A Solution to the Hot Running D2 Engines

Swedjen2

Well-known member
Sep 12, 2018
516
95
California
I installed an inline thermostat kit.
Highway temps went from 198 plus/minus 2 degrees depending on outside temp and grade, to 182. I had a 3 hour drive from Placerville to San Jose, Ca.

Stop and go around town went from 204 plus/minus to 186 plus/minus 2.

I set the cruise control at 2250 rpms - 65 MPH . I used DigiHUD app to set the speed.
Ambient temp was 81 deg. Engine temp based on Scangage readout.
 

Howski

Well-known member
Oct 19, 2009
1,214
97
Alabama
I did an in-line setup for awhile and could never get it quite right. It wouldn't get up to temp in the winter on my shorter drives which was a pain in the ass. Went back to a factory 180 t stat like K-rover and has similar temps.
 

Swedjen2

Well-known member
Sep 12, 2018
516
95
California
What does the kit do?

Gets rid of the "T" and stock thermostat. Easy to change in a new thermostat or change temp. range. Finally, you get to spend some money and get rid of some plastic.
The kit is around $70.00

My running temps are 15 to 20 degrees cooler.
The radiator and water pump are < 2 years old.
 
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1of40

Well-known member
Oct 23, 2017
59
15
Va
Have a son moving to Colorado from KY after
Graduation this summer. Wondering how likely his D2, which hovers in the 190’s, is going to handle the mountain grades.
 

Discomania

Active member
Feb 10, 2017
36
9
NM
Honestly, if his cooling system is in good shape, he shouldn't have any problems. It gets hotter here and I don't have any problems in the mountains. But I've thought about the inline setup for a long time. Typical of me, I have made no progress toward its installation.
 
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jastutte

Well-known member
Nov 10, 2009
317
23
my daughter has our '04 at school with her.

i did the Inline Thermostat Mod on the Rover she has so i had one less thing to worry about.
 

Discomania

Active member
Feb 10, 2017
36
9
NM
I wonder if the inline fix would cure my higher temps at 75 or 80 MPH. A couple of summers ago, I was heading south on a damned hot day, doing about 75 and my temps got to 215. New rad, water pump, 180 thermostat. Just not enough cooling system. Never anywhere near that hot otherwise.
 

1of40

Well-known member
Oct 23, 2017
59
15
Va
Honestly, if his cooling system is in good shape, he shouldn't have any problems. It gets hotter here and I don't have any problems in the mountains. But I've thought about the inline setup for a long time. Typical of me, I have made no progress toward its installation.
Thanks. He runs an obd2 Bluetooth scan tool to check engine temps just in case.
 

best4x4

Well-known member
Mar 1, 2015
497
36
Beaumont, TX
65-70MPH seems to be the threshold limits of a D2 cooling system. It can completely handle itself up to those speeds and keep itself happy, but go past 70MPH and your temps will start to climb. To small of grill opening/radiator surface. H3 Alpha with the 5.3L V8 had the same issue. I've run 180F OEM Grey stats, and I've got that inline thermostat shown above. The main difference is without a doubt the inline setup can idle much much much longer without the temps climbing and climbing which is a very good thing out on the trail when you are waiting for someone up ahead to clear an obstacle.
 

Discomania

Active member
Feb 10, 2017
36
9
NM
Thanks, Best. Kinda what I thought, but it's good to hear it's more of a universal experience and not just mine. I'll just stay in the right lane, which is where LRs belong anyway!
 
Aug 20, 2007
2,631
15
Nashville TN
I love my inline thermostat. I'll peak at 188-190 on a hot day and then it drops down to 183 or so. Great piece of kit and a lot of folks are running them with no issues.
 

best4x4

Well-known member
Mar 1, 2015
497
36
Beaumont, TX
65-70MPH on a D2 is where the grill opening/radiator surface area reaches the tipping point of where it's no longer effective at keeping the temps stable. Not saying she's gonna blow by any means, but temps will start to creep past those speeds especially on a modified and lifted D2. I can cruise 55-60MPH and never break 193F with the HVAC on full blast, but speed up to 65-75MPH and the temps will go up to 206F range and sometimes 210F depending on the load on the engine (mountains/hills or hauling heavy cargo).

Inline mod makes it act more like a D1 and it certainly can idle for longer periods of time before the temps start to rise.