My daughter had driven through a large puddle of water. I received a phone call, “the car engine has stopped and it won’t start?” I grabbed a tow rope and headed off in the pouring rain to go and rescue her, this is what I found (and how I fixed the issue)…
Topics:
All combustion engines need the oxygen in the air around us as part of the air fuel mixture to run the engine. Vehicles suck in air through an air intake, (usually near the front of the vehicle).
When going through a large puddle of water, engines can suck this water into the engine through the air intake. Some vehicles are more prone to sucking in water (when going through large puddles), as each vehicle can have their air intake positioned at a different height.
Hence… When driving through water, it’s important that you drive slowly. This is so you don’t cause a bow wave of water which can reach the air intake, (causing water to get sucked into the engine). If the water is really deep, it doesn’t matter what you do. If the height of the water is greater than the height of the air intake, the engine can suck in water. This is why you see some 4×4 vehicles fitted with air snorkels, so they can go through deeper water.
Image Showing the location of an air intake and intercooler (usually hidden behind the bumper).
When water reaches the engine cylinders, it can get compressed by the pistons. The compression of the water causes a hydraulic action (hydrolock, or hydrostatic lock), which in turn prevents the pistons from moving. It can also sometimes cause damage to engine components.
A good illustration of hydraulic force can be seen with a mechanical digger or excavator. A mechanical digger uses hydraulics to power it’s arms and digging buckets. The hydraulic force allows a digger to easily lift heavy objects and dig big holes. Hence the potential for possible damage to engine components from a water based hydraulic action inside the engine.
In many cases, as long as you were traveling at slow speed, the engine will stop (stall) before any damage occurs. However, if travelling at speed, major damage can occur.
Section Topics:
Water can get into an air filter. Normally this should only be in small amounts. It’s a normal occurrence, (damp air, rain, fog, etc). Often the air filter housing (box) will have a drain in it for these reasons. However, if the car goes through a large puddle and the engine has sucked in water and stopped, it’s a different matter. There is a difference between a slightly damp air filter and a sopping wet one.
Note:
Its is always preferable to have a dry air filter…
Turbo’s don’t usually like water. However, if you have just been through a puddle and sucked up some water (and you were driving slowly) you should probably be OK, (if the turbo is not sat in water long term, and all the oil seals are good). Check your engine oil for water contamination though, as this may have an effect.
Some examples:
If the engine won’t start…
If this is the case, there is probably nothing else for it, other than to wade into the large puddle and attach a tow rope to get the vehicle home.
Note:
It may be tempting to try and bump start the vehicle, but you could cause damage (if there is water inside the engine)… It’s best to get the vehicle home and investigate.
This applies to both diesel and petrol engines. The repair may involve different tasks, dependent on what’s fitted to the engine.
A List of Potential Issues:
In the order that water would have entered into the engine:
The first thing to get flooded is the air filter and air filter box. As water gates sucked in, the air filter box fills with water and the air filter will get saturated.
The turbo is next (if fitted). The turbo can also suck water in, as well as blow it into the engine. Generally, it just fills with water.
The intercooler (if fitted) cools the air as it exits the turbo. It’s a small radiator that is normally positioned near the front of the car for cooling purposes (see the intercooler image above). Don’t get confused with the water filled engine cooling radiator, which is often situated near the intercooler. The intercooler can be difficult to see, as it can be hidden behind the front bumper. This can also fill with water.
Any of the air intake pipework can have water in it. If water is present, it will have to be drained or blown out.
When the engines pistons go up and down, it will cause a suction. This pulls in any water that is in the air intake system pipework. Because of the density of water, and the lack of combustion (due to the ingress of water) the engine stops and any rotation becomes locked by the hydraulic action of the water (hydrolock, or hydrostatic lock).
The exhaust on a vehicle is normally on the underside at the lowest point. It will usually blow away any water. But, if the vehicle becomes overwhelmed by the depth and the engine stops, water will flood in.
Water can also enter the exhaust from the engine. It can get sucked in through the air intake and the pistons will try and expel the water out through the exhaust. Just in the same way as it expels the spent gases from the combustion of fuel.
If the water is really deep, it can enter the fuel and oil system, especially if the vehicle has been sat in water for some time:
Both the oil and fuel can be drained and flushed. Any filters will have to be replaced.
For diesel engines, the glow plugs can be damaged when you try and start the engine (when full of water). This is because the glow plugs are trying to heat a large body of water, rather than just an air fuel mixture. The damage may only become apparent later on during cold weather, when the glow plugs are most needed.
Therefore, disconnect the electrical connections from the glow plugs whilst attempting to turn over a diesel engine (when full of water).
More information on glow plugs can be found here: Diesel Won’t Start When Cold – How to Fix Glow Plugs: (Opens in a new window / tab)
The order in which the water is removed from the engine is only a suggestion, but it may make it an easier process…
The method here is split into three parts:
Part 1:
Emptying the water so the engine can run…
Part 2:
Starting the engine…
Part 3:
Removing the rest of the water…
Part 1:
If your engine has sucked in water, there could be water in most of the pipework and air intake components. If you clear the water from the engine cylinders, you could end up sucking in more water, from the rest of the air intake system that’s still flooded. Therefore you need to break apart the air intake system (make gaps) to prevent more water flooding in.
Where to break open (undo) the air intake pipework to let water out (this does not drain the water from the engines cylinders):
Notes:
Once you have prevented any further water from entering the engine, we can now start to remove (expel) the water from the engine cylinders.
Safety Precautions:
Make sure no-one is standing near the engine when it is being turned over. Water and fuel can be ejected with force causing injuries. Please wear the appropriate PPE.
Section Topics:
Petrol Engines:
Diesel Engines:
Note:
Method B will eject water through a much smaller hole. Therefore the water is under greater pressure. An attempt should be made to turn the engine over by hand first, to lower the risk of causing damage to the engine, and for safety reasons (water pressure). If there are any issues, stop and remove the injectors to expel any water.
Notes:
If you have sucked water into the engine, the exhaust will have filled with water. This is because of the depth of water and the exhaust being normally fitted on the underside of the vehicle, the lowest point (other than the wheels).
In pushing the vehicle from the water, and towing it home, you will have hopefully passed a few small upward hills. This would allow the water to run out of the exhaust. There may be some water still in the exhaust, (in the low lying areas). This can get blown out of the exhaust when the engine eventually gets started, though you may get some dirt, soot and muck come out of the exhaust at the same time.
Part 2:
Make sure you have completed the following:
In this example, the engine is being started with the air filter, turbo (if fitted) and intercooler (if fitted), disconnected.
The reason we try and start the engine before clearing water out of all the other components, is to prove no damage has occurred to the engine, (so as not to waste effort). And… we may be able to use a running engine to assist us in removing water from the ancillary pipework (see below).
Important:
I.e. When the engine is started, air will be sucked into the engine. This suction could draw any water left in the remaining pipework back into the engine causing it to lock up.
Try to start the engine.
It may take a little while for the engine to start, as there may be water still in the exhaust that needs to be blown clear.
A diesel engine may be difficult to start, if the glow plugs (they heat the cylinders to aid starting) have been damaged by water in the engine cylinders. This will be more noticeable during colder weather. I have another article on glow plugs ‘My Diesel Won’t Start When Cold…‘ if you need more info.
If the engine starts successfully, we can now look at emptying water from the rest of the air intake system.
Notes:
Part 3:
There are two potential methods:
Notes:
There are two potential methods:
Notes:
If you’re lucky, may may be able to blow water out of the turbo and intercooler at the same time. I did this by:
Notes:
Beware of the following…
If you’ve sucked water into your engine, the water will have to have gone through the air filter and its housing. You will need to dry this out and remove any debris:
Hopefully you won’t need many parts (it’s just a case of flushing the water out). But if you do, you can get an estimate of the cost using the table below…
Ordering Parts – Examples of what you can buy & how much they cost:
Glow Plug Prices | |
---|---|
Item | Location |
Glow Plugs | |
Test Equipment | |
Glow Plug Tools | |
Jumper Cables | |
Glow Plugs | |
Test Equipment | |
Glow Plug Tools | |
Jumper Cables | |
Glow Plugs | |
Test Equipment | |
Glow Plug Tools | |
Jumper Cables | |
Glow Plugs | |
Test Equipment | |
Glow Plug Tools | |
Jumper Cables | |
Glow Plugs | |
Test Equipment | |
Glow Plug Tools | |
Jumper Cables |
Hope this helps… 😃