ok so it's not the coolant.........

You have no evidence that the coolant is getting into the engine.

wrote

It doesn't have to be milky and you can still have an internal leak from the intake manifold gaskets. Did you happen to "taste" the emulsified "stuff"? You can taste the coolant in it, if it's there.

None of these tests will tell anyone anything about coolant leaking from the intake gaskets. Even the pressure test is not a guaranteed way of checking as the gaskets will often only leak at very specific times/temps...etc.

Just keep at them. The coolant isn't "magically" disappearing, so they should be able to figure it out.

Ian

if you really want to know, before test comes back, if coolant is in the foam you found on the bottom of your oil filler cap, or PCV valve ..........taste it! not a tablespoon. just touch it to the tongue. anytime coolant is present...its sweet............kjun

btw: of the hundreds ive seen on this repetative gasket failure the first signs are slow, unexplained coolant loss and the foam on oil filler cap, pcv valve and inside pcv tube. if left alone and unattended it will drain enuff coolant to overheat or scour the bearing shells to the point of bearing failure. normally overheat comes soon enuff to shut engine off. my sons 3.1 was draing a quart a day to the crankcase before i found time to change gaskets. for most of a week i got up and went and changed his oil before the sun came up.....then spent good part of the next saturday doing what had to be done. .................poor, poor, pitiful....kjun

not to sound too stupid , but why wouldn't a leaky intake gasket produce a pressure drop when the cooling system is put under pressure?

ok thats easy enough.

that sounds just like what the dealer said. funny thing though.....they changed oil for the first 30k while it was under warranty ,and I've done it every 3000 mi ever since , and the white crap was NEVER there prior to the start of coolant loss. So .....where do YOU suppose it's going ?

I will have to chime in here. On my 2001 Impala 3400, it took me frickin' forever to find out where I was losing coolant. The leak developed VERY slowly - as in, over 2-3 years. I went nuts, because in the morning, I would find coolant on the garage floor, but no visible leakage around the gaskets. My oil stayed fine, so I knew the coolant was dumping out somewhere external. I *finally* caught it leaking after a long, high-speed run, followed by leaping out of the car and tossing open the hood. There was a little pinhole leak next to the thermostat, which stopped quickly. I will note that even when the leak got much worse, it still could never be observed when the car was just sitting in the garage idling, regardless of thermostat temp.

Coolant running low every week or so is about right. Do yourself a favor and change out the intake manifold gaskets, and your problems will go away.

- Larry A.

That's a dedicated dad, kjun. I let my daughter's 3.1 go too long and within a month or two of changing out the gaskets it finally developed that telling knock that says "rods aren't happy!".

Just an off the wall guess because I once had a similar problem and the leak that no one could find was a very minor defect in the seam of the plastic overflow tank.

I would put big bucks on the intake manifold gasket having failed. They have a nearly 100% failure rate on those engines.

Because the leak may not happen unless the engine is running and hot. Rarely does anyone do a cooling system pressure leak down test with the vehicle running and hot.