Tools & Tips

Keepin’ Cool

Not much attention or training is given to coolant in buses. It seems to be either a summer drain, flush, & fill routine or ignore it until something happens. We can’t do either any more. Coolant & diesel engines are a whole lot different now. We deal with two primary coolant failures these days, hot spots & cavitation.

Unless you like the annual drain flush & fill routine, you may want to get away from the old green colored coolant. This anti-freeze contains silicates that like to deposit in narrow places & block coolant flow. This green-goo is what you are flushing out of your system every year. Modern Pre-Charged Extended Life & Organic Acid Ling life coolants do not have silicates. Most of what Thomas Bus has delivered over the past 7 years has been the SCA Extended Life pre-charged coolant.

Cavitation is a big cause of failed gaskets, injection cups & liners. Failures of major castings like the head & block are often because of cavitation. These are the tiny pressurized air bubbles flowing in your coolant. When these bubbles hit a solid surface, they explode, taking a chunk out of it. After a while, you end up with a leak where you would never expect it.

Both Extended Life & Long Life coolants have additives to prevent cavitation. Extended life has SCAs while Long Life has DCAs built into their products. It is considered routine maintenance to maintain the right levels of additives in your coolant system. Routine testing is required & additives poured in as needed. When you are doing an oil change, dip in a test strip for the coolant you are using.

Testing is very important on new engines. The new metals are absorbing the additives at a faster rate. You may want to check new buses every 45-60 days until the level gets stable. While you are at it, take out the turkey baster & check the freeze/boil levels.

Hot spots are caused by mineral scaling. These minerals usually come in when shops mix their own water with the coolant. The minerals cook out of the coolant & grab onto casting surfaces. These deposits grab heat and cause gaskets to fail. Most coolants recommend water that has only 170 parts per million (ppm) of mineral in the water getting mixed with the coolant. Very few city systems get down to 170ppm. If you are pulling water from a well in Michigan, it’s probably even worse. Your best bet is to buy the coolant pre-mixed from your coolant vendor.

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