Building a diesel powered RHD TJ Wrangler (Picture Heavy)

Hey TJers,

I think I have finally fixed my cooling system issues on my Kubota diesel swapped RHD TJ Wrangler. I replaced the water pump, thermostat and housing while also discovering another problem being the location of my temperature sensor!

Here's the video if you want to watch it:

I never would have predicted that the biggest hurdle in this swap was going to be getting the cooling system to work correctly. I've always been told and read about how thermally efficient this Kubota diesel engines were so I never thought about having cooling system problems!

While I want to say the location of my sensor was part of my problem, I had to other issues as well that contributed to my cooling system functionality.

First I was not running a thermostat. I had replaced my original faulty thermostat with a fender washer because I wanted to keep driving my diesel swapped TJ to get as many miles on it as possible. The problem with that is the coolant would become saturated in terms of temperature. New thermostat fixed that!

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The second issue I was running into was having the wrong ratio of coolant concentrate to water. I've always just ball-parked the coolant to water ratio in my vehicles. In talking with KubotaSwappers, I learned that while coolant is great for preventing water from freezing, it reduces the cooling systems ability to cool the engine, it's a trade off. So I changed the ratio of coolant concentrate to water and I can tell you it's working much better!

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My final issue was not getting a proper coolant temperature reading from my sensor. I had installed a brass fittings to create a "T" system for my coolant temperature sensor and switch. What I didn't think about was how that was a dead end system, meaning that coolant was getting no flow. That means the coolant around my temperature sensor was getting saturated with heat and not giving me an accurate reading of how hot the Kubota diesel engine was running.

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To fix this I moved the coolant temperature sensor behind number #4 cylinder which would be the hottest place on the Kubota V2403 engine block. I'm now getting both an accurate reading of the coolant in the motor AND the sensor is seeing constant flow so I don't have to worry about coolant getting saturated with heat.

Let me know what you think!

Thanks
Grant aka Rusty Autoholic Guy!
 
Hey TJers,

I've fixed my rear driveline vibration that I have been experiencing since I got my diesel swapped TJ running by installing a set of Core4x4 Tier 1 Adjustable Control Arms on the Dana 44 rear axle!

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Here's the video if you want to watch it:

This entire project has been a great learning experience on how pinion angles, driveshafts and double cardan joints work.

The initial cause of all my vibrations started when I tucked my entire driveline above the bottom of the frame rails on my TJ Wrangler. I did this for maximum ground clearance but in doing so I created an extreme angle difference between my transfer case and my rear Dana 44 axle, more specifically my rear driveshaft and Dana 44 rear yoke.

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Before replacing the stock control arms, the angle on the yoke of the transfer case was around 18° and the angle of the yoke on my Dana 44 rear axle yoke was around 29°. This created a sever angle on the driveshaft u-joint going to my Dana 44 yoke.

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What I didn't know at the time and have since learned was that since I have a double cardan joint at my transfer case, I needed to have my rear axle rotated so that the rear driveshaft and Dana 44 rear axle yoke point at my transfer case. This extreme angle was causing all the vibrations I was feeling once I got over about 40mph.

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To fix this I order a complete set of Tier 1 Adjustable Control Arms from Core4x4. I can't not stress how much I like the Adjustable Control Arms from Core4x4. Made in the USA, lifetime warranty and 4 different tiers for different levels of builds that people might be doing!

I was hoping these adjustable control arms might reduce the vibrations I was experiencing at the rear and but pleasantly surprised when all my vibrations disappeared. Currently the difference in angles between my rear driveshaft and rear axle yoke is 1.3° and everything seems to be working perfectly now.

At this time I have only installed the rear adjustable control arms because that is where my vibrations were coming from but I will be installing the front control arms very soon!

Let me know what you think!

Thanks
Grant
 
Well done Grant. I was happy to see the vibrations cleared on the first setting. I've had to change the pinion length more times than I could count in the past.

Do you have a rear track bar relocation bracket? If not you'll likely experience some bind when you cycle the suspension but maybe you'll get lucky.

side note: A video on how to properly cycle your suspension on a TJ to set bumps and check clearances would likely get a decent amount of hits. If you decide to go that route I'd chat with @BuildBreakRepeat along with a few others to make sure the information you spread is solid.
 
Well done Grant. I was happy to see the vibrations cleared on the first setting. I've had to change the pinion length more times than I could count in the past.

Do you have a rear track bar relocation bracket? If not you'll likely experience some bind when you cycle the suspension but maybe you'll get lucky.

side note: A video on how to properly cycle your suspension on a TJ to set bumps and check clearances would likely get a decent amount of hits. If you decide to go that route I'd chat with @BuildBreakRepeat along with a few others to make sure the information you spread is solid.

@Alex01 so far I seem to have lucked out with the trackbar, I was really concerned about it binding up but it seems to be okay for now, I'm keeping an eye on it!

Also thank you so much for the idea on cycling the suspension. I'll reach out to @BuildBreakRepeat and a few others to make sure I properly know not only how to do it but how to explain it as well!

-Grant
 
Well done Grant. I was happy to see the vibrations cleared on the first setting. I've had to change the pinion length more times than I could count in the past.

Do you have a rear track bar relocation bracket? If not you'll likely experience some bind when you cycle the suspension but maybe you'll get lucky.

side note: A video on how to properly cycle your suspension on a TJ to set bumps and check clearances would likely get a decent amount of hits. If you decide to go that route I'd chat with @BuildBreakRepeat along with a few others to make sure the information you spread is solid.
Well done Grant. I was happy to see the vibrations cleared on the first setting. I've had to change the pinion length more times than I could count in the past.

Do you have a rear track bar relocation bracket? If not you'll likely experience some bind when you cycle the suspension but maybe you'll get lucky.

side note: A video on how to properly cycle your suspension on a TJ to set bumps and check clearances would likely get a decent amount of hits. If you decide to go that route I'd chat with @BuildBreakRepeat along with a few others to make sure the information you spread is solid.
Happy to help! There is a shocking lack of correct tj suspension videos on YouTube to educate and walk that stuff through, would be awesome to get one out there. Great work @RustyAutoholicGuy - I love that you got this swap to work well.
 
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Happy to help! There is a shocking lack of correct tj suspension videos on YouTube to educate and walk that stuff through, would be awesome to get one out there. Great work @RustyAutoholicGuy - I love that you got this swap to work well.

I'm more than welling to learn and make sure I have the information correct before I share it! I think it would make a great video as well! Thank you so much @BuildBreakRepeat I'll probably message you in the next few days, work is kind of crazy at the moment and I'm SO close to having the tuning figured out on the transmission so that I can daily my TJ!
 
Hey TJers,

I installed the front Tier 1 Adjustable Control Arms from Core4x4 on my Kubota diesel swapped TJ Wrangler. Truthfully I wasn't expecting much of difference in terms of ride and handling however I was surprised to find both were significantly improved!

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Here's the video if you want to watch it:

Overall replacing the front adjustable control arms is just as simple as replacing the rear adjustable controls, though the side where the pumpkin is on the front is axle tight on space.

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The one problem I ran into was installing the nylon locking nuts on the bolts for the upper adjustable control that connected to the frame of the TJ Wrangler. I didn't realize there were slots in the frame rail and dropped one of the locking nuts into my frame. Using a magnet I was able to get the locking nut back out.

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I had forgotten I had also ordered the replacement hardware when I order the Core4x4 Tier 1 kit for my TJ Wrangler. Once I had installed the front adjustable controls, I then moved to the rear of my TJ Wrangler to replace all the fasteners I had reused to install the rear adjustable control arms.

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I remember how amazing my TJ Wrangler felt during my first drive after installing the rear adjustable control arms. This was understandable to me since I had fixed a massive misalignment with my rear pinion angles in my driveline.

I really wasn't expecting anything to be different with my TJ though when I replaced the front control arms though in hindsight I should have known something was going to improve. The entire time I was removing the stock control arms I shocked by how much flex the factory stamped steel control arms would flex and twist.

I didn't notice it at first on my gravel driveway, but as soon as I started getting to the speed limit on pavement, my TJ Wrangler just felt planted. The steering was the best I have ever felt out of a TJ/LJ and I can say with confidence after going out this morning in my LJ, that my RHD TJ Wrangler handles better and feels more planted to the road that my stock LJ Rubicon!

Let me know what you think!
Thanks
Grant
 
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Hey TJers,

I think I have finally resolved all the cooling system issues on my Kubota diesel swap TJ Wrangler. I knew doing an engine swap, especially a fuel swap was going to be a challenge but I really wasn't expecting to run into so many cooling issues.

At this point I've pretty much overhauled the entire cooling system on my Kubota powered TJ Wrangler. New water pump, new radiator, new thermostat, housing, and gasket. I've also relocated my temperature sensor and switch to get things better.

The last piece of the puzzle was the fan. I knew I had done something to my Mishimoto electric fan a while ago, it wasn't spinning anymore and would blow the 30amp fuse constantly.

I can't say anything terrible about the Mishimoto fan either as I bought it second hand for cheap and it did work for a while until things started getting way too hot. I think the fan being locked up also caused my Kubota engine to run hot at speeds as well because it was restricting air flow through the radiator.

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Instead of going with another fan from Mishimoto I went with a two speed fan from Derale instead. Part of the reason for this was how loud the Mishimoto fan was when it came on. Honestly it was louder than my Kubota diesel engine.

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The only issues I ran into was the Derale fan is a 17" diameter compared to the Mishimoto being a 16" diameter fan. I ended up just drilling some new mounting holes into the fan shroud which seems to have worked just fan. Also I had to move the coolant overflow tank to the other side of the radiator which was easy enough to do.

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I haven't tested the high speed setting yet but I can confirm the Derale moves more air at low speed and at a much lower volume as well which is a welcome change.

With just the low speed connected on the Derale fan, my Kubota V2403 is now finally keeping cool. I can leave it parked running and don't have to worry about it getting to hot and when I'm driving down the road it stays cool as well.

Let me know what you think and here's the video if you want to watch it:

Thanks
Grant aka Rusty Autoholic Guy
 
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If you can figure out how to make the temp switch operate the fan on both speeds, as you mentioned, that would be awesome. That way when you're sitting on a hill in Moab or on the long journey through all the different microclimates, you don't need to be hyper-alert of the temp gauge.

I can't wait to see this rig in person next year.
 
If you can figure out how to make the temp switch operate the fan on both speeds, as you mentioned, that would be awesome. That way when you're sitting on a hill in Moab or on the long journey through all the different microclimates, you don't need to be hyper-alert of the temp gauge.

I can't wait to see this rig in person next year.

Yeah I think that is what I'm going to do. I'll need to remove the thermostat housing so I can drill and tap my other temperature switch into the housing. I'm actually thinking about putting both temperature switches into the housing so that the switches will be getting flow across the sensors so the coolant around them doesn't get heat soaked which I've already had happen in the past.

I'm very excited to see how this swap does not only at Moab but also getting out to Moab as well. I've already talked to @Chris about getting him behind the wheel for his opinion, I'd like for you to try driving it as well and getting your honest opinion of the swap.

I was driving around my TJ last night and realized I'm almost below ½ of fuel left and I last put diesel fuel in my TJ in May!

-Grant
 
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Oh yeah, I can’t wait to see this thing and drive it. Hopefully by next year you’ve got it all sorted out. I have to imagine that’s enough time to get all the little details worked out.
 
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Oh yeah, I can’t wait to see this thing and drive it. Hopefully by next year you’ve got it all sorted out. I have to imagine that’s enough time to get all the little details worked out.

I hope so! So another update with no videos or pictures.

I had made a couple of assumptions about this entire build, but basically the following were givens to me:

  • 55mph would be done in 4th gear
  • I need a water to air intercooler for wheeling
  • My Kubota V2403 would be happiest below 1800rpm
All three of those facts were from what I have read and been told by several people. What I found out today was the following:

  • 55mph is done in 3rd gear with torque lockup
  • I need an air to air intercooler for speeds OVER 45mph
  • I don't generate any boost below 1400 rpm and I don't need it when wheeling
  • My Kubota V2403 seems happiest between 1900 ~ 2400 rpm for cruising speeds
It might not seem like much, but I had tuned my TCU, what little bit I have done, to shift into the next gear a soon as possible to keep the RPMs lower, and I'm finding out my Kubota engine actually like the RPMs a bit higher. Also I never thought when I built this setup that I would be cruising at 55mph in 3rd gear.

Also I need to figure out how to mount an air-to-air intercooler to bring my EGTs down while I'm cruising. If anyone has any ideas on how or where to buy an intercooler setup for a TJ that would be a great help!

I went and did some light wheeling today on my property and I never my EGTs over 400°, both the engine and coolant stayed super cool and I had more than enough torque to do what I was doing.

Thanks
Grant
 
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For what it's worth, when I was going to install the Magnum Powers supercharger on my last TJ, Charles (the owner and designer of that supercharger) told me that he regularly mounts the intercoolers under the vehicle, tucked up inside the frame rails.

He said he hasn't had any issues with this, and I believe it, as the popular DeRale transmission cooler is also mounted in the same place.
 
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For what it's worth, when I was going to install the Magnum Powers supercharger on my last TJ, Charles (the owner and designer of that supercharger) told me that he regularly mounts the intercoolers under the vehicle, tucked up inside the frame rails.

He said he hasn't had any issues with this, and I believe it, as the popular DeRale transmission cooler is also mounted in the same place.

Actually that is not a terrible idea at all. I'd like to do an air to air for the simplicity of it but if I have to go water to air that would work as well, thought going water to air would also still be fairly easy to setup in my engine bay I do have a ton of room.

I just realized, I'm seeing upwards of 15psi of boost, won't I be generating more horsepower and torque if I cool the charged air?
 
Actually that is not a terrible idea at all. I'd like to do an air to air for the simplicity of it but if I have to go water to air that would work as well, thought going water to air would also still be fairly easy to setup in my engine bay I do have a ton of room.

I just realized, I'm seeing upwards of 15psi of boost, won't I be generating more horsepower and torque if I cool the charged air?

Oh yes, I should have mentioned his intercooler setup is water to air, so that's part of it. Still, I think either would work. Water to air would actually be pretty easy and probably get the temps down even more.

Yes, if you cool the air, you'll see more HP and torque for sure. That's the name of the game (y)
 
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Oh yes, I should have mentioned his intercooler setup is water to air, so that's part of it. Still, I think either would work. Water to air would actually be pretty easy and probably get the temps down even more.

Yes, if you cool the air, you'll see more HP and torque for sure. That's the name of the game (y)

Yeah I just realized I'll probably hold speed easier if I can get my EGTs and incoming charged air cooler, which means less stress on my engine and potential more fuel economy at the same time which is a triple win!
 
Yeah I just realized I'll probably hold speed easier if I can get my EGTs and incoming charged air cooler, which means less stress on my engine and potential more fuel economy at the same time which is a triple win!

Yep, that's the way I would go 100%, water-to-air.

It will be a win-win, and you'll be able to get cooler temps and post bigger numbers, all with more efficiency in the process.
 
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Yep, that's the way I would go 100%, water-to-air.

It will be a win-win, and you'll be able to get cooler temps and post bigger numbers, all with more efficiency in the process.

So I'm actually going to try an air-to-air setup first just because I found out my friend as a slim intercooler for an atv/motorcycle that should fit just about perfectly in the front grill and I can route the piping underneath my radiator.

@Chris while I do understand the water-to-air benefits, an air-to-air has less parts that I need to worry about. I don't need to worry about an electric water pump and a secondary cooling system to put into my engine bay.

Honestly putting the doubler into my TJ has been awesome BUT the affect of moving the engine 7" forward has made doing other modifications like the intercooler setup interesting. I'm running out of room quickly as I'm still working on adding air conditioning back to my TJ as well!

-Grant
 
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So I'm actually going to try an air-to-air setup first just because I found out my friend as a slim intercooler for an atv/motorcycle that should fit just about perfectly in the front grill and I can route the piping underneath my radiator.

@Chris while I do understand the water-to-air benefits, an air-to-air has less parts that I need to worry about. I don't need to worry about an electric water pump and a secondary cooling system to put into my engine bay.

Honestly putting the doubler into my TJ has been awesome BUT the affect of moving the engine 7" forward has made doing other modifications like the intercooler setup interesting. I'm running out of room quickly as I'm still working on adding air conditioning back to my TJ as well!

-Grant

Yes, I can imagine if your engine wasn’t 7” forward, you’d have quite a lot of extra room.
 
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Yes, I can imagine if your engine wasn’t 7” forward, you’d have quite a lot of extra room.

Yeah I'm being to wonder if I'll regret that at some point. If I had skipped the doubler, I could have keep my stock shifter for my transmission and transfer case, I probably would have finished the swap a solid 6 months earlier, figuring out the doubler and support bar took forever. Also I could have had the engine further towards the firewall, which would have made more space for the intercooler and AC components.

On the other hand I really like 2-Lo with the doubler, it's so smooth and double low is crazy low, I can basically idle up anything in doubler low range.

I've already resigned myself to the fact that I will be having to cut part of my front grill to fit the intercooler as well. I need the room at the bottom of the grill for the intercooler piping.