Air break leak or?

This only happens when hooked to a trailer or with the tractor itself?

 

yes.
Need to get fixed

 

It's not necessarily a "air brake" leak, it's just a air leak. It could be coming from any number of places. The best thing to do is to get it into a Shop ASAP.

 

Check your red and blue glad hands and couplers. It could be your air bags themselves; best bet is to take it to a shop; better safe than sorry

 

next time you park. pull both your brake valves and see if the leak slows down. that can tell you if its in the truck or the trailer.

i always run pretty close to empty when i leave any trailer open. pull both valves and i'll still have enough to start driving without waiting for pressure to build back up. course, if it's winter. i'll let the truck and oil flow warm up a little first.

your trailer might be perfectly fine. but keeping the RED glad hand from slowly draining is a hard thing to do.

red is supply, air always flows through. blue is the return and only has air when brakes are applied.

losing air is not uncommon. fire engines fire there trucks up every few hours to keep the tanks pumped up. can't have a emegerncy with empty air tanks. that truck needs to roll IMMEDIATELY.

 

it's a Volvo and they are known for having air leaks.....

to check the air line going to the trailer (that's not where it's leaking) unhook the red air line and put the red glad hand in a bucket of water (this after you pull the red knob) you will know if it's leaking...

having a air leak is no fun but as long as it passes the pre trip air brake test it's OK........ if it builds up fast when you start the truck it's not a bad leak..... if you can't hear it it's not bad.... and if you can't see the psi dropping when it's running it's not bad..... you need to get it fixed but as long as the compressor isn't running more than every 5-10 min you'll be fine for now....

 

I like snowwys idea... next time you break, set your trailer brakes also. After the 10 hour break, If the air pressure is still built up, (which it probably will be) problem is with trailer. Still needs to go to shop, but you know it's somewhere on trailer. If pressure still drops, you know it's on truck, since air flow to trailer was blocked off

 

Blue is not a return, it only has pressure from tractor when service brakes are applied.