Way to pressurize

Does your under hood tank have a drain that you could install a nipple in to in order to add the pressure? You shouldn't need more than a few psi to hopefully find the leak.

have you confirmed its actually from the HX?
it could be from the engine. I remember reading on here about a leak that occurs and burns off the engine before you see it on the ground

There are coolant system pressure tester tools, hopefully one would have a fitting for the HX cap?

Do not overpressurize the HX look unless you know the brick won’t be the piece that blows a leak.


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First step, do a leakdown test on the engine coolant system to see if that's where the leak is. If the engine coolant system holds pressure, then you can start to worry about how to pressure test the HX system. Low hanging fruit first.

+1 for the Harbor Freight tool. I bought this one from harbor freight for my radiator coolant system and used it with my air compressor, but it might be a little too much pressure for the HX system. Still a great way to build pressure in the coolant system and suck in fresh coolant to eliminate air bubbles. Hopefully you figure it out bro!

The brick can be leaking with no coolant in there. Consider that most of the time your car is operating there is a vacuum being pulled under that lid, sometimes as low as 20kpa or less. It would. These bricks are known to leak. I took mine out, pumped about 10psi of air in there with a mittyvac and put in a bucket of water and sure enough it was leaking, The loop going to the heat exchanger is not complicated and you can test similarly by pulling both hoses and pulling a vacuum on the loop and watching for a leak.

If you don't want to take the brick out I'd disconnect the hoses, but a cork in one of the inlets and pull a 8 psi vacuum. This is comparable to the force on the brick with stock boost. Then see if the pressure drops.

Are you smelling coolant? I chased a coolant smell for months without having to add any.
That small clip-on fitting at the front of intake under throttle body had a hairline crack. It didn't leak and quit smelling after warming up
Its the small coolant line that runs from drivers fender across where air filter box was