Air comes in break with c1344 code

I know this is an old post. But if anyone has info on this code I’d appreciate it. It makes a loud knocking sound on the RL brake line when the pump goes off. You can also hear a hissing sound in the back above the gas tank where the lines go if anyone has any insight there

 

Hissing sound where the lines go can be bad news. Do you hear the sound with the brake pedal released, or only when applying the brakes?

I had an old truck where one rear brake line had rusted and split. The split was invisible and would only open under the highest pressures when the pedal was pushed hard, and then fluid shot out in a high-pressure jet. Took a while to find the leak because there was a spot of brake fluid but it was on the opposite frame rail clear on the other side of the truck.

If anything like that is suspected, don't get anywhere near it while trying to find it. You can set up a video camera and watch it remotely, drape rags over the line and look for wet spots after applying the brakes, etc.

A jet of high-pressure fluid like that can cause grievous injuries if it shoots through your skin.

Injection injuries: seemingly minor injuries with major consequences - PMC

 

I know this is a late reply. But replacing the actuator fixed it. I think in some cases servicing the rear brakes might not fix the issue. But it would allow more freedom of movement so a weaker actuator might last a little while longer.

Either way that’s the issue.