VERY slow coolant loss

[allen_m]

I have an '02 S80 with under 60,000 miles. Recently I got a low coolant warning. I topped off the coolant with around a quart of water and within miles received another warning, so I put it in the local independent shop (dealer 100+ miles away...) for a pressure test. He found no pressure loss and suggested I order a new cap, which I did. Problem solved, I thought. Coolant level steady for around 400 miles until yesterday when I got the dread low coolant warning again...

Incidentally, the engine has never exceeded a normal operating temperature throughout this ordeal...

Any thoughts greatly appreciated...

I guess maybe I fill 'er up and hope she makes it the 100 miles to the dealer and let them take a look while performing a 60k service...

-A

[claymore850]

Is your S80 turbo??? Check the cooling water inlet on the lower side of the turbo. Check for cracked hoses on the heater, near the fire wall. Also check your interior carpets, maybe your heater is cracked...

[neworleans]

I've had the same problem on my S80, even though the level was ok, it was still giving the aggravating message, I ended up replacing the sensor underneath the reservoir. It was around 25 bucks. You can change it your self. 5 min job...

[allen_m]

Non turbo model and I don't suspect heater core(dry carpet and all hoses look remarkably good condition) or reservoir sensor (actually losing coolant). Honestly, I am afraid it may be a slow head gasket leak.

I have heard this may be diagnosed by watching the 1st few seconds of exhaust after allowing the engine to cool. Theory being that the leak is far too slow to see white smoke in exhaust yet; however, cool-down pressure may be enough to allow some coolant to seep into heads as the engine cools- perhaps enough to see a small puff of white at initial start-up.

Will check this when wife gets home tonight...

-A