Need some tips brazing large bulk area

[LardArse]

I'm trying to braze a pipe from my suction line to the pipe for liquid of this heatxchanger

http://bravo.ausgamers.com/lardarse/lard/gpuhx2.JPG

However, the HX keeps pulling the heat way from the pipe and I can't get the HX pipe hot enough to melt my brazing rod. Any ideas how to retain the heat at the pipe?

[berkut]

Start by putting the hx in some sand, it will heat up in it and the sand will work as a insulator, after a while you will be able to braze it easylly

[NitroRat]

sounds like your torch isn't hot enough,you using mapp gas or propane alone, this may be the problem.

[bowman1964]

easiest thing is to take one normal torch and heat 6 inches from where you want to brase...while this is going after 5 minutes or so.then take the torch you brase with and start to heat your joint.

it may take 2 people to do this but it is the easiest way i think.

[LardArse]

Bowman I wish I have an assistant to help me do that :)
Thx guys for the advice, it took very very long for the pipe to get hot enough but eventually it did. Well, at least I'm assured that there surface area inside is big :)