Originally Posted by My 2003 Impala
Has no leaks whatsoever, I have put some miles on it and coolant level has not gone down. Not overheating, the coolant just looks tired and dirty, I could just flush out radiator with clean water,, but my other question, is how do I get the old coolant drained out of the block, is there a block drain plug on the 3.4?
That's good that it has no leaks.
If you wanted to blast a garden hose into the system to clean it out - which I've considered but never done - you would need to remove the thermostat, which is a bit of a pain on the 3.4. What I had envisioned was to disconnect the two radiator hoses (from the radiator), and shoot the garden hose into the top radiator hose and let the bottom one drain on the ground. I'm not sure what all that implies - does the engine need to be running so the water pump is turning? - or whether it will be very effective.
For sure, you do not want to directly connect the garden hose to the system - ie, you do not want a sealed connection. Tap pressure is much greater than the system is designed for, on the order of 100 psi versus 20. It can do a lot of damage.
I tend to favor just draining, filling, and running the engine, then repeat. Doing that 2 or 3 times will get most of the old stuff out, enough to not worry about the little bit that's left.
The first or second cycle would include the cleaning/flushing additive. The additive instructions may call for several water-only flushings afterward, so that will determine how many cycles total.
Regarding draining, I would just pull the bottom hose to drain it. You can try the petcock on the radiator, but I've become cynical about those silly things - seems like they start leaking after they've been opened and reclosed once
That is, I end up chasing that for a while and have to put a new petcock in. Which makes removing the hose more appealing
[Edit]Thinking about this some more, it occurs to me that the upper radiator hose flows _from_ the engine _to_ the radiator, so blasting the garden hose into it (as described above) would be backwards with respect to normal flow. So if the water pump was turning, that might be an issue.