Minor leak in Radiator fins? Suggested fixes?

I have a pretty minor leak on the fins of my radiator, it is an aftermarket 3 core radiator that a previous owner installed. It looks a lot like it's coming from fins in front of the clutch fan, but not 100% that it's the radiator for sure.

It is a pretty minor leak, very intermittent (seems to be more when the XJ is sitting vs driving hard/hot), I can get by with topping off the reservoir every month or two so it's not a immediate problem. It's kinda annoying to always have to keep an eye on, and probably not good for the environment, but I don't know if it's worth going out and replacing the whole radiator to fix it (I'm not even 100% it is the radiator).

I am planning on replacing the radiator hoses soon, and will have to drain the system anyway. Looks like it's pretty easy to take out the radiator once the system is drained. Do you guys have any suggestions for things I could do to try and patch up this leak on the radiator? Anyone have any experience with Flex Seal or any of the spray on sealants? Will those work on the fins of the radiator? They seem to be rubber based, which seems like it would just melt off a hot radiator, maybe use a high temp spray paint? I really do not want to use one of those additives to the coolant that will just gum up my cooling system, but I figure if a spray on sealant fails I'll be replacing the radiator anyway. Any other options?

Replace the radiator if it is leaking. A coolant system pressure tester that pressurizes the system to 15-16 psi should be able to pinpoint the leak immediately.

I patched up a hole in the fins with jbweld once. Just cleaned the area with acetone and then stuffed a small lump of it over the area.

Wasn't expecting it to work but it actually did.

md21722 said:

Replace the radiator if it is leaking. A coolant system pressure tester that pressurizes the system to 15-16 psi should be able to pinpoint the leak immediately.

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Radiator fluid is about $10 a jug, if have to top off the radiator with 1/8th of a jug once a month, that's $1.25 a month. A decent replacement 3 core radiator is ~$250, so that means I could spend 16 years (250/1.25/12=16.6) topping off this radiator before it makes sense to replace it. Even if I replace it with a new one, I'd expect something to happen in 16 years that would make me replace it again anyway.

I don't want to be dripping everywhere I go, but it doesn't make a ton of sense to be replacing the whole radiator at this point. That's why I'm looking at spray on options. I like the JB weld idea but I'll need to find out specifically where the leak is. The radiator pressure test kit is a good idea but it looks like those are like $150 from harbor freight, might as well just replace the radiator at that point, can you rent those anywhere?

Yea! Napa, Oriley's,....there may be others...

Greenspan said:

Radiator fluid is about $10 a jug, if have to top off the radiator with 1/8th of a jug once a month, that's $1.25 a month. A decent replacement 3 core radiator is ~$250, so that means I could spend 16 years (250/1.25/12=16.6) topping off this radiator before it makes sense to replace it. Even if I replace it with a new one, I'd expect something to happen in 16 years that would make me replace it again anyway.

I don't want to be dripping everywhere I go, but it doesn't make a ton of sense to be replacing the whole radiator at this point. That's why I'm looking at spray on options. I like the JB weld idea but I'll need to find out specifically where the leak is. The radiator pressure test kit is a good idea but it looks like those are like $150 from harbor freight, might as well just replace the radiator at that point, can you rent those anywhere?

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That's assuming the rate of the leak remains constant.

I don't know what all you do with your Jeep but getting stranded on I-10 in the desert because the radiator blew is probably going to be more expensive than fixing it before it does.

O'Reilly's may rent a radiator tester for free, otherwise Stant 12270 costs $72 https://www.amazon.com/Stant-12270-...r=8-1&keywords=STANT+RADIATOR+PRESSURE+TESTER. Stant is the OE supplier for Snap On, Matco, Mac, etc.

Greenspan said:

Radiator fluid is about $10 a jug, if have to top off the radiator with 1/8th of a jug once a month, that's $1.25 a month. A decent replacement 3 core radiator is ~$250, so that means I could spend 16 years (250/1.25/12=16.6) topping off this radiator before it makes sense to replace it. Even if I replace it with a new one, I'd expect something to happen in 16 years that would make me replace it again anyway.

I don't want to be dripping everywhere I go, but it doesn't make a ton of sense to be replacing the whole radiator at this point. That's why I'm looking at spray on options. I like the JB weld idea but I'll need to find out specifically where the leak is. The radiator pressure test kit is a good idea but it looks like those are like $150 from harbor freight, might as well just replace the radiator at that point, can you rent those anywhere?

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Your coolant system works on pressure. What you see as a small leak on the driveway is a way for your system to loose pressure. The boiling rates and the ability of the coolant to do it's job can be seriously affected by the loss of that pressure within the system. It's not about what it costs you in coolant, it's about what you're going to spend on a head gasket or a warped head when it finally overheats.

Stock aluminum radiators are $100. Many people have gone to all metal, 2 core, 3 core, all aluminum, deep, wide, tall, extra special radiators and have realized that the stock one that chrysler put in there workst just fine.

At $100, your 16 year math doesn't work. Doesn't make any sense to try and bandaid the problem when there's much more expensive stuff riding on that component.

That all sounds really scary, but the bottom line is I don't have any cooling problems right now other than this pinhole leak. It doesn't overheat, it doesn't leak at temperature. Yeah, the system could randomly catastrophically fail but that could happen to anyone. If there is a simpler/cheaper solution then swapping the radiator, I'd like to hear it and give it a shot first. Seems like a spray on sealant would be appropriate, but I don't know if they would work on the fins, in the end if that doesn't cut it then at that point I can replace it.

Of course the best answer is to throw money at the problem and replace everything, I'm looking to see if there are any passable answers that are more cost effective.

I don't think you're throwing money at a problem and hoping it sticks if you've identified the problem.

Do some googling. See all those radiator stop leaks and fixes? If that stuff worked and didn't destroy your coolant packages all of the radiator manufacturers would stop making radiators.

There isn't a cheaper fix. Eventually that radiator has to be replaced. Or you live with the leak and hope it doesn't turn worse when you least expect it.

A spray on rubberized sealant isnt going to stick with the heat, pressure, and anti freeze. Your best bet would be some form of epoxy like jb weld. You will have to find the actual hole in order to use epoxy however.

Greenspan said:

Radiator fluid is about $10 a jug, if have to top off the radiator with 1/8th of a jug once a month, that's $1.25 a month. A decent replacement 3 core radiator is ~$250, so that means I could spend 16 years (250/1.25/12=16.6) topping off this radiator before it makes sense to replace it. Even if I replace it with a new one, I'd expect something to happen in 16 years that would make me replace it again anyway.

I don't want to be dripping everywhere I go, but it doesn't make a ton of sense to be replacing the whole radiator at this point. That's why I'm looking at spray on options. I like the JB weld idea but I'll need to find out specifically where the leak is. The radiator pressure test kit is a good idea but it looks like those are like $150 from harbor freight, might as well just replace the radiator at that point, can you rent those anywhere?

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You can rent the pressure tester from autozone free of charge!!

RedHeep said:

Stock aluminum radiators are $100 .... the stock one that chrysler put in there workst just fine.....

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Not to piggyback the thread, but which stock radiator are you referring to? Do you have a part number or specific recommendation? Mine has a drip at the drain plug and needs replacing, but all I have been able to find are well over $250. Been looking at Mopar 52080104AC, but not sure about any other brands. You can PM me the info if I'm treading too heavy in this thread (see what I did there :laugh3: ). Thanks.

you're gambling an head gasket job or cracked head on a 250$ part.

smart.

Mighty.Mighty_XJ said:

Not to piggyback the thread, but which stock radiator are you referring to? Do you have a part number or specific recommendation? Mine has a drip at the drain plug and needs replacing, but all I have been able to find are well over $250. Been looking at Mopar 52080104AC, but not sure about any other brands. You can PM me the info if I'm treading too heavy in this thread (see what I did there :laugh3: ). Thanks.

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*Personal opinion*

If you're driving a stock jeep, any of the parts store radiators will work just fine. All of them come with lifetime warranties and radiators take about 30 minutes to change. I've had no luck with all brass CSF ones, extra heavy duty 3 core, etc radiators. Some people have and that's what they recommend. I had one plastic tank radiator (the OEM one) leak at the plastic tank splice. It was 16 years old. Seems like an ok run for that.

There's been theories upon theories about coolant flow, restriction, thermostats, core size, fin size, material, placement, electric fans and different clutches for the past 30 years. My experience with all the jeeps I've seen on the trail and the two I've owned has taught me that there's nothing wrong with the stock coolant system on a stock engine on a relatively stock jeep. OEM's spend a whole lot more money on research than we do.

If your jeep is not stock or close to it (31's), then do yourself a favor and spend the money on a Mopar HD. I chased every possible theory behind an overheating XJ for 2 years. The exhaust leak, the head gasket, the bigger fan clutch, electric fans, aluminum radiators. All of it went away when I bought an OEM radiator designed for severe duty. It's been riding on the thermostat temp ever since, on the trail and on the highway.

*personal opinion off*