Minimum psi in front tanks?

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Minimum psi in front tanks?

March 18, 2014, 09:22:13 pm

I had noticed when parked in Travel (HWH turned off), the aux compressor comes on a bit at times and also that I had zero pressure in the two main tanks. I told some service techs and they want to check it out, I think the zero mainly.

As I hear it, (our coach) the two front main air tank pressures should not go below 60 psi when parked (for weeks), that there is some type of pressure sensing or controlling device that keeps those tank pressures no less than 60.

By dropping below 60 psi, as I heard it, that indicates a leak at the tank or between the tank and or at that valve. I think I have that right.

I hope to find out tomorrow where that device is located - back at the wet tank, up on the two main tanks? I will try to get a picture if I think any interest. Maybe just a simple check valve?

Perhaps unrelated to the zero pressure in the two main tanks, the aux compressor activates and, as I understand, pressurizes the small front tank that in turn keeps pressure in the air springs. I guess that air would not flow from the main tanks to the air springs parked.

I looked at a diagram Barry posted in 2012, trying to see what and where that valve is located, but have not understood it. Then Steve posted in that timeframe describing the various air lines. I need to dig out that diagram from my manual, reread Steve's post.

P.S. Several friends tell me they never heard of such, their tanks go to zero. Oh where is Don Hay when I need him!

have a blessed week, Mike

Re: Minimum psi in front tanks?

Reply #1 – March 18, 2014, 09:51:56 pm

I lowered mine to a bit below 60psi. THere is a pressure switch right next to my HWH pump. I also turn it off when I park it in the garage with a switch and the air will still stay above 0 for a few weeks but at a month I will have close to zero in the tanks.

Re: Minimum psi in front tanks?

Reply #2 – March 18, 2014, 10:53:30 pm

You have a newer coach than mine, so might be different. The compressor runs if it needs to re-level the coach when left in automatic. I don't have any air spring leaks to speak of, so I turn the HWH off after it's level. In auto level sometimes just moving around in the coach causes it to release some air, which it then has to replace later. You probably know all that though. I have two tanks in front and one in the back. My front tanks will bleed down below 60 in a week.

Re: Minimum psi in front tanks?

Reply #3 – March 18, 2014, 11:11:11 pm

My CDL manual says the the drain down to zero is allowed to happen on the brake system in 8 hours per DOT. Foretravel built and sold the coaches that hold for days, way more than required.

Much has been written about how long our dash brake gauges will show the holding pressures. Mine will hold above 70 for a day or two, which allows me to start and move the coach right away, if needed. A concern is a coach near by catching fire and not being able to get the air up, and the parking brake released in time.

Air leveling and slides adds more air needs of course.

Re: Minimum psi in front tanks?

Reply #4 – March 18, 2014, 11:32:08 pm

Dave, I have been going for weeks without going to zero after changed out the step and tightened up a few leaks. Seems similar to John's report. People cited the DOT to me in the past but not on this, maybe they go back to that tomorrow but they said two options for the cause. TBD

Jerry, I too note it may adjust a bit when in level and move around. But off after I level I have not really tried except when I park to store a few weeks, then develops a bit of lean very slowly and those tanks going to zero when technicians say should not.

John, I did not know about the pressure switch nor how to use it. Gotta look into that.

Thanks all,

Mike

Re: Minimum psi in front tanks?

Reply #5 – March 19, 2014, 06:06:07 am

Mike the check valves are on the input side of you air tanks (the single large line) should be 2 on the front, one on the rear at the tank or air dryer outlet. Mine for a 1999 are Haldex KH23000 got 3 of them here on my desk. On the out put side of the tanks there is a pressure regulator that will not allow things to work(except brakes) until air pressure builds to 60 or 70 psi most are not adjustable. I replaced mine last year because they where leaking. Going to install the check valves next time
I'm under there.

Re: Minimum psi in front tanks?

Reply #6 – March 19, 2014, 11:20:38 am

Quote from: Dave and Dolly Cobb – March 18, 2014, 11:11:11 pm

A concern is a coach near by catching fire and not being able to get the air up, and the parking brake released in time.

It is a concern, but the engine can usually overpower the parking brake, and minimal damage even if air springs completely dumped. Try moving your coach with the parking brake on, should hold until the engine is past 1000 rpm. Weak springs or slack adjusters out of adjustment reduce the parking brake holding power. Don't want to take the topic off thread though.

Re: Minimum psi in front tanks?

Reply #7 – March 19, 2014, 12:34:49 pm

I would guess that the check valves 23000 are to blame for most of air loss from tanks as that was problem on mine + the one on dryer system. I would lose almost all pressure overnight but now will stay above 50 for weeks then go down. The stair cover slide cylinder seal is another big cause of air loss, so I put a NC solenoid on the supply line-problem solved.
JohnH

Re: Minimum psi in front tanks?

Reply #8 – March 19, 2014, 01:13:11 pm

John, thanks.....I was waiting until I go visit the technicians, but they called before spending money, explained this.

A check valve between the wet tank and the front tanks had failed. There is a way to test for this, as Mike R. explained....hope I have it right. Crank and fill the tanks, then open the drain valve on the wet tank. If the front tanks drop too below the 60 psi, then that check valve is bad. I am not sure if it is the valve number you cited John.

Besides that, the solenoid for the retarder was bad (my technical term, I am not sure what was going on because of that). The step cover cylinder also leaking.

that is the status after they had the coach about an hour today,

Mike

Re: Minimum psi in front tanks?

Reply #9 – March 19, 2014, 06:04:03 pm

yes Mike that is correct way to test tank, but I would replace all 3 of them--only $8 each.
The step cover is expensive for FOT to replace so do not do it unless you have lots of money to throw away. I took mine off, simple as I have the pit but they make a big deal of it. You can fix that problem for $30 if you look at my posting on Forum. See link below, but you just need a 3/8th NC solenoid ($25 Amazon) and a couple of brass pipe reducer fittings, very easy and takes 15 mins then no more leaking. The solenoid is controlled by a switch on dash you add and wire to solenoid, and when you want to slide step you switch it on and use normal slide one. Once it it in position you want to stay then flip the solenoid switch to stop air going to valve--no more leaky!! and you do not have to touch cylinder at all.
JohnH
stair slide air leak--no more!!

Re: Minimum psi in front tanks?

Reply #10 – March 19, 2014, 08:31:28 pm

Quote from: Michael & Jackie – March 19, 2014, 01:13:11 pm

Besides that, the solenoid for the retarder was bad (my technical term, I am not sure what was going on because of that).

Mike - possibly the valve discussed in this thread? Replacing transmission retarder valve (split from What did you do to your coach) Several of us have had to replace it.

Re: Minimum psi in front tanks?

Reply #11 – March 19, 2014, 10:59:06 pm

Michelle I think that is it, they are to show me tomorrow. I asked mike weaver if it caused retarder to malfunction, said no. It was said evident when hearing an air pop off when retarder functions but not cause it to not work.

Thanks for that link, and thanks Dick for that original report.

Mike

Re: Minimum psi in front tanks?

Reply #12 – March 19, 2014, 11:22:35 pm

I just replaced the one on retarder for 240 with a new one, got it off amazon for $125-brand new in Allison box, simple replacement- 5 mins.
JohnH

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Minimum psi in front tanks?

March 18, 2014, 09:22:13 pm

Re: Minimum psi in front tanks?

Reply #1 – March 18, 2014, 09:51:56 pm

Re: Minimum psi in front tanks?

Reply #2 – March 18, 2014, 10:53:30 pm

Re: Minimum psi in front tanks?

Reply #3 – March 18, 2014, 11:11:11 pm

Re: Minimum psi in front tanks?

Reply #4 – March 18, 2014, 11:32:08 pm

Re: Minimum psi in front tanks?

Reply #5 – March 19, 2014, 06:06:07 am

Re: Minimum psi in front tanks?

Reply #6 – March 19, 2014, 11:20:38 am

Re: Minimum psi in front tanks?

Reply #7 – March 19, 2014, 12:34:49 pm

Re: Minimum psi in front tanks?

Reply #8 – March 19, 2014, 01:13:11 pm

Re: Minimum psi in front tanks?

Reply #9 – March 19, 2014, 06:04:03 pm

Re: Minimum psi in front tanks?

Reply #10 – March 19, 2014, 08:31:28 pm

Re: Minimum psi in front tanks?

Reply #11 – March 19, 2014, 10:59:06 pm

Re: Minimum psi in front tanks?

Reply #12 – March 19, 2014, 11:22:35 pm

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