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Disappearing coolant

B

Bob Hancock

NAXJA Forum User
Location
Warner Robins & Blairsville, GA
My Jeep is a stock XJ, 4WD, 4.0L with 134,500 miles. Jeep starts and runs great....no problems. Except.....about every 700 miles I notice the engine running just a bit above normal in temp. When I check the coolant, the overflow tank is empty and the radiator is low. Last night I filled the overflow tank and added about 3/4 gallon to the radiator. Today temp is normal, no complaints. But this is not a new thing and begs the question, where is it going? It's not leaking on the garage floor, and the only puddles I find are when I have the A/C going, as would be expected. Could this be a cracked head that leaks into something? Oil appearance and usage is normal.
I'm stumped. Thanks for any ideas/advice you guys might have.
 
WHY DON"T YOU GIVE YOUR YEAR? Sorry, but I can't help yelling. Let me guess.............2000 or 2001. Cracked head syndrom (0331). Look on the bottom of the oil fill cap for mayonaisse. Welcome to the club! Search "0331 head".
 
My coolant is disappearing through a not-so-small crack in my radiator. I think it's pretty cool. Every time I park in a new area, my Jeep likes to make its mark. It's like, a wolf marking its territory. Yep.

If you don't see anything on the ground, chances are it's a problem with the reservoir bottle or like winterbeater said.
 
No mayonnaise so this tells me it's not getting into the oil. Since I added water last night I checked the coolant tonight and with about 50 miles on the engine the radiator is full and the tank was half empty. But still no spillage that I can tell. Maybe on the road but not when stopped? I guess if it's not worse I can just keep an eye on it and not worry. Still puzzling.
 
Bob Hancock said:
No mayonnaise so this tells me it's not getting into the oil. Since I added water last night I checked the coolant tonight and with about 50 miles on the engine the radiator is full and the tank was half empty. But still no spillage that I can tell. Maybe on the road but not when stopped? I guess if it's not worse I can just keep an eye on it and not worry. Still puzzling.
Click to expand...

Does your exhaust seem overly WET, even during warm weather?
 
uRabbit said:
My coolant is disappearing through a not-so-small crack in my radiator. I think it's pretty cool. Every time I park in a new area, my Jeep likes to make its mark. It's like, a wolf marking its territory. Yep.

If you don't see anything on the ground, chances are it's a problem with the reservoir bottle or like winterbeater said.
Click to expand...
Ha, I have the same problem. I'm adding about a gallon of water a day to it, and not driving unless absolutely necessary. The worst part is that I got the radiator replaced last year and it's still under warranty, but the shop is 300 miles away. I gotta make that trip in about 3 weeks, so I'm trying to be easy on it until then.
 
When the engine is running and temps are "normal" ... the coolant system is under pressure.

A small leak that wont drip when cold may be evaporating on the hot engine whilst mobile.

In addition to the doom & gloom late model head situation ..... The radiator cap ... and overflow bottle as mentioned.

You could also check for leaks or white/green/rusty stains around the welch plugs ( freezeplugs ? ), hose clamps, radiator tank seals, Waterpump weep hole etc.

Welch plugs were the cause of my slow coolant loss .... Until the stooopid plastic rad tank got jealous of the little leak and let go the lot .... :laugh:
 
Disappearing coolant: weep hole on the water pump and the fans/heat gets rid of the evidence; bad headgasket with coolant seeping into the combustion chamber just enough to slowly make the coolant disappear out the exhaust, small leaks at hose clamps or in the other system components that don't show up easily.

You can purchase UV dye for checking the coolant system at most parts stores.
 
Bob Hancock said:
A good list of things to consider. Thanks.
Click to expand...

While doing a tune up last autumn, I had the airbox out and noticed the telltale signs of a coolant leak around the plastic plug in my replacement radiator. Plastic plug was cracked.

100_6287.jpg


In Renix engines, the coolant temperature sensor lives there. Couldn't find a new plastic plug so I just bought a cheap Renix era coolant sensor and cut the harness off. Cured the leak.

100_6290.jpg
 
You can also pull the spark plugs out to see if any look like they have been steam cleaned.

By far, the best way to find a leak is with a radiator pressure test gage. You will be able to see streaming coolant from the weep hole, etc, without the hot engine running. And you can start the engine up with the gage on to see if the needle fluctuates wildly indicating a head gasket leak.

My bet is still with the cracked head though. It's just not getting to the oil (or something).
 
Bob Hancock said:
No mayonnaise so this tells me it's not getting into the oil. Since I added water last night I checked the coolant tonight and with about 50 miles on the engine the radiator is full and the tank was half empty. But still no spillage that I can tell. Maybe on the road but not when stopped? I guess if it's not worse I can just keep an eye on it and not worry. Still puzzling.
Click to expand...
Well I try not to be an idiot but sometimes I just can't help myself. Checked the cap today in the light and there's mayo for sure. Dang. :doh:

So I guess this means I need a new head...right? Are the new ones any better than the originals? Is this an expensive project since I'll have to have it done? This is such a fine little Jeep and now this. Pretty bummed. Thanks to all those who helped.
 
Well I took it to the local Jeep expert and he doesn't think it's a cracked head. Looked high and low for evidence of leaks. Only thing he suspects is maybe the heater coil....but not sure. But he did find evidence of faulty radiator cap. So, I replaced that.
He was not impressed with the small amount of mayo under the oil filler cap, as other clues, like under the valve cover and clean oil said it was just condensation over the years that can do this.

So....I'll see how it goes. Good news is that it's safe to drive so I have time to look and evaluate.
 
Just keep an eye on the oil pressure, and its appearance. If it clouds up quickly, and starts to look like chocolate milk, instead of just getting blacker, you're getting coolant into the crankcase. If the oil pressure goes down, start praying for C4C, Part Deux.
 
Will do. The oil pressure has been fine and hasn't changed. Oil is getting dirty like it should. Mr. Jeep thought the oil looked fine too.

FWIW, one of the first tests he did was fill the radiator to the top, and with the cap off I started the engine. He said that if there was a cracked head it would have expelled coolant showing compression leaking into the radiator.

He also put a compression testor on the radiator and it held pretty well but not completely. We couldn't find anything though.

If it does continue to mysteriously leak then he recommended trying stuff called "Dykes" which is a stop leak.

Well that's about all I know at this time.
 
A bad radiator cap can cause excess antifreeze to go in and out of the overflow bottle too much and because it is hot, you get evaporation. Radiator caps should be 16# and replaced every two years.
 
My 01 was losing coolant and it turned out even though the oil looked fine there was a small crack in the head. Take a look in the oil fill hole and look for a hairline crack. If the crack has been leaking for some time there will be a clean spot around the crack where the water has washed away the oil residue. I assume that mine was leaking at such a slow rate the coolant was cooked out of the oil.
 
If you have: combustion gases in the coolant; oil in the coolant; coolant in the oil; Stanley-steamer exhaust; Old Faithful in the cooling system; steam-cleaned spark plugs; hydro-locked engine, or some combination, you might want to check the head gasket.
 
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