Air leaks

Topic: Air leaks (Read 1035 times) previous topic - next topic

Air leaks

May 03, 2019, 04:40:47 pm

I was going to work on some air leaks today on the coach, primarily a leak on the actuator for the step slide. I messed with it for about 30 minutes and could not get it to leak. Tanks are holding air quite well. I have noticed in the past that air leaks are easier to find in cold weather as opposed to mild weather. I was told by a truck mechanic that this is the norm. He claimed leaks were more prevalent in cold weather. If I can't make it leak, I can't fix it. Has anyone else noticed this about leaks. Just curious. Thanks.

Re: Air leaks

Reply #1 – May 03, 2019, 04:45:07 pm

Yes, and the same with water leaks

Re: Air leaks

Reply #2 – May 03, 2019, 05:49:10 pm

Things contract in cold weather and expand in warm weather.

Re: Air leaks

Reply #3 – May 03, 2019, 07:12:51 pm

And don't forget Murphy. You may be able to get it to leak, but there is no way it will leak if you are paying $100+/hour for someone else to find the leak.

Re: Air leaks

Reply #4 – May 03, 2019, 07:19:20 pm

Murphy usually never helps me either.

Re: Air leaks

Reply #5 – May 03, 2019, 10:58:06 pm

CNDNPF

Re: Air leaks

Reply #6 – May 05, 2019, 09:27:40 pm

Thanks I just found my new saying for work, maybe a T-shirt or tattoo!

Re: Air leaks

Reply #7 – May 05, 2019, 10:30:30 pm

Quote from: Hammer2100 – May 05, 2019, 09:27:40 pm

Thanks I just found my new saying for work, maybe a T-shirt or tattoo!

Especially if you didn't look. See no evil, hear no evil, speak no evil. Everything is just hunky dory.

Re: Air leaks

Reply #8 – May 09, 2021, 08:44:35 pm

Old topic but new issues
Rebuilt both six packs this week --aired system up then proceeded to crawl around under coach and spray everything I could find with bubbley --cant find any leaks but system is still loosing air. Any suggestions would be appreciated
Chris

Re: Air leaks

Reply #9 – May 09, 2021, 09:09:01 pm

Discovered my brake treadle valve was losing air out the exhaust port. Ordered and received a new valve but have not replaced it yet so not sure if that is the problem. It is difficult to remove and replace.

Re: Air leaks

Reply #10 – May 09, 2021, 09:09:19 pm

Chris,

Is it just the HWH side or the whole system?
Are you loosing air in both your front and rear air tanks? If so-
Have you checked to see if you have bad check valve seats in the check valves that are on you front/rear air tanks? You may also have a leaking check valve on the discharge side of your air dryer. This can cause an internal air leak that is hard to run down.

Check your step cover cylinder and step flapper cylinders for leaks.

Mike

Re: Air leaks

Reply #11 – May 09, 2021, 09:25:25 pm

The best way to check your step is to plug the line going into the rear PRV under the step and if the pressure holds then you have found that the leak is some where in the step systems or vacuum pump

Re: Air leaks

Reply #12 – May 09, 2021, 09:43:28 pm

I'm loosing air from both front and rear tanks
have not checked foot valve did check park valve
Checked step cylinder already replaced valves for stem and step cover they are not leaking.
Mike is the dryer check valve mounted to tank or in line?
Ed, did you loose air from both tanks with foot valve leak?
Thanks guys
Chris

Re: Air leaks

Reply #13 – May 09, 2021, 09:46:31 pm

Lots of tiny leaks from dried sealer on both front tank fittings. Just takes time for them to show. So small they may take a few minutes to show up as small groups of small bubbles.

I rebuilt my rear 6 pack, and buggered a O ring. Took a while to find it, when I sprayed soap on end of solenoid where wires come out.

Lastly, make sure bubble water is really soapy. May fool you.

Chris

Re: Air leaks

Reply #14 – May 09, 2021, 09:53:48 pm

I was using the bubbley that kids make bubbles with, I figured that should work but it may not be good enough
Chris

Re: Air leaks

Reply #15 – May 09, 2021, 09:56:32 pm

Quote from: Chris m lang – May 09, 2021, 08:44:35 pm

...cant find any leaks but system is still loosing air. Any suggestions would be appreciated

Chris,

I can't help you find leaks. Heck, I can't even find all the leaks on MY coach.

BUT, I can offer a couple ways to narrow down your "search area".

First, you might consider adding a pressure gauge to the wet tank. It is very handy to be able to monitor wet tank pressure versus the pressure in the front and rear brake tanks. You have one-way check valves at the inlet to the brake tanks. If these work correctly, you can lose all the pressure in your wet tank and still maintain pressure in your brake tanks. In that case, you would know that the leak was somewhere upstream of the check valves. That narrows it down considerably. The easiest place to tap into wet tank pressure is at the D2 governor. You can connect a gauge, either directly or with a length of tubing, to the extra unused port that reads wet tank pressure. You could also rig up a gauge on the tire filler connection (if you have one) or on the wet tank water bleed valve air line.

Another "trick" to narrow down the search. Say you start out with system air pressure at 120 psi. The pressure then falls rapidly on both dash pressure gauges AND the wet tank gauge until it gets to about 60psi or so. It then abruptly levels off and either holds there or continues to drop, but very slowly. That tells you two things: first that your protection valves on the brake tanks are working correctly, and second that the air leak is downstream from the protection valves. Once again, you have narrowed the search area considerably.

After you try these two tricks, then it is a matter of studying your air system diagram and looking at each air line and air powered device that is within the predetermined "search area".

Re: Air leaks

Reply #16 – May 09, 2021, 10:16:09 pm

Chris, yes, I was losing air in both front and rear systems....Ed

Re: Air leaks

Reply #17 – May 09, 2021, 11:09:59 pm

Quote from: Chuck & Jeannie – May 09, 2021, 09:56:32 pm

Chris,

I

Another "trick" to narrow down the search. Say you start out with system air pressure at 120 psi. The pressure then falls rapidly on both dash pressure gauges AND the wet tank gauge until it gets to about 60psi or so. It then abruptly levels off and either holds there or continues to drop, but very slowly. That tells you two things: first that your protection valves on the brake tanks are working correctly, and second that the air leak is downstream from the protection valves. Once again, you have narrowed the search area considerably.

This would have help me before I found the leak. I still have really slow leaks so when the pandemic is over I'm taking a friend of mine over to his brothers shop as he has some kind of device that is suppose to find any leak. I'm really curious about this device.

Re: Air leaks

Reply #18 – May 09, 2021, 11:29:11 pm

Quote from: oldguy – May 09, 2021, 11:09:59 pm

...he has some kind of device that is suppose to find any leak. I'm really curious about this device.

Try the Forum search tool - look for "ultrasonic leak detector"? There has been some past discussion of these instruments.

Re: Air leaks

Reply #19 – May 10, 2021, 12:15:57 am

Thanks Chuck. One day I will see one in operation and it will be the state of the art, he only buys the best.

Re: Air leaks

Reply #20 – May 10, 2021, 06:45:33 am

Quote from: Chris m lang – May 09, 2021, 09:43:28 pm

I'm loosing air from both front and rear tanks

Mike is the dryer check valve mounted to tank or in line?

Chris,

Take your inlet check valves to your front and rear air tanks apart and check the seats.
If you have the Pure Air Plus it has a check valve in the base where the discharge hose to the wet tank attaches. There have been reports here on the Forum where this check valve was installed backwards in dryers that were rebuilds from various venders.

Kids bubbles are great for finding leaks. Cheep at the $ store

Mike

Re: Air leaks

Reply #21 – May 10, 2021, 07:37:12 am

Just a thought but was your ignition switch on? I think there is a vacuum generator for the dash air system that uses air pressure through a Venturi to produce a vacuum for the system to work. Try checking for leaks with ignition off.

Re: Air leaks

Reply #22 – May 10, 2021, 09:21:48 am

Quote from: Ed &Jo – May 09, 2021, 10:16:09 pm

I was losing air in both front and rear systems....Ed

The problem is, you don't know which direction the air is going out of the brake tanks - downstream past the protection valves or "backwards" past the inlet check valves to the wet tank and air dryer.

Mike's suggestion to pull the brake tank inlet check valves and clean or replace them is one way to verify their performance.

My suggestion (Reply #15) to add a pressure gauge to the wet tank also allows you to test the brake tank inlet check valves.

Choice probably hinges on which is easier to do. If the inlet check valves have never been replaced they can be tough to remove, especially in tight working quarters.

But then again, if they have never been replaced they are very likely leaking and will eventually need to be replaced. Up to you.

There should also be a check valve at the inlet to the wet tank. If you are replacing check valves might as well get all three of them!

Part Number Collection

Re: Air leaks

Reply #23 – May 10, 2021, 10:30:03 am

Quote from: Forewheelers – May 03, 2019, 04:40:47 pm

I was going to work on some air leaks today on the coach, primarily a leak on the actuator for the step slide. I messed with it for about 30 minutes and could not get it to leak. Tanks are holding air quite well. I have noticed in the past that air leaks are easier to find in cold weather as opposed to mild weather. I was told by a truck mechanic that this is the norm. He claimed leaks were more prevalent in cold weather. If I can't make it leak, I can't fix it. Has anyone else noticed this about leaks. Just curious. Thanks.

THIS is normal with humans too, if it is cold outside you visit the bathroom more for a leak!
JohnH

Re: Air leaks

Reply #24 – May 10, 2021, 01:00:21 pm

Quote from: Pamela & Mike – May 10, 2021, 06:45:33 am

Chris,

Take your inlet check valves to your front and rear air tanks apart and check the seats.
If you have the Pure Air Plus it has a check valve in the base where the discharge hose to the wet tank attaches. There have been reports here on the Forum where this check valve was installed backwards in dryers that were rebuilds from various venders.

Kids bubbles are great for finding leaks. Cheep at the $ store

Mike

I use dish soap/water in spray bottle. Kids soap good too.

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