Finding air brake leak

[jlynn37064]

On 3/6/2023 at 8:04 AM, DZZippy said:

Hey all. A lot of good information and everyone is accurate in my opinion. I have spent a couple decades working on fire trucks and emergency vehicles and obviously they have air systems and in many cases, more complex than our coaches. As an emergency vehicle technician, I had to follow DOT on top of a few more stringent items required by NFPA. Regarding air systems, the DOT tests that were referenced, are accurate. However there are a couple tests by DOT that are supposed to be conducted to detect air brake leak down rates as well. Some of these have been referenced already by you folks of leak down rates with engine off and engine running vs parking brake released, etc. In addition to,  air build up within a certain amount of time to pop off pressure based on engine speed. One of the other tests that I am referring more to in my replay, has to do with the engine running, parking brakes released, and service brake applied. The air compressor should still be able to maintain and build pressure to pop off by the governor. Based on the symptom / complaint, I have a feeling that test would fail. As many have eluded to, sounds like a leak on brake application side such as a ruptured diaphragm in a chamber of any sort (parking or not) on the service brake side, relay valve, or even “sense line” coming from the treadle valve (brake pedal) that goes to one of the relay valves. Possible hoses going from really valve to the service side of the chambers as well (I have found those to be insufficient many times). On a side note, if there is a ruptured diaphragm in a chamber, strong possibility that it will not produce bubbles with a soapy solution. The leak is internal of the chamber and can vent to atmosphere without producing bubbles inside the chamber. It does have a distinctive sound though. Just my $.02

Thanks Kurtis, I have 6 brake chambers. How can I detect which one is leaking if soapy water won’t identify it?

I took time to video the underside and the parts that I have been soaping down. Here is a link if you are curious. Underside of 2006 Beaver

 My next step is to use pinch off pliers and pinch off the air lines to each chamber one at a time to see if I can get the air leak to stop. Hopefully this will identify a bad chamber. 

[DZZippy]

1 hour ago, jlynn37064 said:

Thanks Kurtis, I have 6 brake chambers. How can I detect which one is leaking if soapy water won’t identify it?

I took time to video the underside and the parts that I have been soaping down. Here is a link if you are curious. Underside of 2006 Beaver

 My next step is to use pinch off pliers and pinch off the air lines to each chamber one at a time to see if I can get the air leak to stop. Hopefully this will identify a bad chamber. 

Great video and definitely gives everybody a better understanding what your looking at for sure. What you refer to as the caging bolt is indeed correct. The numbers you found on the drive axle chamber are indeed your model numbers. If for whatever you can’t identify it by part number any local heavy duty truck part place can manage for acquisition. 
 

Regarding the situation,  A couple things I definitely want to confirm though. It is my understanding that this only occurs when the service brake / brake pedal / treadle valve (different names names for the same for clarity). So, just for clarification:

1. Obviously no modifications to the air system where recently done and is “as is from the factory”. This is also assuming no recent work as well before you noticed the problem and changed your relay valve. Just making the statement in general as to the possibility of crossing an air line when performing any recent work by anyone.

2. After running the engine driven air compressor until full pressure and air dryer pop off / purge, the system holds pressure if the engine is shut down. Then, after blocking the wheels to make sure the coach doesn’t move, the parking brake is released and the system continues to maintain pressure after air equalization from releasing the brakes. 
 

3. the rush of air you hear is only when pushing the brake pedal and holding it with the second step completed. 
 

4. you don’t have an Air Force one braking system for a toad…..or similar system

PM or contact me or I will try and contact you in the meantime. We can discuss some various items or steps that could help. However, all I ask in return is that you post any findings here so we can all learn from our issues.

6 minutes ago, DZZippy said:

Great video and definitely gives everybody a better understanding what your looking at for sure. What you refer to as the caging bolt is indeed correct. The numbers you found on the drive axle chamber are indeed your model numbers. If for whatever you can’t identify it by part number any local heavy duty truck part place can manage for acquisition. 
 

Regarding the situation,  A couple things I definitely want to confirm though. It is my understanding that this only occurs when the service brake / brake pedal / treadle valve (different names names for the same for clarity). So, just for clarification:

1. Obviously no modifications to the air system where recently done and is “as is from the factory”. This is also assuming no recent work as well before you noticed the problem and changed your relay valve. Just making the statement in general as to the possibility of crossing an air line when performing any recent work by anyone.

2. After running the engine driven air compressor until full pressure and air dryer pop off / purge, the system holds pressure if the engine is shut down. Then, after blocking the wheels to make sure the coach doesn’t move, the parking brake is released and the system continues to maintain pressure after air equalization from releasing the brakes. 
 

3. the rush of air you hear is only when pushing the brake pedal and holding it with the second step completed. 
 

4. you don’t have an Air Force one braking system for a toad…..or similar system

PM or contact me or I will try and contact you in the meantime. We can discuss some various items or steps that could help. However, all I ask in return is that you post any findings here so we can all learn from our issues.

I just sent you a message with my phone number

[jlynn37064]

On 3/7/2023 at 10:03 AM, DZZippy said:

Great video and definitely gives everybody a better understanding what your looking at for sure. What you refer to as the caging bolt is indeed correct. The numbers you found on the drive axle chamber are indeed your model numbers. If for whatever you can’t identify it by part number any local heavy duty truck part place can manage for acquisition. 
 

Regarding the situation,  A couple things I definitely want to confirm though. It is my understanding that this only occurs when the service brake / brake pedal / treadle valve (different names names for the same for clarity). So, just for clarification:

1. Obviously no modifications to the air system where recently done and is “as is from the factory”. This is also assuming no recent work as well before you noticed the problem and changed your relay valve. Just making the statement in general as to the possibility of crossing an air line when performing any recent work by anyone.

2. After running the engine driven air compressor until full pressure and air dryer pop off / purge, the system holds pressure if the engine is shut down. Then, after blocking the wheels to make sure the coach doesn’t move, the parking brake is released and the system continues to maintain pressure after air equalization from releasing the brakes. 
 

3. the rush of air you hear is only when pushing the brake pedal and holding it with the second step completed. 
 

4. you don’t have an Air Force one braking system for a toad…..or similar system

PM or contact me or I will try and contact you in the meantime. We can discuss some various items or steps that could help. However, all I ask in return is that you post any findings here so we can all learn from our issues.

I just sent you a message with my phone number

Kurtis, I found it.  You were right in the location of the male air line next to my generator. I was able to use that to attach a line from my garage compressor to have a constant supply of air.  By having my wife push the brake I finally felt air coming from somewhere. The noise of the air resonating in the tank was drowning out the sound of the air leak. I was able to feel the air near the hose.  I sprayed it with soapy water and the bubbles revealed the leak.  It’s the hose going to the driver’s side   Any recommendations for a source of brake hoses? 
 

thanks again for the help

[96 EVO]

Congrats!

I'm not sure about sourcing.

Myself, I'd probably remove it and head to a hydraulics repair shop.

[Jdw12345]

If you go to a heavy duty truck parts store you can buy the hose in bulk and the fittings you might need.

  Just google air brake hose and fittings, most Napa stores carry this type of supplies too.

[DZZippy]

1 hour ago, jlynn37064 said:

Kurtis, I found it.  You were right in the location of the male air line next to my generator. I was able to use that to attach a line from my garage compressor to have a constant supply of air.  By having my wife push the brake I finally felt air coming from somewhere. The noise of the air resonating in the tank was drowning out the sound of the air leak. I was able to feel the air near the hose.  I sprayed it with soapy water and the bubbles revealed the leak.  It’s the hose going to the driver’s side   Any recommendations for a source of brake hoses? 
 

thanks again for the help

Great news! I know it has been mentioned already, any local heavy duty truck parts place will have it or can source it. Just a suggestion, you may want to check the other hoses as well for overall condition. Thanks for the info.

[Jdw12345]

This is just for informational purposes only, in regards to airlines.

 

 

[jlynn37064]

1 hour ago, Jdw12345 said:

This is just for informational purposes only, in regards to airlines.

 

 

Very informative. Thanks for sharing 

[jlynn37064]

Thanks everyone for you help. I replaced the leaking air hose and as well as the other 7 hoses. I'm ready to get back on the road.  The new hoses cost my $100 each, which hurt my feelings, but it only took about 20 minutes to remove the old ones and install the new ones. A simple task as long as you can get under your rig safely. 

[Georgia Mike]

Quote

 

I made this listening device to find air leaks. Its a 2 foot piece of 1/2 inch pvc and 5/8 vinyl tubing. Hold the vinyl tubing end to your ear and probe with the pvc pipe in the area that is suspect. If there’s a leak you will hear it with this. It’s cheap and it works.

[jlynn37064]

5 hours ago, Georgia Mike said:

I made this listening device to find air leaks. Its a 2 foot piece of 1/2 inch pvc and 5/8 vinyl tubing. Hold the vinyl tubing end to your ear and probe with the pvc pipe in the area that is suspect. If there’s a leak you will hear it with this. It’s cheap and it works.

Ingenious. Thanks for sharing