10-23-2019, 07:21 AM
I finally made it to Newell and got some time to look into this.
Here are the things I observed over the summer:
1) Stuck on side of road, one of the air lines coming out of the distribution manifold (what Newell calls the "air dryer", although I think really it is more like a governor + distribution + air dryer assembly) blows out at its fitting. Replaced that line and drove on.
2) Stuck on side of road again three days later, female coupler at shop air inlet ruined (gasket/spring mechanism mangled inside the fitting) and air blowing straight out of it at full bore. Replaced with new fitting and drove on.
3) Intermittent issues when pulling into a campground and getting ready to level: seal deflation ran out of air many times, no supply air being produced. Went back to manifold and safety pop-off valve was stuck open. Pushed valve back in and pressure builds again. I think that safety valve is designed to stay open when it pops.
4) Intermittent issue with air hissing under front when underway, usually five minutes into a drive at a stop light or something. This is definitely the height control trying to release air, but for some reason it "releases" air for five or seven minutes before stopping, instead of 5 or 7 seconds. The coach never got out of proper travel height.
5) When we drive, we hear constant pop-pop-popping from the rear.
6) When we come to a stop and shut down the engine, there is a blow off of air in the engine area that lasts 15-60 seconds every time.
When we got to Newell this week, immediately they noticed that the 1/4-inch air line between the governor and the air compressor was blown off the compressor fitting and just hanging around loose in the engine compartment.
They checked a few things and noticed that the compressor was running constantly rather than just until the tanks were full. (That's #5 above.)
Newell decided to swap the entire dryer/manifold/governor assembly with a new one ($600). This new piece did nothing to change the behavior, so they backed it out and put my old one back in.
Newell called CAT and someone there told them to replace the whole air compressor ($1600). I actually went to Joplin to pick up this part, and I talked to one of the techs there. He said that these compressors rarely fail, and that the problem is probably elsewhere.
The first thing he suggested was to put a fresh 1/4" air line into the control port on the compressor and then pressurize it with a standalone tank or compressor, to test to see if the airflow into that line shuts the compressor off. We did that, and indeed the compressor just kept pumping.
The next thing we did is to replace the unloader valve. This is the exact same thing that Dave did above. The unloader valve kit is what you need, about $100. If you have a CAT engine, it is the same kit for all the engines and air compressors that they ever made or installed, so it's pretty easy to source.
The new unloader valve took about 10 minutes to install, and all the problems went away.
Except the height control related issue (#4 above), which we haven't had an opportunity to test yet. I'm not quite sure how the problem in the rear could induce this problem, but I guess my flimsy theory is that the overpressure in the lines was somehow preventing the raise solenoid from fully closing. Because this problem requires driving and is intermittent, it'll take a while to know whether it was also a symptom of the failed unloader valve.
Easy peasy! Except for the driving back and forth to Joplin, intermediating the conversation with CAT, and keeping Newell from throwing $1500 parts at the problem.
Here are the things I observed over the summer:
1) Stuck on side of road, one of the air lines coming out of the distribution manifold (what Newell calls the "air dryer", although I think really it is more like a governor + distribution + air dryer assembly) blows out at its fitting. Replaced that line and drove on.
2) Stuck on side of road again three days later, female coupler at shop air inlet ruined (gasket/spring mechanism mangled inside the fitting) and air blowing straight out of it at full bore. Replaced with new fitting and drove on.
3) Intermittent issues when pulling into a campground and getting ready to level: seal deflation ran out of air many times, no supply air being produced. Went back to manifold and safety pop-off valve was stuck open. Pushed valve back in and pressure builds again. I think that safety valve is designed to stay open when it pops.
4) Intermittent issue with air hissing under front when underway, usually five minutes into a drive at a stop light or something. This is definitely the height control trying to release air, but for some reason it "releases" air for five or seven minutes before stopping, instead of 5 or 7 seconds. The coach never got out of proper travel height.
5) When we drive, we hear constant pop-pop-popping from the rear.
6) When we come to a stop and shut down the engine, there is a blow off of air in the engine area that lasts 15-60 seconds every time.
When we got to Newell this week, immediately they noticed that the 1/4-inch air line between the governor and the air compressor was blown off the compressor fitting and just hanging around loose in the engine compartment.
They checked a few things and noticed that the compressor was running constantly rather than just until the tanks were full. (That's #5 above.)
Newell decided to swap the entire dryer/manifold/governor assembly with a new one ($600). This new piece did nothing to change the behavior, so they backed it out and put my old one back in.
Newell called CAT and someone there told them to replace the whole air compressor ($1600). I actually went to Joplin to pick up this part, and I talked to one of the techs there. He said that these compressors rarely fail, and that the problem is probably elsewhere.
The first thing he suggested was to put a fresh 1/4" air line into the control port on the compressor and then pressurize it with a standalone tank or compressor, to test to see if the airflow into that line shuts the compressor off. We did that, and indeed the compressor just kept pumping.
The next thing we did is to replace the unloader valve. This is the exact same thing that Dave did above. The unloader valve kit is what you need, about $100. If you have a CAT engine, it is the same kit for all the engines and air compressors that they ever made or installed, so it's pretty easy to source.
The new unloader valve took about 10 minutes to install, and all the problems went away.
Except the height control related issue (#4 above), which we haven't had an opportunity to test yet. I'm not quite sure how the problem in the rear could induce this problem, but I guess my flimsy theory is that the overpressure in the lines was somehow preventing the raise solenoid from fully closing. Because this problem requires driving and is intermittent, it'll take a while to know whether it was also a symptom of the failed unloader valve.
Easy peasy! Except for the driving back and forth to Joplin, intermediating the conversation with CAT, and keeping Newell from throwing $1500 parts at the problem.
2008 Newell #1234
Boulder, CO