Katerina Swanson
Draining the water separator of your diesel engine is an essential skill for any owner. If you don't drain the filter, and it gets full of water, then you're likely to end up with ruined injectors. Water in the fuel can cause the water to explode into steam under extreme pressure, which will blow up your injectors. This is because water in the fuel can be converted to steam under the extreme pressure of the compression stroke of a diesel engine. This is why it is recommended to drain the water separator monthly, or at least every 6 months.
There are a few things to keep in mind when draining your water separator. First, make sure the engine is not running. Second, locate the drain valve, which is usually at the bottom of the water separator. Place a container underneath the valve to collect the fuel and water. Open the valve for about 20 seconds, then close it again. Check for any air trapped in the system after draining by running the engine.
How to Drain Bosch Diesel Fuel Water Separator
| Characteristics | Values |
|---|---|
| Frequency of draining | Every 6 months or every year |
| When to drain | When the water symbol on the dash shows up or when there is water in the fuel |
| How to drain | Open the drain at the bottom of the water separator/filter (without removing the filter) and collect the fuel/water in a container |
| Preventing siphon effect | Open the bleed screw at the top of the separator or close the upstream valve at the fuel tank |
| Disposing of drained fuel | Take it to a recycling center, burn it, or use it for cleaning |
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What You'll Learn
How often to drain the water separator
The frequency with which you should drain the water separator in a diesel engine depends on several factors. These include the region in which you live, the climate, the quality of fuel, and the use of fuel additives.
For example, if you live in a humid climate, condensation is more likely to occur in the fuel tank, which can lead to water build-up in the separator. In such cases, it is recommended to drain the separator more frequently, possibly once a month or every few weeks. This is especially true if you buy your fuel from smaller, less busy retailers, as fuel from larger, busier truck stops is less likely to have had time to accumulate condensation.
On the other hand, if you live in a dry climate and always purchase high-quality fuel, you may find that you rarely, if ever, need to drain the water separator. For instance, one individual reported that in 12 years and 198,000 miles of owning a diesel pickup, they never once needed to drain the separator because they consistently bought their fuel from busy truck stops.
Ultimately, the best practice is to check the water separator regularly and drain it whenever water is present. Some individuals recommend checking it monthly, even if there is no "water in fuel" warning light illuminated. This can be done by crawling under the truck and looking for a round canister mounted on the inside frame rail on the driver's side. If water is present, simply open the drain for 20 seconds (with the engine off) and catch the fluid in a glass or jar to inspect for water.
It is worth noting that some individuals report draining their water separators as frequently as every oil change (three times per year), while others do it twice a year, and some never drain it at all. However, waiting for the "water in fuel" light to come on before draining the separator is not advisable, as this could lead to water-damaged fuel injectors, which are costly to replace and typically not covered by warranty.
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How to check if draining is needed
It is recommended that you check the water collection bowl of your diesel fuel water separator at least weekly. This is because diesel fuel attracts water, usually from condensation, and if left unchecked, water in the fuel can cause serious damage to your engine.
Water in the fuel can cause your injectors to fail as the water explodes into steam under extreme pressure. This can also cause rust, pump failure, and other expensive problems. If you live in a humid climate, or if your fuel tank is partially full, condensation is more likely to occur.
To check if draining is needed, locate the water collection bowl at the bottom of the filter. Here, you will be able to see the water level in the bowl. If there is water in the bowl, it needs to be drained.
It is a simple process to drain the water. Place a container under the collection bowl, unscrew the drain plug, and let the water flow out. Be sure to re-tighten the drain plug after draining.
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Steps to drain the water separator
Firstly, it is important to note that you should not wait until the "water in fuel" light comes on to drain the water separator. Instead, aim to drain it monthly or at least every six months to prevent water build-up, which can cause damage to the injectors.
To begin the draining process, locate the water separator/filter, which is usually a round canister mounted on the inside frame rail on the driver's side of the truck. Next, place a container, such as a jar, bowl, or glass, underneath the drain valve to collect the fuel and water.
Before opening the drain, it is crucial to close off the feed line to prevent unfiltered fuel from entering the system. You can then open the drain valve at the bottom of the water separator by turning it a couple of times. Allow the fuel and water to drain into the container.
After approximately 20 seconds, close the drain valve, and let the collected fluid sit for a while. If there is water in the fuel, you will see it separate and settle at the bottom of the container.
Finally, check for any trapped air in the system by running the engine. If necessary, you may need to bleed the fuel system to remove any air bubbles. Additionally, remember to top up the water separator with fuel after draining to avoid leaving an air bubble in the system.
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Avoiding air bubbles when draining
To avoid air bubbles when draining a Bosch diesel fuel water separator, there are several methods you can employ.
Firstly, it is important to understand that air bubbles can enter the system when the water separator is drained, especially if it is positioned above the fuel tank. This can cause a siphon effect, pulling fuel back into the tank and introducing air into the lines. To mitigate this, you can utilise valves on either side of the separator, or a non-return valve integral to the separator, to prevent reverse flow. By closing these valves during the draining process, you can avoid air bubbles from entering the system.
Another technique to avoid air bubbles is to ensure that you only open the drain for a short period, as recommended in the Diesel Supplement book. It advises opening the drain for only 20 seconds, with the engine not running. By limiting the draining time, you reduce the chances of introducing air into the system.
Additionally, some separators have a check ball or a supply tube positioned well below the top of the separator. This design allows for some fuel to be drained without lowering the fuel level below the tube, thus preventing air bubbles from forming.
Furthermore, if your separator has a bleed screw, you can open it before opening the drain. This process helps to release any built-up air or pressure in the system, reducing the likelihood of air bubbles entering during the draining process.
Lastly, it is recommended to top up the separator with fuel after draining to avoid leaving a bubble. By sealing the separator and opening the valves, you can ensure that the system is fully primed and ready for operation.
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What to do with drained diesel
It is important to dispose of drained diesel correctly. One should never pour diesel down a drain, onto the ground, or into the ocean. Instead, drained diesel should be taken to a certified disposal facility or a recycling centre. Many cities have specific sites or designated days for hazardous waste collection.
If you are draining your fuel tank, it is likely that you will be left with a small amount of diesel. In this case, you can collect it in a container and take it to the recycling centre with your used engine oil.
If you have a larger quantity of drained diesel, you may need to contact a specialist disposal company. Some companies will collect the waste from you, while others may require you to take it to a designated drop-off point.
It is worth noting that some recycling centres and disposal facilities may have specific requirements for the containers used to store the drained diesel. For example, some places may refuse to accept diesel stored in a yellow jug, as they associate this colour with fuel contamination. Therefore, it is important to check with your local facility before attempting to dispose of any drained diesel.
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Frequently asked questions
It is recommended to drain your fuel water separator every month. However, this depends on your climate and where you buy your fuel. If you live in a humid climate, condensation is more likely to build up in your water separator. Similarly, if you buy your fuel from a small store, it may include more condensation, so draining it more frequently is recommended.
First, open the bleed screw at the top of the separator to prevent air from entering the system. Next, place a container underneath the separator to collect the drained fuel and water. Then, open the drain valve at the bottom of the separator and let the fuel and water flow out. Once drained, close the valve and check for any trapped air by running the engine.
The drained fuel and water should be disposed of properly. Some options include taking it to a recycling center or using it for heat in a smudge pot. Do not dump it into the ocean or onto your neighbour's grass.
