First, understand the difference between coolant change and coolant flush. If a customer regularly changes their coolant every 3 years or 40,000 miles, no coolant flush is ever needed. If a customer thinks the dealer is right when they told you that you “never” have to change the “Lifetime Coolant”, then you will certainly need a flush. If the cooling system seeps or leaks, and all that is done is to add water, then eventually the protection levels go down. Then the engine can rust, which makes the coolant brown and contaminated with rust. That engine will be prone to boil over in hot weather, and the water can freeze solid during a ski trip to Lake Tahoe, and crack the block. Then it is too late to do a coolant flush. Often a rusty cooling system will need multiple coolant flushes to get as much rust out as possible.
Early water pump failure can also be caused by flushing with any compound that contains muriatic acid, as it can damage the pump shaft, disintegrate the water pump seal, and can also destroy the glue seams of a radiator or heater core. Muriatic acid also turns bare aluminum black, leaving direct evidence that it was used. At our shop, this voids any warranty. Failing to flush out debris from the cooling system can also lead to premature water pump failure. Coolant can become electrically conductive when it is old and has debris, and it can turn acidic. A bad electric ground can and will corrode your cooling system. Ask any sailboat owner about electrolysis. Electrical systems should be kept clean and any corrosion eliminated. A simple test with a voltmeter will reveal any problem. Put one probe in the coolant and the other probe on the negative battery post. Run the engine and turn all the accessories on. Preferable is that no voltage is present. Readings over .25 volts indicate an issue. Coolant also turns acidic over time. The gycol breaks down into glycolic and formic acids. Coolant with a pH value under .70 are too acidic, and need to be changed. Coolant should be changed at least every 40,000 miles to prevent debris and corrosion.
If your engine’s oil cooler rots out and fails, then the coolant looks like a chocolate milkshake. If the transmission cooler goes, then a vanilla or strawberry milkshake, depending on the model. Such oil or fluid contamination requires flushing with a very different compound to get the oil out. If some oil is left inside the cooling system, the coolant hoses will rot out from the inside, which could bring a surprise to your vacation. Doing a coolant flush on an oil contaminated system is a real project. First as much oil as possible gets drained from the system. Multiple cleanser flushes need to be done until the cleaning solution gets white as the milkshake is gone, usually 3 flushes, sometimes up to 7 or 9. Then multiple fresh water flushes need to be done until all the white foam is gone, usually 3 times is enough. Then the system is finally drained and a coolant water mix is loaded in. Sound like it takes all day? Sometimes longer.
What NOT To Put In Your Cooling System
Understand that the coolant in your system is likely different from anything you can buy at a parts store. Sometimes only slightly different, Sometimes that’s all it takes. Slightly incompatible mixes may cause no harm. Incompatible differences can cause light deposits, sometimes like eggshells. Not good. Very incompatible coolant differences can cause heavy deposits, sometimes like concrete. Really not good. Using water from Sacramento or well water from a farm can cause really bad deposits. The water is full of heavy minerals. Check the toilet. The worst deposits are from Radiator-Repair-In-A-Can additives. Those cans worked fine for cars from the 1950’s when you could drop a quarter all the way through your radiator. Modern radiators and heater cores are made so finely, that they will clog up easily. By the way, those cans WON’T cure a leaking water pump or a breaking coolant hose. Only a mechanic can cure that, not a can.
Any mechanic that tells you that some Stop Leak would cure a blown head gasket, cracked head or cracked block that is pushing combustion gases into the cooling system simply does not understand engines. Cooling systems develop 14 to 17 psi of pressure, limited by the valve in the coolant cap. Gas engine combustion creates pressures in excess of 800 to 1000 psi, diesel engine combustion is about twice that. How is that Stop Leak ever going to cure up that problem permanently?
Somehow, at Karmakanix, we find some percentage of cars near or over 10 years old with the heater cores clogged solid. Solid! No heat at all. But the radiators seem to be doing OK, although only a Central Valley summer freeway spree would prove it for sure. We believe that this heater core clog issue is due to a thermal expansion problem. When a cast iron block gets coated with a ceramic like substance while is it hot, there may be some chemical and molecular tension right at the bonding surface when the engine cools off. As the cast iron heats up from cold, it expands way more rapidly than the concrete like deposits. The deposits tend to spit off especially given a bump or two. During warm up, the thermostat is closed, and the radiator is not in the cooling circuit, i.e.; nothing flowing through it. But the heater core is always flowing, there is no valve on a modern car to shut it off, that system ended in the 80’s. So the flow of deposits in the coolant has nowhere else to go except through the heater core. Ever see a car apart for a heater core? Everything in front of the seats gets removed. Most jobs are from 6 to 12 hours long.
A coolant change, not a flush, takes between 1/2 hour to one hour, depending on the model and motor. The easiest way to fill a modern cooling system is with a device called an Air Lift. The tool evacuates all the air out of the cooling system until it pulls almost a full vacuum. Then the system is timed out for 15-20 minutes to check for leaks. The vacuum then pulls the coolant in, filling every void that could form an air pocket. Serious overheat can occur within minutes if an air pocket is left inside the engine block. Anybody ever done that to your car? Are you sure? Now do you feel like changing your car’s Lifetime Coolant? Ask your Karmakanix Service Advisor if a coolant change has ever been done, if you are not sure. Get some good advice.