dcwpainting

I have a 2001 Jeep Cherokee. Bought it about 1.5 years ago. last summer had no issues with overheating at all. pulling my 1500-2000 pound boat trailer combination last summer without problems. A few months ago I had a severe overheating issue. After replacing the head gasket, resurfacing the head, replacing the thermostat and finding that the waterpump was bad. Yes that got replaced too. using proper methods filled the cooling system with the proper mix of coolant after flushing the system fully. the issue i have is that I can drive the jeep all day and have no issue with overheating but when I put the boat on the back i overheat within 5-10 miles. I live in the country so 5-10 miles is not that far for me.
Any help or thoughts would be greatly appreciated

Firestorm500

Jeep 4.0s from 2000-01 have a factory casting flaw in the head. They crack, usually between #3 and #4 cylinders.

If everything else in your cooling system is OK, then replace the head with a good aftermarket new one. People seem to like the ones from Clearwater Heads.

dcwpainting

Ok when I got the head resurfaced o checked if carefully and so did the machine shop owner that I took it to and we couldn't see any cracks anywhere

Firestorm500

Sometimes they have a crack in them that you can't see when it is lying there cold on the bench.

They can and do crack inside that can't be seen externally.

Personal experience talking here.

dcwpainting

Well it would likely explain the slight loss of coolant and the cylinder 3 and 4 misfire

Firestorm500

Yep. Bad head. Sorry.

dcwpainting

Well thank you I now have a direction to go to get the engine to stop overheating while pulling the boat will update when work is completed in a few weeks

extrashaky

Yep. Sounds like another 0331 head crack.

What may be happening is a crack in your 0331 head is opening under the heavier load and allowing exhaust gas to enter the coolant system and causing your coolant temp to shoot up. The exhaust gas will boil the water out of the coolant, leaving brown sludge behind. The brown sludge clogs up everything and can waste a brand new water pump in a matter of months. If you're losing coolant also, it's probably going into the oil, where it is eating away at the bearings.

If this is what's happening, you want to take care of it as quickly as possible to avoid bottom end damage that will eventually require a full engine swap. Because of the bulletproof reputation of the 4.0L engines up to 2000, many mechanics not familiar with the 0331 head problems diagnose these issues as a blown head gasket and don't even consider that the head could be cracked, because up to 2000 it wasn't very common. I had two very experienced mechanics miss mine.

You can test for exhaust gas in your coolant by either purchasing a $50 combustion leak test kit or just getting a local mechanic to test it for you if he has a kit. You can do a compression test, but I recall reading where someone with a crack that was opening intermittently had inconclusive results.

You can test for coolant in your oil by sending a sample off to Blackstone or a similar lab ($25, and they send you the test kit free). You won't necessarily be able to see with the naked eye that your oil is contaminated, because the modern detergent packages in the current oils bond with the water and keep it from emulsifying and turning milky like oil used to.

The crack typically happens between the #3 and #4 cylinders. If the crack has progressed far enough, you may actually be able to see coolant weeping between the #3 and #4 cylinders by looking right down through the oil filler hole in the valve cover. That's not always the case, though.

The 0331 head was on every 2000 and 2001 XJ, so don't try to replace it with a junk yard head from one of those years. The easiest replacement is to get a new aftermarket head from Clearwater for about $450. You can bolt that into the truck in an afternoon and drive it another 200K miles.

You can use an 0630 head out of a '99 or earlier, but that head has different exhaust ports and no provision for the coil rail on the 2001. You'll have to either rig up some brackets for the rail or do the "Viper" coil rail conversion to relocate the coil pack and install plug wires.

You can also use a later 0331 TUPY head that was installed on 4.0L engines in other Jeeps after 2001. When Chrysler discovered they had a problem with the original 0331 head, they quietly changed suppliers to the Tupy foundry in Brazil. These heads have "TUPY" cast into the head between the #3 and #4 to differentiate them from the original crack-prone heads. They're not easy to find in junk yards, and when you do, you'll have to have it checked at a machine shop at a minimum, so you may not end up saving that much money.

So unless you're really tight on money, Clearwater is the way to go.

If you start having oil pressure issues (that you can verify with a mechanical gauge), you've probably let it go too long and have worn the bearings. If that happens, you may want to rethink replacing the head at all, since it doesn't make sense to spend money on a block with bad bearings that'll have to come out later on. In that case you might as well look for a full swap. This is why you don't want to let this go, even if it performs fine when you're not towing your boat.

Firestorm500

If this stuff goes on long enough, you will have a boat anchor to go with your boat.