Same deal with my cloth-covered "Made in Germany" hose, after ~3 yrs they were leaking profusely. Seemed to have started all at once, and every section was wet, so at least the hose is consistent. I have been running Diesel HPR for several years, on and off when I had the car vs my son. I first tried silicone vacuum hose on one section since I had it, then read "doesn't work" and indeed it started swelling in a day. I now have Viton tubing for >2 weeks, and looks fine, but a few years to really tell. I bought from China $19 for 10 ft on ebay, claimed good for bio-diesel. Any way to tell if genuine Viton? Maybe a bite test, like a gold coin? It is a flat grey color, if that tells anything. Maybe cut off a piece and immerse in solvent for a day? I have ethanol, MEK, acetone, and xylol.

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1984 & 1985 CA 300D's
1964 & 65 Mopar's - Valiant, Dart, Newport
1996 & 2002 Chrysler minivans