DEF in the Radiator?

Oct. 14, 2014

Recently there was a question about an engine failure and DEF accidently being put in the radiator based on a strong odor of DEF in the coolant. The engine failure was traced to corrosion of some injector cups resulting in a major engine failure stacking up the dollars while still under perceived warranty. Asked to research this issue, I was confident that the effort needed to put DEF in the DEF tank or even fuel tank was much less than what it would take to tip the hood and climb to the coolant tank. While not impossible, it seemed HIGHLY unlikely, but nothing ceases to amaze me. 

Since I didn’t have any direct experience with this problem, I contacted some fellow trusted TMC members and asked them about the problem as common sense told me that there must be some chemical reaction to the coolants, colors and additives that was creating this.  Maybe some brook water?

I inspected the coolant that came out of the truck in question, but 30 different trucks in different locations with different owners reported the same issue, and I could find no connection or common denominator. The coolant was clear-ish, looked like green tea, with an odor that was slightly less than the ammonia under your sink.  

I talked to a number of my TMC fleet peers and no one had experienced this. But talking to a TMC coolant expert, he explained clearly in 5 minutes what was going on, and said they had seen it before. That week I also visited a big fleet, and when I mention this issue, he said they’d seen the same thing 2 years ago. I ask, “What did you do?” He said nothing, and that the OEM told them it was ok to operate as is. I was a little shocked.

I then reached out to another TMC engine member. He’d also seen a few cases, and provided me with a technical bulletin that described the clues exonerating the driver from DEF-ing the coolant system.

Back to my original engine failure, coolant test samples and vehicle cooling system components were then reviewed with the repairing dealer.  It was determined that the coolant can turn clear due to the coolant dye composition and inhibitor interaction with bare aluminum, flux, or solder exposed due to a possible component failure.  Although a temporary increase in pH may be experienced, which can generate ammonia (the pungent odor), the performance and durability of the coolant, as I am told, are not affected as long as the coolant is properly maintained. I was told that the dye composition has been modified to prevent the coolant from turning clear, but that seems not the case today, unless the OEM’s recommended new colored coolant dye does not work.

I was surprised on a couple of things. First, this is not a new subject, as it goes back almost ten years. Second, I’ve never heard this mentioned in any conversations at TMC meetings either in the Shop or Fleet Talk sessions. Third, this issue turned up on some current trucks with under 100,000 miles and some as low as 25,000 miles.

One thing I am sure of though, when digging into the problem, it was TMC members both yellow and blue badges who helped me solve this mystery. Interestingly enough, the coolant company had the immediate answer. Thank you to my TMC friends.

About the Author

Darry Stuart | President

Darry Stuart has more than 45 years of experience in the transportation industry. As President/ CEO of DWS Fleet Management Services, he has been providing “Limited Time Executive" services in transportation and fleet equipment management to a variety of companies.

An ASE-certified master technician, Stuart began his career on the shop floor before moving on to fleet management executive positions at Perdue Chicken, BFI (Browning-Ferris Industries), United Truck Leasing, the  Keen  Companies, and Cumberland Farms/Gulf Oil.

For 35 years, Stuart has been an active member of the Technology & Maintenance Council (TMC) of the American Trucking Assns., serving as the group’s general chairman from 2007-2008. He is the recipient of numerous industry awards, including TMC's Silver Spark Plug, which is given in recognition of an individual's outstanding contributions to the cause of excellence in heavy-duty vehicle maintenance management. He has been cited as an industry expert or authored over  250 articles on equipment and fleet management topics.

Sponsored Recommendations

Reducing CSA Violations & Increasing Safety With Advanced Trailer Telematics

Keep the roads safer with advanced trailer telematics. In this whitepaper, see how you can gain insights that lead to increased safety and reduced roadside incidents—keeping drivers...

80% Fewer Towable Accidents - 10 Key Strategies

After installing grille guards on all of their Class 8 trucks, a major Midwest fleet reported they had reduced their number of towable accidents by 80% post installation – including...

Proactive Fleet Safety: A Guide to Improved Efficiency and Profitability

Each year, carriers lose around 32.6 billion vehicle hours as a result of weather-related congestion. Discover how to shift from reactive to proactive, improve efficiency, and...

Tackling the Tech Shortage: Lessons in Recruiting Talent and Reducing Turnover

Discover innovative strategies for recruiting and retaining tech talent in the trucking industry at our April 16th webinar, where experts will share insights on competitive pay...

Voice your opinion!

To join the conversation, and become an exclusive member of FleetOwner, create an account today!