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We built a few extreme duty radiators, those things were solid. They were built using Caterpillar Tractor components. Dual headers on each side, steel tanks soldered to a HD copper core it was a brick. None of them leaked even after extreme off-roading/flexing.

Problem was the cost, about $2k. Just the core cost almost $800 bare.
 
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I'm getting tired of swapping the radiators out. Bothers me that high quality and expensive radiators are being destroyed so easily. Just installed the latest 52mm HD from RPM Extreme. Very nice and well made unit. I agree with everything Jon @rpm said on the issue in this thread. The flexing is mostly being exerted diagonally (I believe) on the radiator as opposed to front and rear but it is flexing both ways for sure. Tried to rig up something to measure the deflection but got very crude results but the frame and body are flexing for sure. I didn't cut the alignment pins off the bottom pad mounts this time but did take a larger drill and reamed the holes out so the pins could move sideways some. Then I carefully ground the upper rubber mounts so that when the bolt is tightened up the radiator can move some from side to side if it wants too. Now I am fabricating two new upper connections that will hold the radiator in position but allow it to "rack" which is what is happening when the frame twists. Seems like diagonal bracing on the radiators would help some but not sure. Basically, the new upper mounts will be similar to the stock but there will be a much larger hole thru the middle of the rubber grommet and I'm going to drill out the welded-in nut in the cross member and run a longer bolt thru the cross member and install an a/c nut on the backside. The two bolts will be left slightly loose. That way, if the radiator wants to move sideways the bolts can freely move within the larger holes in the rubber grommets and not transfer the stress to the radiator, or at least reduce it significantly. Will let you know if it works as designed. The ideal solution would be to have the radiator entirely free floating in its mounts but that may not be feasible. Good luck to all and keep us posted on what works for you all.
We have continued to tweak the design of the radiators and have incorporated a lot of improvements over the years. I think our biggest issue at this point is the flexing-twisting of the radiator thru the upper mounts. We are designing a new upper mount system that should help eliminate a lot of the stress and flexing.

The funny thing is we have seen multiple failures on the same Jeeps and then we have 100+ jeeps with no issues reported. I think we are very close to having this thing figured out once and for all..... in the mean time REDDOG is correct. Try and run the upper bolts loose so the radiator can move separate of the upper core support.

The reason the factory units don't leak near as much is they are plastic tanks and are glued and crimped to the core. They can move a lot more without stressing the core tubes. The aluminum radiator is welded to the core tubes so all the force is transferred to the very thin tube and it will eventually crack if flexed enough. Its not build quality or welding is just metal fatigue..... if you flex anything enough it will break.
 
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Reddog,

You are not alone, I am on my fourth radiator in 30k.
One of the four was a dual pass with a different hose mounting location. It had several more inches of hose. I have had leaks on both sides.
Motech has been great about replacing them under warranty. The radiator manufacturer sends an 18 or 20 lb. cap with them, I've been thinking maybe it is building to much pressure.
I have gotten really quick at swapping them out.
I wouldn't think the pressure on the cap would be causing these failures.
We usually try and stay with the factory JK rated cap, I would worry more about blowing out a heater core or something with too high of a pressure cap........ you really don't want to have to replace a heater core in a JK.

The failures seem to be more tube failures cracking due to flexing. The tubes are very thin and can only take so much flexing and twisting before they crack.
 

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Reviving this old thread. I have a JKU with an AEV Hemi swap done in 2010 and I'm on my AEV 3rd radiator and it's pretty much leaked since day one. I'd like to get this next one right so this is a done issue. Is the C&R the way to go? Do you need to the bracket modification with the C&R? With my current AEV radiator and factory fan set up I have almost zero clearance to the pulley on the front of the engine so I'm also worried if a thicker radiator is going to effect this distance. Any feedback would be appreciated.
 

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Reviving this old thread. I have a JKU with an AEV Hemi swap done in 2010 and I'm on my AEV 3rd radiator and it's pretty much leaked since day one. I'd like to get this next one right so this is a done issue. Is the C&R the way to go? Do you need to the bracket modification with the C&R? With my current AEV radiator and factory fan set up I have almost zero clearance to the pulley on the front of the engine so I'm also worried if a thicker radiator is going to effect this distance. Any feedback would be appreciated.
Any pics of your setup? I thought AEV uses the C&R. Also thought the car timing cover doesn't stick out as far as the truck's. You may want to also swap to the 2012+ (3.6) fan - it's more powerful and is about 3/4" shallower than the 3.8 fan.

Another potential problem is that the newer coolants work great in the long term, but they need about 5-6,000 miles to build up the protective corrosion barrier from what I've read out there. I suspect those coolants may not protect very well in those first miles; and when the radiator is the shiniest, newest chunk of metal in a system that's been seasoned over many thousands of miles and many years, I think the radiator gets beat up early and often. I'm going to be running Amsoil heavy duty coolant. For now my strategy is to never complete the swap - it's lasted perfectly fine so far :laughing:

Others have used the GM tablets that dissolve into the coolant, or a sacrificial anode on the fill cap or drain petcock. I'm also running a diode wire from the radiator to ground (helps prevent corrosion by allowing stray potential to go to chassis ground but only when it does not promote corrosion). Hope I didn't repeat a bunch of stuff already on this thread - didn't re-read lol.

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My current AEV radiator is from 2015 so I'm not sure if this is the new "AEV" style radiator. They offered me a slight discount toward a new one however I did not want to buy the same radiator again. If someone knows the new AEV radiators are C&R I will buy it from them.
 

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When I was looking for a radiator for my 6.4 Hemi swap I personally talked to the owner of C&R and he had a Jeep just like my that they designed the radiator for. I believe it was 2015 when AEV made the switch to C&&R. The older ones were made by Michigan Brazing, I was told. So I bought one and it never leaked a drop! The C&R also cooled better. I still have my AEV radiator,2014 model & it never leaked but I always err on the side of better performance. I'll sell my old one for a $100. to anyone who wants it. I'm in Northern Colorado. I think it would cost a fair amount to ship it though. I paid $1100. for the C&R radiator and I think it was worth the price.
 

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I also just purchased a C&R radiator for my 6.0 jku after 2 csr radiators failing within a couple months of being installed. I also removed the steel insert from the upper mounts. This radiator definitely cools better than the scf! I never get over 200 deg on or off roading. The C&R was expensive but worth the cost in my opinion. I guess time will tell how its going to hold up.
 

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...even after extreme off-roading/flexing...
RPMExtreme said:
...crack if flexed enough. Its not build quality or welding is just metal fatigue..... if you flex anything enough it will break.

I think I probably have V1.0 of RPMExtremes radiator, but lets be real here, it didn't take extreme flexing for it to leak. Unless mine's a unicorn and 30k miles of potholes at 55mph is extreme.
 
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I think I probably have V1.0 of RPMExtremes radiator, but lets be real here, it didn't take extreme flexing for it to leak. Unless mine's a unicorn and 30k miles of potholes at 55mph is extreme.
Im not sure what "version #" we are on now. we have made a ton of improvements in the radiator design through out the years.

It seems like every manufacture is having issues keeping aluminum radiators in the JK for some reason. Our current version seems to be working well... but most of the leaks usually start appearing in the winter and in colder areas. so we will see.
 

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Has anyone had any luck with the Northern radiators? They are a lot cheaper than the C&R but if they have issues the cost is irrelevant to me. My CSF is leaking only after 2500 miles on swap so I would like to upgrade once to eliminate the problem. A big issue with my 5.3 is the outlet orientation on the passenger side of the radiator. If the outlet was pointed 90 degrees (and shorter) or at a down angle it would be manageable but the tilt up makes it a pain to deal with as there is to much crowding at the top with the intake plenum. I don't like currently having to go across the radiator with a solid tube and would prefer looping down.
 

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I know of others that have been through several Northern radiators. They are about a third the cost of C&R. Last year, I had both the Northern and C&R (and OEM) in hand for a couple of days. My Northern radiator was obviously poorly made (looked like I could have thrown it together in my garage), with a warped top of the core. The OEM radiator was clearly better made. The C&R radiator made the Northern look like a hot pile of garbage. However, I think some Northerns have run OK so it might be worth a try, but also take every precaution to minimize flexing and electrolysis either way.
 

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Leaking LS Converted Radiators - Update

Well its Nov 2019 and I have a radiator in my JK that is a beast. It's built like something that you would see as an oil cooler in an M-1 tank engine. It has held up thus far very well. Brice Thomas Radiator took my last radiator that started leaking (one of theirs) and re-cored it with a super heavy duty core that has performed perfectly. I have now gone thru a hot summer and freezing fall (6 deg) on my last trip out west and the radiator performed perfectly. The core fins and tubes are very heavy duty and by appearances, you would look at this thing and wonder how air could go thru it, but it works perfectly. I'm running a Pentastar variable speed fan. I believe that traditional constructed aluminum radiators are too thin for the LS Jeeps but I stopped trying to figure out the problem a while ago. After four HD radiators in as many years, I just accept it as an issue with them. The jeep runs around 195-208 in summer and 195 +/- in freezing weather conditions while going over the Rockies. In fact, I needed to put a cloth over part of the radiator in the mountains as it was running around 190 with an outside ambient of 6 deg. The cloth was just enough to bring the temp back up to around 197-200 deg. Yeah, that is slightly on cold side for the LS3 but I'm not worried. I believe that when Brice Thomas Radiator built mine, there was only one other out there like it at the time. Call Jon @ RPM Extreme or Chris @ Brice Thomas Radiator if you have questions about it. Just a note but both Jon @ RPM Extreme and Chris Culp @ Brice Thomas are excellent to work with and as knowledgeable as anyone when it comes to LS JK's. Both those guys are customer oriented and problem solvers. I'm a happy old guy now.
 

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Discussion Starter · #54 ·
Reddog,

Thanks for the update. I too wanted to share my own findings:

Replaced my dual core CFS with a stock radiator, but upgraded to the Camaro SS fan. Knock on wood, it’s been 4 months and no leaks!

Now, running down the road, my 5.3 gen V would get to about 197 with the aluminum radiator. Now, with the stock rad it runs about 208, but as soon as the fan comes on, it cools down in a hurry! It has so much more power. I hammered on it pretty hard off road and pulling a boat, and it never went past the 215 fan set point.
 

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Just an update from me also. My C&R radiator is working perfectly. No leaks and temp is holding steady at 195-200 all the time. I am also running a pentastar fan controlled by the gm computer. It was an expensive radiator but worth every penny so far!
 

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I installed a custom C&R radiator in my 09’ Wrangler with 5.3L last September and it has developed a leak in the weld at the bottom of the r/h tank. Very disappointed I now have to send radiator back for repair but at least I saved the box.
 

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I installed a custom C&R radiator in my 09’ Wrangler with 5.3L last September and it has developed a leak in the weld at the bottom of the r/h tank. Very disappointed I now have to send radiator back for repair but at least I saved the box.
Was the leak at the drain petcock, at a core-to-tank weld, or somewhere else? Just curious because I have a C&R as well - it's been wet and running for about five months now with no problems. My coolant-to-ground voltage has been consistently low at 0.1V so not expecting any corrosion problems...

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I got my latest replacement for the replacement of the original one just over a year ago and had not done any offroading until this last summer up in Colorado. All had been good but now I am smelling antifreeze since we got back but I can not seem to find a leak. Keeping my eye on it and will see what happens.

This is from RPM's supplier. Still had to pay for it thou, even though it started leaking within 2 years of getting it as a warranty for the first one.
 
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