How do I tighten these fittings? Two are leaking where the black line goes into the fitting.
A picture will help. Or a better description, there are to many fittings to speculate.
You don't. They are push on fitting. You can either call Foretravel, nearest O'REILLY, Truck place, or Napa. If you give me the hose size, pipe size and if straight or ? I can give you both press on and compression fitting Gates part numbers.
To remove the hose, take a small wrench, press down on outer ring and hose, while still pushing down on ring, pull on hose and it will come out of the fitting.
Welcome to the wack a mole, air leak fun
You can also order the fittings from Amazon, possibly cheaper. They have a lot of no name brands, but I have ordered Utah Pneumatic and Mytee products. They both seem to be quality products and reputable companies.
Push connect fittings work fine, as long as the tubing is installed correctly. Correct installation requires a clean, undamaged tubing end which is cut off squarely. The tubing must be pushed straight into the connector until it bottoms out, then pulled back slightly to lock the teeth. Once the tubing is locked in place, be sure there is no lateral (sideways) strain on the tubing.
To repair a leaking fitting, pull the tubing out. Inspect the tubing end to see if it is damaged or distorted. If damaged, cut off a short (one inch) piece with a proper tubing cutter to "refresh" the tubing end. Then wet the tubing end (a little spit works great) and push it straight into the fitting. If there is any lateral strain on the tubing where it exits the fitting, re-route the tubing to remove the strain.
Amazon.com: PTFE Teflon tube cutter, cut up to 3/4'' OD tube- Allen tech :... (https://www.amazon.com/PTFE-Teflon-cutter-tube-Allen/dp/B0756D2T73/ref=sr_1_1?keywords=air%2Bline%2Bcutter&qid=1690546772&sr=8-1&th=1)
See the video below for a good primer on push connect fittings. The video is talking about liquid lines, but the basic principles are the same for air line connections.
https://www.youtube.com/watch?v=sdkmNL3R8YQ
Can you give me the compression parts number from Gates?
Part # depends on type of fitting and hose and hose/pipe sizes.
Here is a little table that I have started has both Compression and push on. I prefer to use the Compression but when in a pinch I will use the push on.
Size to dash #
1/8" - 02
1/4" - 04
3/8" - 06
1/2" - 08