Coach fails the 2 minute brake test

[Woody O]

When doing my pretrip braking tests, I found a problem. My 2006 Dynasty failed the "Holding the brake peddle down for 2 minutes with the engine off" and not losing more than 4 psi of air pressure. The front air tank looses 20 psi and the rear tank looses 25 psi! After building up pressure and cutting off the engine and I slide under the coach, I don't hear any air exhausing. What is my problem?

[Chargerman]

Sounds like you would have to check it out with someone stepping on the pedal. 

[WayneC]

Morning 

Reminder!

Trained and qualified technicians to crawl under coaches! Especially if there are Air problems

Safety first

Wayne

1999 Monaco signature Caesar 

[dl_racing427]

On 1/29/2021 at 1:43 AM, Woody O said:

When doing my pretrip braking tests, I found a problem. My 2006 Dynasty failed the "Holding the brake peddle down for 2 minutes with the engine off" and not losing more than 4 psi of air pressure. The front air tank looses 20 psi and the rear tank looses 25 psi! After building up pressure and cutting off the engine and I slide under the coach, I don't hear any air exhausing. What is my problem?

Not again.... 😨  NEVER get under a coach that is supported by air suspension or hydraulic jacks, as a single failure can drop the coach to the ground, crushing your skull.

Get a set of jack stands that are rated for the load, raise the coach with the jacks, and set it solidly on the jack stands before working underneath.

Now for your brake problem, you'll probably be able to hear that big of a leak, but you'll need to have someone depress the brake pedal while you listen underneath.

Also, be sure they release the parking brake so you can check those lines as well.  (The park brake uses air to RELEASE the brakes, which is opposite of the service brakes.

It's most likely a bad fitting or line, which are pretty easy to fix.  Just be sure to use DOT rated hose and fittings.

If you find it's a brake chamber itself leaking, the fronts can be replaced pretty easily.
The rears, however, have very powerful springs that must be caged before removing.  These springs can kill you, so if you're not familiar with the procedures to work on them, I'd suggest having a truck repair place handle that repair.

Edited January 30, 2021 by dl_racing427

[Woody O]

I used 2   4"sq x 1/4"wall steel tubing to block up the coach and also chock the wheels. I ran the engine to get air pressure up to cut off which on my coach is 125 psi. I then released the parking brake and went to the rear of the coach and climbed under at which time my wife applied firm even pressure to the brake pedal.  No air hissing except about every 20 seconds, the pressure relief valve would exhaust a short burst of air, which adds up to 6 short burst of air released in the 2 minute test. So, what now?

[dl_racing427]

3 hours ago, Woody O said:

I used 2   4"sq x 1/4"wall steel tubing to block up the coach and also chock the wheels. I ran the engine to get air pressure up to cut off which on my coach is 125 psi. I then released the parking brake and went to the rear of the coach and climbed under at which time my wife applied firm even pressure to the brake pedal.  No air hissing except about every 20 seconds, the pressure relief valve would exhaust a short burst of air, which adds up to 6 short burst of air released in the 2 minute test. So, what now?

Glad to hear you're using the blocks. 😄

You did this test with the engine off, correct?
Did the system still lose the 20-25psi during this time?

The relief valve you spoke of, is this the one on the air dryer, or could you be hearing the quick-release valves on the brake system, which allow for rapid bleeding of brake pressure when the brake pedal is released.  These valves are triggered anytime the brake line pressure reduces, normally whenever the brake pedal is released, even slightly.  A leak in the system which allows brake pressure to bleed off could also trigger them.
What I mean is the release valves triggering could be caused by a small leak elsewhere, and would just be adding to the magnitude of the leak.

You may have to resort to checking each connection with a soap solution, while the brake pedal is depressed.

Good luck, and stay safe.

[glang11082]

Speaking of ramps I have built  an  outside ramp  12 ft long and I can stand up under the coach to work , its very safe made of steel beams and  built to hold a 54000LB Prevost 45ft I had until a few years ago. I drive on my ramp to check the front then back on to check the rear area. As I do all my own maintenance and repairs  its great to have. I will say that some air leaks are hard to find but dish soap and water in a spray bottle works great. Check  the push on air connectors if you have any and replace with approved brass connectors , make sure you get them for air lines with the internal brass sleeve that goes inside the air line. As an option You can cut 1/4 off the Synflex air line  to get rid of the old grove and  that will make  a new seal but I prefer to replace all push in connectors.

[Ivan K]

10 minutes ago, glang11082 said:

Speaking of ramps I have built  an  outside ramp  12 ft long and I can stand up under the coach to work , its very safe made of steel beams and  built to hold a 54000LB Prevost 45ft I had until a few years ago. I drive on my ramp to check the front then back on to check the rear area. As I do all my own maintenance and repairs  its great to have. I will say that some air leaks are hard to find but dish soap and water in a spray bottle works great. Check  the push on air connectors if you have any and replace with approved brass connectors , make sure you get them for air lines with the internal brass sleeve that goes inside the air line. As an option You can cut 1/4 off the Synflex air line  to get rid of the old grove and  that will make  a new seal but I prefer to replace all push in connectors.

Can you share a picture of your ramp?

[Woody O]

Here is a photo of the item that exhaust a small amount of air about every 20 seconds and yes, the engine is turned off when running this test.

[Dave Pumphrey]

1 hour ago, Woody O said:

Here is a photo of the item that exhaust a small amount of air about every 20 seconds and yes, the engine is turned off when running this test.

This is the drier, should only blow off with engine running, after reaching cut out pressure. 

[WayneC]

1 hour ago, Ivan K said:

Can you share a picture of your ramp?

 

Gary 

2 questions if you don't mind, yes I would be interested in seeing pictures of ramps,question 2, why from Provost to Monaco if you don't mind me asking

Happy Saturday 

Wayne 

1999 Monaco signature Caesar 

[Woody O]

18 hours ago, Dave Pumphrey said:

This is the drier, should only blow off with engine running, after reaching cut out pressure. 

Dave, since the dryer is releasing air with the engine off, is there an adjustment or do I replace the dryer? And is it something I must do immediately?

[Ivan K]

If this is where your leak is, then you can replace it. It's called a purge valve. The c-clip holds it in place. You do not want to have any air pressure behind it when you do it...

[walt2137]

Woody the picture does not look like your air dryer, your coach should have came with a meritor wabco R955205 air dryer that takes a R950011 filter. Need to back off a little further to identify but it looks like your inversion valve but not sure.

 

walt

[Dave Pumphrey]

I agree with Walt, I may be mistaken that it is the drier.

The drier would only blow off at the end of the compressor cycle, with engine running.

Can you post a pic from a bit further back, so we can see location better, Like Walt said.

Some things look similar up close.

The drier would be mounted to the frame by the engine.

[birdshill123]

Repairs to air brakes should be done  by professionals.  

[Chargerman]

33 minutes ago, birdshill123 said:

Repairs to air brakes should be done  by professionals.  

Agreed, especially in a case like this where the OP appears to not be very well versed it the systems. (No disrespect intended at all). 

[glang11082]

On 1/30/2021 at 3:47 PM, wayne.cerven@gmail.com said:

 

Gary 

2 questions if you don't mind, yes I would be interested in seeing pictures of ramps,question 2, why from Provost to Monaco if you don't mind me asking

Happy Saturday 

Wayne 

1999 Monaco signature Caesar 

 had two Prevosts and loved them. The last one was a Marathon Conversion and very nice ,well built, we loved it.  However my wife had some health problems and we decided to winter home  in Canada and not Florida as we had for 16 years.  I was  now 2000 miles from a Marathon service center and had to do my own  repairs  I asked Marathon for a set of electrical draws (Prevost house wiring is very complicated  without drawing almost impossible to repair )  however they said no way their drawing were propriety and not given to customers ever.  My only option was to sell it so I did.  We found a good 2007 Ambassador ,got a full set of drawings from REV last Summer and although its not a Prevost we are very happy with it. More slides so more Grandkids are able to join us. Happy Trails.

 

[WayneC]

Gary

I really appreciate your response.

Northern Ontario winter has been very kind to us this year , no complaints considering what is going on around the world. Marathon coach, best of the best ! We have been entertaining the Idea of a Marathon and or other Prevost conversions , we have had some talks back and forth with Marathon (Oregon) in regards to many used coaches in their inventory, so in saying that listening to someone like yourself with the knowledge and experience helps me (everyone reading) to make logical decisions. A friend of mine owned my coach for 14 years prior to me purchasing it 4 years ago. Going with plan B, it has never been out in the sun unless it is on the road, 100k miles, going to spend 50k on end to end, updating/repairing little things and call it a day. I know the coach pretty much end to end.

Thanks again Gary

Wayne

1999 Monaco Signature Caesar

[glang11082]

2 hours ago, wayne.cerven@gmail.com said:

Gary

I really appreciate your response.

Northern Ontario winter has been very kind to us this year , no complaints considering what is going on around the world. Marathon coach, best of the best ! We have been entertaining the Idea of a Marathon and or other Prevost conversions , we have had some talks back and forth with Marathon (Oregon) in regards to many used coaches in their inventory, so in saying that listening to someone like yourself with the knowledge and experience helps me (everyone reading) to make logical decisions. A friend of mine owned my coach for 14 years prior to me purchasing it 4 years ago. Going with plan B, it has never been out in the sun unless it is on the road, 100k miles, going to spend 50k on end to end, updating/repairing little things and call it a day. I know the coach pretty much end to end.

Thanks again Gary

Wayne

1999 Monaco Signature Caesar

 I had Prevost coaches for 18 years. Can't beat a Prevost for ride and durability . If I had bought a Royal instead of a Marathon I'd still have it as Royals are way less complicated. Electrical is not problem for me repairing passenger elevators 33 years but without schematics the Marathon had to go.

By the way we are in Nova Scotia. We've been mostly snow free, Day time Temp -2 to +5 Celsius. We are close to the coast so we've had a fair bit of rain this Winter. Good luck  in your hunt and travels.

Gary

2007 HR Ambassador

On 1/30/2021 at 3:47 PM, wayne.cerven@gmail.com said:

 

Gary 

2 questions if you don't mind, yes I would be interested in seeing pictures of ramps,question 2, why from Provost to Monaco if you don't mind me asking

Happy Saturday 

Wayne 

1999 Monaco signature Caesar 

Text me, ill send pictures of ramp. 9024564039

Gary

[Bobbyboy]

I have a question relative to the brake test;  what is the difference in doing the test with the engine on vs the engine off.  If you hold the brake with the engine running and the compressor never kicks on, seems to me you can watch to see if you lose any air in the two minute span.  Of course if pressure drops to where the compressor kicks on you know you got problems.  I have performed the test both ways, never lost any air either way.  So what am I missing???  Same with the spring brake.   If engine is running and compressor doesn't come on and you don't lose any air other than what it took to release the spring brake the system should be good, correct?? I have an inquiring mind.  Sorry if I have missed something obvious.

Bob L.. 08 dynasty

 

[glang11082]

On 1/30/2021 at 1:51 PM, Ivan K said:

Can you share a picture of your ramp?

Text me 9024564039 i'll send a couple 

Gary

[Dave Pumphrey]

10 hours ago, Bobbyboy said:

I have a question relative to the brake test;  what is the difference in doing the test with the engine on vs the engine off.  If you hold the brake with the engine running and the compressor never kicks on, seems to me you can watch to see if you lose any air in the two minute span.  Of course if pressure drops to where the compressor kicks on you know you got problems.  I have performed the test both ways, never lost any air either way.  So what am I missing???  Same with the spring brake.   If engine is running and compressor doesn't come on and you don't lose any air other than what it took to release the spring brake the system should be good, correct?? I have an inquiring mind.  Sorry if I have missed something obvious.

Bob L.. 08 dynasty

 

The engine off is the way the DOT requires it to be done.

Because of this, it is the industry standard.

You are correct you get the same results if you abort the test should the compressor kick in, but then you would have already failed the test.

[dl_racing427]

22 hours ago, glang11082 said:

 had two Prevosts and loved them. The last one was a Marathon Conversion and very nice ,well built, we loved it.  However my wife had some health problems and we decided to winter home  in Canada and not Florida as we had for 16 years.  I was  now 2000 miles from a Marathon service center and had to do my own  repairs  I asked Marathon for a set of electrical draws (Prevost house wiring is very complicated  without drawing almost impossible to repair )  however they said no way their drawing were propriety and not given to customers ever.  My only option was to sell it so I did.  We found a good 2007 Ambassador ,got a full set of drawings from REV last Summer and although its not a Prevost we are very happy with it. More slides so more Grandkids are able to join us. Happy Trails.

 

WOW!  Such a shame that a company that builds such a nice coach has such horrible customer service.🤬

If I ever had the inclination and finances for a new coach, Prevost would've been in the running, but after hearing that this is how they treat their customers, I'd never consider buying one. 😪

[glang11082]

To clarify Prevost Canada will supply lots of chassis electrical drawing and fantastic support. It was Marathon ,  the converter that would not provide schematics for the House part. To be fair to Marathon they do have a tech support hot line that is helpful but in my case that wasn't sufficient to solve some problems I encountered and visiting their nearest service center was not an option (4400 miles return trip ) .