2002 3400 Chevy

[BodybyFisher]

I am not that fast even with step by step directions which I have used both times. I plod, methodically, inspecting and cleaning as I go. But its my time, so I don't mind, I could not make a living at the rate I go.

I have done a 3100 and 3400, here is the other one I did

http://caddyinfo.ipbhost.com/index.php?sho...ontiac&st=0

I am an old timer, I am not comfortable with working on aluminum engines and these seals yet. I am learning now, not looking for speed. When I get done, every wire, harness, clip and ignition wire is located exactly where it goes and the engine compartment sparkles. I look at everything, replacing and cleaning as I go, this last job I used 5 cans of brake clean and vacuumed out junk before I pulled parts apart.

I am a firm believer in the saying, I used to be slow, but now I am half-fast.

[Cadillac Jim]

Contamination? You'll have to explain that one Jim. A bad radiator cap does not hold pressure. How does that contaminate the coolant and with what?

A cooling system that does not hold pressure cycles to its hot running pressure, if any, and leaks down back to ambient hot and inhales ambient air as it cools down every time it is driven. The underhood air that is brought into the system to replace condensing steam and the reduced volume of cooling air. A cooing system that breathes this way for a year is going to have a lot of its oxidation resistance used up.

An unsealed system will use coolant. Without the seal, steam and antifreeze vapor will escape. This changes the antifreeze percentage and the concentration of anticorrosion components. Enough coolant will be used for most users to refill with tap water.

[Ranger]

Every time you shut down, the coolant heats and expands as the pump is no longer turning and the coolant is not flowing through the radiator. It's called "after boil". As the coolant expands it vents the air in the surge tank overboard. As it cools, ambient air is drawn back in. So what you are saying is bad, is the normal process and happens every drive cycle.

[Texas Jim]

Every time you shut down, the coolant heats and expands as the pump is no longer turning and the coolant is not flowing through the radiator. It's called "after boil". As the coolant expands it vents the air in the surge tank overboard. As it cools, ambient air is drawn back in. So what you are saying is bad, is the normal process and happens every drive cycle.

I have to beg to disagree here.

If the surge tank is filled with the correct amount of coolant... air NEVER reaches the actual radiator. as the coolant expands and contracts from the heat... it only draws COOLANT back into the radiator. Never draws air. The only air is in the surge tank.

But maybe that is what you were saying. If so I apoligize.

[Ranger]

That is exactly what I am saying Tex. That coolant in the surge tank is then cycled back through the cooling system. The process is the same on an engine with an overflow reservoir, except that the tank is not pressurized and is always vented to atmosphere.