Front Air leak, Safety Stands, etc.

Topic: Front Air leak, Safety Stands, etc. (Read 1085 times) previous topic - next topic

Front Air leak, Safety Stands, etc.

June 12, 2015, 11:01:08 pm

My transitory front air leak has returned. I was in Colorado and noticed a loud hiss and posted about it. It went away, and all was well when I got to HWH for a slide lock replacement. HWH thought it might have been a "flake" of something that had been in a valve. Now it has come back. My first clue was the compressor staying on this afternoon. Here is what I have done:

1. Started the coach, made sure it was still level, and brought the slide in so the coach level wouldn't get wonky.
2. Raised the coach to the max, and gingerly stuck my head in there to hear that it is not an airbag, but something making a loud hiss in the "plumbing" that was way too far in for me to risk sticking my head in to actually locate.
3. Lowered the coach back down, turned the engine off (and had previously turned off the supplemental air compressor).
4. Left the slide in.

My intent is to go to Harbor Freight and buy the 12" by 2" hitch pieces to use as safety stands. Then:
1. Air the system back up to raise it the 12" needed for the insertion of the tubes.
2. After building the air pressure, I will quickly get under the front and try to see and try to take a picture of where the hiss is coming from.

My questions:
1. Do I really need 4 of the safety stands up front? Or just 2? My plan is to raise the whole coach to level, then raise the front enough to get the stands in place.
2. Does anyone have a "likely culprit" here? Michelle told me a couple of weeks ago that it might be some $20 valve, but I didn't pursue it after HWH dismissed it as transitory and likely nothing wrong.

At least I am parked for a month and not frantic. Christine wasn't too happy when I brought the slide in, tho, so I want to get it resolved ASAP to be able to safely keep the slide out.

Thanks!!!!

Re: Front Air leak, Safety Stands, etc.

Reply #1 – June 12, 2015, 11:04:54 pm

Blocks of wood work too.

Re: Front Air leak, Safety Stands, etc.

Reply #2 – June 12, 2015, 11:10:18 pm

Quote from: Brad & Christine Slaughter – June 12, 2015, 11:01:08 pm

1. Do I really need 4 of the safety stands up front? Or just 2? My plan is to raise the whole coach to level, then raise the front enough to get the stands in place.
2. Does anyone have a "likely culprit" here?

We use 1 block per corner, so only 2 are needed up front. We block the entire coach (so 4 blocks) when dumping the air to work on the air system. Chock the tires as well, and best done on a level surface. Wouldn't recommend working on a raised coach without it being on a level site and with the wheels chocked. You might be fine, but safety first IMHO.

Possible culprit, since you mention well interior from air bags, is the front adjustable (set to 60-65) psi regulator that keeps the front from raising too fast compared to the rear. I believe it is a FT part, not an HWH one - you can either buy their version or (as we have) get a Cobalt one from Lowes near the air compressors for about $20. It has a dial on it and hangs near the centerline of the front axle.

Re: Front Air leak, Safety Stands, etc.

Reply #3 – June 12, 2015, 11:18:17 pm

Quote from: Michelle – June 12, 2015, 11:10:18 pm

We use 1 block per corner, so only 2 are needed up front. We block the entire coach (so 4 blocks) when dumping the air to work on the air system.

Do you notice any type of twisting on the "H" frame that the axle is bolted to? I've always used 4 blocks per axle. When I changed airbags, the blocks were indented (4 per axle).

Re: Front Air leak, Safety Stands, etc.

Reply #4 – June 12, 2015, 11:31:36 pm

Quote from: Michelle – June 12, 2015, 11:10:18 pm

Possible culprit, since you mention well interior from air bags, is the front adjustable (set to 60-65) psi regulator that keeps the front from raising too fast compared to the rear. I believe it is a FT part, not an HWH one - you can either buy their version or (as we have) get a Cobalt one from Lowes near the air compressors for about $20. It has a dial on it and hangs near the centerline of the front axle.

Hope this turns out to be the problem. Lowes is 1/4 mile up the road from us! Thanks Michelle. 4 up front really seemed like overkill. If it is the regulator, am I going to need to dump the air completely to replace it?

Re: Front Air leak, Safety Stands, etc.

Reply #5 – June 12, 2015, 11:40:06 pm

Michelle,
Which corners do you block, especially in the back? My observation is that putting blocks on only one end of the "H" frame is like a loading one end of a teeter-totter. Putting the blocks in front of the rear axle for instance will push that end (the one connected to the bulkhead joint by the trailing arms) away from the basement. That is in essence how I controlled the separation of the bulkhead joint the entire time I was rebuilding the basement structure. If your bulkhead joint is sound, it would likely be okay with that extra loading, especially if the air bags don't get dumped or leak down. But knowing what I know and seeing what I have seen, I would advise against that option for work that would have the coach sitting heavily on the stands. If it is to do a quick check under one area, then blocking one end could be a life saver. If however, working with the air bags dumped or removed, I would not set the coach down with just one stand in front of each end of the rear axle. Not only is it safer in the event of a catastrophic sir system failure to hold pressure, but it is less stressful on the structure, IMHO. When I am blocking the coach all the way up for some serious work, I always use 8 stands because it gives me the warm fuzzies to do so

. If the work is all focused on one end, say the rear, then I will possibly block up the rear with four and just use two in front as a just in case option. The front suspension is not tethered to the front bulkhead joint like the rear because there are no trailing arms acting as an axle locator, so using two in the front would still put stress on the suspension components in the event of an air dump, but the basement to bulkhead joint would not be unaffected. Of course everyone must do what their own assessment of the physics of the situation tells them is best.
Don

Quote from: Michelle – June 12, 2015, 11:10:18 pm

We use 1 block per corner, so only 2 are needed up front. We block the entire coach (so 4 blocks) when dumping the air to work on the air system.

Re: Front Air leak, Safety Stands, etc.

Reply #6 – June 13, 2015, 12:27:03 am

Quote from: acousticart – June 12, 2015, 11:40:06 pm

I always use 8 stands because it gives me the warm fuzzies to do so

X2 on 8 safety stands. The sprung weight at each corner is held up by 2 air bags, so it makes sense (to me) to use 2 "stand-ins" per corner.

Re: Front Air leak, Safety Stands, etc.

Reply #7 – June 13, 2015, 12:36:13 am

1 block for each bag

Re: Front Air leak, Safety Stands, etc.

Reply #8 – June 13, 2015, 10:07:19 am

Brad, be safe, use four up front and four in the back, always. My 12" 2"x2" receiver tube sections were less than $12 each. It will take more than $24 to fix you up if you get squished.

Do everything with safety in mind. Wear eye protection, hearing protection when needed and be very aware of what is going on around you. Be sure to use wheel chocks. A few seconds of getting prepared can save your life.

I think Michelle was only talking about the front end when she said use one per side. But you have to raise up the coach anyway so why not use four.

Please be careful. Roger

Re: Front Air leak, Safety Stands, etc.

Reply #9 – June 13, 2015, 11:51:41 am

Brad, there's an old saying, " better safe than sorry". To me that apples any time I'm working under the coach.

Re: Front Air leak, Safety Stands, etc.

Reply #10 – June 13, 2015, 03:12:57 pm

Status report:

I bought the ONLY 2 hitch pieces that HF had. (With one of them at a 20% discount, it was $27 in this no-tax land.)

Came back to the coach (which I had fully lowered yesterday) and noted that the tank gauges were still at about 40 PSI, so they did not continue to release air until there was none (I had the compressor off since yesterday afternoon when I noticed it running and heard the hiss).

I turned the motor on, and I turned the aux compressor back on, and fully raised the coach once pressure built. Then I turned off the engine. NO LEAK, NO HISS, and the aux compressor had shut off as it should. I examined the room I would have if the coach came all the way back down, and I am not that big as to be flattened. So I put in the 2 safety stands I had in position BEHIND the wheels, next to the airbags, and there was about 3/4" of extra space. I crawled under the front and saw/heard no indication anywhere of any leak now. I saw two things that looked like relief valves (holes in the bottom centers), and I saw the pressure adjuster that Steve & Michelle were talking about. Nothing remarkable about anything. Everything looks normal.

I lowered the coach and waited. Everything remained fine. I put the slide back out, and have been sitting here a while. No trouble at all.

I absolutely hate transitory problems. Seems like some relief valve or something is sticky. Maybe a LONG mechanic's stethoscope probe the next time it happens, and I can then identify the place of the "hiss"

Re: Front Air leak, Safety Stands, etc.

Reply #11 – June 13, 2015, 03:26:32 pm

Brad, Did you try the soap bubble test? Easy to detect small leaks.

Jerry

Re: Front Air leak, Safety Stands, etc.

Reply #12 – June 13, 2015, 03:55:42 pm

Brad,
Try to eliminate what part of your air system is leaking.
When you hear the leak is the coach coming down? That would be the air coming out of the air bags.
If that is what is happening try to cycle the dump solenoids by using the manual right then left down buttons to see if the valve will seat and not leak.
If that doesn't effect the leak it may be a leak before air goes into the HWH manifold.
You could cycle your coach brakes to see if that has any effect.
If the step or stair well cover pressure regulators are failing and set to low those actuators can leak. Push or pull on the step or stair well cover to see if the air sound changes.
At least you can eliminate some things.
JD

Re: Front Air leak, Safety Stands, etc.

Reply #13 – June 13, 2015, 04:06:59 pm

Quote from: coastprt – June 13, 2015, 03:26:32 pm

Brad, Did you try the soap bubble test? Easy to detect small leaks.

Jerry

Jerry, this is a huge "hiss", just like when the coach is being lowered manually. I think there are probably tiny leaks to contend with, and I will eventually get around to trying to seek them out when I have more air losses over time, but this is huge, like a valve is opening up when it should not do so. If I find that the "leak" is coming from one of the relief ports, as I suspect, then it will be a matter of finding what valve is sending air to the port when it should not be doing so.
But when the leak occurs, the process of trying to raise the coach, put blocks in place, and jump under it before it stops leaking hasn't worked well yet. Mainly the issue of the slide. I don't want to do all those gyrations with the slide out, so it needs to be in when I look for this thing. I'll just hope the slide is in the next time it starts hissing.

And thanks for the ideas, John. You are right. I should be able to learn something by fiddling with the air control pad as it happens. Pressing one of the up buttons may give me an indication of no response...or stopping the hiss response. The step is fine, and it doesn't seem to have anything to do with the brakes. Frankly, I haven't measured, but I think the front comes down slowly. Next time, I will try to quickly shut off the engine to make any drop more noticeable.

Re: Front Air leak, Safety Stands, etc.

Reply #14 – June 13, 2015, 08:32:14 pm

Brad,

Does your coach have a 3rd air tank up front that is for slide bladder? If so you may need to check the relief valve on it as it may have a spring that is going bad causing it to open premature.

Pamela & Mike

Re: Front Air leak, Safety Stands, etc.

Reply #15 – June 13, 2015, 09:52:33 pm

Quote from: Pamela & Mike – June 13, 2015, 08:32:14 pm

coach have a 3rd air tank up front that is for slide bladder? If so you may need to check the relief valve on it as it may have a spring that is going bad causing it to open premature.

Pamela & Mike

There are two tanks up front, but the issue seems to be with leveling. The first time this happened was at a rest area when I leveled the coach, as I generally always do when I stop for a rest/lunch/dogwalk. I got out and thought it was an airbag hissing. I was parked with the front high, so I stuck my head in the wheelwell and realized it was coming from the center of the coach, where all the plumbing is.

Sitting level with the slide out since my last report...and no problem.

Re: Front Air leak, Safety Stands, etc.

Reply #16 – June 13, 2015, 10:23:45 pm

Brad,
That sounds like a travel solenoid is leaking air to the ride height valve and it is trying to let air out to achieve ride height even though you are in level mode.

Pamela & Mike

Re: Front Air leak, Safety Stands, etc.

Reply #17 – June 13, 2015, 10:47:48 pm

Brad,

Try Northern Tool

Ultra-Tow 2-Inch Standard Weld-On Receiver Tube with Collar — 48in. Length |...

48" receiver tube, $45, three cuts, four safety stands.

Roger

Re: Front Air leak, Safety Stands, etc.

Reply #18 – June 14, 2015, 10:22:49 am

If you have the air operated fold down step or the floor slide, the control valve could be hanging up. I have found that my floor slide valve hangs from time to time and the sound from in front of the RV is the same sound as when you release air from the air bags. On my coach the valves are on the back of the step under the front.

I have not replaced the valve yet but I carry a cap so I can cap off the air line going to the value if I can not get it to stop.

Re: Front Air leak, Safety Stands, etc.

Reply #19 – June 14, 2015, 12:15:46 pm

Quote from: turbojack – June 14, 2015, 10:22:49 am

If you have the air operated fold down step or the floor slide, the control valve could be hanging up. I have found that my floor slide valve hangs from time to time and the sound from in front of the RV is the same sound as when you release air from the air bags. On my coach the valves are on the back of the step under the front.

I have not replaced the valve yet but I carry a cap so I can cap off the air line going to the value if I can not get it to stop.

I have previously replaced the cylinders in the air step...but this "Hiss" is not coming from the step cylinders at all. About 20 hours later, no returned hiss yet. But I will focus on the floor slide next time. I hadn't considered that one...and of course, operating it has happened close to the hiss appearing. I do think I am going to invest in a mechanic's stethoscope and possibly a little aluminum extension rod if it isn't long enough. Thanks for the idea.

Re: Front Air leak, Safety Stands, etc.

Reply #20 – June 14, 2015, 01:16:33 pm

Brad,

If you run the step slide out with the door open, you can pull the pin releasing the slide and retract the shaft. If sprayed with soapy water while the shaft is extended, probably no bubbles. But with the shaft retracted, I bet you will see bubbles at the shaft seal.

Keith Risch got my cylinder out in less than 15 minutes (still don't know how he pulled that off). It is a $200+ part so I really like John H's simpler, less expensive solution of installing a 12 vdc solenoid valves that isolates the step slide cylinder when the ignition switch is off.

This solution could also isolate the step cylinders getting two leak sources in one repair.

Re: Front Air leak, Safety Stands, etc.

Reply #21 – June 15, 2015, 10:36:59 am

I am not talking about the cylinders but the electric solenoid that routes the air to the cylinder to open or close. On my 1997 U295 it is mounted to the back side of the step under the coach. It has air line going to it and then has two lines going to the cylinder. I am not positive as to the operation of it but I think that when it diverts the air to one side of the cylinder, it then opens the other side to purge the air so the cylinder would then open or close. This valve hangs up some time and that is where I am getting the hissing noise.

Edited.

I found the following talking about the step & slide valves

How the inside step slide and outside step operate

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