Marks2000XJ

2002 Grand Cherokee with inline 6. I keep having to add coolant to the overflow reservoir because it mysteriously keeps getting low and my overhead display keeps coming on saying low coolant.

I can't figure out where the coolant keeps going. I can't find any obvious leaks but it has to be leaking somewhere. Any ideas what is going on?

Yesterday I had a total loss of coolant and the GC went into the red. Stopped it immediately and shut it off. Went out this morning to look at everything. No busted hoses, no obvious leaks. Topped everything back off and let it run and burp with the heat full blast. Got it up to running temp and no issues. Drove it around town for several miles and temp stayed below the halfway mark.

Checked coolant level when I got back and no apparent loss. Nothing leaking anywhere I could see.

I would think if I had a cracked radiator there would be coolant on the ground or if a bad water pump coolant would be leaking. Not sure what is going on. Fortunately I did not blow a head gasket...

Mr. Pink

pressure test the system.

Cane

your username states 2000 XJ but your profile says 1998, which one is it?

if it's the 2000, don't look further than a cracked head unfortunately. still wise to test everything before drawing this conclusion, but it can't vanish, it's going somewhere. and if it's not on the ground....

dave1123

Cane, it's a 2002 4.0 as stated in his post.

I think I know where the mysterious slow loss of coolant goes, but where the sudden total loss went, I haven't a clue. A total loss wouldn't seal itself again and it would be obvious from the mess where it went.

I had a slow loss of coolant from the reservoir over a period of about 2 weeks that got to be about 1 week before I found it. The older water pumps had a "weep" hole on the bottom of the impeller bearing that would drip coolant and you could see it. The newer ones have a "weep chamber" that holds about a tablespoon of coolant that is allowed to evaporate without you seeing it. After the leak gets large enough it drips into the back of the belt pulley and is thrown off on startup. I only found this after starting it up while it was up on a lift to bleed the brakes. When it started, a torrent of coolant sprayed down the front of the engine, then stopped! After looking in a catalog for water pumps, the AC Delco listings explained this chamber. SOAB! Why did they design that?

Getting back to your total loss, you may still have the 0331 head on yours because they were fazed out sometime during the 02 production run. Mine cracked into an exhaust port and was dumping coolant out the tailpipe with dripping and steam. Luckily, it did not get into the oil. Take the oil cap off and shine a strong flashlight down the hole. The "new" head has a "TUPY" cast into the head right where you can see it. If not, you have the old head. If it's cracked into the valve area, you'll see a milky white line at the bottom of the hole between the valves. If you see the line, check your oil for coolant contamination and hope you caught it before it destroyed the bearings. This is a worst case scenario and I hope it isn't the case for you.

I replaced mine with an Odessa head, $455 complete with valves and shipping both ways. (core return) Mine cracked at 145K but is still running strong at 197K. The converters smelled funny for awhile until they burnt out the coolant.

CR-Snow

2002 huh? Might check to see if you have the TUPY head or not. From 00- early 2002 Chrysler had problems with the 0331 casting heads, which you have. They fixed the problem in 2002 some time. If you pull the oil cap off and look between the two cylinders there should be a marking that reads TUPY. If that marking isn't there, you could have a cracked head.

Pop that oil cap off and look for sludge on the cap. Modern oil doesn't milk up nearly as easy as older stuff so that's not usually a great indicator.

A pressure test is good advice too. But figuring out which head you have will help too.

dave1123

For those of you who are interested, the TUPY head and the 0331 head are identical except the TUPY was cast in Brazil with a different metal compound added to it. Chrysler never admitted there was a problem with the 0331 that didn't originate with poor maintenance or overheating, yet they "fixed" it. Go figure!

The Odessa head is a heavy casting that weighs 7 lbs more than the 0331. There's more metal over the top of the chambers that you can see because the valve spring pockets are cut deeper.

Cane

you're right it was so obvious i missed it. i still stand by what I said, it can't just dissapear. check oil and do a compression test, go from there.

dave1123

Yeah, I've been told my crack was a rare one in that it only cracked into the exhaust port. I got lucky, I guess.

Cherokee_Mike

I had a problem with my 2000 GC 4.0 I6 with slow coolant loss for about 3 years - no sign of any leaks, just kept topping it up every 3 - 4 months - put it down to evaporation. Earlier this year the rate of coolant loss increased but was irregular - would go 2 weeks before needing a top up sometimes, other times every couple of days - but still no sign of where it was going !
Looking at the engine I noticed the serpentine belt showed some wear on the smooth side - I had only replaced it a few months before as I had noticed a few minor cracks in it - I wobbled the fan pulley and discovered some serious play in the water pump bearing - problem found at last. Moving the pulley from side to side I could see a slow trickle of coolant but when I let the pulley return to rest position the trickle stopped. The premature wear showing on the serpentine belt was obviously caused by the water pump pulley moving around and causing it to chafe.
New water pump and all well again.
I had begun to dread the problem was a cracked head but having only done 73k miles was rather hoping that was not the case as the Jeep is on great condition and has many years of life left in it.

Marks2000XJ

I have a 2002 Grand Cherokee in addition to a 1998 Cherokee Sport. When I originally signed up on CF I had a 2000 Cherokee Sport which I sold a while back.

Marks2000XJ

Let me back up for a minute. My son was driving the car when the loss of coolant happened. I was at work at the time so he was giving me the information over the phone. He said a hose came off and when I go home he showed me the one on the overflow reservoir. I said that is just a drain hose and that would not let all the coolant come out like that.

Got to looking at it again this morning and sure enough I found the hose that popped off. It was the lower heater core hose up against the fire wall. I guess the factory clamp broke due to age maybe? So that explains the sudden coolant loss.

As for the slow leak I am suspecting the water pump as stated by a few of you. I will pressure test the system first to make sure I don't have a blown head gasket.

I bought the 2002 in hopes it had the better head because I knew that was the year for the better ones. I will check and see what I can see. Will report back.

Thanks for everyone's replies.

Marks2000XJ

I checked and do have the TUPY stamp on the head. Oil looks like oil. No obvious coolant mixed in. Going to use that bulb with the blue chemical in it to test for gases in the coolant to make sure no blown head gasket.

May do a compression test too just to be sure.

bigbadon

I had the same problem....could not find it until it got worse about a year later. Replaced water pump and coolant has remained same level last 2 years.

dave1123

Whew! That's a relief! I REALLY hate it when the problem is something that's totally beyond your control, like a design fault! When I went looking for a new Jeep after my ZJ, I knew nothing about this head problem. HAD I KNOWN, I would have spent another $1000 and bought a 2002. I DID know about the 4.7 so I was reluctant to buy one used.

So the mystery coolant loss is no longer a mystery.

CR-Snow

Shoot, if I knew about this head problem I would have spent $1000 less and found a 98 or 99. I put $1000 into it in the first 6 months chasing misfire and O2 demons, only to find out a few months later that my oil has trace amounts of coolant in it.