Well, after having the air pressure governor replaced last Saturday, the coach ran fine without any issues until yesterday. The guy that was cleaning my tanks called to say it wouldn't shift into gear. I went out and started it up and a couple of minutes later, I had good pressure and we moved it to where he could work on it. It seemed a bit slow to build up. We are scheduled to leave in the morning so I figured I'd turn it around now so I wouldn't wake the neighbors at 5:30AM when we leave. No luck, I let it run and the pressure remains constant around 75 PSI. I shut it off and started it back up, no change.

I have called A-1 Mobile Service, they replaced the governor last week and I feel when he aired up the tank manually, it masked the problem by taking awhile to leak back down.

A-1 will be out again in the morning and mentioned by-passing the dryer. Personally, I'd like it replaced if it is causing problems. Can anyone tell me where the dryer is located on a 1990 38' Regnecy w/ a 32008TA diesel pusher. The air leak is coming from the tanks in front of the right front tire. I was not able to find out specifically where it is coming from but I can certainly hear it.

Get a spray bottle and fill it with soapy water and start spraying your air lines and fittings to find the leak. If you can hear it, it doesn't take long to lose pressure. I just fixed 2 leaks on my bus that i could hear and it slowed down the air loss but i am still losing air somewhere.....only problem now is i can't hear air leaking anywhere.

The air dryer is controlled by the air gov. If the air dryer backfeeds up the unloader port it will give you the symptoms of a bad gov.

Whenever I diagnose a defective gov I also pinch the unloader line to see if that is the problem. Pinching off the gov unloader line will tell you if it's back feeding or not.

Bypassing a dryer is not that big of a deal this time of the year. If he does bypass it to get you going then take it. Ask him to order up a replacement air dryer or to get a rebuild kit.

When I replace a defective dryer I always recommend a replacement gov... it's cheap insurance.

Replacing an air gov should be straight forward. Unless the unloader port on the air dryer is slightly sticking I can't see him making a mistake about a bad gov really being a bad air dryer. But, it's possible, I wasn't there.

As far as him putting air to the system and it holding all that time while you were driving around... Well, it's just not possible! You consume air with your brakes, vacuum pump, air ride and normal leakage.

Well, it turned out to be a free repair. The windshield wiper knob was not completely in the off position, this resulted in an air leak. After playing with the switch, the leak stopped and pressure began building. The wiper knobs can apparently turn on due to vibration. I'm not sure if this means I need new wiper motors or not but at least the coach is ready to roll. Thanks, Bill

quote:

Originally posted by towerguy:
The air leak is coming from the tanks in front of the right front tire. I was not able to find out specifically where it is coming from but I can certainly hear it.

The wiper knob made air noises near the right front tire?

Mike

The tanks are located there and it sounded like that was where it was coming from. It also sounded like it was coming from above the genset when standing in front. The issue came up again today so I turned the right wiper on slightly, the leak stopped and the pressure came up pretty quick. I still think there might be an issue somewhere else, we'll see.

a little off topic, but close...like to rebuild air dryer but have been told its probably easier and not much more money to just replace the whole unit. Any thoughts out there from someone whos been there/done that?

I replaced the decadent and filter element in my dryer just after the purchase to chase down a slow air build, turned out it was a broken hose from the pump to the dryer.

I think it was fairly expense IIRC around US$80 for the pieces, didn't price the complete dryer but it wasn't hard replace the elements. Lots of nuts and a couple of "O" rings to watch and have to make sure you get the right replacement element/parts. I took the unit out and to the shop so they could match it up.

During the problems I had with low air pressure, I found a little tidbit that might come in handy for others in the future. When the air pressure was too low, I was unable to help it along by raising the RPM since the accelerator pedal is also controlled by air pressure. One way to override this problem is to turn the crusie control on, press "set" and then press "resume." Once the engine is properly warmed up, this part of the crusie feature will rev the engine up to about 1500 RPM. If you press resume more than once, it will raise the RPM up in 500 RPM increments so don't get carried away or you're likely to upset people camping around you. I found this out when I didn't think this cruise feature was doing anything and pressed resume several times. I walked outside to secure the basement doors and the RPM suddenly began to climb, leveling off at 3000 RPM. I am guessing it did this because the engine wasn't yet to operating temperature but "stored" the number of times I pushed resume into it's memory. I was quite surprised to see a feature like this on a 1990 motorhoem but very happy it is there. If I am getting the procedure wrong, please correct me so others can get it right.

If you are somehow raising the rpm's of a diesel engine to 3,000 I would be very concerned, as they are not designed to do that. My manuals say the operating limits of a Cat 3208 are about 2400 rpm under full load. Might check with a Cat Dealer for information.
Good luck.

Luckily I caught it, the engine started accelerating as I was coming through the door and I shut off the cruise as it was climbing in RPM's. I have also been told that the engine (computer?) will not allow it to over rev. As far as RPM, I have been wondering what the red line is since the red line goes all the way around the dial. Maybe my tach is not accurate but it routinely goes above 2400 when accelerating or climbing a hill under full load.

"...it routinely goes above 2400 when accelerating or climbing a hill under full load."

Being a fiscal conservative (as well as other types) I'd be very nervous if my diesel engine did that; especially if I induced it to rev that high, regardless of "load".

There is something called diesel runaway that can occur under certain conditions, not by making the cruise open the throttle more it wouldn't appear.
It does however highlight the fact a diesel motor can be very difficult to shutdown and can "over rev" itself to destruction and more.
This website http://www.amotusa.com/Z_Dead%20Datasheets/4261.asp is worth a read and gives a little chart on various rpm ranges and their possible consequences. I know very little about diesels other than the basics, but try to pass along anything that might help me or someone else avoid problems.
The thing that really puzzled and concerned me was that a cruise control was changing the throttle without the vehicle being underway. I have never had a vehicle that would do that, cruise controls I thought were designed to disengage and not function under a certain roadspeed like around 25mph.
The fact that you are able to operate the cruise with the vehicle parked is very alarming, suppose for example you accidentally engaged the transmission with the engine spinning at 3000rpm and the coach connected to shore power, sewer etc. Maybe this isn't possible, I don't know that much but it would worry me.
I remember the day I was eating a sandwich at the summit of highway 17 between San Jose and Santa Cruz CA and a gas truck eased to a stop across the highway, the driver hopped out and came across to get a sandwich, the truck idling across the highway, somehow "dropped into gear" and "idled" down about a hundred fifty foot embankment, rolled on its side and burst into flames, the diesel engine just kept running, wheels spinning, tires burning, flinging the burning rubber into surrounding brush, thankfully the tanker portion stayed in tact, but it took several air tankers and fifty or more firefighters to gain control over the fire that engulfed the top of the mountain for several hours.

This feature of the cruise control is for maint. From what I understand, it will not allow the transmission to engage, I did not feel it wise to check and see if that were true. It apparently will not allow the engine to over rev either, something else I don't care to check.

It sounds similur to our king cruise control. we had ours installed shortly after we bought the Barth and love it. We can turn the cruise on and bump the switch and it will lock on idle. bumping up will increace rpm in increments as you describe. I usually set mine at 1000 for a few when warming up and bulding air pressure after sitting. I don't reccommend this but my accelerator cable froze up a couple winters ago and i couldn't move the pedal. (non air controlled) I started the coach turned on the cruise and by bumping the rpms up and hitting the coast/accel lever i drove ours 17 miles to a repair facility where i was scheduled for other work. They drove it inside same way, warmed it up and it was fixed.
An aside on rpms is that the DD 8.2 is designed to max at about 3400 in drive. 62/64 mph is running about 2750 rpms. I don't know of other deisels that are designed to rev that high.