Maddox MH5-1 Owner's Manual & Safety Instructions page 4

Important Considerations About Compression Loss Testing
1. There will always be some compression
loss past piston rings, even in a new
engine. You will never see a 0 PSI
compression loss, and this lost pressure
should be audible at the oil dipstick port.
2. If the Gauge shows very high or 100%
compression loss, the cylinder may
not be at Top Dead Center (TDC)
on the compression stroke.
Make sure the cylinder is at TDC, so
the valves are closed. Reference
your vehicle service manual for
instructions on how to do this.
3. A "good" reading will show compression
loss of all cylinders at about the
same rate. A difference of 5 PSI
between cylinders is acceptable.
A larger difference of 10 to 15 PSI
comparing one cylinder to the
others indicates a problem.
Operating Instructions
Read the ENTIRE IMPORTANT SAFETY INFORMATION section at the
beginning of this document including all text under subheadings therein
before set up or use of this product.
WARNING! Always run an engine in a
well ventilated space. Running engines
produce Carbon Monoxide, a colorless,
odorless gas which can cause serious
personal injury or death if inhaled.
WARNING! Wear protective gloves and
ANSI-approved eye protection when
working on a hot engine. Keep hands
away from the fan and other moving parts,
and protect yourself from electrical shock
or burns. Be aware that working on a
gasoline engine is inherently dangerous,
and suitable precautions must be taken.
Page 4 For technical questions, please call 1-888-866-5797.
4. Leakage rate readings may vary by
up to 10% when taking repeated
readings of the same cylinder. Piston
position and engine temperature can
cause variable readings. Take several
readings and average the results for
a recorded reading for each cylinder.
5. Diagnosing an engine problem with this
tool involves using a listening device
(not included). A length of hose or a
mechanic's stethoscope are suggested.
6. The lower the sound pitch of
escaping pressure indicates a larger
leak. Small leaks will typically
make a higher pitched sound.
7. If the engine has multiple problems, the
Cylinder Leak-Down Tester may show
only the most pronounced problems.
A large problem may overwhelm a
smaller problem during testing.
1. Turn the Pressure Regulator Knob
fully counterclockwise before
connecting the Cylinder Leak-
Down Tester to a pressurized
air source. Failure to do so may
result in damage to the tool.
2. The engine must be at normal operating
temperature for accurate testing.
Start the engine and let it warm up
to normal operating temperature,
then turn it off and disconnect ground
(negative) battery cable before testing
to prevent accidental starting.
Item 64918