Yes, the rubber ones tend to leak pretty easily. I use some black RTV or black non hardening gasket sealer like Permatex on both sides and have had good luck keeping them sealed, goop on both sides can be a pain when you remove them because of all the extra clean up but they do seal nice that way. Once rubber gets a leak the oil will find the pathway and leak forever, tightening the bolts only makes it worse. It has to be VERY clean on all areas and have a nice even compression from bolt torque without over tightening to get a good seal.