Coolant level ?

Is it possible to loose very small amount of coolant and Not have a leak ?

If the coolant level changes there is a leak. Now the leak may be "normal". By this I mean the techs tell me it is ok that say the water pump seal leak a bit of coolant. The leak is known by the presence of dried anti-freeze residue stain on the water pump housing. I was told there is a callout to the allowable size of the stain but this was not supplied. (The techs knew I'd post it here though if they told/asked me not too I would not have posted it anywhere.) What they did tell me is at no time should there be any liquid coolant present. So, given the above then a perfectly healthy cooling system can lose coolant, but in my experience not enough over say 5K miles to cause a drop in the coolant level worth noting. And because I have my cars serviced at a dealer not worthy noting by the tech either, who is quite thorough and informs me of brake pad/rotor thickness, tread depth, etc. Also, the cap can vent excessive pressure. If one turns off a hot engine and the radiator fans are running because of the engine's coolant temperature (above 212F possibly even hotter) the heat load of the engine can raise the coolant's temperature even more and raise its pressure beyond an allowable limit and the cap can vent this pressure. In doing so water vapor is allowed to escape and this can lower the coolant level over time. But again my experience is the amount lost is so small that at no time in 5K miles of driving even in the hottest temperatures this region or other warm regions of the country can throw at one has the coolant level dropped significantly. And when I have the car serviced and the tech checks fluids he has never once approached me about excessively low coolant levels. By way of comparison when what proved to be a defective coolant cap was leaking the coolant level would drop in about a month of normal driving (max. about 200 to 300 miles per week) to where the low coolant level warning light would come on and I would have to add nearly a gallon of distilled water to bring the level up to where it should be. If you are finding the coolant level low enough to have to top up the level - and you didn't say this but I'm reading -- maybe incorrectly -- between the lines -- there is more than just a normal loss of coolant and the source needs to be found and addressed.

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It's possible, depends on the amount and how long it takes to lose that much and whether the drop continuous.

I'd say it is possible but in my case, it was the first tell-tale sign that the water pump bearing was going. I lost about a half shot glass of coolant pretty much every time I drove it and it didn't seem to matter too much how far I drove it. I took it to my indie twice and they could find nothing. On the third try they left the system pressurized overnight and found the leak at the bearing. Sure beats having the impeller shatter so I'm glad I kept after it. Since then, until that car's demise in an accident about 16 months later, it never lost a drop that I could detect and most of my driving was in 80-115 degree weather. That said, a poorly sealed or defective coolant cap, a sticky pressure relief, an almost impossible to see expansion tank leak could all cause coolant loss but I doubt you would have noticeable loss without some kind of a leak or pressure problem. These cars have a lot of plumbing so finding a tiny leak can get involved but the coolant went somewhere...

Zanzibar, since you didn't really give a lot of information, I'll share my other anecdote as well in case it helps. When I bought my current 996 I didn't see any coolant loss but after a few days of ownership I did notice that some time after parking after a drive there was the distinct odor of coolant. Now a 996 has some pretty interesting smells after a spirited drive but coolant isn't one of them. I poked around a lot and could find nothing and the coolant level did not seem to drop. None the less, since I needed to replace the motor mounts anyway I pulled the expansion tank and replaced it at the same time. I could never find the leak on the old tank but no more coolant smells.

I've had pump/tank replaced and the tech Suspects it may have "Burped" or had a air pocket I'm going to keep a eye on it

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half a shot glass? How did you measure that? That is 3/4 oz

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You can drive with the bleeder valve open for a few days and check the level again (when cold). It should stabilize.

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I'm wondering the same.

I believe that's the US equivalent of Hurdi's famous "half an egg cup."

I'd lose about a 6oz cup of coolant during a week. Couldn't measure it daily and really see anything but after a few days it would be down some. Finally figured it out to somewhere around 1/2-1 oz per trip.

Zanzibar, That makes perfect sense. When they first replaced my water pump they didn't purge the system very well and it burped enough to trigger the low coolant warning before I got home. Hope that is all it was. Good luck.

Thanks All for your helpful replys

I have found that my car is happy when the coolant level is just at the min. mark when cold. Any more than that and it will eventually **** (burp) a little out after a good hot drive. Once settled at this mark, it is dry thereafter.

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Thanks for your useful post