I really appreciate all the feedback and ideas. I'll address each person individually, but I'll start by clarifying something: The radiator shop tested everything they could on my pickup to try to find the cause of my problem. They gave me a clean bill of health, so I am hesitant to blame the vehicle. The radiator shop has not charged me for ANY of the labor they spent diagnosing the issue, so they have plenty of motivation to blame the vehicle to recoup some of the cost.

What is everyone's opinion on stop-leak? I would rather not use it as I don't want it in the cooling system, but at this point I'm willing to try just about anything.

I agree there has to be something wrong with the pickup. I have bad luck, but this is ridiculous! My hoses feel really hard when the engine is warm, but I don't have anything to compare it to. The only possible cause I can think of is body mounts, but if a bumpy ride causes a radiator to crack, it was a poor product to begin with in my opinion.
It's always where the fins meet the tanks. Unrepairable. I haven't driven the pickup anywhere but streets.
Which brand OE style did you go with? How long have you had it?
When I initially filled the coolant after I did head gaskets last summer, I used distilled water. I think I used tap water for the Champion and first Cold Case. The second and third Cold Cases I had the shop install. The shop tested for stray voltages and electrolysis and said they didn't see anything wrong with the pickup. Our tap water has some minerals; I don't know how much relatively.
I installed the Champion and first Cold Case myself, then got sick of doing it and paid the shop to install the second Cold Case. The same shop installed the third Cold Case under warranty.

All radiators have leaked where the fins/tubes meet the tanks.

Believe me, I've been driving myself crazy thinking about what could be the issue. That's why I turned to the experts here!

Thanks again to everyone for the ideas.

- Joe

 

I don't believe in stop leak, it's a band-aid/patch/hack.

Do you drive on gravel roads lots?

Your radiators came with a cap? Toss it, and get a decent 13lb cap.

 

I've used them from various parts stores and never noticed much difference since all have fit and worked fine and lasted for quite some time afterwards with most never needing to be replaced again even years later. I would venture to say that the Napa one should be fine. I know the 5.0 and 5.8 trucks have standard and super cooling options. You might try the super cooling version if yours didn't come equipped that way originally, but you will need the appropriate shroud.

I agree with the statement about using a quality radiator cap and not the cheesy ones that sometimes come on the aftermarket radiators esp performance all aluminum ones.

These really sounds as though the Cold Case radiators have poor quality control or a defective batch went out.

Any type of stop leak is really just a band aid fix, but it does sometimes work. I would only really do it on something your just hoping will limp along for a while.

 

All I can think of is to remove the rad, measure distances between the radiator mounts, then jack it up on one corner and measure again--see if the front end is flexing in some way that it shouldn't and stressing the radiator. I've heard of the frame cracking around the steering box, never heard of it taking out the rad though.

Were the failures you've had pinholes, or were they cracks?

 

When it comes to chemical stop leak, I consider it a bandaid that's only really useful for "getting it back to the shop" and fixing it properly.

That being said?

Anytime I replace the radiator, water pump, hoses, etc on something with some years and miles on it, I do pitch a fist full of coarse ground black pepper in before filling it. It could entirely be bunk in the grand scheme of things, but it's something I learned at my first job bending wrenches from one of the old-timers, and I don't seem to end up needing to chase those little leaks for the rest of the time I've got the truck.

And it doesn't *appear* to cause any sort of gumming or blockage, that I've seen when cracking the system later.

 

my experience with aluminum radiators is with diesel engines.
and with that said. the vibrations of the idi diesel engine will tear aluminum radiators apart real quick. 2 trucks, 6 radiators. three in each within 20,000 miles time.
i had stock radiators shipped in, and never had issues again. the radiator in my 88 has 495,000 miles on it. it has been reconditioned twice.
i don't know what i will do if it ever fails as the shop i used to use is no longer in business.

 

I've got the same issue. The old school radiator shop that I used to use, the owner retired last year, and his kids had no interest in running the business.

I have no idea what I'm going to do the next time I need a radiator.

 

I don't drive much on gravel roads. I bought the pickup to build over time. I can't say for sure whether the radiators came with a cap of the shop installed one when they installed the radiator. The shop and radiator manufacturer each take a hit when the radiator fails under warranty, so I assume they would have ruled that out. I had a motorad 13lb cap on hand that i just threw on there before writing this. We'll see if that helps.
What baffles me is the radiator shop has NEVER had to warranty one in three years, yet I am on my third one!
I think they were cracks. I can't say for sure, because I took it in to get tested. Where should I jack up the vehicle to best find flexing?
I have never heard of that before. I assume it would void the warranty, not?
Sounds like another vote for OE style. I thought solid aluminum would be stronger than aluminum and plastic, but apparently not. Which brand did you get?

Thanks again. You guys are awesome! I'm afraid to even start the pig now since it has been so cold. I want to eliminate "user error" as much as I can.

- Joe

 

If I remember correctly they were from modine. It is a good 20 years now since I got them.

 

Maybe? I've never had warranty rejected for it. But I can tell you from personal experience, NAPA/OReilly/Autozone/et al? More often than not, they aren't checking *anything* on warranty returns, unless it's something where you've returned the same part a number of times.

Such as, when Store Manager for one of the FLAPS a few years back...

Customer had an OBS, he kept coming in about every three weeks, like clockwork, he was in there asking for warranty on fuel pumps, after the second time, I go in, and look at the history on it, he'd been doing this for about a year before I became the store manager. So I pull the pumps he had warranted most recently, full of rust. The Warranty qualifications require a fuel system flush, obviously, he'd never done that.

Had another one that kept coming and warranting starters for a Big Block Chevy, every one of them with a broken nose cone, after the fourth one, I cut him off, because it was obvious he wasn't shimming it properly.

 

I would try to get the jack under the frame towards the front. If it's flexing bad enough to cause problems, I doubt it'll be too important where you put the jack, so long as it's not so far back you're just tipping the whole truck sideways. Cracking makes sense if it's a flex issue.

GM has crushed walnut shell pellets that are supposed to stop leaks in porous castings. I've heard of pepper as a roadside fix, probably works about the same. With the rust and crap in the average cooling system, I doubt anyone would notice a little pepper in a returned radiator, unless you used the whole bag and clogged something up.

 

Silly question - Do you still have your rubber lower radiator isolators? I could see if they were missing that more NVH being transmitted into the stiffer aluminum radiators causing them to crack.

 

So, this is an interesting thought.
for a few years, I was having an issue where the fan would scrape the shroud, but only when I turned hard to the left. I would move the shroud a bit and it would help for a while. After doing this several times, I just kind of gave up. Then, while I had the trans out for a rebuild, I thought this would be a great time to change the mounts, you know, they are original probably anyway. The new mounts not stopped a clanking noise under power, but also fixed the fan rubbing issue. The old mounts had virtually no rubber left, and one was actually in 2 pieces. Just a thought

 

Have you installed electric cooling fans?

 

Yes I do. The shop was actually impressed.
Mounts as in cab mounts? I have a new set, just waiting for it to warm up a bit before tackling it. What gets me on that is there are plenty of vehicles that get put through a rougher terrain than mine, and obviously they don't develop leak every month. Hell, some performance cars actually swap subframe mounts for solid aluminum!
No. Factory fan and shroud.