How much pressure should I use to test a heater core? It didn`t leak when removed but I wanted to test it before putting it back in. I would have just bought a new one but it isn`t available.

no more than about 20 psi

ok, thanks

Typical cooling system is about 14-16 lbs so 20 should be adequate

What kind of pressure does a home water hose carry?

90 pounds here.

Whatever is stamped on your radiator cap.

????

Simple question. When you open the outside faucet what kind of pressure does it put out.

Why would you do that?

System pressure might, at max, be 20 psi.

four and a half times that is unreasonable and more likely to cause a failure due to over stressing things.

Normally, 40-80 PSI

Would be easier to test using compressed air hose. Plug 1 end of core, air into other. That way you can slowly increase air press., while core is submerged in water, and observe for bubbles. I'd go 2x times max cap rating. If replacing it is a REAL pain, as some are, test at min 2x or have recored & not woory down the road..

where i worked and supervised on the midnight shift [42+ years] we water tested many of our products.
the lowest pressure vessels were tested to 1 1/2 times their working pressure, except for some specialty items that were tested to 2 times working pressure.
our high pressure vessels were tested at three times working pressure, except for a few items that were tested up to five times working pressure, depending on application.
these products were CLEARLY marked as to the working pressure to be NOT exceeded.
however, heater cores in my opinion, should be tested at 25# [roughly two times cap pressure of 13#]. this is on the condition the outside appearance looks VERY GOOD. if it looks bad on the outside, i consider the internal condition to be the same or worse. if that's the case, a re-core or replacement is about the only choice you have.
remember, this is only MY opinion, your results will vary.

That was i was going to do. I was just wondering why people were talking about the pressure of a garden hose. No replacement available that I know of. I will probably have to have a radiator shop recore it if I need to.

Has anyone ever experienced a radiator cap not vent - ever?

Because I have used a garden hose to pressure test a heater core when I didn't have a compressor to use. I just opened the faucet a little at a time.

Once, had a chunk of loose RTV keep the thermostat from opening and it blew out a core plug.

That's reason why RTV or such shouldn't be used on any fitting/gasket/bolt involving the coolant system. Ever look inside a rad core & find pcs of silicone lodged in tubes? Have also seem them lodged onto the oil pickup screens. When cured it never dissolves in antifreeze or breakdown. On brushon liquid sealants. Shame: some people believe those silicone based products are "miracle cures" .

Yes, well I learned that lesson in 91, that and never use a potmetal chrome water outlet they are crap.

As mentioned, 20-25lbs pressure should do it. If it happens to be an A/C car, then be sure to pressure test the bypass valve as well.