Before I aquired my coolant exchange machine, I would flush cooling systems with one of those Prestone flushing kits. This would leave pure water in the cooling system. I would then drain as much of water out of the cooling system as possible. I would then look up the cooling system capacity. I would then add pure antifreeze that equaled 50% of the cooling system capacity and finish filling the system with water.
Never a problem using this method.
Tester
'Nuf said on the assertion that antifreeze and water do not mix in an engine, but let me predict the response Tom and Ray would give: “Bo-o-o-gus!.”
Pre mixing coolant for later top offs is a good idea for filling because the sticker on the radiator is missing or you’re too lazy to look up telling you how much capacity the system has. Unlike cars, some other water cooled equipment I have are not closed systems and require occasional topping off. Pre mixing then is a good idea. I keep a gallon or two that I have premixed around for that reason. I also use it that way topping off when idling to get the air out after filling. Other then that, I fail to see any reason to pre mix. I have done it both ways in cars with no thought to it not mixing adequately and my only concern has been having the right amount of antifreeze to make a 50% concentration. So, pre mixing is more convenient, sometimes, but that’s it.
Seems easy to decide, one way or the other. It's science after all. Anybody actually done the experiment? Drain everything out, then put in pure coolant and pure water into a cold engine, and every 30 minutes of drives, take a sample, measure the specific gravity?
Yes…Every time I change my fluid. I rarely buy the 50/50 solution. I buy the 100% and add water. Most of the time I’m pretty close to the -40 (50/50)…but sometimes I have to add water or fluid.
They don/t have petcocks or even drain bolts on blocks anymore so you can't get everything out
What vehicles are you buying that don’t have petcocks?? I’ve only owned ONE vehicle on the past 40 years that didn’t have a petcock…and that was a Chevy Vega.
Because you don’t know exactly how much it will take to fill the radiator, I usually have it mixed in a jug before hand, however, it will mix just fine in the radiator.
BTW do you suppose that when you fill your gas tank that the new gas will not mix with the old gas?
What if you did an experiment, filled a 6 foot tall 3 inch diameter vertically oriented pipe, closed at the bottom, half full of 100% coolant, then the top half w/pure water. At first the coolant would be on the bottom and the water on top. Leave it for an hour. Then measure the top to determine the mixture with a specific gravity meter. What do you think? Is an hour enough time for it to mix without any agitation at all, in a 3 inch pipe? If you measured it, would it measure 50% coolant from a sample at the top? If so, it would be hard to claim that it wouldn’t mix in an engine even more quickly. Maybe that is the experimental way to prove/disprove this theory.
Someone is thinking too hard. Just pouring water into half a jug of 100% coolant is enough to mix it practically homogeneously. A moment of shaking, and it’s uniformily mixed. Does the same inside a car engine.
GM stopped putting petcocks on their radiators a few years ago
What’s even worse is that their replacement radiators for older vehicles often don’t have one
I recently replaced a 1998 GMC Jimmy radiator, because the tank was leaking
The old radiator had a petcock
The new FACTORY radiator did NOT have a petcock
I think the aftermarket $99 special replacement radiator I put on my Corolla didn’t have a petcock either. But at $99, since it keeps the engine cool enough, no complaints.
I think he said petcock on the block, which is true, they just use a drain bolt now. That is all I have seen on a block for many years now.
The radiators have drain valves, whether you would call it a petcock or not is up to you, but it is a valve of some sort.
A lot of newer vehicles don’t have a feature that allows the radiator to be drained. Unless you remove the lower radiator hose.
Tester
What is infuriating about newer GM radiators is that the little drain hose and the hole where the petcock would be are there.
The plastic just hasn’t been punched out at the factory. But even if you did punch it out yourself, I don’t think you could just put in a petcock . . .