I tried doing some searches to see if I could get a solid answer but not totally sold so here goes. I have a 2001 XJ that I bought in April and about 3 weeks ago I parked the truck and the coolant overflowed back out the holding tank and all over the road. Ironically it happened at an auto parts store while buying coolant as my reservoir was very low. Didn’t notice any leaks before so thought maybe it was a slow leak that I didn’t see or it was just low when I bought her and never noticed. Anyway, I filled the coolant when I got home after it cooled off and the next time I drove it overflowed again the first time I parked after driving about 30 minutes. Engine temp seems to be fine running between 200-210. I did a coolant flush and all seemed to be going ok until Wednesday this week when I noticed a small coolant puddle under truck after parking for about 35 minutes after driving for 10. Drove her home and coolant was leaking a little (like a fast drip) from front of engine on driver’s side but stopped after a minute or so. I let her sit overnight as I was changing the valve cover gasket yesterday and when I removed the valve cover, coolant suddenly began to pour out of the same front engine, driver’s side area. In order to removed cover I removed the heater hose from engine. Thought maybe it was something to do with hose removal, but when I replaced the hose after gasket was done and refilled coolant, it immediately poured right back out. Coolant is/was running down the lower left hand hose. Is this likely the water pump/seal? This is my first Jeep and I have minimal experience working on vehicles but want to learn as I go on this. Thanks in advance.

 

I had the exact same issue in my 99, it was the fan clutch. Not a hard repair.
It would overflow occasionally from the overflow tank when I parked it after driving on a hot day (the ground would be clean when I parked, but upon returning like 10 minutes later it was full of antifeeze). Don't buy the no name one from autozone people have issues with it. I purchased a HAYDEN 2625 at rockauto for like $35 a few years ago and it is still running great (and was made in the USA). Amazazon had it For $32.
https://www.amazon.com/Hayden-Automo.../dp/B000C3DD1S

 

Thanks! The clutch fan looks to be a project within my abilities. Gonna replace water pump today too as my guy says thats the key to the other leak.

 

1. The fan clutch cannot leak coolant. It has no coolant in it, no contact with the engine coolant.
2. Finding a leak isn't normally very difficult. Eyeballs, a flashlight, and paper towels are your friends.
3. Swapping parts is an expensive, frustrating, and ineffective way to fix problems.
4. It's not a truck. It's an SUV.

 

Like Mark said don't throwing parts at it but find the real problem first, then you can replace everything else as all are old. Start by looking at the bottom of the water pump there is a weep hole there you should be able to see it from the bottom. Just use a flashlight and wipe it clean then wait till it drips again (most likely if that is the problem).


Then advise back.

 

Typically when the water pump is going, it will leak from the weep hole on the underside. You will usually see coolant running down the lower hose and dripping from the lowest point on the hose. Not sure about the coolant overflowing too much into the overflow bottle. I have never experienced that. All of the cooling system components are easily accessible and pretty simple to check. If you don't know the history of the cooling system, it's pretty cheap insurance to drain it and change the thermostat while. If you have to change the waterpump anyway, you will be removing the thermostat at the same time. While you are there, you can loosen all of the hose clamps and check the hoses since they rot from the inside out. Make sure there are no cracks etc. when you have them off.

 

compression test.

 

Or a combustion leak test.

I bolded the clues you gave us, which point in an ominous direction.

The 2000 and 2001 XJs had the original casting 0331 head that is prone to cracking. The early warning symptom is coolant disappearing without any visible leaks. If you have a blown head gasket or a cracked head or block, you can also get leaks of combustion gases from a cylinder into the cooling system. That can manifest itself as unexplained temperature spikes and/or boiling over when you stop, even when the engine isn't overheating.

You can detect a cracked head or blown head gasket several ways. On some of them, you can actually see the crack and coolant weeping up by looking down into the oil filler hole in the valve cover with a flashlight, since the 0331 likes to crack between the #3 and #4 cylinder. If coolant is getting into your oil, you may not actually be able to see it in the oil itself because of improvements in the detergent packages in modern motor oil, but a $28 oil analysis from a lab like Blackstone will tell you definitively whether that's happening. You can do a compression test, which will tell you if one or more of the cylinders is no longer sealing up. You can get a $50 combustion leak test kit (or find a mechanic who has one) and test for the presence of exhaust gas in your coolant (which I strongly suspect you have).

You must not let this go. If the 0331 is cracked and you catch it early enough, it's just a matter of swapping heads on a Saturday afternoon. If you don't catch it early enough, you will lose the entire long block.

If you do have to replace it, your best bet is a Clearwater head for around $500. There are other options, but that's usually the easiest.

 

You are right that a fan clutch won't leak coolant, but if it does not do its job properly, the coolant will boil and overflow, which you many times you see after parking the car. I had to change mine at 65,000 miles and had the same symptoms as the OP and it cured the issue.