By the ALLDATA Community Automotive Diagnostic Team
By ALLDATA Community
Automotive Diagnostic Team
Occasionally a customer will drop their vehicle off with a tire
that’s slowly losing air pressure over a period of days or weeks.
The Tire Pressure Monitor light is glowing and the customer is
tired of adding air. Now it’s up to you to find out why.
By placing the tire in a water dunk tank, you can determine the
source of the air leak by looking for bubbles. In this case, the
problem is not a leaking Schrader valve or a nail. The air
bubbles are coming from the tire bead.
It is possible that abrasive and corrosive elements have intruded
between the tire and wheel and have eaten away at the wheel’s
bead seat. The good news — it can be repaired! In most cases,
the damage is not visible from the outside so let’s remove the
tire from the wheel and get a closer look.
Bead seat corrosion is identified by what appears to be
blistering of the wheel finish, causing a rough or uneven surface
that makes it difficult for the tire to maintain a proper seal.
NOTE: If the total combined linear area of
repairable corrosion is more than eight inches (200 mm), replace
the wheel. If the corrosion extends up the lip of the flange and
would be visible with the tire mounted, ask the customer if they
are okay with the repair before proceeding.
Many manufacturers such as General Motors recommend this repair
for their wheels. Use a clean-up (fine cut) sanding disc or
biscuit to remove the corrosion and any flaking paint. You should
remove the corrosion back far enough until you reach material
that is stable and firmly bonded to the wheel. Try to taper the
edge of any flaking paint as best you can in order to avoid sharp
edges that may increase the chance of a leak reoccurring.
CAUTION: ONLY remove the material required to
eliminate the corrosion from the bead seating surface. DO NOT
remove excessive amounts of material. ALWAYS keep the sealing
surface as smooth and level as possible.
Once the corrosion has been eliminated, coat the repaired area
with a commercially available wheel bead sealant. Commercially
available sealants are black rubber-like coatings that will
permanently fill and seal the resurfaced bead seat. Be sure to
follow the manufacturer’s directions for best results.
All that’s left to do is remount the tire, test for leaks and
install the repaired wheel and tire assembly.
Written by the ALLDATA®
Automotive Diagnostic Team, a select group of automotive experts
dedicated to helping technicians fix hard-to-repair vehicles more
efficiently. Meet the team by visiting http://support.alldata.com/alldata-community.