Pressure testing cooling system

[Cleve]

I have a Blue Print 302 ford engine in my cobra. Had a cooling system issue. I ordered the largest cooling system pressure testing kit. A couple dozen adaptors testing radiator caps came in the kit. None of those fit my FF supplied radiator cap requirements. Does anyone know where I could purchase a pressure testing cap for testing my cooling system.? Is there any type of nomenclature to help me locate the correct pressure testing cap.
Thank You
Cleve

[bobl]

I've been using a cylinder leak down tester for many year to test cooing systems. Just plumb is into a temp sensor port. turn the pressure up to 14 or so pounds and shut the air off. You can see if the pressure drops, if so keep air on it and look for leaks. That way you are also testing your pressure cap, not an adapter.

[MB750]

I've been using a cylinder leak down tester for many year to test cooing systems. Just plumb is into a temp sensor port. turn the pressure up to 14 or so pounds and shut the air off. You can see if the pressure drops, if so keep air on it and look for leaks. That way you are also testing your pressure cap, not an adapter.

I did something very similar on my DIY SBF, only 10 psi. I figure if I'm testing the coolant system it'll be empty, so just remove one of the many fittings from the manifold and hit up Home Depot for a couple brass fittings to make air go in.

[JMD]

I test fit mine by filling and running it...not too many places for it to fail! I had a small leak from a lower hose after the first few times of getting up to temp...but all good after that. Sorry, not a helpful comment, I know. Carry on. ;)

[Nigel Allen]

I did something very similar on my DIY SBF, only 10 psi. I figure if I'm testing the coolant system it'll be empty, so just remove one of the many fittings from the manifold and hit up Home Depot for a couple brass fittings to make air go in.

G'day Matt,

I always thought it was supposed to be done with the cooling system full:
1. You can see where it is leaking when fluid comes out under pressure.
2. If you have a large volume of air in the cooling system and no non-compressible fluid (coolant), it is going to take a lot longer to bleed the air pressure down if your leak is small.

JMHO. cheers, Nige

[Cleve]

Thank you for all the great replies and insight. All very helpful. Looking forward to my first ride.
Cleve

[MB750]

G'day Matt,

I always thought it was supposed to be done with the cooling system full:
1. You can see where it is leaking when fluid comes out under pressure.
2. If you have a large volume of air in the cooling system and no non-compressible fluid (coolant), it is going to take a lot longer to bleed the air pressure down if your leak is small.

JMHO. cheers, Nige

I guess there's really no reason it has to be one way or the other. All I did was charge it up and wait a few hours. When the pressure doesn't change, you know there's no leak. I also went lower in pressure because I didn't want the cap to open.

I can see why the radiator cap pressure test is convenient though. You don't have to drain the coolant system, and wherever it bleeds out is your leak. I'd be worried about an inner cylinder leak though (filling the CC with antifreeze), but I'd bet that would be plenty noticeable way before a pressure test anyway. I was tracking down a leak on my engine anyway so my system was empty.

FYI, I didn't use enough PTFE thread sealant on one of the head studs, so I pulled them all and made sure I used enough the second time.

[JimLev]

Most autoparts stores will lend you one, just pay a refundable deposit.
I was lucky, I bought one like this from a gas station/shop that was closing down for ~$25.
https://www.autozone.com/test-scan-and-specialty-tools/radiator-pressure-tester/p/oemtools-universal-cooling-system-pressure-test-kit/434717_0_0