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® CommunitySM 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.