That 737 bleed leak changed how I do torque checks

I was working on a 737-800 at O'Hare last month, had a stubborn bleed air leak on the 5th stage. Kept finding loose clamps everywhere, just couldn't figure out why. Then this lead mechanic came over, watched me for a minute, and said I wasn't going back to retorque after the first heat cycle. Tried it after the next engine run and everything stayed tight. Has anyone else found that makes a difference on the CFM56?

3 comments

3 Comments

abbyp6111d agoProlific Poster

Yeah but hold on, re-read what @theas28 said. He's dead wrong about that 4th and 9th stage bleed being the only options on the -7B. I've seen plenty of -800s with bleed mods that tap into the 5th stage for crossbleed starts. You sure you weren't on a heavily modded -800? Those clamps loosening up after first heat soak is common on any engine, but location matters. If you were pulling clamps on a 5th stage line, that's a different ballgame for torque specs.

theas2811d ago

Gotta stop you there real quick... the CFM56 doesn't have a 5th stage bleed. The 737-800 uses the CFM56-7B, and that engine's bleed air comes from the high pressure compressor, which is the 9th stage and the 4th stage. The 5th stage is on the older 737-300/400/500s with the CFM56-3 engines. So if you were pulling clamps on a 5th stage bleed system at O'Hare, you were most likely working on a -300 or -400, not an -800. But you're right about the retorque thing though, those clamps always loosen up after the first heat soak, especially around the bleed valve area.

adam_baker11d ago

You had me thinking with the clamps, but doesn't IP bleed just run hotter on the -7B than the -3?