Need Cooling Help for Hemi Swap

[Abendage]

While my V8 is not of the Hemi type (6.0L LQ4), I have had great success with the stock TJ single core radiator and shroud with the mechanical fan and clutch from my donor vehicle. Granted I’m in Colorado so I don’t get super hot, 102 ambient is the hottest I’ve seen since the swap, but with the A/C running it does fine. Around town it is no issue, 195 all day long. On the highway when it’s above 100 with the A/C on I’ve seen 215 once, but it usually runs 205-210.

Hottest I’ve ever seen is running Red Elephant at 90 degrees ambient. This trail has an elevation gain of 3,300+ feet and the majority of it is the first 2 miles. The first couple miles is steep and slow going, 5mph or less for a lot of it. With the A/C going it’d get up to 220, I’d shut the A/C off for a few minutes to drop it back down below 200, then turn it on again, rinse and repeat. If I could have kept the RPMs higher I don’t think the A/C would have been an issue at all.

Anyways, I agree with AEV, mechanical fan for the win.

 

[Agar426]

At least in my case, I run a 4 speed Atlas clocked flat, and above the frame rails, but I can't run a flat belly skid because the 545RFE pan drops down too far. Just check that before you look at a flat belly pan.

Post up a good picture of the fan - we may be able to identify it.

Thanks for the tip! I am wondering if that's the reason this Jeep doesn't have the Nth degree tummy tucker?

 

[Agar426]

While my V8 is not of the Hemi type (6.0L LQ4), I have had great success with the stock TJ single core radiator and shroud with the mechanical fan and clutch from my donor vehicle. Granted I’m in Colorado so I don’t get super hot, 102 ambient is the hottest I’ve seen since the swap, but with the A/C running it does fine. Around town it is no issue, 195 all day long. On the highway when it’s above 100 with the A/C on I’ve seen 215 once, but it usually runs 205-210.

Hottest I’ve ever seen is running Red Elephant at 90 degrees ambient. This trail has an elevation gain of 3,300+ feet and the majority of it is the first 2 miles. The first couple miles is steep and slow going, 5mph or less for a lot of it. With the A/C going it’d get up to 220, I’d shut the A/C off for a few minutes to drop it back down below 200, then turn it on again, rinse and repeat. If I could have kept the RPMs higher I don’t think the A/C would have been an issue at all.

Anyways, I agree with AEV, mechanical fan for the win.

I don't recall if they used the Ram fan, or the TJ fan, but he swears by it. A tummy tuck would push the nose on the engine down, correct? So I'd either have to move the shroud down, or relocate the entire radiator and shroud down an inch or so?

 

[Abendage]

I don't recall if they used the Ram fan, or the TJ fan, but he swears by it. A tummy tuck would push the nose on the engine down, correct? So I'd either have to move the shroud down, or relocate the entire radiator and shroud down an inch or so?

Hard to say where the fan ends up depending on a whole bunch of factors with the motor swap. If it were me, I’d do the tummy tuck and get everything where you want it and adjust the shroud to fit. Doubtful you’d have to move the radiator and moving the shroud an inch or so in any direction isn’t all that difficult. In my case, elevation of the shroud was fine, but I did have to move it slightly to the passenger side to clear. Easy to do by drilling new holes in the shroud.

 

[Agar426]

Hard to say where the fan ends up depending on a whole bunch of factors with the motor swap. If it were me, I’d do the tummy tuck and get everything where you want it and adjust the shroud to fit. Doubtful you’d have to move the radiator and moving the shroud an inch or so in any direction isn’t all that difficult. In my case, elevation of the shroud was fine, but I did have to move it slightly to the passenger side to clear. Easy to do by drilling new holes in the shroud.

Great point.....I tend to overthink things. It's not like this is a space shuttle or something like that.

 

[Agar426]

While my V8 is not of the Hemi type (6.0L LQ4), I have had great success with the stock TJ single core radiator and shroud with the mechanical fan and clutch from my donor vehicle. Granted I’m in Colorado so I don’t get super hot, 102 ambient is the hottest I’ve seen since the swap, but with the A/C running it does fine. Around town it is no issue, 195 all day long. On the highway when it’s above 100 with the A/C on I’ve seen 215 once, but it usually runs 205-210.

Hottest I’ve ever seen is running Red Elephant at 90 degrees ambient. This trail has an elevation gain of 3,300+ feet and the majority of it is the first 2 miles. The first couple miles is steep and slow going, 5mph or less for a lot of it. With the A/C going it’d get up to 220, I’d shut the A/C off for a few minutes to drop it back down below 200, then turn it on again, rinse and repeat. If I could have kept the RPMs higher I don’t think the A/C would have been an issue at all.

Anyways, I agree with AEV, mechanical fan for the win.

What are you running for suspension, and do you have a body lift?

 

[Abendage]

What are you running for suspension, and do you have a body lift?

Yes, I have a 1.25” body lift. I’m still on short arms for now but will be upgrading to a mid arm style set up in the future. I also have highline fenders so that changes things a bit.

 

[Agar426]

Yes, I have a 1.25” body lift. I’m still on short arms for now but will be upgrading to a mid arm style set up in the future. I also have highline fenders so that changes things a bit.

Thank you! It sounds like you've had success with both a mechanical fan and a body lift, which is a good sign for me! There's no MM lift option, out side of some custom fab, with the hemi installation (at least not that I've been able to find).

I don't have the Jeep at my house right now, it's at the shop. I plan on heading over today to see what other information I can gather. If you look at the pic I posted, it seems to still have the fan/clutch mounting provisions, so I don't think I need to get new pulleys, etc., to make the switch.

 

[Abendage]

Thank you! It sounds like you've had success with both a mechanical fan and a body lift, which is a good sign for me! There's no MM lift option, out side of some custom fab, with the hemi installation (at least not that I've been able to find).

I don't have the Jeep at my house right now, it's at the shop. I plan on heading over today to see what other information I can gather. If you look at the pic I posted, it seems to still have the fan/clutch mounting provisions, so I don't think I need to get new pulleys, etc., to make the switch.

Apples and oranges between our swaps, so my experience with the body lift wouldn’t translate to your build. The motors are different, motor mounts are different, nothing would be the same. Just throw a fan on it and see what you need for a shroud. Looks like you have the space for one between the radiator and the engine, that’s the main concern. Wherever it ends up just modify or build a shroud to fit. You can get longer and shorter stemmed fan clutches if need be. If you have a mechanical fan and clutch, I’d try that first, if it is too long and hits the radiator, research a shorter clutch. If it’s too short, look for a longer one, etc. once you get it in and spaced front to back find/make/modify a shroud to fit.

 

[Agar426]

Apples and oranges between our swaps, so my experience with the body lift wouldn’t translate to your build. The motors are different, motor mounts are different, nothing would be the same. Just throw a fan on it and see what you need for a shroud. Looks like you have the space for one between the radiator and the engine, that’s the main concern. Wherever it ends up just modify or build a shroud to fit. You can get longer and shorter stemmed fan clutches if need be. If you have a mechanical fan and clutch, I’d try that first, if it is too long and hits the radiator, research a shorter clutch. If it’s too short, look for a longer one, etc. once you get it in and spaced front to back find/make/modify a shroud to fit.

Fair points!

 

[Abendage]

Here’s a pic of mine. I think the fan clutch was out of an early 2000’s ram or something like that and was almost an inch longer than the stock clutch to get the fan more in the shroud. It could be longer even but it works just fine.

 

[Agar426]

Here’s a pic of mine. I think the fan clutch was out of an early 2000’s ram or something like that and was almost an inch longer than the stock clutch to get the fan more in the shroud. It could be longer even but it works just fine.

View attachment 651019

Awesome, thank you! Great pic! And the shroud is the OEM TJ shroud?

 

[Abendage]

Awesome, thank you! Great pic! And the shroud is the OEM TJ shroud?

Yes, OEM 4.0L.

 

[Agar426]

Yes, OEM 4.0L.

Thank you sir!

 

[Wildman]

Let me give you a little back history. I had a Magnum V-8 in my TJ to start with and had done the original V-8 swap in 2006. Drove the Jeep for 6 years like that then had to park it due to overheating issues. Then due to health issues I had it parked for 8 years. In 2020 I started the rebuild and had built a new 5.9 Magnum V-8 with a stroker crank making it a 6.7 (408) Then in the spring of 2024 I found out my block was cracked and about the same time I'd come across this 97 TJ with a Hemi in it that had a bad transmission due to the radiator cooler leaking coolant into the transmission. So in April of 2024 I drove to AZ to pick up the donor jeep and brought it home. Because my TJ was already built it made more sense to swap the Hemi into my TJ instead of building the Jeep that had the Hemi in it. Then in the spring of 2025 right before I was going to head to Moab with my Jeep my alternator and hydroboost went out...
So my first trip out with my TJ was in June of 2025 I finally got it out for it's first trail run... And I'd screwed up & hadn't added enough ATF to the transmission and broke the shifter cable. Then in Aug I went on another trip after replacing the shifter cable which was when I started having over heating issues. I hadn't had any prior to this which is why I'm fairly certain that it's the thermostat.

Here's the only pictures I've got of the Donor Jeep to show you the room it had. It was running a mechanical fan.

This is why I'm saying you need to measure to see if you can fit a mechanical fan or not as it depends on the core thickness of the radiator. I've been laid up for the past two months but think I'll be able to finally work on my Jeep soon and when I do I can try to get you some measurements on mine since I'll be pulling the radiator back out when I swap out my fan for a Camero 850 watt fan.

 

[Agar426]

Let me give you a little back history. I had a Magnum V-8 in my TJ to start with and had done the original V-8 swap in 2006. Drove the Jeep for 6 years like that then had to park it due to overheating issues. Then due to health issues I had it parked for 8 years. In 2020 I started the rebuild and had built a new 5.9 Magnum V-8 with a stroker crank making it a 6.7 (408) Then in the spring of 2024 I found out my block was cracked and about the same time I'd come across this 97 TJ with a Hemi in it that had a bad transmission due to the radiator cooler leaking coolant into the transmission. So in April of 2024 I drove to AZ to pick up the donor jeep and brought it home. Because my TJ was already built it made more sense to swap the Hemi into my TJ instead of building the Jeep that had the Hemi in it. Then in the spring of 2025 right before I was going to head to Moab with my Jeep my alternator and hydroboost went out...
So my first trip out with my TJ was in June of 2025 I finally got it out for it's first trail run... And I'd screwed up & hadn't added enough ATF to the transmission and broke the shifter cable. Then in Aug I went on another trip after replacing the shifter cable which was when I started having over heating issues. I hadn't had any prior to this which is why I'm fairly certain that it's the thermostat.

Here's the only pictures I've got of the Donor Jeep to show you the room it had. It was running a mechanical fan.

View attachment 651013

View attachment 651014

This is why I'm saying you need to measure to see if you can fit a mechanical fan or not as it depends on the core thickness of the radiator. I've been laid up for the past two months but think I'll be able to finally work on my Jeep soon and when I do I can try to get you some measurements on mine since I'll be pulling the radiator back out when I swap out my fan for a Camero 850 watt fan.

Thank you so much......thank all of you! Lots to think about, and multiple solutions, which is great! The other wrinkle is finding a set of hoses that will work. I saw some NAPA part #s referenced in a different thread, and I've got a part number of the radiator it was associated with (Jeep Speed Shop used these parts), so I think I may use that radiator (CG&J brand?), and get a mechanical fan back in there. If that doesn't work, I will go with the 850W fan.

 

[Wildman]

Thank you! It sounds like you've had success with both a mechanical fan and a body lift, which is a good sign for me! There's no MM lift option, out side of some custom fab, with the hemi installation (at least not that I've been able to find).

I don't have the Jeep at my house right now, it's at the shop. I plan on heading over today to see what other information I can gather. If you look at the pic I posted, it seems to still have the fan/clutch mounting provisions, so I don't think I need to get new pulleys, etc., to make the switch.

If you decide to do a body lift and mechanical fan you might have to move the shroud down somehow. Might just need some metal straps that mount at the stock locations and then bolt to the shroud to drop it down 1.25". That is how some of the body lift kits in the 80's did it with the 2" & 3" versions.

Try to get some better pictures of the area between your engine and radiator to give us a better idea of if you have the room for a mechanical fan. Hopefully we can help you get this all figured out and get it on the road so it's reliable and you can start enjoying it.

 

[Agar426]

If you decide to do a body lift and mechanical fan you might have to move the shroud down somehow. Might just need some metal straps that mount at the stock locations and then bolt to the shroud to drop it down 1.25". That is how some of the body lift kits in the 80's did it with the 2" & 3" versions.

Try to get some better pictures of the area between your engine and radiator to give us a better idea of if you have the room for a mechanical fan. Hopefully we can help you get this all figured out and get it on the road so it's reliable and you can start enjoying it.

This is awesome, you've all been great to me, a new face to the forum, treating me like an old friend!

 

[Wildman]

If you were closer I'd just give you the mechanical fan I have laying around. I'd guess it'd cost more to try to ship it to you than it'd cost you to buy it locally.

 

[Agar426]

If you were closer I'd just give you the mechanical fan I have laying around. I'd guess it'd cost more to try to ship it to you than it'd cost you to buy it locally.

Much appreciated! That would have been handy! The shop the Jeep is at is also the FLAPS, so it should work out. Thank you!