fabosworth Report post Posted October 18, 2015 I have a air leak on my 1999 HR Endeavor 37ft. I traced to what I believe is a safety relief valve. It leaks until pressure drops to around 80 lbs. Is this normal? My air dryer dumps about every 20 sec? Thanks Share this post Link to post Share on other sites
desertdeals69 Report post Posted October 19, 2015 Is the valve on the dryer or air tank? Share this post Link to post Share on other sites
fabosworth Report post Posted October 19, 2015 Thanks, The leak is in a valve on the I think primary air tank, I can push it down and it will only stay down if pressure drops below 80. This valve only has a airline attached and screwed into top of tank. thanks Share this post Link to post Share on other sites
lewengel Report post Posted October 19, 2015 One of those valves on the air tank reduces the pressure to about 80 lbs. for the air bag system. Mine was leaking also. I found one at the Freightliner dealer. Share this post Link to post Share on other sites
fabosworth Report post Posted October 20, 2015 Thanks, Lew. Will check it out. Share this post Link to post Share on other sites
obedb Report post Posted October 20, 2015 Must be a bad leak to cause an air dryer to cycle every 20 seconds. Share this post Link to post Share on other sites
fabosworth Report post Posted October 21, 2015 How often should it be on the air discharge from the dryer if there are no leaks? thanks Share this post Link to post Share on other sites
wolfe10 Report post Posted October 21, 2015 The answer is "it depends". The dryer purges when the air governor reaches "cut-out" pressure. Then as air is used for brakes and suspension (yes, or leaks) PSI drops to the "cut-in pressure. The governor closes the valves on the compressor (in effect turning on the compressor) until cut-out PSI is reached. Cycle repeats. If concerned about short cycling, start with the standard air brake test. This from an article published a couple of years ago in the FMCA Magazine: Air Brake System Pre-trip Check 1. Be on reasonably level ground. Block wheels so the coach can not move even with the parking brake off. 2. Start engine and run until full air pressure is reached. Listen for the dryer to purge (about 120 PSI). 3. Shut off the engine. 4. Release the parking brake by pushing in the yellow button (make sure you don't roll, and do NOT apply the brake pedal). 5. After the initial pressure drop, the system should not loose more than 2 PSI per minute. 6. Apply the brake pedal firmly (still with the parking brake OFF). 7. After the initial pressure drop, the system should not loose any more than 3 PSI per minute. 8. With the engine off, ignition on and parking brake off, rapidly pump the brake pedal to bleed down the air supply. During this stage you should watch for the warning light and buzzer at about 60 PSI and then the yellow button (parking brake) should pop out at about 30 PSI. 9. Restart the engine and build up air pressure again. While building up pressure, check how long it takes for pressure to go from 85 to 100 PSI at “cruising RPM”. It should be less than 45 seconds. Share this post Link to post Share on other sites
hermanmullins Report post Posted October 21, 2015 fabosworth, if you are messing around with any of your air lines be sure to have your wheels chocked. The more the better. And have heavy duty Jack Stands under the frame if you plan on getting under your coach. It's hard to dial 911 with your coach on your chest. BE SAFE. Herman Share this post Link to post Share on other sites
