I wanted to know were I can take the Cmi's to get pressure tested here in Miami.

call allen at extreeme marine in miami . he did mine a few month's back

question is, they told me that they might not leak when they're cold but once they get hot they might.....Is that true ? If so do they test them under heat ?

TNT will be able to do the test. We use 60PSI cold. Be carefull with the plugs at this pressure.

if you find a shop that has hot water to test, that would allow you to see prob under norm use...

Yes, that is true.

You might want to test them yourself... You'll need warm water, propane torch and a small water valve.

Hook up the water valve to the outlet on the header and hook up the hose to the inlet hose on the header. run the water until all the air is bled out of the header and then close the valve. Once the valve is closed, heat up the inside of the tubes around the exhaust flange, also use the torch to heat up inside the collector area... check for leaks...

You will probably also need a small flashlight and a mirror.

Check them thoroughly and check them often!

Buizilla has it right, fill with air & submerge. We have a 50 gal drum we use.

I've found that method to be unreliable. First you can't see inside the tubes if the leak isn't in plain sight and if it needs to be fixed you can't mark it. Second, if the leak is very small or if it doesn't leak unless it is hot you wont be able see it that way. I've had headers that didn't leak, then you put some heat too it and it starts to sizzle and seep out.

Everyone has their own method though...

Sometimes using air alone will not have a leak show up. When heat is applied the metal will expand showing the crack.

You're not seeing the point.... some headers don't leak unless they are heated up....the metal expands allowing the water, or in your case air, to escape...

When it's submerged in water can't see inside each individual pipes to find out where the leak is coming from, so good luck having it repaired properly..

Do whatever you want and whatever works for you....

Exactly.....