[Vwdiesel] Water as a cleaner (More weekend science)

Mark Shepherd mark at shepher.fsnet.co.uk
Sat Oct 30 16:33:05 EDT 2004

I just came across this thread through a search engine...
All credits there

From: Mark Weiss <mark_weiss at earthlink.net>
Date: Wed, 13 Mar 1996 10:43:54 -0700
Subject: BMW: Squirting water, I tried, it worked!

I had heard decarbonising an engine by squirting water into
the intake
before. The principle is that the water droplets are large
enough that
they don't evaporate before they hit the combustion chamber.
Once there,
the water suddenly becomes steam, and the force of this is
supposed to
strip away the carbon.

I deciced to give this a try on an R75 that I was going to
tear down
anyway. I used a small flashlight to peek through the
sparkplug holes
and verified that both piston crowns appeared equally
coated. I used an
old Windex sprayer, adjusted just to the spray side of a
stream so that
I had a fairly coarse spray. Once the engine was up to
temperature I
removed the left carb to airbox tube and then increased revs
to about
3k. As I began to spray the water into the carb, the revs
dropped and
the engine began to run roughly. I let the engine recover
and then began
spraying again, this time I paced the spraying so that the
revs did not
drop much below 2k. Every 10 to 12 sprays I let the engine
return to
smooth running. I continued this until I had exhausted the
entire quart
of water.

After I was finished I rode the bike for a few miles and
then took it to
my garage for a teardown. The result was remarkable! The
left piston and
combustion chamber were almost completely clear of carbon
buildup. The
whole area was about as clean as if it had been scrubbed
with a solvent
soaked rag. It looked somewhat like I would have expected of
an engine
with only a few thousand miles on it.

Based on my results, I think that if done carefully, this
could be pretty useful. Especially in older engines that are
pre-ignition problems.

These are some precautions that I recommend:
1. If the engine develops a hard misfire, stop spraying and
let it
recover. You don't want to get liquid water into the
2. Spray slowly and steadily, you don't want to overload a
cylinder and
get liquid water into a cylinder.
3. This takes time, make sure you have adequate cooling
airflow to the
4. Clean out float bowls afterwards, you may have some water
in them.( I
did not, but it seems possible )
5. Change your oil and filter afterwards, any water that got
past the
rings and into the crankcase will mix with the oil and
byproducts and form acid.
6. Peek into the cylinder and see if you need to do this. If
you don't
have a lot of buildup, why bother?

P.S. I also tried this on a 4-cylinder bike. It was much
easier to do by
simply removing the air filter, and spraying into the
airbox. The engine
protesed less, and I got all the cylinders at once!
- --
Mark S. Weiss
MSF Ceriified Instructor
Dedicated BMW rider and RoadRace enthusiast!
Chandler ( SE of Phoenix ) Arizona

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