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.
