MACS Monthly Newsletter - 2020 - JAN7

Should you lubricate the core?

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It's important to lubricate the external seal of valve
cores (or integrated valves) just before installation to
avoid damaging the seal. But be careful not to use too
much! Excess oil on the seal will confound a leak test by
providing a second sealing element. It can also migrate
to the threads reducing the coeﬃcient of friction (making
it easier to turn). This will increase the amount of torque
transferred to the core body and may cause core failure
within the torque value. Use the same oil that's used in
the system, so that chemical compatibility between the
lubricant and seal is assured.

Standard core: 3-6 in-lbs.
JRA: 5-10 in-lbs.
8mm: 10-20 in-lbs.
10mm: 15-30 in-lbs.
Primary seal (HS): 7-10 ft-lbs.
Primary seal (LS): 5-7 ft-lbs.

Pin Height
You've probably never checked it before, but it's important to note the installed location of the top of the
pin relative to the top of the housing. All pins have
a recommended maximum and minimum distance
they can travel without damaging the valve core. In
fact, there have been instances where pins have been
crushed and bent by poorly designed service couplers.

Valve core service tools
Several service tools are required for working with
valve cores (there is no "one size fits all" driver), including driver tips to fit the various core sizes, sockets for the
valves and caps, and torque drivers. See Figure 15.

Caps

Steve Schaeber

Finally, the most important step before sending the
vehicle out is making sure the caps are on! Contrary
to popular belief, caps are the PRIMARY SEAL of the
service port (not the valve core), and play and integral
role in assuring system integrity. Not only are they a
redundant seal, but they also keep the valve and port
surfaces clean. Although some caps display a torque
value (Figure 17), most do not and those should be
firmly finger tight.
So, were many valve cores replaced unnecessarily?
We can't even begin to guess, and we'll just have to
wait through the next round of surveys to see how and
if the data changes.
For now though, let's all start "servicing the port"
the right way! ■

Figure 15: Tip sizes vary in width and depth to accommodate the core's "bridge" and have a hole drilled out of the
center to make way for pin length and diameter.

Installation torque

Steve Schaeber

Valve cores require specific torque values, so their seals
are not damaged or destroyed. Each will be diﬀerent due
to the varied thread sizes, and a special torque driver
must be used (Figure 16). The recommendations are for
dry threads.

Figure 17: Cap on left says it should be torqued to 2.5 inlb. Cap on right says nothing, but "firmly finger tight" is
good when you can't find a spec.

Figure 16: Never heard of torqueing valve cores? It's an
important step to ensure the valve core is not too loose,
and not too tight, but just right!

January 2020

MACS Service Reports

MACS Monthly Newsletter - 2020

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