Skip to main content ↑ ↓
Topic: Compressor for air brakes in 1995 U300 (Read 1353 times) previous topic - next topic

Re: Compressor for air brakes in 1995 U300

Reply #25 –
Quote from: Rocky1down –
We tried pressing the brake with the engine off. The gauge just kept dropping. No leak was heard by the drivers front tire.
Tried holding the brake with it running. It dropped down to 55 and the alarm for leveling sounded.
Just idling with the brakes not on, it stays at 108.

Rocky1down wrote: "No leak was heard by the drivers front tire."

I write, this was in response to a comment from texhub, a forum member also tracing down air leaks.

Quote
Quote from: Texhub  -  A day ago

    On my U270. Holding pedal down I have sound of air escaping to my left.

Rocky1down also wrote: "Tried holding the brake with it running. It dropped down to 55 and the alarm for leveling sounded.
Just idling with the brakes not on, it stays at 108."

Pierce and Gaylie Stewart told you what to do but not the reason why.  At each wheel is a rubber diaphragm'd brake canister that applies force to the brake mechanism for that wheel.  These brake cans are the most common failure point for loss of air incidents in an air brake system.  Second in my humble opinion is the D2 Governor on the engine driven air compressor.  The D2 is the pressure regulator for the air compressor and also controls the purge cycle of the air dryer.

So when you do your morning brake system test, the part where you turn off the engine and apply and hold the brakes to see if the air pressure falls, the four corners are where you listen first.

FWIW, for what it's worth, the cans on the rear wheel brakes are double cans one of which contains a heavy spring to apply the rear brakes in case of air pressure failure. If this one fails there is a special bolt used to compress the spring.  The Tee shaped bolt can break free with some force if not properly applied.

Art
1992 Foretravel Grand Villa
U225 SBID Build No. 4134
1986 Rockwood Driftwood
1968 S.I.A.T.A. Spring
1962 Studebaker Lark
1986 Honda VF700C
1983 Honda VF750C
Charlie, the Dog was broken out of jail 24 Oct 2023
N1RPN
AA1OH (H)e who must be obeyed.

Re: Compressor for air brakes in 1995 U300

Reply #26 –
Trying to sort out this type of problem long distance is very difficult.  Especially when we start talking to two different members in the same thread.  Big confusion can result.

That said, when any member is having a "rapid loss of air pressure" problem, I think it best to take a logical approach to solution.

IMO and based on what has been reported so far, I think Susan and Bob (the thread originators) may have TWO problems:

First, they have a big air leak that seems somehow related to the brake system.

Second, the air compressor on their coach is not keeping up with the air loss from the mystery leak.

With engine running, and with brake applied (causing the leak), the system air pressure should never be allowed to reach 55psi.  The compressor should cut in around 80-90psi.  It should run continuously until system pressure reaches cut-out pressure.

For the air pressure to drop to 55psi, one of two conditions must exist:

Either the air compressor is NOT cutting in at 80-90psi, which would point to a bad D2 governor, OR the air compressor IS cutting in at 80-90psi but it cannot keep up with the leak in the brake system.  That would suggest a very large leak which should be easy to find.

It would be helpful to know if the engine air compressor is operating correctly.  This could be easily tested.  Start the engine and let air pressure build to normal cut-out pressure (110-120psi).  While watching the dash air gauges, have someone open the wet tank water drain valve.  At some point, the compressor should cut back in and try to keep up with the loss of air from the open drain valve.  Note that pressure.  If the compressor does NOT cut in and the gauges continue to fall to 55psi, then the D2 should be replaced.

Once it is insured that the engine air compressor and D2 are operating correctly, THEN move on to locating the leak in the brake system.
1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"

Re: Compressor for air brakes in 1995 U300

Reply #27 –
I wonder if there is a fourm members in her area that might be able to check it out.
Andy & Eileen
MONTROSE COLORADO
1992 U300  40' 6V92 TA
2016 4 Runner
1998 Jeep Grand cherokee

1998 Jeep Grand Cherokee) Build # 4135 Skp# 122921

Re: Compressor for air brakes in 1995 U300

Reply #28 –
Chuck, You have an awesome ability to explain complex issues in a concise and non-complicated way. Thank you for that. Your guidance and problem solving, along with others on the Foreforum helps me keep my coach on the road.

Foreforum is amazing.

I hope to meet you on the road at some point to pick your brain. The adult beverages will be on me!

Jeff
1993 U300 40ft GV SE
Build # 4344

Re: Compressor for air brakes in 1995 U300

Reply #29 –
I had a similar air issue a few months ago. My air pressure was slow to build up and using the brakes depleted the pressure. Thanks to Forum trouble shooting suggestions I was able to fix it.

With a helper outside we couldn't find any obvious leks when depressing the brakes.

So we:

1. Replaced D2 - helped a little, good idea to always have a spare D2 on hand.

2. Replaced air hose from compressor to air dryer - it was original and had visible cracks on the hose. Didn't help

3. Air Dryer. I was due so we replaced it with factory reman unit. Helped a little.

4. Replaced air compressor. Once we got it off the engine we realized this was the issue. It was original and worn out. There were loose parts inside you could hear clinking around in the compressor when you shook it.

That fixed my issue.
1993 U300 40ft GV SE
Build # 4344

Re: Compressor for air brakes in 1995 U300

Reply #30 –
Quote from: Jeff & Sandy –
4. Replaced air compressor. Once we got it off the engine we realized this was the issue. It was original and worn out. There were loose parts inside you could hear clinking around in the compressor when you shook it.

I didn't even think to mention the possibility of a "bad" air compressor, because (from my reading on the Forum) it is such a unusual occurrence.  And yet, as you have just illustrated, it IS something to consider.  However, since air compressor R&R is probably a lot of work, I would really try to eliminate the "easier" stuff first.

Another possibility.  I think it was Craneman (not sure - need to search for the old thread) who had a air compressor problem caused by sticking "unloader valves".  They are located in the cylinder head of the compressor.  If they get sticky, the compressor will not function properly.  SO, if trouble shooting leads to suspect a broken compressor, then one might investigate the "unloader valves" before removing the whole unit.
1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"

Re: Compressor for air brakes in 1995 U300

Reply #31 –
Read Jerry and Cindy Maddux's (coastprt) post a year or so ago about overhauling his compressor. I looked, could not find it but message him.

Pierce
Pierce and Gaylie Stewart
'93 U300/36 WTBI
Detroit 6V-92TA Jake
1140 watts on the roof
SBFD (ret)

Re: Compressor for air brakes in 1995 U300

Reply #32 –
Quote from: Andy 2 –
I wonder if there is a fourm members in her area that might be able to check it out.

cubesphere is the closest to them that owns a Foretravel.
Future Foretravel Owners
2019 Jeep Cherokee Trailhawk
Retired USAF, Retired DOD Civ's
FAA A&P, Indust. Eng., Acft Depot Lvl. Maint.
Larry and Becky Rountree
 

Re: Compressor for air brakes in 1995 U300

Reply #33 –
My unloader stuck open. Sprayed wD into the inlet and good ever since. Cranmans suggestion
It might jingle if ya shake it. It does when unloaded .
 I doubt a bad compressor.