Coolant disappearing with no visible leak - Page 2 - JeepForum.com
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post #16 of 24 Old 09-08-2021, 04:41 AM
jpcallan
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Time for coolant leak tracing dye

Add coolant dye to the radiator and wait a week. The leak location will be marked with a bright green stain under UV or violet light. You may need to borrow or rent a UV inspection light. See:

https://tracerproducts.com/leakfinde...s/coolant-dye/

LF3001CS is the single dose size available on Amazon for $7.

Fluorescent dyes are often available in different colors to differentiate the medium being traced. Yellow for refrigerant, blue for motor oil or transmission fluid, etc.

A friend had a beloved BMW 733i he bought new that picked up the habit of constantly losing coolant. The BMW dealer sold him a new radiator, hoses, service after service, ultimately amounting to big $$$, but the coolant loss continued. He finally trusted me to try to find the leak with dye. I added yellow Tracerline dye. After a week of driving, he brought the car over after dark for an inspection. There were two leaks - the top of the white plastic radiator expansion tank had subtle fatigue cracks with a big fried egg yellow dye stain on top; leak number two was a white plastic heater valve with tiny cracks and a small yellow dye stain. I changed the expansion tank, but was not equipped to remove the dash to change the heater valve, but the bottom line is the leaking stopped.

These leaks can be hard to isolate because often water vapor is leaking, not liquid water. If the leak is in the heater core, you may see green dye stains in the condensate dripping from the air conditioning evaporator drain.

Be sure to use distilled water as make-up water and not tap water to avoid plugging up your radiator with mineral deposits from hard water.

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post #17 of 24 Old 09-08-2021, 10:29 AM
BlueOffroader
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When I was trying to figure out where my coolant went. It ended up in passenger side floor carpet. Whole thing was soaked due to broken heater core.
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post #18 of 24 Old 09-08-2021, 03:53 PM
CraigMBAx
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Quote:
Originally Posted by Rylxmp View Post
The mechanic said that he found no other leaks after preforming a pressure test on the cooling system and also no signs of a bad headgasket.
Welp it's going somewhere, and the number of places it can go is limited. If it's not on the ground it's out the exhaust.

Just because he can't find it doesn't mean it's not disappearing.

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post #19 of 24 Old 09-09-2021, 07:50 AM
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Probably just steaming out of a defective radiator cap.
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post #20 of 24 Old 09-09-2021, 11:17 AM
Delta0
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Quote:
Originally Posted by snowbuggy View Post
Probably just steaming out of a defective radiator cap.
Ditto
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post #21 of 24 Old 09-09-2021, 11:37 AM
jpcallan
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Heater core leak

Quote:
Originally Posted by BlueOffroader View Post
When I was trying to figure out where my coolant went. It ended up in passenger side floor carpet. Whole thing was soaked due to broken heater core.
The wife's 1996 ZJ suffered the same fate as @BlueOffroader . We took the dash out and replaced the heater core early this spring, 2021.

Our coolant leak symptoms were strange. We had 'waterfall noise' frequently from the heater for years and wet carpet (but no antifreeze) to confuse things (rain leak). The engine, trans, and transfer case were all rebuilt last fall with the body sitting undriven for about 2 months in fairly warm weather. When the cooling system was refilled, the heater core leaked like mad at first, the carpets obviously stained with sweet-tasting antifreeze. A new heater core was quickly purchased, but for no explicable reason, the leaking quickly stopped and the radiator held pressure. We again had 'waterfall noise', and the rain leak into the cabin, but no antifreeze soaked carpet. Somehow the heater core had healed itself.

This past spring of 2021 we bit the bullet, pulled the dash and installed the new heater core purchased the previous fall; rain leaks were caulked. No more 'waterfall noise' nor wet carpet. On inspection of the old heater core, there were multiple blue-green stains where it had been leaking, but after back-flushing the core in the kitchen sink, a ton of blue-green sludge came out.

My theory is the sludge was plugging the holes; the sludge dried out and shrank while the vehicle was under repair, so the core leaked like mad initially, then the sludge re-hydrated and expanded to plug the leaks. After driving, when the engine cooled off, air entered the heater core, causing the 'waterfall noise'. Many Jeep GC owners have reported 'water sound', 'waterfall noise', 'sloshing noise', etc. I suspect these are all heater core leak sufferers with air in the heater core.
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post #22 of 24 Old 09-09-2021, 11:50 AM
jpcallan
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Leaking radiator cap

Quote:
Originally Posted by snowbuggy View Post
Probably just steaming out of a defective radiator cap.
Buy a new Stant radiator cap at a NAPA or get a MOPAR part from the dealer, and see if the pressure loss stops. @snowbuggy 's advice may save you a lot of fruitless effort.

I spent my career as a mainframe systems programming consultant. When the computer system would suddenly misbehave, the first question always asked was "What was changed recently?" For you it sounds like the answer to that question is the new radiator cap.

Another question, is the coolant in the expansion tank going up and down, or is it pretty much stuck at one level?

You might also take a peek down the radiator's water neck and look for bits of crud or nicks in the seat where the radiator cap seal rides.
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post #23 of 24 Old 09-12-2021, 11:01 AM
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Quote:
Originally Posted by CraigMBAx View Post
Welp it's going somewhere, and the number of places it can go is limited. If it's not on the ground it's out the exhaust.

Just because he can't find it doesn't mean it's not disappearing.

it could be paranormal activity in his cooling system.
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post #24 of 24 Old 10-14-2021, 01:21 PM
RadarRider
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Have you had any luck finding the problem yet?
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