What is involved in a coolant compression test for coolant leak? What exactly is it? Does it involve blowing compressed air into your radiator and see where the coolant comes rushing out? After overnight parking I recently repeatedly see a small puddle of anti-freeze under where the radiator drain plug would be and wonder if its a real leak or just the hose or even leaky drainpip. I left my car at a mechanic for a compression test, and he did confirmed it has a leak on that side. Anyway, I am just curious if this test is in fact blowing air into the system. I suspect it is because now the car stalls unexpectedly at stop signs and it idles funny. The last time this happened was when I changed the heater core or do something that introduces air bubbles into the cooling system. What someone told me is that when you have air bubbles in there it comes times cause coolant flow to stop flowing in some part of the engine causing minor overheat and causing the engine to cut out. Sounds sensible enough.
So now I am trying to drive the car furiously on the highway to bleed out the air bubbles. This car has the coolant reservoir connected to the radiator cap hose and this valved radiator cap allows air bubbles to flow out after driving for a while.