Cool Running

| May 06, 2004

The coolant drain cock on this engine is on the lower radiator hose just above the front spring. One of the valves for the coolant filter is just above it on the same line.

After engine oil, coolant is the most critical fluid for long engine life. Monitoring it, and changing it periodically, will prevent a host of troubles.

Your truck diesel works harder than a lot of other types of engines. And it has replaceable cylinder liners, which are vulnerable to cooling system-related troubles. Liners vibrate inside the block because of the high pressure and rough combustion of a diesel engine, and the coolant vibrates violently against the liner outside wall. Unless corrosion protection is nearly perfect, the result is often pitting of liners from the outside and eventual destruction. This means your coolant needs to be properly maintained.

Cooling systems use antifreeze, which is normally a 50/50 mixture of ethylene-glycol and water. This mix freezes at -34 degrees F and boils at a higher temperature than plain water. Because tiny amounts of exhaust gases and oxygen get into the cooling system through liner and water pump seals, antifreeze is subject to rust or corrosion and deposits. Traditional coolants use Supplemental Coolant Additives to protect the system.

These SCAs coat the metal surfaces to protect them from the corrosive action of the coolant. Periodic replacement of these additives when using traditional coolants is one part of coolant maintenance. This is easily done by periodically replacing a coolant filter that contains SCAs at oil changes. An easier solution is much less frequent (120,000-150,000 mile) replacement of “need-release” type filters that add the SCAs only as they decompose inside the system. Need-release filters allow the antifreeze to stay in past 600,000 miles.

Most antifreeze suppliers have Extended Life Coolants that are easier to maintain than any of the traditional systems using SCAs. They require only that you add a small bottle of extender halfway through their life. This is because they use carboxylic acid or “carboxylates” to coat the metal surfaces, and these typically stick around for at least 600,000 miles. Rich Armstrong, one of the developers of Chevron Delo Extended Life Coolant, explains that the carboxylates are “very robust molecules that are heat- and chemically-resistant,” hence the long life.

All coolants eventually need to be replaced. Those using SCAs will sooner or later develop trouble from solids that accumulate from long-term addition of those additives. They may also become acidic. ELCs eventually need to be replaced to add a fresh charge of carboxylates, as the original charge may have started to break down, though Armstrong insists the mileage limit isn’t known yet. Replacing your coolant at recommended intervals will ensure that undesirable solids, and possibly deposits, have been removed and that protection has been restored.

How to change to extended life coolants
I visited a TravelCenters of America service department in Baltimore, Md., to watch technician Bill Dickens do a coolant conversion on Troy Mott’s Detroit Diesel powered Freightliner Century Class. Dickens and ChevronTexaco’s Armstrong outlined how to perform the change correctly as they converted Mott’s Series 60, which has about 477,000 miles on it, from a traditional coolant using SCAs to an ELC using the following steps:

  1. Shut off the engine and allow it to cool to below operating temperature. While the engine cools, take time to chock the wheels. Make sure the parking brake is properly set and the transmission is in neutral, as you will later be running the engine at fast idle. Letting the engine cool will allow safe removal of the radiator pressure cap or overflow bottle filler cap. This vehicle has a coolant drain on a right-side, lower radiator hose. Dickens turned the steering wheel well to the right just before engine shutdown for easier access.

    Note: Many trucks now use an overflow tank rather than a tank on the top of the radiator. The overflow tank is typically mounted on the cowl and is used to allow the hoodline to be lower at the front, for better aerodynamics. The tank is connected to the block or water pump via a large hose, and a small hose connects it to the top of the radiator so air or vapor bubbles will vent into the overflow tank. The tank has a standard pressure cap much like those used on radiators at the top. A plastic fill cap with rubber gasket inside will be installed on the end of the tank where the driver can easily reach it from the ground. With overflow tanks, the fill cap is the one that should be used to drain and flush the system.

  2. Once coolant temperature has dropped to about 160 degrees, remove the radiator pressure cap or coolant overflow tank filler cap. Next, carefully position a large container underneath the coolant drain cock and unscrew it. On the Series 60 in a Century Class, this is located on a metal pipe that forms most of the lower radiator hose. It runs from the bottom of the radiator to the water pump, with rubber hose connections at either end and is accessible from under the right side fender. Just turn the cock counter-clockwise to open, like removing any bolt.
  3. If the engine has a drain plug in the block, remove it. These are normally located near the water pump. Doing this removes much more of the old coolant and makes flushing the system much easier and faster. This particular engine did not have an in-block drain plug.
  4. While the system is draining, turn off the two valves isolating the coolant filter from the rest of the system. On this vehicle, one valve was near the system drain in the lower radiator hose, while the other was located inside the frame rail. The coolant filter will be appropriately labeled and will always be connected into the system via two small hoses with a shutoff valve on each.

    Note: Keep drained coolant separate from drained engine oil. Each can be recycled, but once mixed, they become a disposal problem.

  5. Once coolant has stopped draining, reinstall the drain plug into the block and close off the drain cock in the radiator or hose.
  6. Refill the system with clean water. This is just a rinse, so tap water is fine. Once the radiator or overflow tank has been filled to within an inch or two of the top (not until the system is full), start the engine and then set the hand throttle or electronic throttle control to run the engine at 1,300-1,500 rpm to accelerate the heating of the water.
  7. The engine needs to run past the point where the thermostat opens. When this occurs, you’ll typically see a drop in the water level in the radiator or overflow tank. Keep the water supply handy and make sure to refill the cooling system to the top as the water level drops. Now turn the cab heater on all the way and open the two heater shutoff valves if they are closed. Once the system water level has stabilized, continue idling for 15 minutes to circulate the water. Then return the engine to idle and shut it down.
  8. After the engine has cooled again, remove the radiator or filler cap. Then drain the water by unscrewing the drain cock and removing the drain plug if the engine has one. Dispose of this water properly. If the water is more than very slightly discolored (obviously red or green), you will need to repeat the flushing operation (steps 6-8). The rinse water should be almost clear to ensure that most of the old antifreeze has been removed from the system. Removing the old coolant will help eliminate old SCAs from the system, and this is important because they can interfere with the protection of the carboxylates if there are enough of them. They may also reduce heat transfer and system performance. Having the coolant clean will also ensure a bright, clear-looking red color, instead of a muddy brown look if the red ELC and green standard heavy-duty antifreezes mix.
  9. Now close the drain cock. If there is a drain plug, coat the threads with a sealer designed for cooling systems and install the plug, tightening it till just snug.
  10. Remove the coolant filter with a strap wrench of the right size.

    Note: Don’t replace with the same type of filter if you’ve been using SCAs. Replace the coolant filter, instead, with a “zero charge” or “blank” coolant filter. This, of course, means having no SCAs. You can simply bypass the filter-mounting if the right zero-charge filter is not available.

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