Diagnosing and Fixing Air Leaks

Topic: Diagnosing and Fixing Air Leaks (Read 984 times) previous topic - next topic

Diagnosing and Fixing Air Leaks

August 15, 2021, 10:35:35 pm

I am needing to fix some air leaks. According to the gauges, both tanks went from 120 to about 30 PSI in 32 hours. The top gauge seems to drop a little faster, this is the front I believe. I do not think this is normal but would like to confirm. One of the techs at MOT said air loss of under 11 PSI/hour is acceptable. Using this, I am withing spec but that does seem to be more than I would like. Can someone confirm that?

I also noticed the step cover lid did not work this morning due to low air, once I started the rig and air was built up, it worked as it should.

I have the schematic and search has revealed some helpful information, but neither tell what I am looking at or where they are located so I can continue with diagnosing/fixing.

I went around with soapy water and sprayed the fittings I could see and reach with my long arms and the sprayer stream. I need to get the steel bars before I go under. I checked all the airbags and the lines/valves on/around the front tank, whatever I could reach, although I could have missed what I can't see.

I found the below 2 items leaking:
1- the front side of the right rear airbag, leaking along the backside of the 90 degree fitting, probably needs more plumbers tape or tightened more
2- there is a grouping of lines/valves on left front, just behind the headlight and to the right of the gearbox shaft/yoke. I don't know what this is, is this the 6 pack? If not, what is this? I have a photo attached of the line, the gearbox/yoke is on the left

MOT just replaced all of the air bags and put new o rings in 3 of the solenoids on the six pack. I will call them tomorrow to see what how they want to handle the air bag.

Re: Diagnosing and Fixing Air Leaks

Reply #1 – August 15, 2021, 10:42:54 pm

That is your brake treadle valve.

Re: Diagnosing and Fixing Air Leaks

Reply #2 – August 15, 2021, 11:20:53 pm

Quote from: Jason – August 15, 2021, 10:35:35 pm

1- ...90 degree fitting, probably needs more plumbers tape or tightened more.
2- ...is this the 6 pack?

1. Do not use "plumber's tape" (teflon tape) on air system fittings. Use a good thread sealant paste such as Permatex or Loctite.

PermatexÂ® High Temperature Thread Sealant â€“ Permatex

Amazon.com: Loctite 483631 592 Thread Sealant, 6-Mililiter Tube : Automotive

2. For future reference, the 6-pack looks like the photos below (view of both sides of front 6-pack manifold).

As an Amazon Associate Foretravel Owners' Forum earns from qualifying purchases.

Re: Diagnosing and Fixing Air Leaks

Reply #3 – August 16, 2021, 08:44:35 am

And that 6 pack looks really, really clean.

Re: Diagnosing and Fixing Air Leaks

Reply #4 – August 16, 2021, 10:03:54 am

Thanx. That was right after my rebuild. Not quite that shiny now...but still pretty clean.

Re: Diagnosing and Fixing Air Leaks

Reply #5 – August 16, 2021, 10:07:26 am

Appreciate the replies. Loctite ordered! Where is the 6 pack located?

And is there a parts catalog somewhere? The only thing I can find is Brake Pedal Valve - looking for a link

Re: Diagnosing and Fixing Air Leaks

Reply #6 – August 16, 2021, 10:19:31 am

Quote from: Jason – August 16, 2021, 10:07:26 am

Where is the 6 pack located?

Coach has two 6-pack manifolds (plus one additional manifold if it has tag axle).

Front 6-pack is usually tucked up in the vicinity of the two front-mounted air tanks - perhaps viewable looking into the wheel wells behind one of the front tires.

Rear 6-pack is tucked up underneath near the rear axle - perhaps viewable looking into one of the rearmost bay doors (battery bay or filter bay?)

Most 6-packs are more easily viewed when under the coach on a creeper (coach supported with safety stands, of course).

Re: Diagnosing and Fixing Air Leaks

Reply #7 – August 16, 2021, 10:24:47 am

Quote from: Chuck & Jeannie – August 16, 2021, 10:19:31 am

Most 6-packs are more easily viewed when under the coach on a creeper (coach supported with safety stands, of course).

Emphasis on the safety stands

Working Safely around your Foretravel

Re: Diagnosing and Fixing Air Leaks

Reply #8 – August 16, 2021, 12:03:25 pm

You will never get the air System 100% airtight some times my coach will hold its air for a couple of days other time's it'll lose the air over a week it will go to zero but with the HWH computer leveling the air bags will stay level and you're steps cover will only operate with air pressure above 70 pounds I believe. but there is always 1 out of a 100 that will say there's is air tight with no leaks what they told you is true your coach is with in specs air leaks are are like a ghost try to find them some times it's is in possible if it's big enough you'll find it if it's small you may never the same for a tire that sat all winter you lose air but drive your coach daily or weekly and the tires seem to be always at the proper air pressure

Re: Diagnosing and Fixing Air Leaks

Reply #9 – August 16, 2021, 12:15:42 pm

Other common culprits that are easy to check:

The air piston that moves the step cover. While you're outside with the door open, extend the cover, and spray the area where the arm enters the cylinder with soapy water

Norgren valves behind the step enclosure. Air the tanks up, block the suspension with safety stands, and crawl under the front of the coach, just behind the front steps. You'll see two norgren vales attached to the back side of the "box" that is your front step. Spray those as well

Re: Diagnosing and Fixing Air Leaks

Reply #10 – August 16, 2021, 12:26:17 pm

Thanks. I realize the system will not be 100%, it's air. I have a turbo car as well, similar. Goal is to get any major leaks done. It is usable now, but I do want fix things if they are not terribly difficult.

For the blocks, I see Barry said 4 but I thought recall seeing 8, one for each bag. It is 4 or 8? I sent a request to my fab shop for 8 to be cut/made.

Re: Diagnosing and Fixing Air Leaks

Reply #11 – August 16, 2021, 12:32:10 pm

Quote from: Jason – August 16, 2021, 12:26:17 pm

For the blocks, I see Barry said 4 but I thought recall seeing 8, one for each bag. It is 4 or 8? I sent a request to my fab shop for 8 to be cut/made.

You will ultimately want eight. Whether or not you use all eight, or only four, when you go under one end of the coach is a topic of some debate. Some say always block all eight, others say you only need four for the end you're working under. Everyone agrees that four is the minimum. I do all eight because it's low effort for certainty in a high stakes game.

Re: Diagnosing and Fixing Air Leaks

Reply #12 – August 16, 2021, 01:30:14 pm

I made ramps out of 6x6 treated post cutoffs, about 3 ft for the ramp and 1 ft or more for the tire to sit on, 2 for each wheel. so drive up on the ramps, set brakes and chocks, raise all the way, insert safety blocks. Then I can sit up under the front end and work on the elusive air leaks or anything else. An extra 5.5" of room makes a big difference.

If you have a woven patio mat slide that underneath. Pretty easy to slide around on those. I have a plastic boot tray too that all the tools and parts I am using are in. That is easy to slide around and things don't get misplaced too often.

Re: Diagnosing and Fixing Air Leaks

Reply #13 – August 16, 2021, 06:34:41 pm

"120 to about 30 PSI in 32 hours" sounds acceptable.

Re: Diagnosing and Fixing Air Leaks

Reply #14 – August 18, 2021, 02:13:43 pm

Yesterday I picked up 8 steel tubes per Barry's specs from my fab shop. Very pleased with the quality and less than the HF option, even with crazy steel prices.

Elliot- I did check behind the step and inside the step for leaks, all looks good there, thanks for letting me know about those.

Loctite came in, so I need to undo the line/fitting on the single airbag that is leaking, then put on some of this and reinstall. Any special instruction/advice for this? It look like I can do this without removing the bag itself, just unscrew the fitting.

I will also use those tubes and crawl under and check for leaks too. I still have not seen a 6 pack.

Re: Diagnosing and Fixing Air Leaks

Reply #15 – August 18, 2021, 02:54:05 pm

Quote from: Jason – August 18, 2021, 02:13:43 pm

Any special instruction/advice for this?

Be careful with the fitting given how soft it is. If I recall correctly, that loctite is pretty runny so have a rag handy.

Re: Diagnosing and Fixing Air Leaks

Reply #16 – August 18, 2021, 09:40:10 pm

I have been using RectorSeal Tru-Blu for a while now with good results. It is thick, no drips.
Amazon.com: Rectorseal 31631 1/4 Pint Brush Top Tru-Blu Pipe Thread Sealant...

As an Amazon Associate Foretravel Owners' Forum earns from qualifying purchases.

Re: Diagnosing and Fixing Air Leaks

Reply #17 – August 19, 2021, 10:46:36 pm

Also check behind the dash, the parking brake.

Re: Diagnosing and Fixing Air Leaks

Reply #18 – August 21, 2021, 02:16:46 pm

This morning, I fixed the rear leaking airbag fitting using loctite, that stuff is awesome, so much better than teflon! The 8 steel tubes worked great too.

With it on blocks, I was able to go around and test all the air connections I could find. Nothing new bubbled which is good. At some point I will replace the treadle valve though.

I did run into something interesting that I wanted to check with the experts- I can hear air flowing from the left rear height control valve. I am thinking it is an internal o ring that has gone?? The right side does not do this. Again, no bubbles externally. It's a Wabco 013 but the parts manual shows it as part # 4640024430 and it does look the same. WABCO 4640024430 Chassis Height Control Valve: AnythingTruck.com, Truck &... Is Wabco the OEM supplier? I have seen others reference Haldex.

How critical is this to fix? Does any height calibration need to be done, or can I just remove the single bolt with the lever and reattach?

Re: Diagnosing and Fixing Air Leaks

Reply #19 – August 21, 2021, 02:32:00 pm

If air comes out of anything except the exhaust port it needs to be replaced.

And, if air comes out the exhaust port with ride height is correct (i.e. valve should not be exhausting) it needs to be replaced.

And, yes, you will need to check/adjust ride height with the new valve (or old one for that matter).

Re: Diagnosing and Fixing Air Leaks

Reply #20 – August 21, 2021, 02:40:59 pm

Quote from: wolfe10 – August 21, 2021, 02:32:00 pm

If air comes out of anything except the exhaust port it needs to be replaced.

And, if air comes out the exhaust port with ride height is correct (i.e. valve should not be exhausting) it needs to be replaced.

And, yes, you will need to check/adjust ride height with the new valve (or old one for that matter).

Thanks Brett. I guess the exhaust port is on the bottom, where the cap is missing? It seems to constantly do this, so your second sentence seems to be what is happening. I will get another one ordered.

Re: Diagnosing and Fixing Air Leaks

Reply #21 – August 21, 2021, 03:19:50 pm

And, it is common for the "filter" that protects the exhaust port from dirt and insects to rot long before the valve fails.

Many have either purchased new ones or just used homemade ones to keep dirt out.

Affiliate Notice