I was excited to install the inline but it’s now arriving on Monday. I’m done with those plastics thermostats. After last weeks scare my engine or head gaskets could have been cooked

 

@redwhitekat yea I get it, but I want to play with mounting locations on the inline and that take more time than I have right now. But it will be a good data point to get.

 

Richard, thanks for that summary. It was very helpful.

I just spent most of last year replacing a blown head gasket on my 04 Disco II. I'm now worried that it's running hotter than it should. So i'm going to try and summarize my stats and diagnostics like you did. I'm thinking from the diagnostics below that my 180F Tstat isn't opening at 180F and therefore i should think about a new one. The Tstat is brand new from Atlantic British who are usually pretty reliable so i'm wondering if my diagnosis is correct. I think this is a reasonable start for things to look at when troubleshooting overheating problems but please let me know if missed anything and if anyone has a different recommendation please let me know. Thanks.

Engine Temps:
-Hwy temps in Michigan (70ish deg F) are 208-212F
-After Hwy driving, in traffic temps spike to 220-225F
-Monitoring temps w/ Ultragauge

Cooling System Setup:
-Replaced Tstat during my HG job with a 180F White MotoRad Tstat from Atlantic British. I'm now kicking myself for not checking w/ boiling water before installing.
-Replaced Engine Coolant Temp Sensor when I replaced the HG
-Running Peak Global Lifetime 50/50 premix amber (Disco Mike recommended if I remember correctly) with Purple Ice water wetter
-Reverse flushed the radiator when doing the HG job. Didn't see that much gunk coming out and seemed to flow ok but I've never done that before so I didn't really know what to look for.

Diagnostics:
-Pressurized system to 20 psi for 1/2 hr with no loss of pressure. (Pressure testing kit was about $80 on amazon, well worth it. Anytime i mess with hoses etc.. now I can check for leaks before getting onto the road)
-Opened bleed screw and checked for air pocket. Water was up to the top.
-I can see coolant movement in expansion tank where the throttle body heater return port is on start up (pump is pumping at least something?)
-After running for a minute or two I can stop the fan with a stiff piece of cardboard (i.e. freewheeling). This is expected fan clutch behavior per the Rave manual and wouldn't really explain my problem if the clutch was engaged at startup. I'm glad I did this though so I had a feel for what freewheeling feels like when did this again at a higher temp.
-After idling up to temperature, I can't slow down the fan when I jab at it with my cardboard. Feels therefore like the clutch is engaging properly
-Lower rad hose cool to the touch and reading 82F with IR gun as ultragauge was reading 190F. The lower rad hose didn't start to heat up until engine temp was closer to 200F
-Electric A/C fan came on at 210F with A/C on
-Shut off engine at about 212F
-Checked top of radiator fin temp w/ IR gun and about 6 " lower (that's about the lowest I could get to shooting through the grill openings). No significant difference in temperatures.

Conclusions:
-Fan clutch looks ancient but the fan blades seemed to chew up my little cardboard poker pretty well so i'm assuming not a fan clutch problem
-Water is definitely moving but other than that don't know how well the pump is working
-The radiator actually looks pretty new, I can't imagine its the original. I reverse flushed it when I replaced the head gasket and didn't see much gunk. Lack of a big temp difference from top to bottom makes me think the rad is ok.
-Feels like the Tstat isn't opening as early as it should. Since this is the cheapest and easiest fix i'll probably try this first but i'm a little stumped since I think this brand (MotoRad) and supplier (British Atlantic) are usually reliable.

 

do yourself a favour and get the inline thermostat from extinct. You will never look back

 

There have been a lot of stories on here about Motorad stats not being as labeled, and as well vendors, AB and others, unknowingly selling mislabeled stats in the last few years.

Your temps sound like those of a stock stat.

 

@Detroit Disco Your basic temps are normal for a stock thermostat,if a bit high

In the end my gray soft spring thermostat was the issue it had failed, my rad had some deposits in it so I replaced it (it was also 7 years old)

I got a black 78c from Bearmach I now run 186 -188 highway and have not gone over 197 at idle.
But there is a little more variance in temps as it has a "hard" spring than my old gray one.
A typical drive will see 185-194 around town 20 to 35 miles an hour and 188.6 to 190 hiway. My cooling system is still not fully bled however.

I am however switching to @Extinct inline mod based on @redwhitekat results

I think it worth starting a temps thread sort of what temps, are realized with the various options

 

Been using Motorad 180F Thermostats here lately as I can get them locally and zero issues. To bad there are so many knock off el cheapo's to the what used to be awesome Britpart 180F. I always knew Britpart didn't make it, but whoever their supplier was = excellent. Then a certain vendor started being cheap and selling 12.00 units which were unlabeled and stock temp thermostats.

I am about to experiment with the inline thermostat mod from Extinct as well, but the OEM Grey 180F, original 180F from Britpart, or the Motorad 180F from Auto Zone have never let me down.

Water Pump wise unless the impeller is totally rusted off, or it is clogged up with misc debris, the Water Pump will always provide flow unless the serpentine belt breaks causing it not to rotate.

 

Thanks everyone for the help. Sounds like i'm on the right track w/ investigating the Thermostat. I'm probably going to start with another 180F (probably try the grey one from Rover's North) OEM style but definitely check when its opening first this time. I'm looking to get the truck in running order as soon as possible so I can move on to my next project which will be a vinyl wrap.

 

Just another chime in here among many, but I had the black knock off thermostat in my truck from purchase. Temps would vary wildly from 175-209, until I put a LR branded OEM grey thermostat in. Temps are now 186-188 on the highway, and rise to 190-193 during idle, never higher. I am sold on paying extra for the genuine article, just my own personal experience. Good luck!

Rhys Legge

 

If you want to stop worrying about your thermostat convert to the inline mod. You can forget mislabeling, who made it, is it going to fail, etc, etc. I don't even pause anymore when I get a truck in, I would never run a truck with the factory stat anymore. Inline runs at exactly the temp thermostat I put in. If I have a concern, I can pull it out in 5 minutes and not lose a cup of coolant. I can drive it/test it with NO thermostat in the housing if I want. Easier to bleed, less air trapped, etc. I didn't invent the mod, but I am on #14 and counting and I don't even consider anything else. Best piece of mind you can do to a Disco by far.