Hi, I am about to change the fuel filters on my 355 (has 2 filters, early 95) and Ive noticed that there is white thread sealant on the fittings leading up to and including that of the filter itself. The car is relatively new to me (a few months), and the filters have not yet been changed under my ownership. Is it common practice to use thread sealant? My understanding was that thread sealant is only required for NPT fittings, and surely this is not an NPT fitting, right? Do people typically use thread sealant for the fuel filter fittings? If so, why, and what type of sealant do you use? Thanks, Andrew
There are 2 dressings you can use for fuel fittings. Most of the time I don't use any. But there is a Teflon tape that is fuel resistant and a dressing that you paint on. You probably do need them. Compression fittings should not require them; other fittings it's optional. If you are getting a good seal, then there isn't any point.
EAA Magazine just had a good article for review of this topic for aircraft home builders. There's a tube of Dow Corning that continues to be the norm-- waxy substance. Then the article mentioned a new product from liquid wrench (probably hard to find) and then if you must use tape be sure to leave a couple threads bare. And as mentioned -- none on compression fittings. And don't misuse locking sealants on liquid fittings. Fwiw
You would be amazed on how many new cars have a small dab of a Henkel brand sealer on the threads to prevent themselves from fuel line coming loose lawsuits.
With the exception of pipe threads fittings do not seal at the thread. If there is a failure to seal the fitting is damaged and thread sealant is a dangerous band aid.
Considering the quality of work habits of assembly line workers a great many precautions are taken to minimize the damage of their screw ups. Until they can be eliminated completely by machines new cars will continue to have parts just fall off. A friend was driving his brand new Viper off the lot when he lost control and nearly wiped out a row of brand new cars because the steering rack fell off its mounts.
Not to mention radiator hoses popping off the Hellcats at the radiator, couple gallons antifreeze on the front tires is a wonderful thing with like 800 HP
