When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
If 17x18 is correct -- I think you're going to struggle with that under load.
Also, does this vehicle have any kind of air block or "splash shield" (misnomer) below the radiator? Those devices are there to create an area of low pressure behind/below the radiator to help aid in air flow across the radiator at speed. The old Fox body Mustangs had a black plastic air dam that sat well back of the bumper cover almost underneath the radiator. They were known for getting knocked off or just being removed on lowered cars. Symptom that usually followed was a thread with a title "why does my car overheat on the highway?"
edit - sometimes with a limited core size because of sheet metal, etc., the tendency is to go with a thicker radiator - 3 row, 4 row, etc. That is a less effective approach than most think it will be. As the ambient air picks up heat crossing the first row, the air temp delta it has to work with is continually decreasing as you move across the rad. So the 3rd and 4th rows don't do much. The numbers I've seen go something like this and let's use 17x18 as an example -- call it 300 sq inches of core area. If you double that to 600 sq inches (24 x 25) you get twice (or 100% more) the heat rejection capability. If you go from a 1-row 17x18 to a 2-row - you only get 50% more capability. Adding a 3rd row gives you 25% more on top of that. Adding a 4th row - 10% more on top of that. Probably not an option in this case anyway as I think you're limited on room that way - but perhaps it will help someone who's scratching their head over a similar dilemma.
The small radiator core does seem to be one of the key reasons for the overheating issues.
As far as splash guards, the TJ uses plastic-like air dams on either side and one below the radiator. Due to the design and shape of the vehicle, the bottom one doesn't really extend anywhere. Rather it sits just below the radiator core support to direct air into the rad rather than around it. It seems to be working okay as we have no highway speed cooling issues.
I agree with you on the core dimensions aspect. An extra thick core is a band aid fix for a small core area, and to make up for overall volume and coolant capacity. Most modern cars use a thinner 1 or 2 core radiator design with a much bigger frontal area to drive as much fresh cool air as possible through the fins and they work very well when coupled with modern high CFM fan(s). If given the choice, always go for a bigger core area and ensure adequate ducting around it
An extra thick core is a band aid fix for a small core area, and to make up for overall volume and coolant capacity. Most modern cars use a thinner 1 or 2 core radiator design with a much bigger frontal area to drive as much fresh cool air as possible through the fins and they work very well when coupled with modern high CFM fan(s). If given the choice, always go for a bigger core area and ensure adequate ducting around it
Yup - the choice of just one or two rows is driven by both cost and effectiveness for the OEM's. As mentioned in my post above -- you just don't get much extra heat rejection capability for the 3rd or 4th rows. Sorry about the confusion on the symptom - I keep looking at the 'overheating on the highway' title of the thread without realizing we're on a rabbit trail with yours. A good rabbit trail.
Not much room to make the radiator wider. Maybe two inches on the passenger side. On the drivers side the steering box limits room to that side.
IIRC Griffin makes a "HP" radiator which means it has 1.25" tubes but still a two core. I suspect other radiator manufatures do as well.
I researched the radiators extensively. Several different manufacturers make a LS swap radiator for TJ. They're all nearly identical dimensions - as large as possible while still being able to bolt everything in. Most of them use the same 16" Spal fan. Everybody I've questioned about using them says their engine doesn't stay cool when pushed hard. One friend has had 3 different radiators in his now. He's doing some major cutting and putting something much bigger in there with twin 12" fans.
I had zero trouble with my Jeep in Florida. There's no hills and no offroad areas to push it hard enoyugh to get hot. Once I moved to Lake Tahoe, the problem really became apparent. A 20-30 minute straight climb at highway speeds or having some fun in the sand gets it hot quick. Easy offroading like the Rubicon Trail or just general driving around, it's fine. Some people claim they've never had a problem because they've never put their Jeep in a situation that it could get hot.
I'll report back when I get the new fan in place. I have the pull the front coilovers and check for uptravel clearance for it and I haven't had time to do that lately.
I researched the radiators extensively. Several different manufacturers make a LS swap radiator for TJ. They're all nearly identical dimensions - as large as possible while still being able to bolt everything in. Most of them use the same 16" Spal fan. Everybody I've questioned about using them says their engine doesn't stay cool when pushed hard. One friend has had 3 different radiators in his now. He's doing some major cutting and putting something much bigger in there with twin 12" fans.
I had zero trouble with my Jeep in Florida. There's no hills and no offroad areas to push it hard enoyugh to get hot. Once I moved to Lake Tahoe, the problem really became apparent. A 20-30 minute straight climb at highway speeds or having some fun in the sand gets it hot quick. Easy offroading like the Rubicon Trail or just general driving around, it's fine. Some people claim they've never had a problem because they've never put their Jeep in a situation that it could get hot.
I'll report back when I get the new fan in place. I have the pull the front coilovers and check for uptravel clearance for it and I haven't had time to do that lately.
Keep in mind that you need to account for the air density difference between Florida (basically sea level) and Lake Tahoe (approximately 6,200 ft.).
Just pulled the TJ into the shop so I could do some accurate measuring. I purchased my radiator from Novak over 12 years ago. The Novak mounts use rubber isolators that clamp on the radiator tanks and then bolt into the stock mounting holes. I think its a good design and has held up well for me.
So if you mounted the radiator top and bottom kind of like my 68 C10 LS swap you could add 4" of width with just a small notch in the right inner fender. If you willing to give up a bigger notch in the inner fender you could go 5"? So is that 20-25% more area? I'm not a math guy.
Pic of my 68 radiator mounting.
Did some quick calculations on current fan and shroud depth, accessory clearances, etc. I think if I swap to an LS1/LS2 vette water pump with appropriate 1.5" adapters, I can gain just enough clearance at the WP pulley to allow fitment of a trimmed taurus fan. Can't be sure yet but if it works it means I can still stick with the truck FEAD and Novak radiator. That's about $200-250 in parts so not too costly if it fixes the issue!
Just pulled the TJ into the shop so I could do some accurate measuring. I purchased my radiator from Novak over 12 years ago. The Novak mounts use rubber isolators that clamp on the radiator tanks and then bolt into the stock mounting holes. I think its a good design and has held up well for me.
So if you mounted the radiator top and bottom kind of like my 68 C10 LS swap you could add 4" of width with just a small notch in the right inner fender. If you willing to give up a bigger notch in the inner fender you could go 5"? So is that 20-25% more area? I'm not a math guy.
Pic of my 68 radiator mounting.
Wow. that engine bay . My jeep has not looked that clean ever..
My TJ doesn't look that clean either. On the C10 I spent a fair amount of time hiding all the chassis and engine wiring. On the TJ unless you completely rewire the whole Jeep the engine compartment is a bit busy. My TJ has been bullet proof for over 12 years. I do not beat on it. I did add a 8.8 ford rear axle and 241R transfer case. 4:10 gears and its quite fun off the line. Top comes off tomorrow for some time cruising.
I have the Novak KryoFlow II radiator and accompanying shrouded Spal fan with my L99/6L80E setup. It runs at 195ºF constantly and only gets to 210ºF if I push it hard.(Towing 3,500 pounds usually.) 180ºF thermostat. The fan is PWM controlled by the ECU.
I have the exact same issue. Did it on the last ls motor this go around new everything including new superior radiator,fan and shroud. Has anyone founda real fix?
Originally Posted by Punisher8738
I'll definitely have to follow this thread. I've got a heads/cam forged lq9 in my LJ. On the highway I'm experiencing the same issue. I called Novak and was told I have the older shroud design without the vents. Bad part is its going to take a few weeks to have it shipped. I was also told I have their single core radiator which according to Novak rep cools better than the double....
While waiting on the shroud which I may not use, I'm upgrading to a new Lincoln Mark VIII fan I found on ebay. I honestly believe the Novak shrouds are too shallow of a design and cause the air flow problem.
Like you I've driven without the bumper which would only leave the large trans cooler and ac condenser as an obstruction. Before I swapped in the LQ9 I ran a Ripp supercharger which had a large heat exchanger roughly the same size as the transmission cooler so I'm sceptical of it being a problem.
I realize I started this thread eight years ago and I wish I could report my issues are resolved but no such luck. The Jeep has been in storage for a couple years as life got in the way. Its back in the fold again and high temps under load are still an issue. Saw 230 degrees after a longer drive this past weekend and still want temps lower.
I am hoping to start revisiting the cooling situation once again. If anyone has new information or a successful Jeep V8 swap I'm all ears. I have contacted Novak to see if they have any new insight and will report back.
I'll post up when I make changes or have any new info to share, sort of feel like I'm starting over at this point...
05-29-2020, 10:57 AM
