Where did all my coolant go - JeepForum.com
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post #1 of 10 Old 10-16-2020, 09:18 AM Thread Starter
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1984 CJ7 
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Where did all my coolant go

I overhauled by jeep coolant system a bout 2 years ago, not by choice. I had replaced..... all the hosed, tstat, tstat housing (YJ for new temp probe), water pump, radiator and heater core. That solved my over heating. Life was great for 2 years +/-. Till the other day, I was waiting online at bank and saw the temp rise. Due to being in a public place I decided not to pull a red dawn and fill the radiator on line. So I shut the jeep off.

When i would drive the temp was fine, but if i stopped at a light, the temp went up. When i got home i looked and was down 1 gallon of coolant. I have not seen any leaks. everything looks good. I know its a closed system so not due to evaporation. Suggestions on where to look? BTW, the oil looks fine.

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post #2 of 10 Old 10-16-2020, 10:21 AM
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Do you have a recovery tank? Look for any white residue at any of the connections, it is possible to have a leak when the Jeep is hot and the coolant is being burnt off/evaporating and you won't see a leak.

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post #3 of 10 Old 10-16-2020, 03:15 PM
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Got ya on the "Red Dawn"---Does it come out 50/ 50! LOL!

Oil and coolant are "weekly" checks----Bad bad Jeep owner!

I'd fill him back up and closely watch him everyday, maybe it will show up and be an EZ fix.

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post #4 of 10 Old 10-17-2020, 07:39 AM
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The first thing to do is find the leak. Locate where the puddle is and work back from there.
Under the body: heater core. Usually accompanied with fogging of the windshield with the defroster on and a heavy coolant smell.
Under the engine: Front of engine usually indicates a bad water pump, with coolant leaking out the weep hole. look for fluid trails down the block indicating a bad soft plug or a drip under a hose.
Under the radiator: Look at the overflow tube. A bad cap will blow off steam and cause overheating. inspect the core. fluid on the core or pooling on the top of the bottom tank indicates a radiator leak.

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post #5 of 10 Old 10-17-2020, 08:48 AM
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Why do you think it is a closed system? Do you have a coolant recovery tank? Did you retighten the hose clamps a few days after putting on the new hoses? How often do you check your coolant levels?

I agree with MR. FELLER when he said to fill it up and observe. When it gets to operating temperature look at the engine while the engine is running. If you do this at twilight and use a flashlight steam from pin hole leaks show up better.

The boss' main ride has this super duper computer system that tells you if your oil is low, if you need to add oil, when you need to change oil, if your coolant is low, and even when your tire pressure is low. I tend to ignore it while doing my Monday "preventive maintenance checks and services." That could be a problem if I ignored the Jeep.

Good Luck


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post #6 of 10 Old 10-17-2020, 03:18 PM
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Pull your plugs, if you have one that is bone white your burning your antifreeze in that cylinder. It could be when the cooling system pressurizes it starts leaking into a cylinder.
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post #7 of 10 Old 10-18-2020, 01:45 AM
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Not saying this is your problem but this was my experience


Just in case

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post #8 of 10 Old 10-18-2020, 08:38 AM
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HI something no one touched base on and you didn't say you changed.. is the pressure cap.. even if you did it might be bad now.. But if the pressure cap doesn't hold the proper pressure it can cause the loss of coolant out the overflow of the reserve tank and you won't see the loss as it well usually happen as you drive.. Might be worth checking it out??
good luck
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post #9 of 10 Old Yesterday, 07:43 AM Thread Starter
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1984 CJ7 
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No overflow tank.
i have been watching/ driving for a few days and not seeing a decrease yet
No puddle under jeep that i can see (I park on indoor/outdoor carpet)
Pulled plugs and they look ok.
I think this is going to be a wait and see. I will keep you all updated.
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post #10 of 10 Old Yesterday, 09:36 PM
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1985 CJ7 
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Bought a 258 a few years back. Owner said he was having same problem you describe.

When I started to tear it down for a rebuild found the problem. Couldn't see it till the manifolds were off.

Crack in the block between cylinders 5 & 6 I think, maybe 4 & 5. Could see the white crud from the coolant burning off.

Guess it wouldn't leak until the engine heated up and the coolant pressure built up. When engine cooled pressure down no leak.

Might be able to see it from under the engine but would be very difficult.

Someone on the forum mentioned it was a common place for the 258 to crack.

Currently in pieces - all of them
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