What is normal coolant loss?

Our 2001 Olds Silo seems to have coolant disappearing. I marked the overflow tank and 6 months later it has dropped from high line to the low line. Is this level of loss considered normal with Dexcool on these vans?

There is no evidence of cooant leaks on the ground and the oil looks fine.
There is a slight oil leak on the lower intake gasket that can be seen on the front. The back lower intake is impossible to view on this van.

I am a bit paranoid about it as we had the lower intake gaskets replaced after just one year. Has anyone sent oil to Blackstone labs for verification?

I have been using orange Prestone coolant for 8 years on my Mazda Protege and the level has never dropped this much in such a short period of time.

Thanks.

I have sent oil to Blackstone Labs (http://www.blackstone-labs.com/). I have in Fort Wayne (where they are located) and pass their shop frequently. I highly recommend them. They usually have the results within a few hours of dropping it off. Obviously if you mail it in it takes longer to get there but they will e-mail you the PDF results.

The cooling system is a closed system, so technically any coolant loss is a sign of problems. But in reality, small leaks, evaporation, etc happen. That much coolant though may be a sign of something more though. It also may just mean that you had a decent sized air bubble that just worked its way out and the coolant replaced it.

Remember that as your engine heats and cools, gaps around gaskets can form allowing coolant to escape. If the coolant escapes while the engine is hot, most of the coolant will evaporate on contact. You wouldn't ever see a puddle on the ground. When my intake gasket (and later head gasket) leaked, I would rarely see a puddle...only when I would take a short trip building system pressure but not heating the block to a high enough temperature to boil off the leaking coolant.

The easy check to see if you have coolant in your oil is to look on the underneith side of your oil cap. If you see any goopy substance, often described as runny mayo, you have a leak. You may also show signs of it just inside the filler hole on the valve cover. The lack of the "mayo" doesn't disprove the presence of antifreeze though. Sending a sample into Blackstone is your best bet...a $20 test is much better then $2000 engine.

The test also will tell you a general overall health of your system. High levels of particular metals may indicate particular areas that need looked at and addressed. When I did my last test to confirm my leaky intake gasket, they said my lead levels were high, most likely from the antifreeze prematurely wearing the bearings.

I don't know what is normal and what's not. I know that my Silhouette leaks where the coolant recovery rubber hose enters the recovery tank. I can see dried pink coolant on the rivet that holds the coolant tank in place. I believe that the placement of this recovery hose (near the front of the tank) will leak from around the grommet everytime I apply the brakes allowing the coolant in the tank to be thrown forward in the tank and a small amount will leak out.

I haven't noticed any leaks elsewhere, but, as you stated it it very hard to look at the backside of the engine.

I had read somewhere that if you don't keep the radiator filled with coolant and air gets in it will cause the coolant to cake inside the engine and the engine will overheat causing gasket failure. If your coolant recovery tank goes dry you will be sucking air into the cooling system.

Air entering the system is thought to be a contributing factor in the Dex-cool turning into the brown sludge that many of our vehicles have in the recovery tank.