cooling system water loss

[harry3]

my 6 cyl engine looses water from cooling system, but only sometimes
theres never any trace of water loss and the system has been pressure tested

does this mean I have a head gasket leak that comes and goes, the head was replaced for the previous owner years ago
those stop leak things dont seem to make any difference

 

[detox_nath83]

head gasket leaks dont come and go..
Do u have Milky Oil (white through it.) or is it running rough or excess moisture out your exhaust.
u could have a leak which is leaking onto a hotspot on your engine and is evaporating. either your rad cap is leaking or your overflow bottle has a hole in it...

 

[harry3]

have checked all you mention and its all OK, the water just vanishes every so often, the catch tank then the rediator looses water, a mystery
oil isnt watery
water isnt oily

 

[rb26dett]

Sounds like you have a minor leak in a heater hose.

 

[detox_nath83]

how about any moisture or wet carpet near your Heater Core. Could have a pin hole in it.

 

[harry3]

no wet carpets or evidence of any leaks