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Working on cars is a perpetual learning experience, even for the most decorated veterans of the shadetree mechanic creed. Even with years of experience managing my own crapcan fleet, I just learned that RTV, which stands for room temperature vulcanizing, sealant has an expiration date after doing an oil pan reseal. Unfortunately, this discovery came the hard way.
My 2010 Volkswagen GTI has been leaking a bit more oil lately, and I traced the source down to a leaky oil pan. The job is easy enough on my car, but I should have known the RTV I used went bunk by the smell and appearance of it. It smelled like rancid vinegar and had strange black fluid mixed in the gray RTV. It was certainly a little suspect and my instinct told me to get a new tube, but I forged on having found no definitive answer on RTV expiration that night.
Against my better judgment I glooped the oil pan back onto my leaky Volkswagen and let it cure for a full 24 hours before filling it with oil. Most of my oil leak subsided for a few days until my car started leaving larger and more alarming puddles of oil wherever I parked it. Clambering under the car for a quick inspection I found engine oil positively waterfalling from the edge of my oil pan, past the slight glob of RTV that squeezed out upon installation.
Nothing made sense until I touched that RTV glob. Instead of feeling like rubber, it crumbled like a peanut butter cookie. I had a major problem. RTV is supposed to cure into a rubber-gasket-like material and stay that way for years. I’ve never seen it deteriorate in this way. Clearly, the material expired, and I got to the bottom of it.
Frustratingly, Permatex doesn’t readily list shelf life for any of its automotive-grade RTV sealant. Nor is there a general consensus on the shelf life of any RTV with some touting as short as six months, while others list as long as two years, depending on storage conditions. We reached out to Permatex for clarification on expiration.
According to Don Sutliff, Senior Product Support Specialist, “Silicone compounds have an approximately 24-month shelf life from the date of manufacture unopened.”
So there you have it. RTV does, in fact, expire.
The best guidance I can offer is to store RTV in a climate-controlled room or get a new tube every six months. Put a date on the tube and save yourself trouble when time comes to do a reseal job. I definitely could have saved myself a few hours if I had just gotten fresh sealant in the first place.