Foretravel Owners' Forum For owners and Fans of Foretravel Motorcoaches September 11, 2025 ...

1. I could definitely hear a air leak coming from the right side as you look into the engine compartment.
2. While the engine is running air pressure is around 118 both front and rear - is this safe enough to drive with the leak?
3. I was unable to locate the wet tank for the air system - would it be close to the engine or in one of the basements?

1.On some of the Nimbus coaches they hid the air dryer on that side up behind the tag axle. It could be the purge valve has broken or has trash in it not letting it close. Or it could be a bad hose in that area.
2. Should be unless it gets worse.. How long has this been going on? 
3. The drain should be just in front of the left hand (drivers side) duel wheel hid under the fender skirt down real low. The tank its self is hid above the differential.

Mike

Here are my findings so far. 

I ran the engine and built up the pressure, shut down and went to the engine compartment.  I could definitely hear a air leak coming from the right side as you look into the engine compartment.    I sprayed soapy water but was unable to find an exact location, but there is a definite leak.  Within minutes both front and back air tanks bled down significantly.  While the engine is running air pressure is around 118 both front and rear - is this safe enough to drive with the leak?

I was unable to locate the wet tank for the air system - would it be close to the engine or in one of the basements?

If you mean to drive to a shop, yes but I would get it fixed right away. You Probably need to get under the coach but unless you
have suspension blocks don't go under. Did you open the engine battery door to find the leak.

That thing with the round black cap is your D2 governor.  If the air is coming out the exhaust port then the governor may be/is bad. They are about $25 If the governor was telling the compressor to pump and never shut down then the over pressure valve would be sounding off on the wet tank.

Mike

On edit: That (a governor) is one thing you need to have as a spare that travels with you all the time along with the end wrench that it takes to change it out. If you aren't mechanical inclined  find someone that will show you how to change it out as that is the heart of your air system. It isn't but 2 bolts and hose but important for you to be able to DIY

Leak seem to be coming from this (photo) 
Shared album - James Giordano - Google Photos

To answer a previous question:  Air is coming out of the wet tank when opened.

Only dry air?

No moisture., oil or white powder?

If so, that is GREAT!

Leak, plus, perhaps bad check valve.

I read or heard somewhere that the check valve should stop it at 60psi - is that correct

I read or heard somewhere that the check valve should stop it at 60psi - is that correct

Do you have a air system schematic for your coach?  If so, you need to study it so you understand the flow of air in the system.  Doing so makes it much easier to diagnose problems and narrow down the possible location of air leaks.

The diagram below is a good "generic" depiction of a air system on a coach with tag axle and slide(s).  It may not be exactly like your newer 2009 Nimbus, but it is probably similar.

If you boil the air system down to the basic components, you have the compressor, the dryer, the wet tank, and the 2 brake tanks.  Everything else is ancillary.  The dash pressure gauges read the brake tank pressures, because these are the most critical tanks.  They power the brakes.  The brakes save your butt.

Each brake tank has 2 "check" valves.  The inlet check valve keeps air pressure from escaping "backwards" in case of a big air leak UPSTREAM of the tank.  The protection valve is designed to retain a minimum of 60 psi in the brake tank in the event of a big air leak DOWNSTREAM of the tank.  60 psi is enough to provide braking so you can get the coach to a safe place to park.  It also is enough pressure to keep the emergency spring brakes from activating.  Hence the name "PROTECTION VALVE".  They protect you in a emergency.

If you start out with full pressure (120 psi) in your air system, and after a short time (one night) your dash air gauge shows pressure below 60 psi, then you could have a leak either upstream OR downstream of the brake tanks.  You don't know which check valve is malfunctioning.  The only way to further pin down the leak location is to replace the check valves.  Once you know both sets of check valves are holding THEN you can pursue hunting for the leaks.

Where is the Rear Air Tank located & best way to access it. 

Raise coach and block with safety stands
Slide under front end where ever is good for you
Set up with your back next to the front axle
Look up to the front of the coach
You will see the 2 matching tanks in front of you just behind the back of the generator
On our coach the rear is the one on the passengers side but yours may be different.

Mike

On our coach the rear is the one on the passengers side but yours may be different.

Expanding on Mike's directions, there is one sure way to ID which tank is "Front" and which is "Rear".  It does require that you have the air system diagram for your coach.

When you crawl under the coach, you will notice that most of the air lines in the vicinity of the brake tanks are marked with white tags.  The tags have numbers printed on them.  The tag numbers correspond to the air line ID numbers on the air system diagram.  By matching the numbers on the diagram to the actual air lines, you can positively determine which tank is which.

Note: You can't use the generic diagram I posted earlier for this ID method.  It is not specific to your coach.