Missing Coolant-pics of potential for your thoughts...

Before I take her in, wanted to get thoughts on the following: Pic 1: Note the crusty residue on the 2 screws in the back Pic 2: Pressure relief cap-note the attachment with the metal ring is raised into the air. I was able to push down on it, and much like the button on my wife's pressure cooker, it pops right back up until the car has cooled down. I guess what I'm wondering there is, could it be that it's raising to relieve pressure, by venting off some of my water/coolant as steam? Would that account for the drop in level? Thanks

The position of the bleeding valve is not unusually. That is how the car bleeds air from the coolant system. Any coolant on the ground or around the edge of the cap? If not, then you better have a look to see if it is in your oil. Early caps (part number ending in 00) leak, tanks are known to crack after a while and leak. You could also have a bad hose or hose clamp - really can't tell from the pictures - sorry.

How long would it take to appear in the oil? In other words, how much coolant would it take to make the oil 'milky'? The reason I ask is because I just changed the oil with only about 600 miles on it (realized mechanic used wrong viscosity). During that change, there was no noticeable 'milkyness'...but I'm just wondering if such limited miles would be enough time for the oil to get to the milky state. Any thoughts there?

After the engine cools.....stick your hand in there and start feeling around the side and under the coolant tank (its much bigger than you think). If you feel "crusting" "wetness" or "greasiness", etc. it is a good chance the tank is cracked and needs replaced. Also as Loren says the coolant lose could be from a hose, clamp, etc. If you are concerned about the oil take a sample and send it to a lab like Blackstone for analysis.

If there was a crack, I understand it could evaporate before it appeared on the ground, or visibly in on the engine. But wouldn't I ever 'smell' the dried/evaporating coolant at all? Those with cracked tanks/hoses, did you ever smell the coolant?

first step, replace your coolain cup, if it's part# ending with 00. for less than $20, the new cup is much better. search for coolain cup. you will find a few interesting things.

Any external leak near heat will give a distinct coolant smell. Any substantial internal leak would be seen in the form of steam out the tailpipes or an increase in the measured level of fluid in the crankcase. If you have a vacuum in the tank several hours after shut down, then it is unlikely the tank that is cracked.

I had a cracked tank. Just replaced it a couple of weeks ago. Yes I occasionally but not consistently got a slight "sweet smell" from the drivers side rear wheel well area of the car. Never in the car, never really from the engine compartment. The smell was just ever so slightly noticable in the normal "hot" smell as I call it. You really had to pay attention to notice it. If the tank crack(s) is very slight it may be difficult to detect at first.

Well, I've never seen steam...would it occur at startup, or some other time? As for the crankcase fluid level-are you saying I should watch for an extra bar to light up on the oil level indicator? Or is there an easier way to tell?

How much coolant have you had to add?

The full story is as follows: Purchased car two months ago. Noticed coolant was low after it was delivered. (barely any at all in expansion tank) Removed cap to verify, then closed cap. (No leaks to this point). Drove to work the next day, and discovered large puddle under the car. Turned out I stripped/cracked the cap (original) when I replaced it the night before. Coolant spewed all over engine. Replaced the cap, no more puddling. Wiped down engine best I could, but still some residue from the overflow. (which is making it difficult at this point to spot the source of the leak). Added distilled water (1/3 gallon at most) myself to between the max and midline. Attempted to 'burp' system via methods on here...though never saw a 'burp', and not even sure I had enough air to 'burp'. Drove a week or two (perhaps 5 shorter drives, 15 minutes each)...and then noticed it slightly lower (near the min line or just below) after a longer drive. Added 8 oz to get level back between max and min. Now it seems to be right around min again. So to answer your question, I haven't added all THAT much coolant...and I did lose quite a bit when I cracked the cap. Though I haven't overheated, I really haven't taken many longer drives yet...and am afraid to until I can be assured I won't overheat. I realize I'll probably need to take it in for analysis...but system seems to pressurize (as evidenced by my pic above after a 15 minute drive), and I don't smell any coolant.

I would simply watch the level. You may have had a lot of air in the system and the reduction in tank level was due to this air. Just drive it and enjoy.

Okay, hope you're right. My only concern is why the coolant level was low when I got the car. Guess time will tell. Thanks for your help.

Make sure the heater has been turned on and hot air comes from the heater. If the heater is not run there could be air trapped in the heater core and bleading into the system a bit at a time. Just a thought.

That's a good idea Ray, I hadn't tried that yet. Pretty warm these days...I'll have to wait for a cooler day to test that.

Since I just installed a 3rd radiator, I know a lot about this device. It is a MANUAL bleed valve. It should not be popped up under normal circumstances. If it is, the diaphram is most likely going bad. This will result in a leak and low coolent pressure (very dangerous for the engine). Watch your temperature gauge carefully. Due to the design of the cooling system in our cars with a long distance between the engine and radiators, this valve was placed at the highest point in the cooling system to get a way of bleeding off air in the system. You fold the clip up to open the valve, start the car, let it run up to normal operating temperature, turn it off, let it cool and close the valve. This is the standard bleeding procedure. It should not stick up on its own. In fact, it should have a good amount of pressure to lift the locking clip. Once open, it will bleed out a minor amount of fluid. It is not recommended to drive the car with the valve open.

Well, I've topped off the coolant a couple times when it dropped slightly below the min...is it possible I added too much, and that is causing excessive pressure? On a cold engine, the coolant level is just above the min line...where I understand it should be. Is anyone's 'resting' coolant level normally below the min? Obviously, when the car runs...the coolant level raises...sometimes above the max line. Again, I understand this to be normal. Thoughts?

I'd stop adding coolant unless you get a flashing light and keep eyes and nose open for leaks or coolant smells. You're probably overfilling it and when it gets hot its popping the valve.

Its also not uncommon to have a cracked coolant expansion tank ! My 1999 C2 has the same stuff you described, and that ended up being a cracked coolant tank (better than cracked in the engine!). Anyway, if you keep losing coolant after more than ~5 top offs + hard driving + cooling cycles then chances are you've got a crack or a leak. I'd get the newer cap today itself and use that for those remaining 3-4 top off cycles. That way you can rule out the cap being an issue. If you still get level drops, I'm thinking it mostly a coolant tank crack. These cracks are very fine and almost tight when cold, when with heat and pressure they leak some coolant. When replacing the coolant tank you should go for the newer design which is more crack resistant. If I were you and found that I have the older tank, I'd pull out the coolant tank (huge effort!). Its $150 for a new tank from sunset, but you will have either - fixed the problem there and then - or have prevented the problem (the old tank will eventally get you ). I don't see that as a wasted effort. Of course if you're going to send her in to the dealer, then you could leave the testing to the professionals !

I doubt he is overfilling it. He sees it at/below the MIN level.

Justin, Just drive it and check once in awhile. It can take a few drive cycles to eliminate all the air in the system. I think you wil find that the level stabilizes. DO NOT take it to the dealer as they will automatically assume you need a new tank, whether you do or not. They just love spending your money. Level at or slightly below cold MIN is fine. Your warning light will alert you is you need more.