A very effective method for checking for cooling system leaks
 is to pressurize the cooling system BEFORE you start the engine.
 Once you start the engine you can be fooled by the system
 pressure as the coolant expands as it heats up. You could be
 losing coolant at such a low rate that the pressure remains normal for
 quite some time. The leak could be internal within the engine through
 a water O-ring failure.

 Pressurizing the system when its cold on the other hand will immediately
 show you if there are any leaks.  Here is the guts of the little 12 volt
 electric compressor Perry and I used to trouble shoot his cooling system
failure.
 Available in any auto parts store as an emergency tire pump.

 I am going to mount one of these permanently under the cowl (without
 the black plastic case) with a switch on the instrument panel. It only
 takes a few seconds of operation to get the system up to 30 psi.

 Paul Lamar

Paul,
I agree that a cold pressure check will give you more results earlier than
just heating the engine up.

If the leak is external, it will make it drip, which you can catch during a
preflight exam by looking for the water.  However, it seems that if you have
a slow internal leak, the amount of pressure change could be very small.  You
are pressurizing the air space above the engine, and if the leak is leaking
only coolant, the volume change from losing a few tablespoons of coolant will
not necessarily cause a very big pressure change.

Bill Schertz
KIS Cruiser #4045

I think you have that backwards Bill. Lets look at this in terms of
numbers. Lets say the total cooling system is one cubic foot. Lets say
our airspace is one cubic inch pressurized to 30 psi. Lets say we lose
a half cubic inch coolant to the internal leak in five minutes. We
then have an airspace 1.5 cubic inches with the same number of air
molecules. I would expect the pressure would then be 20 psi. Don't
forget, we turn off the pump when it reaches 30 psi and watch the
gage.

In our case there was a dramatic loss of pressure right away.
Far more dramatic then when starting the cold engine and watching the gage.
It takes time for the coolant system pressure to build up when
you start a cold engine. It may not get above 5 or 10 psi until
you actually take off and climb out.

Nothing new about this technique as radiator shops use this technology
all the time to check for coolant system leaks. Perry and I first
shopped for one of these radiator shop tools in Pep Boys with no luck
so I decided to build the tubeless tire valve adapter and use the
pressure gage that Perry had already installed on the instrument panel.
I already had the emergency tire inflator compressor in the Carvan.

Paul Lamar

    Jim and Larry,
     Method to pressurize cooling system as part of
 preflight to check for leaks.(Add metal shrader valve
 to cooling system)

    Kelly

--
Dyke Delta/13B Rotary Power

Was this for us Kelly?

Paul Lamar
 
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