How to seal heater core connections?

[70spider]

What is the best way to seal the connections to the heater core?
I replaced the control valve and took the old core to the radiator shop, which pressure tested it and no leaks, so I reinstalled it. However the connection between the new valve and the core is leaking, I tightened the nuts as far as I dare with no luck. I used new rubber gaskets. Should I retry with some kind of sealant?
Thanks.

[wizard124]

I like the heat; so I think it is worth the effort to fix it Are you aware that the replacement valve requires a new pipe or you need to bend the old one This could be your issue.

Go here, page 5 :http://fiatspider.com/f08/viewtopic.php ... a&start=60

I secured the valve to the core then installed the core. I used some sealant on the connections. You may be able to straighten the mating edge of the core to get a better seal. Of course this requires dropping it out again

I had to cut some plastic off the heater box to gain bolt access for the pipe connection. Mine is not the preferred method but I wanted to ensure a good junction before re-mounting the core.

[baltobernie]

Try it again with sealant on both surfaces of the gaskets. Do you have the right ones? They look like conical rubber washers. (Two are required; one on either side of the valve.) I use Permatex with the copper additive.

[70spider]

I just ordered a few more rubber gaskets from AutoRicambi, and will give it another go when they get here. I will use permatex this time, I was thinking of this http://www.permatex.com/products-2/prod ... ant-detail I used this in the past on a water pump.
Thanks for the help, I have the worst luck when comes to sealing cooling stuff.