Until Danny L replies, I'll share my procedure at the dealership. Most cars got a general flush and fill. A lot of shops use a special flushing machine that forces water through the system in various directions to dislodge debris. At the first service, there's bound to be casting sand stuck in there that never got fully shaken out at the factory. Some of that sand may have collected in the heater core. One disadvantage to this method is the flushed-out water goes down the drain and could be an environmental issue.
My procedure was to drain the old coolant into a drain pan that gets emptied out into a tank for recycling. By the way, since the mid '90s, most radiator tanks are made of plastic, and have plastic petcocks. I strongly recommend to never use that. Pull the lower radiator hose off instead. We had a rash of radiators that had the plastic crack inside the tank where the rubber o-ring seals up to, then there would be a constant drip about once every five seconds. The only fix for that was to replace the radiator.
With the coolant drained, I remove one heater hose at the engine, not at the heater core. GM uses a lot of heater cores with plastic tubes. I worry about breaking one of those tubes by twisting and tugging on the hose. At this point I drive the car to the garden hose and use that to push water into the heater hose, then the heater core, then the radiator, then finally I overfill the reservoir, pull its hose off the radiator and let it hang so the water will siphon itself out. A pressure washer works well to clean the inside of the reservoir.
When you buy your new antifreeze, do not fall for that "pre-mixed" 50 percent water. That might be fine for a newly-rebuilt engine, but after any flushing procedure, there is going to a lot of clean water left in the engine block that never drains out. If you add that 50 / 50 mix, you'll always have less than 50 percent antifreeze. Instead, for a four-cylinder engine, I started by adding one full gallon of new antifreeze, then I alternated a half gallon of water, then a half gallon of antifreeze, until the system was full. Run the engine long enough for the thermostat to open so the coolant mixes thoroughly, then test the freeze point. You can adjust the freeze point by adding up to a half gallon of water or antifreeze to the reservoir.
Four-cylinder engines in particular often have a thermostat housing design where air remains trapped until it is manually bled out. If you don't do that, the engine will overheat. Thermostats have to be hit with hot liquid to open; hot air won't do it. Many engines have bleeder screws on the thermostat housing for this purpose. If there is none, look for a coolant temperature sensor that can be unscrewed momentarily. Older Chrysler engines also had a threaded plug that could be removed. You don't have to run the engine during this bleeding procedure. Just remove the plug, then fill the system until coolant runs out that hole.
If you do remove a temperature sensor, and you have to unplug it, do that with the ignition switch off. If the switch is on, the Engine Computer will detect the break in the circuit and set a diagnostic fault code that if not erased, could confuse a mechanic in the near future.
Checking the freeze point is a lot more complicated than would seem. Almost all of the testers you can buy calculate the freeze point by comparing the weight of the coolant to the weight of straight water. As you add more and more antifreeze, which is heavier than water, the number of floating balls will increase, or the pointer will go higher on the scale. The issue here is the indicator will falsely indicate a really high freeze point in straight antifreeze, in the order of minus 70 degrees. In reality, the old green antifreeze turns to slush by around minus ten degrees, and water freezes at 32 degrees. It's when the two are mixed that the freeze point becomes lower, but minus 50 degrees is about the lowest it can achieve. To say that a different way, once you pass roughly 60 - 70 percent antifreeze, the common testers will falsely indicate the freeze point is getting lower and lower, but the actual freeze point will turn around and start to go back up toward minus ten degrees. All antifreeze manufacturers recommend a 50 / 50 mix to get the best freeze protection.
Also be aware antifreeze holds relatively little heat so it does a poor job of moving heat from the engine to the radiator. Water is very effective at absorbing and moving heat, so you need a sufficient percentage of water in the system. Antifreeze is good, but more is not better.
If you want to truly know the exact freeze point, you need a tool called a "refractometer". There is a sight glass hat has to be perfectly clean. Dirt adversely affects its accuracy. You place one drop of coolant on the sight glass, close a cover over it, then you sight through the tool. What you see in the window will be light on top and darker on the bottom. At that transition is where you read the freeze point on the scale on the side. Even most professionals don't have or use that tool. As long as you're reasonably close to a 50 / 50 mixture, the inexpensive testers with pointers and floating balls will be within their range where they're pretty accurate.
Saturday, July 25th, 2020 AT 2:09 PM