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Flooded ATV Engine: Symptoms & What to Do (15 Steps)

Water fording is one of the many joys of off-roading and also one of its formidable problem sources. The same can be said for prolonged exposure to moisture and the elements. This guide explores the lowdowns of water interference in a flooded ATV while offering practical solutions for this off-road predicament.

Addressing a flooded ATV entails knowing its telltale signs, being aware of potential flooding triggers, and prompting action when problems arise. However, the best approach to handling the issue is precaution, thorough inspections, and stringent adherence to ATV maintenance.

In dealing with a flooded ATV, rapid and informed responses are crucial to prevent extensive damage. And this article will cover exactly just that! So, without further ado, let’s delve into the most prevalent symptoms of water contamination and the recovery process that will help address these indicators and their root causes.

Riding ATV Through Deep Muddy Water

13 Indications of a Flooded ATV

Water in the engine can manifest through various symptoms. Here’s a list of cues associated with a flooded ATV and a brief explanation for each:

1. Sputtering and Stalling

Water in the engine can disrupt combustion, leading to irregular firing and sputtering.

How exactly? Water interferes with the air-fuel mixture essential for proper combustion because it isn’t incendiary like fuel. It’s an unwarranted element in the combustion process, where only air, fuel, and spark are needed to generate power for an ATV engine.

The fact that water is non-combustible also deceives sensors (e.g., Mass Air Flow sensor) into registering the entry of fuel (instead of water) into the combustion chamber. This misinterpretation disrupts the air-fuel mixture, leading to the flooded ATV operating with a lean mixture, resulting in sputtering, erratic speed changes, and various performance issues. In severe cases, it may result in engine stalling.

2. Strong Odors While Driving

Next to sputtering, intense smells from a quad are arguably the second most prevalent indicator of a flooded ATV. It could be a strong gasoline odor that may be noticeable during operation or a distinct one that’s characteristically sweet due to the coolant’s ethylene glycol content.

The odor you encounter depends on where water enters and interacts with different engine components. Water entering the combustion chamber can lead to unusual exhaust smells or the gas-like odor described earlier.

Water entering the coolant system can dilute the mixture and produce a sweet or unusual scent (the latter typically indicates problems beyond coolant contamination).

3. Unusual Noises

Due to its disruptive effects on combustion and mechanical processes, there are several ways water can contribute to strange ATV noises (as follows):

  • Popping, knocking, or backfiring sounds caused by incomplete or irregular combustion — usually indicative of the engine struggling to burn fuel properly and also particularly true if water reaches the muffler or catalytic converter (view on Amazon)
  • Loud thudding or clunking noises from starting an ATV in hydrolock, a condition where the pistons are prevented from moving because water is incompressible
  • Unsteady idling accompanied by irregular sounds — chugging, thumping, hissing, puffing, spluttering, and coughing — due to an inconsistent rhythm at idle or the engine trying to draw in compromised air-fuel mixture during the combustion cycle
  • Knocking or tapping sounds resulting from water contamination in the oil or other lubrication systems, leading to increased friction and wear of stress-prone engine components
  • Bubbling or gurgling noises when water enters the coolant system and mixes with the coolant

Similar to odors, the kind of noise you hear depends on which part of your ATV the water reaches and how the latter disrupts the integral processes and ratios of these systems.

4. White Smoke from Exhaust

In a not-so-recent post on cars blowing white smoke but not overheating, I’ve discussed the reasons behind the phenomenon in detail. And despite nuances between vehicles and ATVs, I’d say the triggers behind white exhaust smoke for both four-wheelers are the same. There is, however, one item not included in that article, and that’s water contamination.

Water in an ATV engine can produce white smoke in the exhaust (view on Amazon) through steam generation, where the engine vaporizes excess water during combustion. The bullets below summarize how this process works:

  • Stage 1: If water seeps into the combustion chamber, it can mix with the air-fuel mixture supposed to ignite during combustion. When the engine fires, the heat causes the water to vaporize rapidly.
  • Stage 2: The intense heat from the combustion process turns the liquid water into steam, which appears as a white, vapor-like substance.
  • Stage 3: The steam and normal exhaust gases are expelled through the exhaust system. This gives the exhaust a distinct white color.

While white exhaust smoke indicates water or coolant entering the combustion chamber or exhaust system, the occurrence may also result from a blown head gasket or cracked cylinder head (view on Amazon).

Check out the article I referenced for specifics on these other triggers. Additionally, I highly recommend addressing the issue promptly to prevent further damage to the ATV’s engine.

5. Misfiring or Rough Idling

It’s already been established through the preceding items in this list that water in the engine upsets the balance of multiple systems. The same stands true for misfires and rough idling, both resulting from a disruption of the combustion process and can manifest even when an ATV is idling.

The precursor to these outcomes is similar to sputtering. In these situations, however, water-contaminated fuel fails to ignite properly, resulting in incomplete burning of the air-fuel mixture. Inefficiency in combustion produces fluctuations in power output, affecting the engine’s smooth operation at low RPMs.

Misfiring is the catalyst for rough and uneven idling — explaining why they often occur together, if not consecutively.

6. Engine Hesitation

Apart from a disrupted combustion process, a flooded ATV is also marked by delays in its ignition process. These delays result in hesitation in the engine’s responsiveness, which is observed to be more apparent when an ATV is accelerating.

For a quad, disruptions in the ignition process can stem from several origin points, including interference with spark plugs. Water near the plugs disrupts the efficient formation of the spark required to initiate combustion, leading to delays in ignition.

This, in turn, translates to a temporary lack of engine responsiveness — hence, the issue of hesitation. If not addressed promptly, a one-off instance can accelerate spark plug fouling. It can even lead to charging system issues and sensor malfunctions if water seeps into other areas where critical components are located.

7. Power Loss or Surges

Surges in performance or power loss are another aftermath of power delivery fluctuations, a characteristic of a quad with water in its engine. Barring sensor problems and engine defects, you may notice intermittent episodes of these symptoms when driving a flooded ATV. Otherwise, the frequency of performance surges may increase.

Unsurprisingly, a flooded ATV would act up in such a manner, as its engine (like any other motorized vehicle) isn’t naturally equipped to compress water — especially during acceleration. Power output should normalize when the engine receives cleaner, uncontaminated fuel and lubrication.

8. Starting Difficulties

Another telltale sign of a flooded ATV concerning ignition hiccups is no-start issues. Yes, it isn’t exclusively characteristic of having water in the engine. However, it’s one of the more prevalent symptoms.

Water contamination makes it challenging to initiate the combustion process. It can cause starting issues through several mechanisms, including improper compression, compromised fuel injectors, and imbalanced air-fuel mixture (in addition to spark plug interference and incomplete fuel oxidation). Collectively, these factors lead to poor ignition and decreased fuel efficiency, resulting in the same outcome.

9. High Levels of Coolant Contamination

Coolant contamination, another symptom of engine flooding, occurs when water infiltrates the ATV’s coolant system through sources like plugged muffler drains or leaking seals and gaskets.

The increased water levels in engine oil and coolant brought about by these loopholes disrupt the latter’s effectiveness, compromising its ability to regulate engine temperature and potentially causing engine overheating and damage.

10. Corrosion on Engine Components

You might expect corrosion to be higher up on this list of symptoms. Well, it’s not always as readily visible as one might think. Especially in a flooded ATV, rust is usually hidden from sight and often develops within various components — not on external surfaces where it can be easily spotted.

Metal surfaces and electrical connections are two of the most rust-prone areas of an ATV. However, these zones aren’t necessarily exposed all the time. Nor are they frequently inspected (even if they should be).

If corrosion starts to form inside a water-contaminated combustion chamber or engine oil reservoir, the issue may go unnoticed unless a thorough visual inspection of these parts happens regularly.

11. Phase Separation

This is one of the easier indicators of a flooded ATV to identify. But just like corrosion, the extent to which it is evident depends on how promptly and strictly you adhere to regular maintenance.

It can be tricky at times since the visibility of water-fuel separation depends on the water level. If little water is present, you may need to take a closer look to discern if there is phase separation at all.

There aren’t official tiers to phase separation. But based on the severity of water contamination, you may observe one of the following scenarios:

  • Minimal: A slight line or interface between the fuel and water layers, indicating a low level of water contamination.
  • Moderate: A more pronounced separation between fuel and water, suggesting a moderate level of water intrusion.
  • Severe: Extensive and clearly visible separation, indicating a high level of water contamination in the fuel system.

These’ severity tiers’ provide a qualitative assessment of the extent of water intrusion into the fuel, helping to gauge its potential impact on your ATV engine’s performance and the remedial actions you need to take to resolve the issue.

12. Subpar Performance in Wet Conditions

Items #5 to #8 on this list all signify the poor performance of an ATV in wet conditions. These problems worsen when surfaces are slippery or during rain, causing difficulties navigating rugged terrain, hesitation in engine response, and an overall decrease in the ATV’s effectiveness.

As if that weren’t tricky enough, there are instances where performance problems may not be immediately apparent in a flooded ATV under normal riding conditions but become noticeable in wet conditions.

For example, if an ATV has experienced partial water intrusion, performance issues may not be prominent during normal riding. But in wet conditions, the quad is subjected to additional and sustained water exposure — enabling the water in the engine to further disrupt combustion.

13. Poor Fuel Economy

In some cases, reduced fuel mileage can signify a flooded ATV. However, I opted to enlist this engine behavior last as it’s associated with issues other than ATV flooding. Some culprits behind decreased fuel efficiency include incorrect tire pressure, a clogged air filter, and a defective O2 sensor.

Despite its non-exclusivity, a low MPG rating isn’t a factor to be easily brushed off. After all, water contamination adversely affects combustion. Since a flooded ATV causes its engine to struggle with handling the air-fuel mixture, the latter will (expectedly) try to compensate for this shortcoming at the expense of fuel consumption.

How to Get Water Out of an ATV Engine (15 Steps)


ATV in Water

1. Initial Recovery

Retrieve your ATV from water or mud promptly using a winch or towing assistance. Don’t attempt to start the engine right away to avoid potential damage.

If the four-wheeler is submerged, tow it out immediately, tip it 90° backward to drain water, and clean the air intake. Also, drain the carburetor and oil and force water out of the cylinders.

2. Air Filter Check

Once you’ve removed most of the water, inspect the air filter for water contamination. If wet, remove and dry it or replace it.

Clean the airbox and tilt the quad to eliminate excess water (this applies even if you didn’t expose your ATV to deep water fording).

3. Air Inlet Cleaning

After addressing the air filter, clean mud and debris from the air inlet. Inspect and clean the breather tubes, ensuring thorough drying before proceeding.

4. Stator Inspection

From the intake system, move on to the electrical components of your quad. Begin by removing the stator housing and checking its condition.

A water-contaminated stator may appear wet, with visible signs of moisture or water droplets. In severe cases, there might be water pooling or accumulation within the stator housing.

Dry it using an air compressor like the ALL-TOP 12V Dual-Cylinder Air Compressor Kit (view on Amazon), hairdryer, or natural air circulation.

5. CVT or Chain Inspection

For belt-driven ATVs, use the drain plug to remove water. Clean the belt housing if submerged in mud, then wait for complete dryness before riding.

Conversely, meticulously clean the chain and sprockets of chain-driven quads and ensure they’re free from filth or water contamination. Let the chain dry thoroughly and lubricate it per OEM recommendations before riding.

6. Compression Test

Perform a compression test to assess engine condition. If your ATV has low compression, water may still be present. Otherwise, proceed with the following steps.

7. Cooling System Drain

In severe submersion cases, drain the cooling system of contaminated water and refill it with fresh coolant.

8. Tank and Carburetor Maintenance

Empty the fuel tank and carburetor, thoroughly cleaning both components. After which, dismantle the carburetor, meticulously clean it, and inspect for gasket conditions (replacing deteriorated parts as needed).

9. Cylinder Purging

Begin this process by removing the spark plugs or injectors to facilitate water drainage. Rotate the engine to expel any lingering water from the cylinder.

10. Engine Idling

After clearing the cylinder:

  1. Reinstall the spark plugs, initiate start-up, and allow the engine to idle for 5—10 minutes.
  2. During this period, spray a small quantity of WD-40 into the air inlet intermittently.
  3. Expect smoke as a normal part of the clearing process during this idling phase. If your ATV runs rough, replace the spark plugs, as they may be fouled due to residual water.

11. Oil Change

If water contamination is suspected, replace the engine oil by draining the crankcase and substituting mushy or light brown oil with fresh engine oil. For deep water exposure, inspect the piston rings, piston, and cylinder for damage. Then, repeat oil changes until no water is present.

12. Exhaust Drying

This process aims to eliminate any accumulated water within the exhaust system. Perform this by removing the exhaust pipe to facilitate water drainage and ensuring thorough drying of the component.

13. Battery Charging

Especially if the battery has been disconnected, recharging ensures sufficient power to support the electrical components and ignition system.

Before proceeding, however, ensure all electrical components (including battery terminals) are thoroughly dry and free from water contamination. This precaution is crucial for a successful start-up after water exposure.

14. Refilling

After confirming proper electrical function, refill the oil, gas, and coolant to specification and attempt to start your ATV. Monitor for any performance issues and check for milky-colored oil.

15. Final Checks and Testing

Following successful water elimination from the engine and after ensuring components are dry, it’s advisable to double-check the brake system, electric connections, and other components for water contamination.

Once done, test drive your ATV for at least 15—20 minutes. This duration allows the flooded ATV to reach operating temperature, ensuring optimal performance and helping to identify any lingering issues.

Managing Flooded ATV Problems

Riding ATV Quad Through Water

Having explored pertinent symptoms and addressed what to do if you get water in your engine, the next step is understanding how to identify a flooded ATV.

But rather than delving into another list of to-dos, let’s cover the most prevalent sources of water contamination (enumerated below). This way, you’ll be able to manage and stay ahead of potential issues:

  • Rain or water exposure during water crossings or when an ATV is left uncovered
  • Submersion in deep water leading to water entry into critical components
  • Muddy or waterlogged terrains where water can splash onto the ATV’s components
  • Deteriorated seals and gaskets allowing water to infiltrate the engine, transmission, or differential components
  • Cracks or damage in parts like the fuel tank, allowing water to enter 
  • Storing the ATV in a location where it’s exposed to environmental elements
  • Inadequate ventilation in storage areas leading to condensation and water accumulation in the ATV
  • Using excessive water pressure or improper washing techniques during cleanup, forcing water into sensitive areas
  • For liquid-cooled ATVs: Issues with the water-cooled systems, such as a leaking radiator (view on Amazon) or water pump
  • Coolant system failures leading to water mixing with engine coolant and entering engine components
  • Situations where water is present in fuel storage tanks
  • Damage or improper sealing in the ATV’s air intake system, allowing water to enter the engine
  • Breather system problems causing water to enter differentials or other sealed components 
  • Neglecting regular maintenance, allowing seals and protective elements to degrade over time
  • Overflow or spillage of fuel and other fluids leading to water entering various ATV systems

Taking Precautions

Taking precautions is necessary to prevent these situations and many others from translating into a flooded ATV.

These measures include:

  • Installing protective covers or fender extensions (when applicable)
  • Investing in snorkel kits (view on Amazon)
  • Choosing optimal crossing points when water fording
  • Waterproofing relevant engine, transmission, and ignition components.

Regular upkeep of the engine system and its components is paramount and part of these safeguards.

However, preemptively scrutinizing your engine for the presence of water is the best thing you can do for your ATV. That said, regularly check for phase separation in your fluid reservoirs and engine, and keep an ear out for odd, erratic noises when driving or while idle.

Another best practice is applying water-detection paste to your dipstick to identify potential fuel water contamination.

Conclusion — What to Do with a Flooded ATV

The notion that a flooded ATV engine is inherently ruined is a common misconception. Ultimately, the extent of damage hinges on the duration of water exposure and the promptness of recovery efforts.

While rapid intervention is crucial, the resilience of modern ATV engines often allows for successful restoration without permanent damage. Thus, the guidance provided in this guide should suffice in effectively mitigating the risks linked to water exposure in an ATV engine.