I keep an eye on the coolant levels. I checked it a week or so ago in the '96, and it was fine. It was driven about 75 miles. Sunday afternoon I noticed the expansion tank was down at the bottom.

So i topped it and had the pressure checked out. Fine. Now I have driven it 50 miles in the last 2 days, and it'* still fine. I know you can get air trapped, but the last time the coolant was messed with was a flush 3 months ago. Oil is clear, but i switched to synthetic a few weeks ago and don't know if coolant burn would show up.

It'* wierd and the car goes off warranty in a few weeks, so i want to put it on them if it'* starting to go.

Tell them you had coolant disappear. You could get a new UIM and/or LIM gaskets out of it.

When a car is on warranty, things work a little differently. If you take it to a knowledgeable garage under non-warranty, they might go on the UIM. LIM, plenum route. When a car is under warranty you have to go in with a "smoking gun" problem. If it'* leaking it'* not doing it enough to be positive. Actually, LIM and UIM were replaced before i bought the car 6 months ago. And the pressure test is usually a good tell.

But I'm not ruling it out, by any means. We're on the "drive it for a wek and see what happens" program right now.

It just bugs me.

If you have the dealership check out the problem before the warranty runs out, they will warranty it later if they don't find anything to begin with.

I'm wasn't saying the dealership would shotgun the problem. I understand that.

Good point. The dealership is a Saturn. It'* pretty big. They are reailly into "the enthusiastic customer" mission plan. They just aren't very good at the technical side of service, particularly because it'* a Bonneville. They even sent it out to a Pontiac dealer when they couldn't figure out another wierd problem.

I hope I didn't sound condescending about the "warranty" thing. It'* a new perspective for me. Before the kids hit college, I usually bought new or very mint off-lease recent model cars. Seldom were there issues, and when there was, the dealers fell all over themselves squaring it out.

But ya know something..... this is more fun. In fact I can't wait to get the car off-warranty so I can start some serious mods. And none of this would have been possible without the incredible library of knowlege here, and the generously helpful people who back it up.

I'm just curious of what kind of warranty it is? A factory extended (GMPP), an after market warranty (Western Diversified, Total Car Plus, The Auto Club, Warranty Direct, the list goes on forever), I'm just wondering because of the age of the car is all. Usually dealerships jump all over the aftermarket warranty companies to cover anything they can find wrong with the car because they know it is pretty much a guaranteed repair sale. They try real hard to find a problem even if it is an intermittent problem…which they SHOULD do regardless, but sadly, not all do.

Maybe try a different dealership before the warranty is up...a Pontiac dealership.

I would suggest using a leak detection dye in the cooling system and then drive it for a week (still gives you one week of warranty) and then bring it in to a dealer and have them check it with a black light to highlight dye stains. That may help pin point the leak. If you use dye, be very careful not to spill ANY when adding it to the radiator. It must be added to the radiator. You may have to remove some coolant to make room for the dye but it is a very small bottle, usually 1/2 ounce or less.

If you use dye, save the empty bottle so the repair shop can mix it with coolant to get an exact color sample of the activated dye. That way they know what color they are looking for. Not all coolant dyes are the same color.

And BTW, a coolant burp that empties the entire reservoir would have to be one heck of a burp!

Yeah, I know. But then again, the resevoir in the '96 is oddly shaped. To top it off was only about a 1/4 of a gal., if that.

Believe it or else, the warranty is a Saturn bumper to bumper certified. If a **** on the radio breaks, they replace it. Everything.

Interesting about that dye. I'm probably gonna do the Pontiac dealer thing if necessary.

The wife just got home (40 mi roundtrip) and the level is fine.

This is gonna continue to bug me.

You could crack open the bleeder on the stat housing while the system is under pressure to see if air comes out. That will tell you if you are air bound. Is the cap in good condition and the coolant moving from the hot and cold marks in the overflow bottle?

Alright, the monsoon here just ended.

The cap is good, i replaced it when I had the flush. I didn't check the bleeder, i'll do that tomorrow. Tues and Wed it was exact levels on hot and cold.

BUT... tonight the cold level is down a 1/4 in or so. Definitely the wife didn't drive enough today for it to be evap. And I'm getting hard pressed to continue on the trapped air delusion.

The pressure test must have been wrong. there is something going on here. I don't know what else to check. The oil'* clean. It has been continuously damp, so the check for white smoke is not dependable. And the exhaust is not real sweet like the ethyline glycol was when the UIM went in my '95. Is the smell test not valid with Dexcool?

I am stumped. Any further thoughts appreciated.

Some coolant leaks can be very hard to find. Sometimes a leak will only show itself under the right pressure and temperature combination and that combination is not always hot temp and max pressure. It can be slight pressure and cold temp, slight pressure and hot temp, mid pressure and mid temp.........

A pressure test, even though done properly, will not always make the leak appear because of this temp/pressure phenomenon. This is why I suggested dye and drive the car for a weak. If that still shows no signs of a leak (no dye found with black light) then I would move on to performing a block test procedure and running the test for at least one hour.