Yesterday I completed the inline thermostat mod with the kit put together by @Extinct . Honestly, this was on my "sometime down the road" list of things to do but once I saw how easy and well put together it is I decided to pull the trigger on it right away. Before I was running the cheap Dorman 180 thermostat (spoiler alert, not an actual 180 thermostat) and getting generally 193 on the highway and 206 at idle with swings every which way in between, sometimes without rhyme or reason it seemed. Now I'm consistently in the low 180s with dips in to the high 170's. I live in a hilly area so experience a fair amount of high speed/low engine loading while going downhill. This morning it passed the all important drive through coffee idle test at 183 where it used to be at 206-208.

I would say it took me maybe 45 minutes to make the swap, but if you haven't done any cooling system maintenance this would be a good time to change out your coolant and replace the hose clamp with "jubilee" style clamps. Get a cheap hose clamp pliers from amazon, it's well worth it. The last piece of advice I would have is that you do have to trim the upper radiator hose, a hacksaw worked just fine for me and I used a hose clamp as a guide for my cut.

If you are thinking about doing this mod I would make it a priority, it's easy, works, and a great value. Can't recommend the mod and the kit enough.

 

I second all of the above, and will add that the mod eliminates the T and bleed screw that have been known to break, fracture, or collapse outright, along with the weird Jarvik heart down at the bottom of the radiator. Highly recommended.

 

Thanks for the post @greisinb just north of you running a Black OEM TD5 thermostat and I hold those temps in the this nice cool weather. Mine is sitting in the garage ready to go in once it warms up a bit.

 

I would also add that I've made my amateur study of the D2 cooling system (as I'm sure many of you have) and according to the RAVE the stock setup is there get the heater core up to temp faster to warm up the passenger cabin. I drive a pretty regular route so I've been able to observe how long it takes to come up to temp pretty regularly. The inline mod does add some time to the warm up to the point where the heater is really kicking out heat but it's trivially short, cant be more than 2-3 minutes extra.

 

Fine fine

 

Does anyone ever worry about running these engines too cool? It sounds like the online mod holds the temp in a much narrower band (my td5 thermostat runs 185-200) but I'm curious how we all decided on 180 as the desired operating temp. Not knocking the mod at all, honestly just wondering what others think the lower limit should be on these engines.

 

have one of these in both my trucks and highly recommend. These motors have been around for ages (old buick 215s) and if I'm not mistaken those used to run 160 degree t-stats....either way with the increase in emission restrictions, manufacturers have bumped up the engine temps to try and score better or not pay penalties and have higher MPG. My friends run 160 degree t-stats in their RRC with no ill effects (have been doing it for years), I would've been running a 170 in my white one if I wasn't in a rush and needed whatever Extinct could get me the quickest.

 

If I understand the whole situation correctly, LR started to use a 190 thermostat on these trucks to pass more stringent emissions in the US market with the old Rover V8 design. LR sold these vehicles with a stock 180 t-stat in warm weather climates so we know it works and there are direct, OEM 180 degree t-stat parts available. There is a lower limit, and the computer will throw a code if you hit it or take too long to reach it upon startup but it won't do so running the 180 t-stat because it's designed to run the 180.

 

I'm not denying that the 180's work well, I switched to a lower temp myself. It seems like most people run that as insurance against the liner issues, because the factory thermostat just doesn't control the temp very well. I'm curious if running a better design (the inline thermostat) would allow us to run a 190 degree thermostat and gain the benefits that come with higher engine temps without getting into the "danger zone"

 

The 03-04's will throw a code if you run colder thermostats than 180 in the winter (summer not so much because the radiator limits the lower temp to about 180ish), I actually run 170 stats in my 00's with no issues. Actually they seem to get slightly better mpg and power. I did multiple 600 mile road trips this past summer consistently getting 17mpg driving 75 mph on a truck with a 250k mile engine. 160 might throw a code even on the older trucks. My boat had a 140 stat (iron block chevy 350) for running in salt water, so you can run lower without significant issues. Down lower than 160-170 the clearances are a little looser so you might get slightly more oil/fuel dilution but that depends on how long your trips are. My LS camaro had terrible fuel dilution in the oil when I only drove it 3 miles to work because it never got warm, same kinda thing with a Disco running a cold stat.