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Topic: Likely air leak locations  (Read 3720 times) previous topic - next topic

Re: Likely air leak locations

Reply #20 –
Quote from: The Soft Boulders –
  I also noticed for the first time that there are two needles on our air gauge.  The white needle is perfectly aligned with the red as to make it nearly invisible.  I'm not sure if the gauge is broken or if something else is going on but the two have never separated since we've had it. 

One needle is for the front air tank pressure and the other is for the rear air tank pressure. It isn't broken as the 2 needles work on separate air feed lines.

Mike

Re: Likely air leak locations

Reply #21 –
Quote from: The Soft Boulders –
The white needle is perfectly aligned with the red as to make it nearly invisible.  I'm not sure if the gauge is broken or if something else is going on but the two have never separated since we've had it.
Tyler,

The double needle air gauge is common to the older GVs.  As Mike says, two separate air lines to the back of the gauge.  One needle shows "front" air tank pressure - other needle shows "rear" air tank pressure.  Both of these tanks, despite confusing names, are located under the nose of your coach behind the front bumper.  On my coach, the red needle = front tank, and white = rear tank.

Although it is possible that both needles are always showing exactly the same pressure, I would say this is very unusual.  Personally, I would like to verify the fact that both needles are, in fact, registering actual tank pressure.  This can be done with a fairly easy test, but of course first you need to get your air system to the point that it will hold pressure for a reasonable amount of time (like overnight).

When you are ready to try it, see my next post for the test procedure.

Re: Likely air leak locations

Reply #22 –
Testing components of the coach air system can be fairly simple.  To do so, it is most helpful to have the air system schematic for your coach.  Without it, working on the system is very difficult.  Try this test to check some of the important parts of system.

1.  Run engine until air compressor cut-out pressure is achieved.  Shut off engine.  The entire air system is now at the same pressure.

2.  Check (record) the reading on both dash air pressure gauges (or both needles, if single dash gauge).

3.  Open the water drain valve on the WET tank (see air system schematic), and allow pressure to bleed off to zero.
    3a.  What came out of drain valve?  Dry air is good.  Water, or oily grey "mud", or dry white powder is not so good.  Time to service dryer.

4.  Check (record) the reading on both dash air pressure gauges (needles).

5.  If both dash gauges read the same pressure in step #2 and step #4, then the inlet check valves on the respective tanks are good.
    Clarification: With "good" check valves, the "front" and "rear" air tanks should not lose any pressure when you drain the wet tank.

6.  If either, or both, of the dash gauges lost pressure between step #2 and step #4, the inlet check valve on the respective tank is bad, and should be rebuilt or replaced.

7.  Locate your FRONT air tank (see air system schematic), open water drain valve, bleed off pressure to zero.  (See note 3a above)

8.  Check dash air gauge(s).  One gauge(needle) should now show zero pressure - this is your FRONT tank gauge.  Other should still read the same as step 4.

9.  Locate your REAR air tank (see air system schematic), open water drain valve, bleed off pressure to zero.  (See note 3a above)

10.  The remaining dash gauge (needle) should now show zero.  This is your REAR tank gauge.

Re: Likely air leak locations

Reply #23 –
I found the schematic and parts list with the treadle valve on it. 

Re: Likely air leak locations

Reply #24 –
That air diagram is very helpful.  See the numbers on the air lines?  There are paper labels taped to all the OEM air lines - use them to help you find and identify the other valves and components.  The physical location of things on the coach do not necessarily correspond to the position on the diagram, but you can get in the ballpark by tracing the air lines.

Re: Likely air leak locations

Reply #25 –
From my limited knowledge of air systems, it is not recommended to open drain valves at full pressure.  Maybe it is OK to do that once in a while, but should not be a regular thing as I understand it.  This can erode the seat of the valve and make things worse.  Some thing to consider.  Have a great day  ----  Fritz

Re: Likely air leak locations

Reply #26 –
i found a leak in my parking brake switch and one that i chased forever was an air chamber diaphragm

Re: Likely air leak locations

Reply #27 –
Ok, I found two major leaks and a few not so major leaks.  I'm not sure exactly what I'm looking at but do have a couple pictures so maybe someone can help me out.  Both of the low pressure switches connect under the brake pedal are steadily leaking.  That's the not so major leak.  One of the major leaks is coming from what appears to be an air pressure regulator and associated electronic control box located under our entryway stairs.  Both the controller and regulator are leaking pretty severely.  I'm not sure what it's regulating but I did notice that if it set on say 80 psi it will purge air until the tanks read 80 psi and then it stops purging.  It still leaks around the body though.  The second sever leak is coming from a valve body that is bolted to the (I'm assuming) the ecm for the throttle.  It has an inlet and outlet controlled by two solenoids.  It appears to be the solenoids that are leaking.  I removed the assembly and Googled the number on the back with no luck.  Does anyone know what these things are and maybe how they function?

Re: Likely air leak locations

Reply #28 –
Forgot to add pictures, sorry.

Re: Likely air leak locations

Reply #29 –
Let me see if I can help.

The pressure switches under the brake control valve might just need to be tightened up (the fittings).  If not, then they can probably be replaced fairly easily.  You would have to remove them and see if there is any ID number on them, then do a Google search for a suitable substitute.

The thing under the stairs is a control valve that directs the air pressure going to the step cylinders.  The regulator reduces the coach system air to a lower value (60-80 psi) suitable for use in operating the cylinders.  You can remove the whole control assembly and take it apart.  Might be able to clean it up - possibly replace some O-rings, and return it to service.  If it can't be repaired, then you can buy replacement units online.  Again, helps to have a part number when you go hunting.  There is some info in the threads linked below that might be helpful.

GV Entry Step Actuating Cylinder

GV (Unihome) Air Step Mod

The last one is gonna be tough.  Parts for the old Bendix cruise control assembly are like hens teeth - rumored to exist, but virtually impossible to source.  Again, if it is the solenoids leaking, it might be possible to solve that with O-rings.  You have to take them apart and see what you find.  Here is a reference manual for the Bendix unit.  Will help you figure out how it works.  Also, a "corrected" diagram of the cruise control system, showing the additional parts and lines used on our coaches to add the air throttle function.

Re: Likely air leak locations

Reply #31 –
An SOB here in the park has an extended warranty (aftermarket).  The left rear of the coach is lower than the other three coners lately (airbags) so the owner took it to a dealership for warranty work.  When he picked it up the next day they presented him with a bill for $900.00,  told him the extended warranty only covered labor, not diagnosis and they had found nothing leaking.

Re: Likely air leak locations

Reply #32 –
Quote from: Travelin' Man –
When he picked it up the next day they presented him with a bill for $900.00,  told him the extended warranty only covered labor, not diagnosis and they had found nothing leaking.
Wonder if they provided complimentary Super Lube when they "presented" him the bill. 

Re: Likely air leak locations

Reply #33 –
Ok, I did a little more investigating and what I found is that vent no. 5 is leaking when the step is down, the step cylinder around the polished rod is leaking when the step is up and the electronic end of the distribution block is leaking at all times.  I am going to forgo the attempted repair of any of those issues and instead try to install an inline shutoff valve on the air inlet just before the pressure regulator.  I will let everyone know if it works.  It also appears that someone has done installed a toggle switch in the bay to control the up and down of the step from there.  There is another one below the dash to the right of the steering column that also has something to do with the step, but it doesn't seem to do anything. 

Re: Likely air leak locations

Reply #35 –
Tyler. I and a couple of others have done that idea of adding a solenoid valve to the  valve body so when the step is either up or down depending on what you want you just flip a switch on dash and the air is terminated and no more air is lost. I found a great amount of air was bypassing the O ring in main cylinder for step cover and the cylinder could not be taken apart so I left it in and stop any loss of air while driving and this works good. In Beamalarm under Modifications you will see a write up of this and pics..  There is also one on how to wire in a switch to keep the step up when parked, simple wiring job.
JohnH

Re: Likely air leak locations

Reply #36 –
One leak fixed!  It may not be a glamorous fix but it is simple, reliable and effective!  The best part is that there's no electronic wizardry involved and in my book I call that a double win!  Sure it's not as convenient as a switch on the dash but I'm quite capable of bending down and turning a lever by hand.  Now to try and figure out the solenoids in the back.

Re: Likely air leak locations

Reply #37 –
One little suggestion: instead of teflon tape, the smart kids on this Forum recommend using pipe sealing paste when working on the air system.  There is less likelihood of a small bit breaking loose and getting stuck in a valve seat somewhere downstream from your repair.

I've had good results with the product linked below - there are others.  Available in most auto parts stores.  One small tube will last for years.

Permatex® High Temperature Thread Sealant - Permatex

Re: Likely air leak locations

Reply #38 –
We had bottles of that stuff laying around when I was building natural gas skids.  I'll have to get some for the next project.

Re: Likely air leak locations

Reply #39 –
It's been a little over 3 hours and we still have 40psi on the dash!  We're making progress haha!