuel tank latches, they suck to put on. I broke the first one in under 2-minutes.

 

I second that, as I did the same. When hetting a new T/stat make sure that it is a geunie one as there have been reports of failing t/stats.
As for your temps I would love mine to be that low. Be careful of the ultra gauge as SWMBO calls it my panic gauge as I am contantly looking at it. You will find losts of posts on them. Personally I just have mine on one page showing the info that i want and need to know when driving.

 

Good to know about the fuel door latch. I appreciate the advice. I will get two, along with the OEM Tstat. Any chance I could fabricate a door latch out of metal, or is there another car that uses a similar one that is perhaps more heavy duty?

 

When installing the fuel door latch, soak the new latch in hot tap water for about a minute before installing. This will soften the plastic and should save you from breaking the latch during the install.

2003 Discovery 126K with high miles service complete

 

OK, awesome. Thats a really good idea, kind of like when you form fit your mouthpiece for hockey.