A snorkel won't save your engine

I write this up because even though I read heaps of magazines and on the web I never came across this anywhere. It might save your engine...

A snorkel is supposed to keep the water out of your engine. And it does but only to a degree. Even if all your connections are perfectly water tight you might still inhale the wet stuff. How? Many air filter boxes have drainage holes to get moisture and bigger bits out again. If you just drive through water that shouldn't be a problem. I've been in over bonnet deep crossings a few times by now. But if you get bogged in deep water then your filter boxes will happily fill with water which the engine sucks further in. And we all know that's not a good thing.

I've also read many times to let your engine idle if you get stuck in water. I assume to keep water out of the exhaust and to keep higher voltage on the battery? I do wonder now if it would be better to switch off right away if stuck in bonnet deep water. Than at least the engine can't inhale the water which floods the filter box and all you need to do is dry out the filters or replace them once you're out. In addition it's a good idea to take the glow plugs out and turn the engine over just in case water did get in there (it will spit out the holes). Black engine oil alone is no indication that water didn't get in some parts of the engine. In any case I would temporarily block the drain holes before any deep water crossing.

Sounds like you have a story for us Flo-w? Come on, out with it! Details and pics required!!

We've all come unstuck at some point and there is nothing to be embarrassed about, only opportunities to learn from others experiences. eg. check the drain plugs on the air box!

Agree Flo-w, this is exactly why i blocked/sealed my air box drain when i fitted my snorkel, ive had this conversation before on the forum, and it seems a lot of people prefer to, knowingly leave the drain as per factory, so it also lets water OUT of the air box.

I can understand their thinking to a degree, as rain water may enter the snorkel, if you have a safari snorkel (as i do), the head design, and the factory water trap, greatly reduces what water (if any) that may get as far as the air box.

Modifing the intake from factory to seal it better for water crossings, and then putting faith in a small rubber flap hanging from the inner gaurd, only 2 inches above the LHF tyre (on my car) does not make a lot of sense to me, i didn't want to take the risk so blocked it off.

Three points:

If you take out the drain flap in the air box, it will never empty. It's open to sabotage, ie snorkel being filled with a garden hose. Read about it on a land rover forum. Maybe keep the drain, but have a tap to seal it off during high crossings or hardcore trips. Or fit a self priming bilge pump specifically for the airbox.

Secondly, when the engine is switched off, the water will naturally go up the exhaust to equal the water level on the side of the vehicle. Then it will as the engine /turbo cools suck water up further as the air/exhaust cools and contracts.

Thirdly the positive crankcase ventilation (pcv) keeps a positive air pressure inside the engine to help keep water ingress.

For me this is enough to keep my engine running, unless there is imminent evidence/danger of water in the engine. Ie water is pouring in the snorkel. Then I would shut off ASAP, and remove injectors etc before cranking it over.

The drain on the Nissan Air box is long and has a tubular hose on the end and has a slit in it like the old glue bottles from school. The idea is that if there is pressure from outside (Flood) then the hose compresses and blocks limiting the back flow to very little or zero. We are not submarines though. Get out as quickly as you can. in a water crossing a bow wave is your friend as it keeps the water Out of the engine bay by keeping it in front of the car hence the use of the fording bra.

When i moded the air box on the GQ i added a length of bicycle tube to the factory drain . it is 100mm long. good luck leaking back up that. It will float and kink straight away.

If you block the drain then you risk inundation in a rain storm and nowhere for the water to go but into your turbo. The flow out of the air box via the drain plug is a drip.

Never had a problem with rain and hail, even driving during rain we around the 2011 Brisbane floods period, pretty sure that's a good test, as anyone in Brisbane will confirm, we had a shipload of heavy rain, my car was exposed 24/7, so if the snorkel was ever going to fill up with water, im sure it would have then.




Maybe its different for you guys because I have a 4.5L that runs a different air cleaner set up, that reminds me, after my car had its little sleep upside down, my air box carried about 2 litres of oil for well over a year without me knowing, only when I went to change the filter, did the oil come rushing out ! :eek:



I doubt its worth while retaining the drain just in case you roll your car tho (lol)

I've blocked the drain on mine also and had no issues from doing that..

I have however drowned my car because some idiot apprentice at nissan didn't put back in the foam seal correctly when it fell out servicing my car. My filter box had an inch of water in it (prior to sealing the drain)and was running rough so I pulled the glow plugs and turned it over with metho to remove any remaining water, changed oil and filters and cleaned maf and all was good.

great info. thanks everyone

Imagine bad luck of rolling the car in water on the side of the snorkel:)

Even though I have a snorkel fitted and with a drain hole valve in the box I went to the expense of buying a "UNIFILTER" which is covered in sticky oil that keeps water and dust out as well should it ever get into the air box. The filter is one of the best investments I have made and I have had them on all my 4x4's for close on 30 years at a guess, starting with the "Finer Filter" in my 1982 Toyota Hilux.
(Sorry to all you Nissan Diehards but that was a long time ago and I now have a Patrol, so no abuse please)

Most snorkels have a ram head yeah.
If ya look at where they clamp on they have drain holes.
For normal day to day stuff------
Small amounts, normal rain getting in is allowed to drain out before it makes it down to the air box.
At "speed" rain, small amounts, most water is forced onto the ram head inner walls, allowing same drainage.
Probably why most don't get water in their air box.
In theory that is!

Mudrunner is onto something, bicycle rubber tube ext idea,
or even a solid ext that has a floating ball within it,
float & or be sucked up to seal off air box drain as required.
ya can also buy rubber type drains valves made for boats,
these are an over-kill design of the std drain attached to our oem air box.
they replace bung plugs ( also seen em much larger than bungs on trailer boats), drains above water & seal off below water line.
note, unsure of how much water pressure is needed to seal these off.

My concern is less that water gets in from the snorkel, but that it enters from say, the oil dipstick and places like that.
The dipstick on my thing feels snug, but I wouldn't exactly call it a tight fit. Looking at the rubber, it doesn't look worn, and Nissan wanted an arm and a leg for another so I never bothered.