Floods - Why/how do cars break down in/after them?

[Marcellus]

Having just driven through several bits of flooded road and at each one there was usually at least one car parked up broken down Mrs M and I had a discussion as to the cause and couldn't agree so over to the PH massive for the answer!

We came up with two options;
A) the water got into the electrics
B) thw water blocked the exhaust thus suffocating (sp?) the engine

Are either of us right or is the cause something else?

[HustleRussell]

Water getting into the inlet and hydraulic'ing the engine?

[SS2.]

C) Water enters air intake, gets into bore and results in bent valves, conrod punching hole in block, etc..

[saaby93]

Water anywhere? Once it's past the air filter and into the cylinders it doesnt take a piston long to discover water isn't as compressible as air/fuel. Something has to give.
Electrical connectors are usually ok - how many water holes are there in a nicely positioned alternator?

ETA hustlerussel & SS2 got there first

[g3org3y]

Because rather than slowing down and driving though at low speed on steady throttle people barrel through them like heroes causing the damage mentioned above.

Seen this type of driving on more than one occasion today.

[Marcellus]

Well that's interesting, especially as our Landie had a snorkell on it for that exact reason, but we'd both ruled out water into the air intake but guess you can't all be wrong!

[ShayneJ]

Marcellus said:

Well that's interesting, especially as our Landie had a snorkell on it for that exact reason, but we'd both ruled out water into the air intake but guess you can't all be wrong!

Yep most of the time it is water inducted into the engine.

But unless you installed it yourself and sealed it VERY well
don't expect a snorkel to keep water out that is not its job
a snorkel is to raise the intake to reduce {dust and sand}
clogging the filter in motors that spend a lot of time off road.

oh and on a defender if its spending any amount of time in water
remember to fit the wading plugs in the timing case and bellhousing
or you may grind your timing belt up with mud and/or bugger the clutch
and starter motor.

[Raize]

Water in your distributor won't help much either, but your distributor is higher than your air intake generally. Either will make your car die.

[interloper]

I've experienced both electrical and mechanical failure driving through water, I have learnt my lesson now honest!

The electrical issues are obvious, water and electrics, don't mix but are easily fixed! The mechanical failure was a tad more catastrophic... After driving through a flooded village in my old 944, the car suffered a pretty terminal failure. Water got sucked through the inlet manifold into the engine, causing one piston to stay down when it should have come up, end result a con rod poking out of the side of the engine block!

[AmitG]

...and this is why the new 2013 Range Rover has such amazing wading depth. LR came up with a very clever solution for the air intakes...

http://www.ovalnews.com/2012/09/2013-range-rover-q...

They claim a wading depth of 900mm

[mrmr96]

Uranus said:

As has been said, sucking water into the engine is what knacks 'em! Most cars have a cold air feed pipe attached to the air filter, that cold air feed pipe sucks from low down, so even if the water isn't particularly deep it can suck water up!

Most cars I've had have the intake just above or just below the slam panel. I.e. top of the radiator, so reasonably high.

[GAjon]

It's also possible to flood the clutch loosing drive, especially if the driver changes gear mid puddle.

[GAjon]

[saaby93]

If youre talking about wading depth this takes some beating from two months ago
http://www.pistonheads.co.uk/gassing/topic.asp?h=0...

[AnimalMkIV]

When I had the misfortune of driving a Smart ForTwo, I discovered a slight flaw in the guise of a small hole in the bottom side of the gearbox casing. Not sure if it should have been plugged up, but if you drove through a puddle more than a couple of inches deep, water would get forced in. Not a problem until you stopped and turned the engine off. When you tried to start it again, the gearbox would be stuck and unable to select any gears. Took a couple of days to dry out and then would be fine.


Besides that, see above answers - knobs thinking it's cool to pretend to be on a log flume ride and getting water everywhere it shouldn't.

[andye30m3]

My sister car had been damaged in flood water

Water sucked into air filter and combustion camber, I'm not sure exactly why (sudden cooling maybe) but the conrod ended up looking like a banana, I really was surprised at how bent it was, this then wrecked the bottom end

[HustleRussell]

andye30m3 said:

My sister car had been damaged in flood water

Water sucked into air filter and combustion camber, I'm not sure exactly why (sudden cooling maybe) but the conrod ended up looking like a banana, I really was surprised at how bent it was, this then wrecked the bottom end

Basically whereas air/fuel mixture can be compressed in an engine (often to 1/15th of it's volume at atmospheric pressure), Water is not compressible to the same extent- not by a long shot. So when the piston comes up against a cylinder full of water and the valves closed, something has to give (usually the con rod as you say).