My questions are what thermostat to run in the 100+ Texas summer heat?
Are my tire sizes affecting the Kickdown?

Took the ’97 Disco around the Texas hill country yesterday. The temp was 101F out.
I have an UltraGauge. For most of the trip with a/c on the H2O temp showed 212F

Going up a large incline, I put the Automatic tranny into 3 to get up the hill.
The temp spiked to 230F and I immediately pulled over and shut her down.
I opened the hood and there was a strong breeze to help cool it down.

I did not hear any odd noises, boiling, gurgling etc. but I did notice the coolant was about an inch HIGHER in the overflow container.
About twenty minutes later the engine was cooled back down to 210F and we drove it home no issues.

The guy I bought this from put DEX orange coolant in. He’s a Rover mechanic but I’m still going to replace with green 50/50

This D1 has 265/75 16’s and has always had trouble going up hills, not wanting to kickdown. It will once it gets to about 2,200 rpm in fourth.

I think the larger tires are taking it out of the torque curve.

Thanks,
dcphotos

 

You can adjust the kickdown cable to be a bit more sensitive via 2 13mm nuts. I'd run a 180F thermostat and green 50/50. Do both of your E-Fan's run when the AC is on? Very common for the original E-Fan's to die. They're made by Denso, but apparently the LR version just kicks the bucket soon vs the identical E-Fan motor's in the 96 Toyota Corolla (also made by Denso). If you're E-Fan's are inop that will certainly cause issues. My 97 D1 with a severe duty fan clutch, 180F thermostat, nissens radiator, and green coolant normally does no more than 203F on the highway at 75-80MPH in the summer with the AC on. Now at idle out on the trail I've seen as high as 220F, but once moving it quickly goes down to 188/193F on the trail.

The larger tires will of coarse effect your vehicles overall gear ratio's but that shouldn't cause it to overheat.

 

Best4x4,
Thanks for the reply. I bought a 180f T-stat today. The rad hose kit I got from AB came with a 190f T-Stat so I'll put that on the shelf.

Still wondering about the coolant being about an inch more full in the tank when the motor was 230F.

Also, the reason I mention the tire size is why I dropped it into 3rd to get up the hill.

It seems the motor is sluggish. I did a quick test today on the way to get the t-stat.

With my foot OFF the gas pedal, my TPS reads 13% on the UltraGauge AND with my foot as far as it will go on the gas pedal, the TPS reads 87%

Was going to start a new thread on this but I'm wondering if this is the cause of the kickdown issue and not my tire size.

dcphotos

 

The coolant level rose because you were just about to boil over. 4.0L V8 isn't known for speed and dropping to 3rd is pretty common in hilly/mountain terrain. You need to check E-Fan function #1 if they aren't working you will overheat quickly with the AC on. #2 you need to verify your fan clutch is engaging properly. Kickdown should engage once the throttle is about 3/4 of the way to WOT pretty common for them to be out of adjustment on a 25 year old vehicle as cables stretch.

 

Best4x4 again, THANKS for there reply,

Don’t think I was near boiling as it has a 15lbs cap so boiling point would be at 257ºF. I will say, it WAS hot as hell though at 230ºF

I hope the 180ºF t-stat brings it down and I think the fact that the TPS is not registering 100% with the accelerator pedal as far as I can press it is suspect.

I will look at the kickdown cable as well but if the TPS is telling the ECM that it’s NOT 100% open then the AFR is going to be off.

dcphotos

 

Fluids expand as they heat up, that's the reason for cold and hot marks throughout vehicle systems. An inch of expansion in the "expansion" reservoir between 100 and 230 degrees considering the entirety of the cooling system capacity seems reasonable.

 

You could also have the adaptive settings reset. A cheap Bluetooth OBD2 along with the GEMS Reader App for Android phones can do it. I wouldn't worry about TPS figures unless you get a fault code for a TPS.

 

Today, driving at 75-80mph in 92ºF ambient temp the UltraGauge showed 215ºF-219ºF - This was with a/c on.
I flushed the H@LL out of the rad when I replaced the DEX with 50/50 Green. It has a new 180ºF T-Stat, I drilled a hole in and installed at the 12 o'clock position with the spring towards the motor.
The electric fans do turn on when I turn the A/C on.
Should I be worried or is this fine in the Texas heat?

 

I usually see 212F if at idle after driving 70-75mph. While driving 188-203F usually. Offroading in the heat I've got up to 220F but once moving it cools back down to 190's.

 

Just back from grocery store run so not very long of a drive.
It's 93ºF outside. With A/C on, I saw temps of 215ºF

I'm going to try to burp the system oe more time then add some WATER WETTER and double check that BOTH electric fans are running.
After that, looks like I may have to get the Radiator rodded out.
Only time I see temps of 188-203ºF driving is when it goes right past it on it's way to 2150F

Thanks Best4x4 for your input.