In the process of doing this and I cant figure out why it isn't holding any pressure. Got the compressor hooked up, no leaks at the coupler where I hooked the hose to the niple on the cap but no pressure at all. And it's not leaking from anywhere. Any ideas?

 

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Either the coupler that you hooked up to the boost leak tester is actually leaking that you didn't know, or somewhere else is leaking bad. If you are using a regular compressor for inflating tires, try to use something else to pressurizer the tester so that the compressor does not need to be running loud when testing. You can definitely hear it hissing somewhere... I used a compressor (for air tools) that set to pressurized at 15psi.

 

We figured it out. The reasone was a huge leak, but it made no noise so we had to hunt it down. It's all good now. Thanks for the reply.