Community Forums

Cuda67bnl · 09-16-2023, 06:58 AM

Since I got my coach, the front end will lose air and squat over night. The rear stays up. I replaced a leaking fitting at the passenger side front dump valve. I replaced a leaking ride height control valve on the passenger front a few days ago. Yesterday I searched for more leaks, and replaced a fitting on what I’m guessing is a pressure sensor for the low air dash lights, located beside the brake master cylinder reservoir. Air bags are new. I’ve sprayed both front bag fittings, both front ride height valves, both front dump valves, both pressure sensor things, and the manifold/junction block located behind the driver side firewall. No visible leaks noticed.

Is there a schematic somewhere that shows the routing and different connections for all the air lines? Any suggestions on where else to check for leaks?

MrMark52 · 09-16-2023, 08:24 AM

You may have a valve seat that is not closing all the way. Can you access where the air discharges? Maybe tie a balloon or something onto it so you can see if air is slowly bleeding thru yet undetectable, or the opening is too large to get a decent bubble to form, when spraying with soapy water?

Cuda67bnl · 09-16-2023, 11:14 AM

I sprayed some more, and found my driver's side ride height valve was in fact leaking a little bit from the side cover. I tightened the screws, and it doesn't seem to be leaking right now. I probably could've fixed the other one the same way, as it was leaking in the same spot. Gonna let it sit awhile and see if it comes down again. It's raining now, so I'm not messing with it til it stops. Fixing the other leaks definitely slowed down the rate it drops over night, so I'm making progress at least.

Cuda67bnl · 09-17-2023, 06:13 AM

Still up this morning…. Looks like maybe I found em.

MrMark52 · 09-17-2023, 08:23 AM

Thanks for reporting back!

gmcgene · 09-17-2023, 10:56 AM

I have the same issue with the front air-been putting off chasing it down.
You've motivated me! Hoping I can find and repair as easily as you did.

Cuda67bnl · 09-17-2023, 11:27 AM

Both of my height control valves were leaking at the circled cover. There’s just a rubber gasket behind the plate. If yours leak there, try snugging the torx screws a bit.

Mitimet · 09-18-2023, 05:47 PM

I too have the same issue for some time. I bought a leak detection tool; I like tools. These postings contents will surely make my job easier.
Mark(another one)

gmcgene · Yesterday, 10:47 AM

I finally crawled under the beast with a spray bottle of soapy water and found small leaks at the brass fittings connecting the lines to the driver side front height control valve.
I tightened the fittings a bit but couldn't stop the leak completely.

Is thread sealant such as RectorSeal effective for compressed air? I have only used it on low pressure natural gas and water lines.

Thanks for advice.

Cuda67bnl · Yesterday, 11:27 AM

Haldex says not to use teflon tape or pipe sealing compounds. They recommend fittings with pre-applied sealing compounds, and if not available, use a drop of oil or threadlocker. Pretty sure I used a bit of teflon without issue.....

MrMark52 · Yesterday, 11:41 AM

What are the lines and fittings made of?

If “air brake tubing” (a plastic tubing material DOT approved for air brake applications) was used for the tubing (or any type of plastic tubing was used) you need to make sure the barrels were put into the tube end before the tubing was connected to the fitting.
The plastic itself without the barrel will collapse against the ferrule and leak.

If metallic tubing was used - you need to dis-assemble and closely inspect the assembly.

If the fitting is a flare fitting - be suspect of a cracked flare.
If a ferrule was used, be suspect the ferrule was improperly compressed.

The recommendation to use a drop of oil aids in torquing tighter, not necessarily the leak.

gmcgene · Today, 08:02 AM

[QUOTE=MrMark52;6618031]What are the lines and fittings made of?

That is a good question.
The metal parts of the control valve on my coach, which I assume to be original factory installed, are gray like the picture Cuda67 posted above. I thought it MAY be PEWTER and I'm concerned that over tightening the BRASS nipple that screws into it may damage the threads or crack the pewter housing.

The suspension system air lines are 3/8 DOT plastic air brake lines- using a brass fitting to connect to the brass valve nipple.

I have a NEW never installed Haldex height control valve. The metal connection ports are brass. Haldex may have upgraded the parts since 1998.

If I can't get the leak stopped with the existing parts I may replace them with the DOT approved brass Push-On air line fitting which comes with factory installed thread sealant. I used them on my Air Throttle conversion and they don't leak.

Thanks for your input.

MrMark52 · Today, 08:49 AM

[QUOTE=gmcgene;6618679]

Quote:

Originally Posted by MrMark52

What are the lines and fittings made of?

That is a good question.
The metal parts of the control valve on my coach, which I assume to be original factory installed, are gray like the picture Cuda67 posted above. I thought it MAY be PEWTER and I'm concerned that over tightening the BRASS nipple that screws into it may damage the threads or crack the pewter housing.

The suspension system air lines are 3/8 DOT plastic air brake lines- using a brass fitting to connect to the brass valve nipple.

I have a NEW never installed Haldex height control valve. The metal connection ports are brass. Haldex may have upgraded the parts since 1998.

If I can't get the leak stopped with the existing parts I may replace them with the DOT approved brass Push-On air line fitting which comes with factory installed thread sealant. I used them on my Air Throttle conversion and they don't leak.

Thanks for your input.