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Discussion Starter · #1 ·
Any thoughts as to why we would need to fill the reservoir every two weeks or so? Back story. Son took in to have thermostat replaced and general "check up". Shortly afterwards his engine was getting "hot". When he checked the cap was off the radiator (he had no clue what happened to cap - thought it maybe broke and fell off - 20 yr. old). He had to special order a cap from Jeep so it took a few. Vehicle kept getting "hot" and he kept refilling. We have since realized that the cap was left off when the thermostat was replaced. Unfortunately they wouldn't do anything about it because we didn't realize this until the repair warranty had expired. Thinking this has something to do with it needing constant refill. Never any fluid underneath. Before taking to shop just wanted some thoughts. Wishing it would be a recall issue like the engine fan and oil usage issue but haven't seen anything like that. TIA!
 

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The cooling system is a closed system. The cap is set to allow the system to pressurize, so that the coolant will have a higher boiling point. If the cap is left off of the system, the coolant will boil off at a lower temperature than if the system is under pressure. By leaving the cap off, your coolant probably expanded to the point that it overflowed the coolant reservoir, while the vehicle was being operated. If after the reservoir cap is replaced, and you are still losing coolant, have the cooling system pressure checked, and the source of the leak found
 

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Discussion Starter · #3 ·
"The cooling system is a closed system..." Well leak would be preferrable to engine problems. We took it back to the place that did it and they said they did a pressure test and couldn't find anything. It's definitely going somewhere! Maybe they can't get an accurate pressure check when it's not totally cooled off? Thanks for your reply.
 

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How much is it leaking over whst timescale? Max to min? All of the header/expansion tank?

Any signs of sludge in the oil?
 

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In my experience, if a large volume of coolant is boiling off you will smell it. I don't believe it is possible to have both a passing pressure hold test and a significant loss of coolant. Maybe the location of the pressure test apparatus is the location of the leak? Just spitballing.
 

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Discussion Starter · #6 ·
How much is it leaking over whst timescale? Max to min? All of the header/expansion tank?

Any signs of sludge in the oil?
No one has mentioned sludge with any oil changes. Need to have the "oil usage" recall issue checked but probably not related. Don't check it daily but every 2-3 weeks it is below the min. level, sometimes none showing but this week he checked before driving and there didn't appear to be any in it. Drove to our house to put some in it (20 min. drivie?) and when he went to check it, there was some in it.

Tkx for reply.
 

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Discussion Starter · #7 ·
In my experience, if a large volume of coolant is boiling off you will smell it. I don't believe it is possible to have both a passing pressure hold test and a significant loss of coolant. Maybe the location of the pressure test apparatus is the location of the leak? Just spitballing.
Thanks for reply. No clue. Just very odd that there could be no leaks (nothing underneath) but reservoir is emptying that quickly.
 

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Well when you have a big leak, you are going to either smell it getting cooked off of the hot parts it is leaking on, or you are going to to see it leaking on the ground..... unless you are leaking it into your oil, then you have the forbidden milkshake.
 

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Discussion Starter · #9 ·
Well when you have a big leak, you are going to either smell it getting cooked off of the hot parts it is leaking on, or you are going to to see it leaking on the ground..... unless you are leaking it into your oil, then you have the forbidden milkshake.
Tkx for reply. Just had oil changed this week. They have noticed a "milkshake" I would think. Not noticing any smell. Maybe leave it overnight and let them pressure check it first thing while it's cool?
 

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I had a KIA that had a crack in the reservoir tank. the dealer had it in their shop for 3 days and could not find it. I finally figured it out crack would only leak when under pressure.
 

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I had that on 2
I had a KIA that had a crack in the reservoir tank. the dealer had it in their shop for 3 days and could not find it. I finally figured it out crack would only leak when under pressure.

I had the same on 2 previous "Fiat" built cars.
And weeping from the tanks hose connections.

But in all cases they would leak from max to min in about a week. Nothing as bad as OP is describing.
 
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