Posted a few weeks ago about an overheating issue with my 95 E150 5.8. Ended up being a clogged radiator – replaced that and my overheating issues seemed to go away.

I left yesterday on a big road trip and made it about 4-5 hours just fine when suddenly the engine spikes on the temperature gauge as I get off the freeway. I park, shoot the thermostat housing with an IR temp gun and read 230ish so I know it's too hot. I had stopped multiple times on the way with no issues, so I don't think it was directly related to slower vs. faster speeds.

I assumed I was losing coolant since I had been battling some leaks as I was making my previous repairs, but I couldn't see any leaks or coolant in its typical places or on the ground.

Opened up the radiator cap after it had cooled down – no noticeable drop in level, still filled to the top and bright green. Overflow reservoir is at the same level it was when I had started driving, around the cold fill line.

Took it to a shop this morning and they ran a pressure test on the cooling system. They said that my new radiator was cracked and that was the reason for the overheating. Apparently there's a steady drip when hooked up, although I didn't notice a leak or drop in coolant level. I drove 4-5 hours fine, but I guess it could've failed at that moment or boiled over after the loss in pressure or had sucked-in enough air over time to create a hot spot. I'm not sure.

This is the SECOND new radiator I have installed in this van within the last two weeks. The first, from Autozone, lasted all of half a day before coolant started weeping out of the top edge where the metal wraps around the plastic. This NAPA one lasted longer and the guy at the shop said it was leaking from a place that's relatively typical for defective ones. They're going to replace the radiator under NAPA warranty but I have a long drive ahead and I'm worried there might be some other issue(s) at play.

I'm wondering if either a bad radiator cap or blown head gasket might be building up the pressure in my system, then causing a break at the weakest point, which in my case might be these radiators..? I bought a new radiator cap when making the other repairs, but is it plausible that it's no good and is holding too much pressure in? I don't have the classic signs of a blown head gasket – smoke from exhaust, oil in coolant, coolant in oil, etc. and did a block test before I left, which appeared to be negative but I know that's not always conclusive. I asked the shop if a blown head gasket might be causing too much pressure and they seemed to think that wasn't the case. It starts up fine, runs fine, so I haven't felt any performance issues either.

I had to replace my original radiator after clogging it up with a thorough flush – I dislodged crud and it seemed to clog the cores. Is it possible that there's more crud somewhere else in the system? Maybe an inefficient but not entirely bad water pump with no leaks? Heat didn't seem as great right after this last incident, but then seemed to get warmer later in the night when I was running while parked.

Or I may just be super unlucky with these radiators – this is my best case scenario at this point. Any thoughts or advice would be greatly appreciated.

 

I would guess this is a combination of a weak water pump along with terribly bad luck on new radiators. I'd hate suggesting changing the water pump "just because......." however you might be at the point.

I have no idea whether your flush that led to the clogged radiator could cause an issue with the WP. It is highly curious the coolant temp seemed to be fine for a time then suddenly spiked.

Outside of that ^^^ I got nothing if you're not seeing any visible coolant leaks.

 

When I changed out the radiator on my 94 Club Wagon I was very worried about such a scenario, fortunately its been 6 or 7 years with no issues. I installed a Spectra brand. I also changed out all the hoses, and the oil cooler adapter hose or whatever thats called ? and the thermostat at the same time.
Maybe give Spectra a try.

 

If you had a bad head gasket that was blowing pressure into your coolant, you'd be able to tell just by opening up your radiator, it would be pushing your coolant out pretty quick, even a small leak would push it out pretty fast. I going to go with you probably still have crap in your block and it came loose and partially blocked a passage, got caught up in your water pump or as I said in the last post, you're impeller may be worn out on your water pump and cannot move the coolant. Either way, if you get to your destination, I would seriously consider doing another engine flush and maybe even a new water pump. JMO.

 

The radiator cap can be tested for over-pressure. A shop could do it quickly or rent a tester from AZ,etc. Eliminate that possibility.

New thermostat,right? The aftermarket stuff these days is suspect. That would explain sudden overheating but not so much the damaged rads. Since it's easy to get to, I would remove that and see what happens. Replace later so you get proper operating temps.

Check the forums for the amount of hassle or expense you will face if you're thinking of replacing the WP. Rusted,broken bolts can be a nightmare.

BTW: The rad in my '93 was replaced 2-1/2 years ago with one from AZ and it's been fine except for a leak where the drain threads into it but RTV solved the problem. Good luck.