Assistance Needed - Air Dryer Issues

[Neal E Weinmann]

2005 Beaver Monterey Bayview IV, 34'
Cat C9 400HP

Issue discovered when step cover locked out in the covered position. Found evidence of water spray at cover control valving in electrical bay on recent trip. On said trip, also found parking brake knob harder to pull when engaging it. Subsequently noted that the system pressure was operating near 150 psi.

Could not retract cover even after attempting adjustments and/or waiting. After dumping air via drains in service bay, (which had significant moisture exiting from the tank drains), I disconnected the cover from rod, removed cover, dismounted cylinder, loosened the connections to find the cylinder to be pressure locked by water. Once the pressure was released, the rod retracted back into the cylinder.

Coach is now parked and I'm wondering about the next step in diagnosing/servicing the air dryer. I cannot recall hearing the purge valve operating, am wondering if a clogged dryer desiccant canister would produce this water issue, or perhaps a inoperative governor allowed greater pressure and so produced greater moisture.

Finally, can anyone offer whether completely replacing the dryer assembly would be more cost effective than having the dryer assessed and repaired as necessary. Seems to me an R&R may be the most cost effective. I appreciate any advice/recommendations on the issue

[Joel Ashley]

Our Monterey is a year newer than yours, Neal;  18000 miles.  While Henderson's was doing a general service this fall, they determined we needed a new filter on the drier, although there were not yet any symptoms.  Labor was $125 and the filter was $77.  You were probably due for such "air drier clean and service", as Henderson's called it.

Joel

[Dale Walker]

Neal, considering the amount of water is apparent in the system, you have to assume the air dryer, isn't working. If your air pressure gauge is running at 150 lbs. it does not necessarily mean the governor is the problem. If the air dryer hasn't been serviced, I would replace it, that's what I did. I also changed the air governor, more as a precaution, because the governor makes the air dryer operate. Neither one was very expensive.

[Dave Atherton]

Neal, sounds like air governor is stuck, and safety valve on tank is working and dumping
air from air compressor at rated psi of 150 lbs. the air governor is easy to adjust where we
can walk you through process. All that is needed is short flat blade screwdriver and a 7/16
wrench. Use your foot brake and pump off air pressure than remove plastic cap on end of
air governor. Next step hold exposed thread sticking out with flat blade screwdriver than
loosen 7/16 nut ( backout nut 3 turns ) at this point note slot on threads and turn in C.W.
three turns and tighten lock nut. Start engine and note on air pressure gauge where you hear
air governor pop off. May have to adjust few times but bring pressure on air gauge 120 - 125
psi. of which is required with air systems DOT requirement ( correct pressures ).
Dave Atherton Retired Cat Mechanic

[Neal E Weinmann]

Thanks all. Will ponder this helpful guidance and plan my next move. On the face of what's suggested, for a start I think I'll get a service kit, replace the dessicant canister, adjust the governor, fire it up and see what happens. Will report back after I get these steps completed. Thanks again for the quick responses.

P.S. - Dale, did you replace the complete dryer assembly, or just the canister? Also, did you do that work and replace the governor yourself or have it done? If you did it yourself, was it as straightforward as it appears?

[Dave Atherton]

Neal, Just a thought if you choose on replacement of air governor be real sure and put correct
replacement back on. There are two kind of air governors that look the same except one is
preset and cannot be adjusted and the second on can be adjusted. I would suggest getting air governor from a Cat Dealer parts store. If you can give me your engine S/N number I can
pull up your engine arrangement number so you will get air governor for your engine. I can
Also give you your air governor part number also. Dave Atherton Retired Cat Mechanic

[Neal E Weinmann]

Thank you, Dave. My coach's engine serial # is 9DG02760. Please post the appropriate info and I will get the proper governor for my spares box.

Follow up for all - I have replaced the dessicant canister and dialed down the governor three turns as described. Happily, air pressure now builds to a reasonable 125 psi on both gauge needles, stops and maintains, however there does not appear to be a significant purge release from the dryer at the pressure acme. There is, however, the sound of a general low pressure air release in the dryer area while the engine is running but it gradually subsides in 15 seconds or so when the engine is shut off. Could not pinpoint the exact location of this air exhaust.

After the engine was shut off, the green needle remained at 125 while the red needle settled back at about 70 where it has remained. Have not yet checked the drains for moisture. So, with the engine running, the proper operating pressure range appears to be achieved. Further thoughts welcome. Thanks again to all commenters.

[Dave Atherton]

Neal, the following information.  Cat C-9   S/N 9DG-02760.  A/R 263-0690.  Air Governor
4N-9680.   Your engine build date  2004 -10-12,  Test date   2004 - 10 -13

Glad to be of help.  Dave Atherton Retired Cat Mechanic

[Dale Walker]

Neal, my air dryer wouldn't purge as it should, the dessicant cartridge had never been changed, so I replaced the canister, and it still wouldn't build air and so changed the governor. Still no joy, so decided to change the dryer it self. I now works as it's supposed to, and I did all the work, not a big deal. I did have some fittings that tried to give me a problem, but other than that, not at all hard. The governor on the Beaver, was mounted on the back rail in the engine compartment, very handy, air dryer is mounted on the same rail, in the back corner of the coach. I changed the governor on my '99 Discovery, too. That one wasn't quite as simple, it was mounted on the compressor under the coach. The Beaver was a walk in the park compared to that one.

[Dave Atherton]

Gentleman, the air dryer needs addressed as per your maintance manual. Dale in your case
The purge valve on bottom is stuck open and will not allow system to builds air. If this happens
when traveling ( and happens  quite often ). You can do a simple repair by by-passing the
air-dryer, by just connecting the feed hose from air compressor to the air dryer discharge hose.
All you need is one fitting should be for 5/8 hose or 1/2 hose off air dryer. You can tell when
it is time for filter replacement the purge pop off valve will keep cycle every 20 seconds or less.
I would suggest putting the air fitting in your spare parts box. Again all that needs to be removed
Intake hose to air dryer and discharge hose and connect together, you do not touch any other lines.
Dave Atherton Retired Cat Mechanic

[Dale Walker]

Thanks, Dave. I did figure that out when I replaced the dryer. They had a kit to rebuild the original dryer, but in the process of removing the old one I twisted a bolt off in one of the ears of the dryer, (the bolts are threaded into the base), as you know. Trying to get that bolt out was going to be more time consuming than to just replace the whole thing, it was not really that expensive anyway.