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

It is fixed now!

Short version:

Changed to a known good D2 governor and everything is working.

Long version:

So I was trying to fix the issue of AD9 not purging and air pressure keep rising over 140 PSI.
The compressor model no. is Bendix TU-FLOW 501
I tried @Andy 2 post. I couldn't find the any missing nut on the opposite side of the D2 governor right below the alternator. Apparently D2 governor can be installed on both side of the compressor. This side has a nut to fill the hole and it seems just fine.

I really not want to go through what @coastprt suggested. Losing 2 gallon of the coolant, taking the head off. Just too much for my wrenching capability. I want to rule out other possibility before going this road.

First I followed what @Chuck & Jeannie suggested, adding a pressure gauge to one of the port of the Reservoir (1/8 pipe thread). The gauge is showing around 75 PSI when front gauge shows about 120 PSI. That is certainly not right. Without enough pressure, D2 governor won't work. So I took the fitting off the governor and directly connect the gauge to the hose from the reservoir. and I still got about 75 PSI. So the issue is between the hose to the wet tank. Looking into the fitting, I can see there are some rust are blocking the hose. While under pressure, I used a small needle to clean up the hose and decent amount of the rust was blown out. But the pressure gauge was still showing 75 PSI even if the front gauge shows 120PSI. There has to be something down the hose.

So went under the bus to check the wet tank. There is a Tee fitting which connects the hose to governor and a safety valve (Bendix 284142 1/4 NPT). I was trying to take the Tee off the tank, but it was seized really bad. and the male brass fitting was broken into half. It was a major challenge to get the broken fitting out. Luckily, I have this tool

With the help of certain words, I was able to get the broken piece out.

Connecting the safety valve to portable air compressor, it is leaking pretty bad. Connecting to the pressure gauge and 75 PSI even if the tank has over 100 PSI. So that might be the issue! I was super excited and quickly installed everything back, Only to learn that the issue is still there. But the good news is that the pressure gauge shows over 100 PSI now instead of just 75 PSI. Also I know for sure the Air dryer is working fine by directly applying 100PSI pressure to the control line to the dryer. good news.

I bought two D2 governor, one is Torque air governor, the other one is Bendix OR275491X Torque air arrives earlier than the Bendix, so I replaced the one I bough 1 year ago from Napa with the Torque air. I never thought the D2 governor is the cause of the issue. Old one is only 1 year old, new one just bought. But none of these two governor works.



Without knowing exactly how the D2 governor works, I applied 120 PSI air to the reservoir port. I can see the piston moving, but no pressure from the unloader valve. I initially thought it is normal. as the two governor tested the same. How likely 1 year old governor and new governor both failed at the same time? Well, I am the lucky one. Recently I received the Bendix Reman governor and I apply pressure to the reservoir port, there is air come out the unloader/control port. And now everything make sense. The D2 governor is so simple. When reservior reach over 120 PSI, the piston will move and deliver the air pressure to the control/unloader port. The air pressure will then trigger the air dryer purge and compressor unload. Install the new Bendix governor, and I finally heard the purging sound. It never sounds so good! Air pressure also never exceed 120PSI.  All works now!

So the moral of the story is to use name brand part. Had the Bendix governor arrives earlier than the Torque air, I probably won't need to go through all this hassle. Well lesson learned. next time will just buy parts from name brand.