Overheating! water missing, but where?

I just recently bought a 97 Passport. It is a great truck. Dives tight and smooth. I had a 92 Explorer EB. What a difference!
When I bought the Passport it had a leak at one of the small hoses. The dealer (Car lot) replaced the hose and all the coolant. It was fine foor a couple of days and then it started to overheat. When I popped the radiator cap it blassed hot coolant out for all most 30 seconds. It pretty much emptied the radiator. Now, I did release the pressure first. I let it sit with the cap seal cracked for a minute or two before the blast.
I filled it back up and it was fine again for a couple of days. The thermostat will rise and sometimes fall back down. The next couple of times it got hot it was just low on coolant. I took it back and they replaced the thermostat and all the coolant, again. It was fine for a couple of days and last night it was low on coolant again. We have run the truck and looked for a leak and they nor i saw any leak. So... were is it going? Is it possible it is just leaking as we drive? Is it possible it is leaking into the block? I checked the oil and it looks and smells fine.
I need some advice please.
Thanks a million.

How much antifreeze are we talking here??

Anyone looked underneith?

Even if it was running off as you were driving it, there would be *some* sign of a leak, i.e. driveshaft damp, oil pan a little green, etc.

Sounds like they didn't get all the air out of the system when they replaced the hose; i.e. thermostat rising and dropping in temp.

Park the truck, nose up, start it and let it idle with the radiator cap off to allow any air to escape, let it run 10-15 minutes, put cap back on and shut off truck.

After it cools down, i.e. 3-4 hrs, check your reserve tank, if it's low, add more antifreeze.

FWIW - I've discovered this last winter, when one hose starts to go, others are very soon to follow. Your truck is the same age mine is, and I've had to replace a lot of hoses this year; double check every one along with the clamps. Your heater core hoses (passanger side @ firewall) are for sure had their day if they are original.

If it's not a hose, and there is no sign of leakage below, could be a failing waterpump (usually leaves a green sign though) and/or cracked headgasket - I don't believe visually looking at oil on a dipstick gives an accurate measure of whether or not antifreeze is in the oil.

Good luck, keep us posted.

I don't believe visually looking at oil on a dipstick gives an accurate measure of whether or not antifreeze is in the oil.
I dont either. Nobody likes my method of testing though.

Pull the dipstick out, get a drop of oil on your finger, taste it. If it tastes sweet there is coolant in your oil. Its not that bad and its not going to hurt you.

Try to work thru your overheating problem systematically. Rule out one prob. before going to next. Ramblin has a point. Be sure to rule out "air pockets". Is thermostat new/or confirmed ok? Another sneaky problem is pinhole leaks that are very difficult to locate due to being so small, they evaporate to atmosphere, i.e, atomized sprays, as to be undetectable. By the same token, tiny leaks in head gaskets" whereby coolant is escaping into combustion chamber" but, at a rate that remains undetected because it burns up before it has a chance to make it to the oil pan and turn your oil "white". To check for leaky hoses, wait till dark, with hot engine, raise the hood, shine a good strong light across the top of the engine compartment. Any sprigs of coolant escaping are easier to detect with this kind of light. Beware of fan and other moving parts. Shut off engine, ck. again. Good luck ...Theroad

Thanks for the help. So far The thermo has been replaced and the radiator is fairly new along with most of the larger hoses and a couple of the small hoses. This has been going on for almost a month now and I checked it last night and had to add more water. I will try some of the tips given. If water was getting into the oil it would have to be alot because I have added a pretty good bit back to the radiator. I am only adding water untill I find the leak because of cost. I will look hard on Monday and see what happens.
Peace

Could also be a failling water pump.

Hi,
Sounds really like a head gasket problem to me.
These are exactly the same symptoms that happened on my car, sadly.
Get it fixed before it does any more damage like warp the cylinder head.

Don't forget to look with a flashlight at the top of the engine, between the heads, way down in there, for coolant pooling due to a coolant leak at the ends of the metal pipes where there are o-rings.

Pics to reminisce...
http://img.photobucket.com/albums/v380/surferfletch/leakgask.jpg
http://img.photobucket.com/albums/v380/surferfletch/pipegskt.jpg

OK, I think I found it! The only dripping I have noticed is where the A/C drips from. This morning I walked out and ther was water all on the ground creating and nice little steam in the drive. Now, abviously the A/C was not running over night so I started looking. There is a fair amount of dripage (new word) from the back side of the motor. Drips down and falls on top of the trany and over to one of the arms. it is quite wet down there.
Now the problem is that I can't physicaly see where it starts. There are two hoses from the left of the engine that go around the back and it looks like it is in that area. This looks like a really bad spot to have a leak. The only way to get to it is to pull the top of the engine off isn't it?
I plan to take it back to the dealer and see what they will do.

That's where my leak dripped to... I had the leak from the ends of the metal coolant pipes on top of the engine AND from freeze plugs on the back of the block, between the block and the tranny. A pressure test will narrow it down. Good luck. This has to be fixed for the truck to be driveable, obviously.

Those 2 hoses that you talked about are the heater core hoses. You simply might have a leak in the hose or a bad clamp where they attach behind the engine - one to the water manifold and one to the lower coolant pipe on top of the block. You can see where they connect in the first picture I posted. As Ramblin' said, there are a lot of coolant hoses that need changing!

Could be the leak Surferfletch had, and/or heater core hoses - passanger side around back of block. These you can do without removing anything but the old hoses.

Yes, at almost 10yrs of age, any OEM hoses you see, get em out!!

Update?

Update?
Update.
It looks like the same thing Surferfletch had. It was the seal not the hose. I had the lot do the repairs and what do you know, they did it for free with NO hastle. I gotta tell you guys if you are in for a used car in the North Alpharetta area this guy will do you right as far as being good to his word. The leak got so bad that they came and got it on a flat bed because it wouldn't make it the 5 miles or so to the lot. They had it back to me the next day.
Thanks for all the advice and info.
Peace

Wow! Nice.

Get those other hoses out, I'm telling ya, you're gonna have more "peeing" come winter!!

Mine dribbled the ugly green goo many times last winter, I just about slapped a for sale sign on it - cold weather exposed all the bad hoses and it took a while to find them.