Truck Topics

The Tool Box - Cooling Systems

Recently we had a fuel leak into the cooling system.  After the repairs were done, the cooling system was flushed with cleaner to remove the fuel but to our dismay it was too late for our heater core.  As it turns out, Freightliner uses a vendor for its heater cores, and the seal they use on the core is not petroleum resistant.  The heater core failed about 10 days after the cooling system was cleaned out. This got me to thinking about cooling system maintenance.  Also, a heads up if you get oil or fuel into your cooling system keep an eye out for coolant leaks possibly inside the cab, or on the firewall under the air cleaner housing on the passenger side of the truck. You may want to have the thermostats changed as ours failed at the same time as the heater core.

Back to the cooling system:  While doing research for this article I found that there are many types of antifreeze on the market.  Some facts about cooling systems from the EET Corp web site (they make and recycle antifreeze):

Anti Freeze / engine coolant is the most neglected fluid in the vehicle. Cooling system neglect is cited as the principal reason for premature engine & transmission failure. Cooling system failure is the most common roadside breakdown. Just 1/16th of an inch of mineral deposits on 1” of cast iron reduces heat dissipation by 40%.
The most common antifreezes in use today are ethylene glycol and propylene glycol.  Both are similar in chemical composition with ethylene glycol being cheaper to produce and having a slightly higher boiling point then propylene glycol. Ethylene glycol is also the most widely used.  Propylene glycol is less toxic than its counterpart.

Ethylene glycol and propylene glycol can be mixed but most manufactures don’t recommend more than a 10% mix.  Ethylene glycol has better heat transfer properties.  If you are not sure which you have and need to add a great deal of coolant, it might be in your best interests to drain and flush the cooling system.  That way you can fill with the proper mix and you will know which coolant you have.

Speaking of proper mix – NEVER use 100% antifreeze, unless the fluid is designed for use this way; we will talk about that later.  It’s best to purchase a 50/50, glycol/water mix. The antifreeze manufactures use deionized or distilled water in the mix.  I know, you hate to pay that much for water but… too much Antifreeze or water can be harmful to the vehicle.  Antifreeze concentrations higher than the recommended levels can cause corrosion, water pump failure, increased engine wear and lessens its ability to cool or protect from freezing.  A 60/40 glycol/water can be used in northern US and in Canada due to colder climates.  Too much water lowers the concentration of corrosion inhibiters and could freeze (bad thing).

What color is your antifreeze? Older vehicles until around 1996 used green.  This is still a very common coolant color; however newer vehicles have changed to different colors by manufacture choice - red, pink, yellow, orange, and maybe purple - these are typical extended life coolants (ELC). You should not mix the green coolant and the ELC’s. Additive packages in these vary greatly so keeping to the same brand and formulation is very important. The old green antifreeze in a heavy duty diesel engine should be serviced (checked for SCA’s) every 15,000 miles. SCA’s (supplemental coolant additives) inhibit corrosion within the engine and radiator. SCA’s deplete rapidly in HD diesel engines with this type of antifreeze and should be changed at around 150,000 miles or at least annually. If you are using the green antifreeze there are test strips available at parts stores and truck stops. These strips check SCA levels and allow you to add SCA’s as necessary, which can be purchased separately. Be sure the strips are for the type of antifreeze you use. Some engines have water “filter” that have timed release SCA’s, but still need checked regularly.

Most new trucks come with ELC (extended life coolant). This antifreeze has a different type of additive that doesn’t deplete as fast but will still protects the cooling system and engine. The typical life of ELC’s are about 600,000 miles or 4 years before service is needed. Test strips are available for ELC’s also, but they are not the same as the ones for the green antifreeze. For compatibility or if you decide choose a different coolant this chart will help Reference chart.  Do not use antifreeze that is not labeled for heavy duty engines in a truck engine. Automotive gas and diesel engines use different additive packages. Different types of testers are available from auto parts stores just ask.

There is a waterless coolant on the market called NPG+. This is a 100% concentrate at a propylene glycol/ethylene glycol coolant that uses no water.  Waterless allows the cooling systems to run at a higher temp without boil over. NPG+ doesn’t boil until 370 degrees Fahrenheit almost eliminating vaporizing in the water passages in the engine allowing for better heat transfer, for more info on this product Google “ Evan’s NPG+”. The engineers at Detroit Diesel don’t think this is a good idea. The jury is still out for me! 

Coolants can be confusing but the bottom line is, check your coolant regularly. These are the main points to look for:

Color- Know what coolant you have. Clarity- Coolants come in different colors but they should all be clear, if yours is cloudy or has floaties there could be a big problem- get it checked by a shop. Freeze point-this can be checked with a hydrometer, freeze point should be between -25 and -50. Chemical protection-get and use the proper test strips. Add the proper SCA’s as needed.
Until next time keep your cool and don’t freeze out there!