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How to Winterize a DEF System

September 2012


DEF freezes at 12°F (-11°C). When it freezes, it expands by approximately 7%. This can cause damage to your Thunder Creek DEF tank and pumping system. Here's the steps to winterize the DEF system on your Thunder Creek fuel and service trailer.


FST Series Fuel and Service Trailers (2015)

FST Series Trailers have a polyethylene DEF tank located inside the front enclosure. Follow these steps to winterize these DEF systems:

1. Connect the DEF hose female quick connector to the male connector on the DEF auto shut-off nozzle.
2. Push the DEF pump switch to "Trailer Fill". Allow the pump to run while squeezing the nozzle handle for 30 seconds. Unhook the quick coupler from the nozzle WHILE THE PUMP IS RUNNING. This will evacuate the DEF fluid from the nozzle. Install dust cover.
3. Return the pump to "Off" position.
4. Connect the DEF hose female quick connector to the male quick connector on the Micro-Matic RSV coupler. Engage the RSV couple to the RSV valve on the FST DEF tank.
5. Push the DEF switch to "Trailer Fill". Run the pump for 2 minutes. This will evacuate the fluid from the pump and plumbing.
6. Return the DEF pump switch to the "Off" position.
7. The FST DEF tank is capable of freezing and expanding if the fluid level is not above the maximum fill line.Damage will occur to tank if fluid is above the maximum fill line when it freezes.