radiator end cap plastic repair

[Scott Phillips]

Not sure if the area around the crack can be scuffed, enough to provide a sealer a place to bond to. but JB weld makes a waterproof epoxy, in stick form that you mash together to activate the epoxy. Then you can mold it into place. 
As for pressure, I'm using it to repair a couple of holes in the rear muffler of my V8Q, and with the hot/cold and pressure that's in there (can't imagine it's more then 5-6 psi..similar to a cooling system), it's held with no problems. Might be worth a try.
Wal-Mart $4 bucks..or any FLAPS.
HTH.. 
Scott '90 V8Q x2