My BMW R100s is on the lift. Heads and cylinders have been off for a month while I did other stuff. I needed some assembly sealer. There was some weeping at seals and push rod tubes and at the base of the cylinders. BMW recommends TreBond which is nearly unobtanium in these USA. It's expensive, too. So I settled on Hylomar Blue.
The damn push rod tubes have leaked since I've owned the Speedster. When I got the car it had the adjustable tubes that used a large nut to set the length. Complete junk!, So, I changed them to the aluminum spring loaded type with o-ring seals in the barrel. They still leaked. I've changed the seals, used no sealant, used Permatex Aviation sealant and still, they always leaked. Really P.O.'d about the whole thing and was just about to drop the engine and install the factory tubes when the Hylomar arrived. I had read a review on the stuff and the guy said to "only put the stuff on parts you don't want to leak". He was right. Not a drip anywhere.
The BMW is still on the lift.