Stock 1997 GC ZJ, 4.0. ..
Need a new radiator but not sure how many cores the old one has. Any idea how to tell? You can't just look in the filler tube. Unsure if the radiator is the original or not.

 

That would be rows. The core is basically the entire radiator less the tanks on the top and bottom . Pop the cap when its cold and look for the number of tubes from front to back. 2 row,3 row etc. BTW you'll likely have to remove some coolant to see the tubes.

 

we always called them cores. Same thing. Btw, reason i ask I was hoping someone would know the answer because if you have one of these you know you cannot count them from the cap, as I said in my first post, there is some metal shroud thing that blocks the view.

 

You can Google or ask any parts store for a factory replacement. It will "match" OEM Quality
Is your jeep stock? If not, in what ways is it modded? An efficient cooling system can benefit in a lot of ways.
Just because the stock RAD is a 3-row doesn't mean you can't install a 4-row.
Also some careful measurements (and be willing to trim here and there) you can fit a larger (more efficient heat exchanger) RAD instead. Be careful about fan and shroud fitment. Anything can be customized but it may get expensive.

I have a fully welded aluminum 4-core RAD that uses all the original mounting locations, factory-style hose fittings, and a small trans-cooler inside(I don't use it). It was $250 on Fleabay a few years ago and I'm still very happy.

 

Yeah I so far replaced the stuck open thermostat with a carquest 195 and cleaned the stat housing and cts which were pretty corroded up and flushed the heater. That brought my temp up from 165/170 to about 182, I then dumped in some Preston’s flush, drove it a couple days. Still not hotter than 182 ish..
About here I read a post from a 40 yr mechanic that said he always bought 3 stats, cause you might get one that comes up to temp. Heh. Drained the rad yesterday, pretty chocolaty at the bottom, refilled with the 50/50 stuff, took about 1 3/4 gals. Only drove once since, but the cabin heat felt warmer, tho the gauge, which I verified is accurate, still looks a bit low like 175/180. So I think I’ll be trying another stat. Turns out Napa sells a 205 for under $10, which might get me to 195. Also, if you have $40 for a stat, you can find a true Mopar. One of the reviews said “ Finally, a stat that comes up to temp”. I guess you get what you pay for.
so yeah, given the crud I’m flushing out, a radiation probably not a bad idea.

 

You didn't mention your Temp issues.
You said your gauge is verified..... Are you sure? Are we speaking factory gauge or aftermarket?

Don't worry too much about Thermostats, as long as yours works.

If you have a bunch of crud in the system, that's a big problem. There's many ways to flush a coolant system, but the only complete way is to flush several times. NEVER use tap water as the minerals in tap water is likely the cause of your sediment. Tap also causes corrosion inside of the engine.
I like to pull the heater core hose and start with the heater core. Then the upper rad hose and flush as much coolant through the block and out of the water pump. Whatever you do, try not to flush the crud in the RAD deeper into the engine.
If your Jeep is stock, then the OEM RAD is fine and keeping it simple is easier than modifying anything.