Radiator testers can run anywhere between $40-$200 depending on which type you buy, but there is a cheaper alternative, you can go to your local hardware store and make your own for around $20 with cheap materials. Radiator pressure varies from make and model but can range from 4-30 psi (pounds per square inch), be careful to not over pressurize because you can blow your radiator. The standard for most vehicles is between 10-14 psi so use a standard bike pump where you have complete control, and remember, all you are trying to do is find leaks, once you start pumping, start listening, and DO NOT over pressurize your system.
Here is what you need;
(8) hose clamps;
Take the 5/16 “T” shaped barb fitting and attach a piece of 5/16″ hose to each side with a hose clamp. Note; I cut my sizes at 5″, 5″, and 2″ (2″ up top).
Cut the bottom part of the valve stem off (where it starts to widen) if you have a decent saw and clamp to cut it down, otherwise, just use a utility knife and cut it down to bare metal. Once done, insert it into one of the hoses on the sides and attach a hose clamp Note; I wrapped this end with electric tape to avoid cutting my hand on the hose clamp in the future.
Add the 5/16-1/2″ adapter to the top hose, with hose clamp, then add the 1/2″ hose at the end of that with another hose clamp. Note; Hose can be cut to whichever length you prefer, I cut mine around 5″
Attach pressure gauge to 1/2″ hose, with hose clamp. Note; You can use any type of gauge and the top hose can be any size as long as it fits the gauge.
Worked like a charm when finding a leak in an old radiator, leak in freeze plugs and even found a leak by the head gaskets. You can modify this any one you see fit, I’m just throwing out the concept of what you should be looking for.
Final Note and disclaimer; Be sure to use low pressure (10-13psi) when conducting this test, this is just a sample. You can alter it however you see fit.