Excessive air pressure build up/brakes/air ride

[Hotrod2526]

Hello ,

need a little help. 2003 phaeton 330 cat, on our way back from Cali ( live in michigan) i noticed that both air psi gauges would go to about 145/150 psi. on accel only i would hear a hissing noise coming from up front between the seats. ( it is throttle related) looking under the coach this is where the 2 air tanks sit along with the valves. so something is releasing the excessive air build up at 150 psi.
so the question is what controls the air psi and thoughts on failed part?

i never had any issues with air ride and or brakes but i know it to much. looking under the coach i cant see any witness marks from any air escaping

Hotrod

[Finance]

Probably the governor that regulates the air compressor is stuck on. Excess pressure will pop open the safety overpressure relief valve.

[twinboat]

The governor controls the air pressure.

It gets its air signal from an air tank thru a thin, 1/4 line. If that line is leaking, the governor will not work. It could be hard to hear because the small tank it connects to will drain quickly and has no gauge.

You need to get the pressure up, shut down the engine, and quickly listen for any leak before the tank drains.

If the line is good, then you should change the governor. They are adjustable but when they go way off, its broken inside or jambed up. Replace it for $30.

Here is a picture of it. The second picture is it mounted to a Cat engine, air compressor.

[Hotrod2526]

Thanks for the reply's! Twinboat thanks for the pic. i will check it out

Hotrod

[ladagobago]

It might be tight quarters to replace it. Also be sure to check on the exact part number. I found mine to be a little more than 30 and was 50. Also had a hard time removing the one of the two bolts that attach it to the compressor. Was corroded inside the governor. Be sure to mark the two small lines which connect to it also. you don't want to mix them up. I had to remove a trans cooler line to the radiator to get access. The bolts use an allen head tool. also toque to the spec when installing and I used never seize to help in the future.
Be sure to clean the surfaces and install new gaskets.

You may have to transfer some of the plugs on the governor. pay particular attention to which holes are used and which are plugged when installing the new device.

[Hotrod2526]

ok fellas

Michigan weather finally gave us a short break and took the coach for propane fill up and we still have an issue.

i replaced the governor with a OE replacement, at idle i would say its about 130lbs. but driving goes up to 145-150ish how are they adjustable ?

but my original problem still is there once it reaches 150 the safety valve opens up and dumps some air. this only happens on acceleration coasting does not do it.

any other thoughts?

[jacwjames]

Yes, the governor should be adjustable. What was the make/model of the one you installed???

[twinboat]

Governor is not working.

Since you replaced it, that's not the problem and probably wasn't when you changed it.

There is a small line, 1/4", that comes from the wet tank ( first tank that gets air ) and goes to the governor.

If that line is leaking, ( you won't hear it with engine running and it will drain the tank and stop before you get back there to hear it ), the pressure will not get to the governor and tell it to lift the valves and stop the compressor from pumping.

You may not hear the safety valve blowing off, while coasting, because the compressor is turning slower, like the engine. The leak in the line is bleeding off the pressure before it gets to high.

Once you raise the RPMs, the compressor overcomes the leak and again over pressurise the tank and safety valve.

Using it as is, is just overstressing the compressor and air system.

Time to hand it over to the pros.

[Hotrod2526]

Twinboat ,

thanks, has anybody ever used a smoke machine and tee'd it in? (im thinking evap. system repair) this would certainly speed finding the leak.

im not ready to open my wallet to the Pro's

last question, where would one find a schematic for this system?

[cataska]

Easy way to find air leak spray down lines and fittings with soapy water look for bubbles.

[twinboat]

Find the small line from the air tank to the governor. If you can't touch it to feel for holes, remove it and inspect.

Next is the small line from the governor to the air dryer. Follow it and feel for holes. Disconnect from air dryer, plug line and test.

Last, IF the governor is NOT mounted on the compressor, there will be a small line between it and the compressor, same treatment, feel for leaks.

You could try to get the system pressure up, quickly shut engine down, run to rear and listen for a leaks near compressor.

[Hotrod2526]

Good evening,

Just to follow up on this issue, how I choose to find the leak , I disconnected both sides of the air line from the dryer to the governor. Plugged one end and used my hand pump tool to create a vacuum and watch the gauge , needless to say I didnt have to watch any gauge because the leak was big, apparently since it wouldn't even pull vacuum. Instead of looking for the leak I just routed new line.

Works like a champ now.while I was it I also pulled a full maintenance on the dryer unit.

Thanks to those that chimed in appreciate it.

Hotrod

[Revconguy]

Glad everything is fixed. Just thinking out-loud..... I'm wondering if he could have pressurized the system using the schrader valve that is supposed to be on the bottom of the air dryer and then inspect for a leak? One could put a 100psi of pressure in using a external air compressor and then look for leaks audibly or with a soap solution (bubbles).

Just thinking out the problem for future reference in case I ever have similar issues.....

[ladagobago]

Originally Posted by Hotrod2526

Good evening,

Works like a champ now.while I was it I also pulled a full maintenance on the dryer unit.

Thanks to those that chimed in appreciate it.

Hotrod

Glad you found that problem and good that you serviced the dyer too.