I just put a new radiator in and there is no pressure building within the system. There doesn't seem to be any coolant leaking that I can see. How can I pressure test the system here at home? Thanks.

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1974 Dodge Dart Custom, 225, 904, now with a Holley 2300...

What are you observing that indicates no pressure is building in the system? The fix is probably as simple as a new correctly chosen radiator cap, see here.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

After running awhile, either down the highway or around town, the top hose is still soft. I've tried a few different 16lbs caps, no luck. Had pressure with the old radiator.

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1974 Dodge Dart Custom, 225, 904, now with a Holley 2300...

OK, then the new radiator may well have a defect, such as a warped radiator cap seat that prevents the cap making an effective seal. What brand is the radiator, and where did you get it?

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

I went cheap and got an autozone one for about $150. All I could afford right now.

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1974 Dodge Dart Custom, 225, 904, now with a Holley 2300...

While even the highest-class manufacturer can have defective parts now and again, I'm afraid we may have here yet another example of how "cheap" parts often wind up costing more than "expensive" ones in the long run.

What brand is the radiator you bought?

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Ready-Rad is the brand. And I completely agree with the 'cheap' parts comment, told myself a long while back I wouldn't buy any more. Just in a bind and had to get a radiator now, the dart's a daily driver.

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1974 Dodge Dart Custom, 225, 904, now with a Holley 2300...

To bad you couldn't have found a brand new 22" Modine in a wrecking yard for 60 bucks. Did I mention I did? I would try a new cap like suggested....that fixed my cheap-o barely worked 19" radiator a couple of times in the 6 years I ran it. Autozone may have a tester you can rent (the only thing they are good for) to pressure test the system and also check your cap.

Well, even a cheap radiator should have some kind of a warranty. Take it back!

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Yep, it has a warranty. The only reason I went ahead and got this cheap one is cause of it's lifetime warranty. Just want it to last a year or so. But I feel a little silly, there must have been some air caught within the system cause I jacked up the front of the car and filled the radiator as much as I could. Now it's building pressure like it should. Thanks all for your responses.
Now, just keep my fingers crossed and hope this cheapo rad lasts a little while.

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1974 Dodge Dart Custom, 225, 904, now with a Holley 2300...

If you can get away with a 13lb cap, it'll last a good long time.