Here is a pic of how I did it and a lot of folks who know what they are talking about said it was a good method of testing them for leaks. I used 40 psi of air pressure and a tub of water to look for bubbles. Others insist that the cooling jacket should be pressurized with water and wait for wet spots to show near the welds. Still others have said that heat should be applied to the welds while the jacket is pressurized with water. How do you guys do it?

Looks a lot like you but Jer my guy on the boats uses one of his hot chicks to blow in the hose instead of the compressor, I don't know if it works or not but it looks good...

A couple of shops I know do it that way, works for them. I also made up a deal from PVC with a hose fitting, pressure gauge and two places to mount hoses(1 inch PVC). Clamp a hose to one fitting, fill from the other fitting then clamp the other hose there, open the faucet and run have it sit there with 30-40 psi. I suppose you could add heat at the welds too, but you can't get to all of them and I have seen a lot of CMIs leak right from the tube anyway, especially the 525 headers.

I've heard that to check for internal leaks your can roll up a section of newspaper and snake it up the tube that is beeing checked, presureize it with water,pull out the newspaper and check for a wet area.

If you really want to do the best job yourself, use helium gas rather than plain air to pressurize with. Helium molecules are much smaller than any gas contained in plain air and will leak through smaller holes where plain air will not. I manufacture frozen margarita machines and this is the procedure we use.

That's interesting. I guess I could buy a small helium tank.

Yep....go to a party story, if any are near you, they sell/rent tanks for filling ballons.

A back yard trick for finding cracks in headers and engine blocks is to fill them (water Jacket) with CRC just let it sit there don't have to pressurize, if theres a crack it will weep through. You can buy CRC in gallon container at most auto parts stores. If not familiar with CRC its a penetrate ( like WD40 ) for rusty bolts and is sold in gallon cans to refill squirt bottles. Use a paint filter to pour it back into the can and use over again.

I just pressure checked mine this winter, as I suspected a leak. I filled the water jackets with water, pumped up some air pressure into it and just looked around. I eventually found a leak in 1 of my tailpipes. A quick hit with the tig welder stopped it. The pipe was not rusted out, it just had a small crack in it. I am confident the weld will hold.

Why not just heat the water in the tub ?