head gasket cracked-coolant surge tank overflow

[erinar]

Here is a chain of events that I am wondering if you might have any possible insight into (On a 2004 Chevy Malibu Maxx with less than 80,000 mies on it):

-One month ago I had the thermostat replaced (and so was the coolant).

-With minimal driving over the course of a month, at the end of 4 weeks the following scenario happened:

-After a 15 mile drive, with about 10 of it on the highway, as I pulled into my driveway, steam suddenly came out of my hood and it smelled like burnt coolant. (There was no apparent overheating, and the coolant temperature warning light did not come on.)
-After the car cooled down, i opened up the hood to see the coolant surge tank cap askew, and the reservoir was nearly empty.It appeared as if all or most of the coolant had leaked out of the reservoir.
-I added a 50/50 mix, following the manual's instructions and filling it to the appropriate level. After about a minute with the engine on and the cap off (I believe to let any possible air out of the line?), the coolant started to bubble out of the reservoir tank. There was a low coolant light on at this point as well.
-I waited until the next morning to do a test drive around the block to see if it was safe to drive to my mechanic. At this point the service soon light came on, and the car began tending towards the red zone on the coolant temperature gage.

At this point I made the decision to have it towed to the garage where I had recently had the thermostat replaced. What I was told was that the head gasket was cracked, with no apparent cause (aside from the obvious fact that it had overheated).

What seems strange to me is that the car showed no traditional signs of overheating, and no warning lights came on. Are there any elements that you can think of that might have failed that would contribute to a scenario such as this one?

I appreciate any thoughts or insights that you might have, as I am truly puzzled as to what might have happened.

Thank you!

[MagicRat]

A leaking head gasket can sometimes exhibit the same symptoms of overheating, without the engine actualy overheating.

An overheated engine boils the coolant. The boiling pushes some coolant out the coolant tank.

Sometimes a head gasket fails in such a way that pressurized engine combustion gases leak into the cooling system. These gases displace the coolant,pushing it out through the coolant tank, in much the same way that the boiling does, but without actually overheating the engine

[SleepyHead98]

head gaskets on these engines are very common. I am not sure when GM replaced their nylon intake gaskets, as DEXCOOL (death cool, Dex kill, Death Kill) is known to eat them up. I have seen them also eat up head gaskets just enough for corrosion to start taking place, causing head gasket failure. Toyota runs dex cool BTW.

I did an 07 where death cool ate up the head gasket. I might get ridiculed for this comment, but don't use dex cool. Use the walmart 8 dollar a gal, 150000 mile coolant. It seems to be the safest. There are alternatives, but they are expensive. Thing is, aslong as the heads or block is not cracked, it can be fixed. I would do it yourself though, as you are looking at a 1500-2k job for a head gasket job at a shop (materials only cost about 200 for high end gaskets+100 for heads to be planed). Will take you about 3 days to get it done right the first time. Post back or PM me if you have decided to do it yourself and need advice.

With death cool, and all OAT (Organic acid technology) type coolants, they coolant cant get low, air cannot get into the system, and it must be changed out sooner than 150/5 years. If not, it will turn acidic, and start munching on all plastic parts, eventually alum parts.