Coolant very slowly vanishes (update)

ALScott

ALScott

TJ Enthusiast
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Joined
Feb 9, 2021
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133
Location
Alabama
I replaced entire system about a month ago, radiator, thermostat, water pump and hoses. I have put may 50 miles on it since. Coolant in overflow bottle keeps going down very, very slowly. Could it be that bubbles are still working their way through the system? It's driving me nuts. I have crawled around that area and can't see or smell any kind of leak. Just keep putting it back in overflow every now and then and forget about it or is there something else to look for?
 
Are you 100 percent sure its not slowly leaking at the t stat housing? I guess its possible to still be burping air bubbles..Have you gone over and touched/inspected every connection?
 
Sometimes various connections can leak only when hot, some when cold. When they only seep when hot the coolant can be steamed off leaving little to no trace of the leak.
Cooling system pressure tester is another way to check things and a very valuable tool.
 
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I have had any number of vehicles lose coolant very slowly - as in a noticable drop in several hundred miles. My Jeep was once such - first the heater core was leaking, so I bypassed that. That slowed it down by quite a bit, but but didn't stop it completely. The T-stat housing had been replaced just before I bought the Jeep - and it looked a bit suspicious. I tightened its bolts and thus far, I haven't noticed any further coolant drop.

My old Mercedes has done this for literally decades. It seems to like the level in the puke tank to be lower than what's indicated. It will drop to its desired level and then won't noticeably drop after that. I though when I had the engine rebuilt 4 years ago, that it would change. It didn't. No noticeable leaks anywhere. Yes, the radiator cap has been changed - a couple of times!
 
Yes it can be burping air, we used to let them get up to temp with the cap off and watch it circulate till there were no bubbles , when I was a teen and hung around a shop. Not sure if that is recommended now.

keep us posted.
 
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ALScott said:
I replaced entire system about a month ago, radiator, thermostat, water pump and hoses. I have put may 50 miles on it since. Coolant in overflow bottle keeps going down very, very slowly. Could it be that bubbles are still working their way through the system? It's driving me nuts. I have crawled around that area and can't see or smell any kind of leak. Just keep putting it back in overflow every now and then and forget about it or is there something else to look for?
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Dont fill it to the full mark and see if it still goes down further. I could be wrong here ( and I often am) but the overflow is also an expansion tank so will not always show to the full mark, sometimes over sometime under, If it doesn't empty or over fill after a long run then there is not a problem. You have only done 50 miles in a month so that must have been done on short trips to know it keeps going down very very slowly.
I have never owned a vehicle that the coolant level showed to the full mark including my TJ, I dont check under my hood when the motor is hot I check it when its cold or up to temp at idle and my coolant tank has never been on the full mark always lower.
 
Sorry for late reply. Posted this and left to get gas in Jeep and buddy called for front porch beers. I drove about a mile to gas station and there was liquid all under the front on fan blade, back of radiator, from passenger to drivers side. No burning coolant smell and coolant tank was not any lower. I now think it was the flood of condensation the AC on this thing produces. Wife turned on the air and I forgot. I have touched and felt and looked and crawled and I can't see coolant anywhere but that tank drops. However, I don't think it dropped yesterday, if it did it was very small.
 
Rubicon88 said:
Let's back up a step...why did you replace the entire system?
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I have no idea what maintenance has been like and I just don't want to fool with hose or radiator blowing. I will be taking it to farm in fall for hunting season and don't want to have to fool with any repairs there.
 
ALScott said:
I have no idea what maintenance has been like and I just don't want to fool with hose or radiator blowing. I will be taking it to farm in fall for hunting season and don't want to have to fool with any repairs there.
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Ok....fair enough

Did you reuse the factory hose spring clamps?

I'd also check if you got all hoses seated beyond the flare on the inlet/outlet...or a clamp right on the flare...

All of the above can cause a slow leak. Thermostat region as well...
 
Rubicon88 said:
Ok....fair enough

Did you reuse the factory hose spring clamps?

I'd also check if you got all hoses seated beyond the flare on the inlet/outlet...or a clamp right on the flare...

All of the above can cause a slow leak. Thermostat region as well...
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Don't know why, I never do things like this but I did reuse the hose clamps. Had an issue with the one on thermostat where that terrible bend is but moved the clamp around a bit and got it to stop. I keep watching and I just can't see it. Let it idle in the driveway for a long time yesterday and nothing. I am going to keep an eye on it. Hopefully it was still trapped air.
 
Do you have the ability to do a leak down test?
Any other symptoms such as its idling a little rough or different or do you have any white smoke coming out of your exhaust?
Hate to say it, but when mine had disappearing coolant it had a blown head gasket.
 
Bkspear said:
Do you have the ability to do a leak down test?
Any other symptoms such as its idling a little rough or different or do you have any white smoke coming out of your exhaust?
Hate to say it, but when mine had disappearing coolant it had a blown head gasket.
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I would barely idle a little rough after driving it a bit when I stopped. I changed the spark plugs and that appears to have stopped that.
 
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