Air leak, what is normal

[Chuck]

I have had my 2003 VNL 610 for approximately 3 weeks. Been going through as many of the systems as I can to learn. Prior to purchase, I had a DOT and pre purchase inspection. What is normal in regards to air leak down. I hear no air leaks, however, the system looses all air over night. The air bags are all soft in the morning. Upon start up, the compressor builds up to 90 pounds in approximately 1 minute and stops beeping at 90 pounds. Is this over night leak down normal.?

[Alie&Jim's Carrilite]

You do have some leaks.  Check the pass-thru under the dash by your left foot.  Need to remove the kick panel to get to it.  The O-rings are easily replaceable.

[Hewhoknowslittle]

 Overnight is not uncommon for an older truck to lose its air. What did your gauges read?

i worked on my 99 Volvo and got it to hold more than 75 lbs after 3 days. My Freightliner will hold better than 100 lbs for weeks. 

 

[Chuck]

Haven't started since yesterday. One tank reads 0, the other reads about 10.

[NeverEasy]

If you can't get hold of a Whisper leak detector, go to Wally World and buy a two-quart bottle of kid's bubble maker.  Get a sprayer and start looking.  Just spray all the connections you can find.  Some leaks bubble right away.  Others will look like they are growing fur in 2 or 3 minutes.  If the air springs (rear and cab) look cracked/checked then spray them and wait a few minutes.  My biggest leak was on the side of the transmission.  Other leaks were under the dash where there is a tee fitting for the air lines from the tanks to feed the dash air gauges.  Be careful spraying a lot of bubble solution under there.  It might run down the wires to the throttle position sensor (connected to the foot throttle pedal) and ruin it.  Had to buy the whole throttle assembly.  Not cheap.

If you are going to the National HDT Rally, a couple of us will have Whispers to look for leaks.

I have been successful at finding my leaks.  Came home from the WCR on June 27th.  Started it last week (about July 29th) and it was still holding enough air that the air alarms did not sound (over 90 psi). 

 

[Chuck]

Kind of a side note. You mentioned your transmission. I have a gen 2 Eaton 3 pedal. Having intermittent issues with locking in gear. I thoroughly cleaned all connection in the battery compartment. Have not driven yet to test further. My next step is to have all harness connections cleaned. Is air a component of this transmission.?

[NeverEasy]

Yes.  I have the same tranny.  Air comes into the left side, close to the top.  Closer to the back than front.  Look for an airline that runs over from the frame on the left side.

 

 

[jenandjon]

If its going down overnight its not a big deal. I have had brand new trucks that go down over a few hours and old pieces of junk that would hold for 2 days. As long as you can walk up to the truck and not hear a air leak thats good enough for me. I believe that is what DOT requires. No audible air leaks.  You will drive yourself crazy chasing every single little tiny air leak. Once you do find and stop them all you will hit a pot hole and one will come back.

[hone eagle]

mine holds air for 3 days in summer and 1 day in winter - go figure.worst leak I ever found was passenger side seat.

[solo318]

If the bags are going down over night than that is the first place you should look. Spray the bags down and the leveling valve. The bags should actually hold air even if the tanks are empty.  The next really common problem is the o rings as was mentioned earlier. After that (on a first gen vnl) check the trolley valve. they bypass and tend to leak out the vent tube under the hood.

[beemergary]

My 1984 Pete will hold air for a week. The suspension a coup;e months and the seats the same. If the suspension is down and tanks are down you have a leak from the air leveler too the bags. Kids bubbles in a spray bottle worls great for finding leaks.