Disappearing coolant in my 02 Grand Cherokee 4.7 L V8. Heater core replaced this past spring. No issues with the engine running, no white smoke, no milky substance on the oil dipstick, temperature runs fine, as well as oil level, however a bit of white or condensate substance on the inner cap of the oil fill. Doesn't miss a beat doing 80 MPH on the expressway, but I've put damn near a half a bottle of antifreeze in the last two days (In Michigan it's been relatively cold lately). No visible leak on the ground, however, when I drove through the snow yesterday (18" high) some antifreeze showed up on the higher snow, but nothing was dripping. I'm hoping this isn't a head gasket or head because it runs great, but I don't want to keep driving it if it's going to cause damage before I can get it fixed. Need your thoughts or anything I can try at home before potentially dropping a lot of money.

 

Could be a loose hose clamps. Could be the beginning of a leaking water pump. Could also be head gasket if you don't see any leaks. Head gaskets can spend a long time in an intermediate failure stage before they finally let go (years even). But at your rate of coolant loss, if that was a head gasket it must be literally ready to blow. So it may be other things. Do you hear any coolant "gurgling" in your heater core in the morning?

Another issue on these engines back in the day were cracking heads. It would also lead to idle and operational issues. The one I had, (same vehicle but HO 4.7) the dealer ended up replacing a head on it. There should be a lot of heads out there if you needed to replace one. You may want to read up what the conditions are for a cracked head, I don't recall now. But that's another possibility if other tests come up negative. If you have to take it off, you would want to have them pressure tested.

What you could do next is:
1) Park on concrete where you can see leaks better, and start on cold days, ensure no coolant leakage at the hose clamps, radiator, etc. Look 'UP' from the bottom to see if you see any coolant leaking from the underside of the waterpump weep hole (or use an inspection mirror from the top). The water pump may have just started leaking and soon it will leak a lot more.
2) Sniff in the radiator (carefully remove cap) and tailpipe for that anti-freeze smell. They make test strips to pick up on the presence of combustion gasses in coolant. A really good shop or dealer might have an electronic 'sniffer' which could tell more definitively if you wanted to spend a few bucks. I think Autozone sells test strips.
3) Remove spark plugs and look or a 'clean' one which indicates a possible coolant leak at that cylinder and a coolant leak is literally steam-cleaning that spark plug. You'll know immediately if you see a super-clean one.

 

Thank you. I just don't get it, I've YouTubed and the smoking gun seems to be a head gasket or a head, but there's no tell tale signs that's what it is. I've let it idle and looked underneath, and haven't seen any leakage. No noise from the heater core, and this all started happening a couple weeks ago when the weather turned colder...otherwise since the heater core was replaced no issues with losing antifreeze at all. I can let it run idle for quite awhile with no leaks whatsoever even when it warms up in the morning...

 

Remove the radiator cap and sniff in the coolant area for combustion smells, and oil for antifreeze smell. Smell the exhaust (carefully), for coolant. If it's head gasket or head you should smell something. Then look at the plugs like I say.

If you remove the head you can almost always see where the headgasket was degraded, at least I can ..almost always. But even at that point, I'd still take the heads in and get them looked at, tested and valves re-ground/new seals and all that. That's just normal best-practices top engine work ...unless you jeep is real low miles.

Heads are AL, block is cast iron. Different expansion/contraction rates. Eventually they all (headgaskets) pretty much fail at some point given enough time/miles. Add to that extremely cold great-lakes temps.

 

Hmm. Your profile says you have a Cherokee, an XJ. But your thread title and your engine say you have a Grand Cherokee, which is a WJ (for an 02).

A to your leak, don't assume. Head or head gasket failures are not always obvious. With that much coolant disappearing, it's leaking. Either it's external or it's internal. Those are the only two possibilities. You have signs of condensate in your oil cap. That might be a head gasket, or just a clogged PCV valve.

Test the coolant. Believe the results. Denial is not helpful.