How to drain the air tanks Volvo 730?

They turn. If you can't turn by hand then they haven't been drained in a long time and are stuck with gunk. You can try gentle force with a small pair of plyers. They turn 1/4 to 1/2 turn at the little T handle. Be careful not to break it off, although you may if they are frozen bad.

 

You might want to spray them with PB Blast or WD-40 first, THEN try turning them.

Brian is right: SMALL wrench, GENTLY. If you go nuts and heave around on that valve, it WILL snap right off and ruin your day.

You may wish to consider replacing those valves with the pull cord type. If it's a company truck you're stuck with them until they break off, probably.

 

If you can't turn them by hand, wait until you are at the company yard and take it on with a wrench. Make sure they have time to replace them if you break them off. Also make sure that it closes all the way after you open it....

 

look on the other side (ie behind the tanks) , along the beam, a little off to the side of the cab , there might be a pull cable with a valve

 

my GUESS is someone changed the cable pull bleed valves out to the unscrew petcock that your pic shows.

on my Volvo I have that petcock ONLY on the front tank. the back 2 tanks have cable pull on the outside and the front tank has a cable that goes around to the backside to bleed it

go under and check the other side of the tanks.

BTW in the pic the forward bolt on the battery tie down. the little loop on the bolt is there to hold the cables to bleed the tanks...!

 

If that's like drain ####s I'm familiar with, you'll need to turn it CLOCKWISE to get it to open (allow air to exit)

I'm sure they removed the pull drains because they were too easy to get to. Every time you pull one you get closer to a point it won't seal shut anymore, and will leak persistently.

If the air dryer is working, water accumulation typically is never a problem. The bigger problem becomes leaking pull valves.

 

Simply use a wrench, that is all that is needed.. Put the wrench on each and turn to the left, nothing hard about it.. If you get a lot of oil crap out of them, then that means it was not done in a long time or ever.. I had this happen once and it took over a week of draining every day to clear the lines.. Just noticed the center on is missing the tab.. Don't worry, I not sure which but I believe the left tank actually drains the middle as well..

 

Any NAPA will have them, in a pinch you can get pipe plugs from a hardware store like Lowe's or Home Depot if you break one off on the road. They should only be a couple of dollars each and take 30 seconds to change out with a wrench and a little pipe dope to seal the threads on the new valve when you screw it in.