150 psi rear tank? Emergency repair: Yes or no?

Topic: 150 psi rear tank? Emergency repair: Yes or no? (Read 1800 times) previous topic - next topic

Re: 150 psi rear tank? Emergency repair: Yes or no?

Reply #25 – June 06, 2018, 05:01:37 pm

Chappell, I think blowing an airbag would cause an air loss greater than the engine compressor could keep up with. Pressure would get below the low limit, you would get a level system warning light on the dash and at some minimum pressure your parking brake will come on. It cannot be released until there is sufficient pressure. If you are not in gear the low level system warning prevents you from engaging the transmission. If you were moving and the low level system warning came on I don't know what the transmission will do.

Re: 150 psi rear tank? Emergency repair: Yes or no?

Reply #26 – June 06, 2018, 05:10:24 pm

In addition to Roger's comments (above), even if you could plug the hose to the blown air bag and restore system pressure, I think trying to drive the coach that way would be inadvisable. Having only one air bag inflated on a corner of the coach would put a lot of strain on the suspension components, as the other bag tries to maintain ride height. I would be afraid of causing some very expensive damage to hard to replace parts.

Re: 150 psi rear tank? Emergency repair: Yes or no?

Reply #27 – June 06, 2018, 05:13:44 pm

Not a real expert on this, but I think you could move the coach at a slow speed, not really drive it. Had a right rear ride height valve go out once when driving and didn't notice it until I smelled rubber. No real damage, although the thin plastic above the wheel wore through. The frame stops carry the weight of the vehicle when the bags are deflated not the top of the tires, even on the older coaches.

Re: 150 psi rear tank? Emergency repair: Yes or no?

Reply #28 – June 06, 2018, 05:48:16 pm

Thanks, at least you could get off the road with very little damage. Maybe.

Re: 150 psi rear tank? Emergency repair: Yes or no?

Reply #29 – June 07, 2018, 01:24:58 am

Quote from: qcj – June 06, 2018, 03:28:09 pm

Does this mean that one would be able to drive a 02 or later if a air bag should go out?

Chappell,

I'm new to this but can share our experience with a completely blown rear air bag behind rear axle. Had to move coach, but I wouldn't call this "driving" the coach. Site was out of level and had no space alongside busted bag to work. Moved 30 feet to a level open space. At a crawl. Travel light never went out. Warning chime never stopped. Brakes worked. Coach was listing and down in the rear. We dumped all air. I'm thankful there was no further damage. The additional frame strength commented on by Neal is probably why. Plus our 36' length, no slides. (At least I'm hoping this is so. I haven't seen anything tweaked or cracked. Coach goes into shop tomorrow for some inspections and minor repairs. I'll be looking everything over along with a tech.)

Someone said the travel light insufficient to determine fully inflated suspension. We never move until front/rear air is at least110psi. Travel light is green and warning chime stops before 110psi. Hard to say accurately at what psi travel light goes green. Our gauges are acting weird. (See last comment below). We do final walk around and visually check for coach sitting square/level etc.

I started this thread over the erratic reading of our rear tank vs front. Today arriving at OMC in Eugene the rear gauge was all over the place. Hope to repeat it tomorrow. Easier to find culprit.

Re: 150 psi rear tank? Emergency repair: Yes or no?

Reply #30 – June 09, 2018, 09:16:15 pm

Update on rear tank vs front tank air pressure difference, We swapped the electrical connections between the two gauges and the high psi rating swapped as well. Gauges seem okay. At this time, believe problem to be the sensor on rear tank. Schematic doesn't indicate an electrical transducer etc. box under the dash to translate tank pressure to electrical for the dash gauge. See FT drawing of air tank piping. Red dots by the gauges, Blue at the tank sensors.

However, there is an alarm and power box for gauges, (probably under the dash, haven't put eyes on it yet). It is on the 12v wiring diagram. Red dots at gauges, Blue at the alarm/power box.

Current plan is to replace the sensor at tank first. Since the alarm box also supplies power to the gauges. Could be fault is there.

Much appreciate everyone's input/answers to my post! Hope the photos are clear, taken with a phone.

Re: 150 psi rear tank? Emergency repair: Yes or no?

Reply #31 – June 10, 2018, 12:00:27 pm

Chappell,
The green travel lite and 120# of pressure do not insure that you are at travel height.
The travel lite is not a solenoid position indicator, the lite is only an indication that the HWH computer is sending 12 volts to all the travel solenoids. If one solenoid valve doesn't open that corner will remain at the height it was at when the system went into the travel mode.
I learned this one the hard ($) way. Drove home from a campground and found a windshield cracked top to bottom in the curved corner. The left front travel solenoid has failed to open. I had full air pressure and a green travel lite.
You have to walk around and check each corner to insure that you are at travel height.
You can do the Foretravel Shuffle to be sure all the compartment doors are latched and look for leaks on that walk.
I never found a travel height problem again but I felt good as I drove away.

Re: 150 psi rear tank? Emergency repair: Yes or no?

Reply #32 – June 12, 2018, 02:33:07 pm

So previous plan to replace sensor on front/rear has been changed. We already know that the gauges are good. Realize now that the wiring on sensors at tanks should be switched to determine if problem is a sensor or not. After that the problem would be in the alarm and power box under dash that feeds into all the dash gauges. As posted elsewhere on forum there is no replacement for this d...n box whether it is blue or gray!

May have to go to mechanical gauges for air tanks. That is okay, even preferable, IMO. Many of you have done this modification either out of necessity or choice. But, in the future, will I potentially have to replace other dash gauges too as this box degrades? James at FT seemed to think so. Wife isn't too happy about there being no alarms for low air pressure. It doesn't help my discussion with her that we have the Vmspc with alarms programed for everything else except the tank pressures, which are unavailable in the Vmspc.

Possible solution?: Has anyone with mechanical air tank gauges ever installed a tee in each of the gauge airlines so an adjustable 12v air pressure switch can activate an alarm should tank psi drop below a set point? The working air pressure rating on the switch would have to more than cover the normal range of zero to travel mode up to 110-120psi. Wouldn't want a failure in the switch at full coach pressure.

Thanks!

Re: 150 psi rear tank? Emergency repair: Yes or no?

Reply #33 – June 12, 2018, 02:41:15 pm

I see no problem in locating and installing a separate low PSI swithh and wiring it to an in-dash alarm.

Probably look for one in the 80 PSI range (well below normal operating PSI, but well above parking brake set).

Re: 150 psi rear tank? Emergency repair: Yes or no?

Reply #34 – June 12, 2018, 02:55:34 pm

I have looked at adding an a/d box to get both analog (air pressure) and digital (turn signal on/off for example) and adding a single line display above VMSpc to display more information. Lots more work than it would be worth. I have suggested to Silverleaf that some additional inputs would be nice. Someday perhaps.

You can add a low pressure alarm. If you remove the analog gauges from the gray/blue box and its alarm function is still working the annunciator will start beeping and will not stop. Cut the wires to it or add a switch to shut it off. But then you lose the turn signal beeps. You can work around that with a couple diodes and some connections to the turn signal wiring.

Re: 150 psi rear tank? Emergency repair: Yes or no?

Reply #35 – June 12, 2018, 04:26:33 pm

Quote from: Mike J – June 12, 2018, 02:33:07 pm

Possible solution?: Has anyone with mechanical air tank gauges ever installed a tee in each of the gauge airlines so an adjustable 12v air pressure switch can activate an alarm should tank psi drop below a set point? The working air pressure rating on the switch would have to more than cover the normal range of zero to travel mode up to 110-120psi. Wouldn't want a failure in the switch at full coach pressure.

A quick Google search turned up this product page. Looks like they have several different versions of pressure gauges with built-in switches. The gauge pointer acts as one contact, and when it touches the adjustable low limit contact it completes a circuit. Looks like it could activate either a warning light, or a audible alarm, or both. There are probably other similar products on the market...just need to look around.

20P / 25P Series | FW Murphy Production Controls

Re: 150 psi rear tank? Emergency repair: Yes or no?

Reply #36 – June 13, 2018, 09:01:06 pm

Quote from: Chuck & Jeannie – June 12, 2018, 04:26:33 pm

A quick Google search turned up this product page. Looks like they have several different versions of pressure gauges with built-in switches.

Thanks Chuck!

I like this approach. Much appreciated, switch and gauge in one package. I'll do some web searching to see what else may be available.

Best, Mike

Re: 150 psi rear tank? Emergency repair: Yes or no?

Reply #37 – June 13, 2018, 10:29:28 pm

Quote from: Roger & Susan in Home2 – June 12, 2018, 02:55:34 pm

You can add a low pressure alarm. If you remove the analog gauges from the gray/blue box and its alarm function is still working the annunciator will start beeping and will not stop. Cut the wires to it or add a switch to shut it off. But then you lose the turn signal beeps. You can work around that with a couple diodes and some connections to the turn signal wiring.

Hi Roger,
On our coach the turn signal chime has a rheostat to adjust the volume. It also chimes until travel mode is reached. I assume this "ding thing" receives signal from the "blue/gray" alarm/power box? I couldn't locate ding thingie on wiring diagram. I have very limited wiring experience. My apologies for being dense on this. I do better comprehending mechanical modifications.

The most complicated thing I've re-wired so far was a busted weatherstrip sensor on my wheelchair van. Embedded in the rubber was a sensor on the sliding automatic door leading edge. A safety feature to stop door from closing if body parts were in the way. Toyota quoted, $350.00 to replace! Mechanic clued me into where to look on the web for a cheaper work around the problem. Instructions/pictures showed where to put a specific ohm resister into the lead coming from the weather striping. It matched what the "computer" wanted to see. Cost, 6 cents. Door works great again. All I had to do was solder the resistor in and shrink wrap it.

Your fix for the turn signal beep sounds a bit more complicated. Since I'm not able to get under the coach dash somebody else will be doing this for us. I'll need to pre-assemble everything and be able to tell shop guy what to do with it and where. Would greatly appreciate diagrams and how to with pictures if at all possible.

Re: 150 psi rear tank? Emergency repair: Yes or no?

Reply #38 – July 23, 2018, 04:12:37 pm

Update on air gauge replacement: Mechanical gauges are in. We kept the existing electrical gauges for now by installing a tee at each tank. Replaced the OEM tank sensors. Found the OEM electrical gauges read 5-8 psi higher than mechanical ones. Found 12 air leaks and replaced front regulator, tank drain valves, check valves, all front 6pack o-rings and and 2 rear 6pack o-rings. plus some air fittings. At least one brass fitting was cracked. Further testing found two more leaks that we ran out of time on, (another rear o-ring and the flare fitting at wet tank on air line from engine compressor). No leaks we found were very large. Coach has always leveled properly and achieved proper travel height. However, it would settle in front after 24 hours.

The following is all based on mechanical gauge readings. At idle the front is 110-113psi. and rear 115-120psi. However, going back to my original post, there continues to be a substantial? difference between front/rear tanks at times. Confusing to me since the two tanks receive air from the same source. Example: while driving, level road constant speed 60 mph, no braking, the rear gradually declines to 105psi then jumps within 5-10 seconds to 130psi. Once saw it jump back and forth between 130 and 115 several times. The front tank stays constant, slow movements between 102 to 115psi.

Possibly related observation?: Recently the air released during slight braking at very low speeds has begun sounding like a pig squealing. It used to give a pssst sound from coach rear. I've heard semi truck air brakes sound like pigs at rest stops. (please, no disrespect intended). But this is a new sound on our coach. Brake pads are excellent. Sound is air related?

I don't know what to think of the front tank staying pretty constant while the rear tank fluctuates between 105 and 130. And there is that squealing air sound under low speed braking.

Re: 150 psi rear tank? Emergency repair: Yes or no?

Reply #39 – July 23, 2018, 06:28:42 pm

Quote from: Mike J – July 23, 2018, 04:12:37 pm

I don't know what to think of the front tank staying pretty constant while the rear tank fluctuates between 105 and 130. And there is that squealing air sound under low speed braking.

Mike

This fluctuation could indicate that the rear tank check valve is bad causing the tank to fluctuate with the wet tank.
Have you had the dryer serviced? This could be the oinking you hear as it is purging air out the bottom.
You may have a governor (this is the thing that tells the compressor to start working/ pumping air) going bad and it can cause a strange sound.

Mike

Re: 150 psi rear tank? Emergency repair: Yes or no?

Reply #40 – July 23, 2018, 06:52:00 pm

Mike,
I think it is normal to some extent to see the air tanks loose and build pressure as you drive because the leveling valves in the travel mode are constantly dumping and adding air to keep the coach at travel height going over bumps down the road. Mine does it as well. Could also indicate that the leveling valves may have a leak if it is too rapid. I assume worn shocks could cause more suspension travel and cause higher air pressure fluctuations. That's my take on it.

Mark

Re: 150 psi rear tank? Emergency repair: Yes or no?

Reply #41 – July 23, 2018, 07:28:49 pm

The needles on my coach generally move together up and down, but once in a while one of them gets a bit ahead of the other one.

I think I still have a leak somewhere, as the white needle is where it was when I shut down this afternoon. The red needle is down quite a bit.

Re: 150 psi rear tank? Emergency repair: Yes or no?

Reply #42 – July 23, 2018, 07:45:39 pm

Mike J, your tank pressures and ranges and variations seem OK to me. The two tanks are rarely going to be the same. There is only one line from the wet tank that fills both brake service tanks, the front tank is first in line and then the rear tank. They both have different loads on them too. The rear tank feeds the retarder accumulator and two ride height valves. The front tank feed the fold down step and sliding step cover and only one ride height valve.

We all have leaks. It is hard to spend a lot of time on something that is not terribly critical. What is squealing? Next time out when you are first moving turn the retarder off and do a few firm stops. This will deglaze the rotors and pads. This may be what you are hearing at slow speeds with light brake application.

Re: 150 psi rear tank? Emergency repair: Yes or no?

Reply #43 – July 23, 2018, 08:03:53 pm

+/- 3% on a 150 psig guage is pretty good qaulity. Some may go as high as 5% or more. On pumps we only install one guage teed into the suction and discharge side with ball valves on each side to get an accurate differential pressure readings. Not wise on a coach.

Re: 150 psi rear tank? Emergency repair: Yes or no?

Reply #44 – July 24, 2018, 12:40:30 pm

Quote from: Pamela & Mike – July 23, 2018, 06:28:42 pm

This fluctuation could indicate that the rear tank check valve is bad causing the tank to fluctuate with the wet tank.
Have you had the dryer serviced? This could be the oinking you hear as it is purging air out the bottom.
You may have a governor (this is the thing that tells the compressor to start working/ pumping air) going bad and it can cause a strange sound.

Yes, dryer was serviced but shop doing work did not replace the check valve at bottom. We don't go to that shop anymore. They never did the complete air system check, (soapy water) I requested after replacing airbags. Shop we use now, Oregon Motorcoach in Eugene recommended replacing check valve on our next visit, (two weeks). They prefer replacing the valve whenever dryer is serviced. I'll also check into the air compressor governor. Thanks!

Quote from: Roger & Susan in Home2 – July 23, 2018, 07:45:39 pm

The two tanks are rarely going to be the same. There is only one line from the wet tank that fills both brake service tanks, the front tank is first in line and then the rear tank. They both have different loads on them too. The rear tank feeds the retarder accumulator and two ride height valves. The front tank feed the fold down step and sliding step cover and only one ride height valve.

What is squealing? Next time out when you are first moving turn the retarder off and do a few firm stops. This will deglaze the rotors and pads. This may be what you are hearing at slow speeds with light brake application.

Thanks Roger, I understand the tank plumbing better now. Thinking more about the sound. I'm pretty sure it isn't the pads, but will check further. I should have described the sound as a Canadian goose being throttled. Pigs squealing is not very accurate and would be better applied to glazed pads. (I didn't know this thread would devolve into discussion of animal sound)

Thanks all! (BTW: I'm not obsessed with air leaks, Coach was on a lift I could get under with my wheelchair so it was easy for us to check)

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