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Old 05-11-2021, 08:23 AM   #1
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Occasional slow air buildup.

This usually happens when it is below freezing, but has happened when it is much warmer. Occasionally, not often, it will take a long long time for air pressure to build up on my 98 international with the t444e. It will build up to 60 or 70psi and then just stall there. Once it does build up it is no problem and may not happen for weeks. This is a daily driver. Any guidance will be appreciated.

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Old 05-11-2021, 11:47 AM   #2
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I hate intermittent issues. Frustrating.

I don't have any real answer, but here's what my understanding is of how the system works.

IF you have three tanks, Primary (back wheels), Secondary (front) and Auxiliary (accessories and emergency), in general, the auxiliary will not fill up until the primary and secondary have reached whatever the pressure amount is for your buses sensor. I believe this is usually 60lbs.

If for some reason the sensor or fixture that keeps the auxiliary from filling until the other tanks reach 60lbs, maybe that's when it takes longer?

Have you done the soapy water spray test on your air lines and connections?

Just a thought. Hope you resolve it soon.
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Old 05-11-2021, 07:35 PM   #3
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Quote:
Originally Posted by Simplicity View Post
I hate intermittent issues. Frustrating.

I don't have any real answer, but here's what my understanding is of how the system works.

IF you have three tanks, Primary (back wheels), Secondary (front) and Auxiliary (accessories and emergency), in general, the auxiliary will not fill up until the primary and secondary have reached whatever the pressure amount is for your buses sensor. I believe this is usually 60lbs.

If for some reason the sensor or fixture that keeps the auxiliary from filling until the other tanks reach 60lbs, maybe that's when it takes longer?

Have you done the soapy water spray test on your air lines and connections?

Just a thought. Hope you resolve it soon.
Thanks for the input. Yup a few times when it didn't want to build up even at 1000 rpm, I crawled under with the spray bottle. No bingo.
One thing to note: when it is slow both pressure gauges will just get between 20 and 60 then sit.
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Old 05-12-2021, 11:25 AM   #4
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Maybe you can find something in here?


Advanced Troubleshooting Guide for Air Brake Compressors*

https://www.bendix.com/media/documen...otingguide.pdf
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Old 05-12-2021, 11:50 AM   #5
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I'm just learning about air brake systems, so take my comments as just that......
I was waiting to see if anyone else would chime in with more experience, but since not......



I'm guessing the governor needs rebuilding.


I would remove the tube coming off the compressor, and check for oil there. If there is a lot of oil, I'd replace the compressor also. Mine came with the kit to rebuild the governor.


My rebuilt compressor also said to check the said tube for oil that has converted to carbon, which could block the tube and lead to lower pressure or long pressure-build-up times.



If you could, then with the tube still disconnected at the compressor, try to add in a pressure gauge (temporarily) to see if the compressor is actually producing enough pressure. If it is, then it is not the governor. However, it may actually be cheaper and easier to just rebuild the governor than to get the supplies and install them for the temporary gauge.


Dont forget to replace the desiccant filter also.
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Old 05-15-2021, 11:15 PM   #6
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Quote:
Originally Posted by Mountain Gnome View Post
I'm just learning about air brake systems, so take my comments as just that......
I was waiting to see if anyone else would chime in with more experience, but since not......



I'm guessing the governor needs rebuilding.


I would remove the tube coming off the compressor, and check for oil there. If there is a lot of oil, I'd replace the compressor also. Mine came with the kit to rebuild the governor.


My rebuilt compressor also said to check the said tube for oil that has converted to carbon, which could block the tube and lead to lower pressure or long pressure-build-up times.



If you could, then with the tube still disconnected at the compressor, try to add in a pressure gauge (temporarily) to see if the compressor is actually producing enough pressure. If it is, then it is not the governor. However, it may actually be cheaper and easier to just rebuild the governor than to get the supplies and install them for the temporary gauge.


Dont forget to replace the desiccant filter also.
Sounds like you are learning the good stuff right quick. Thanks for the "comments" I think I will find them useful.
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Old 05-15-2021, 11:17 PM   #7
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Quote:
Originally Posted by Simplicity View Post
Maybe you can find something in here?


Advanced Troubleshooting Guide for Air Brake Compressors*

https://www.bendix.com/media/documen...otingguide.pdf
Thank you Steve. This looks like a great resource. I am going to print it out and put it in a binder.
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Old 05-15-2021, 11:57 PM   #8
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After my last post, I was thinking more about the "freezing" part of your description.


My system bleeds down to empty overnight in freezing weather, but not when warm. Metal and seals that shrink when they get cold. Could you have a seriously profound version of that happening? That could affect the seal in the governor. When you checked for leaks, was it freezing at the moment? Hard to do with a spray-bottle of soapy water!


The other thing I'm thinking, is that you may have water in your system. It may be freezing and expanding and then holding a valve open? Or maybe water got into the governor. Again, freezing, and expanding, .....


Have you replaced the desiccant filter?
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Old 05-16-2021, 12:16 AM   #9
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Quote:
Originally Posted by Mountain Gnome View Post
After my last post, I was thinking more about the "freezing" part of your description.


My system bleeds down to empty overnight in freezing weather, but not when warm. Metal and seals that shrink when they get cold. Could you have a seriously profound version of that happening? That could affect the seal in the governor. When you checked for leaks, was it freezing at the moment? Hard to do with a spray-bottle of soapy water!


The other thing I'm thinking, is that you may have water in your system. It may be freezing and expanding and then holding a valve open? Or maybe water got into the governor. Again, freezing, and expanding, .....


Have you replaced the desiccant filter?
I doubt if it is water in the system. It does have a drier that blows of often and we drain the tanks often as well with very little evidence of condensation.

Doesn't have to be freezing cold for this to happen. Below 40 will sometimes mean a long wait for the air to build up.

Where do I find the desiccant filter?

I am thinking the governor may be the culprit, because the last time it happened I went out and tapped on it and the air started building up.
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Old 05-16-2021, 10:37 AM   #10
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The filter is in the "wet" tank. Follow the output line from the compressor, and it first goes to the wet tank.


Tapping on the governor....sounds to me like the problem. Unless there is something else in the system that I don't know about.
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Old 05-17-2021, 07:01 PM   #11
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Quote:
Originally Posted by Rock-N-Ruth View Post

I am thinking the governor may be the culprit, because the last time it happened I went out and tapped on it and the air started building up.
I love that "tapping" on something mechanical still resolves issues, at least temporarily.

If it is the governor, when you go out to fix it, make sure you address it properly in your best cockney accent "Good morn'n Guvner!"
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Old 05-17-2021, 08:46 PM   #12
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Governors are cheap. If whacking on yours gets it to function, replace it. They can get gummy from time to time, especially if they're low in the system.

We don't seem to have much trouble with them when they're mounted on the compressor, but the ones that are mounted low near the tanks seem to have issues with trapping moisture, even with a drier in the system.
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Old 05-18-2021, 10:42 AM   #13
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Do you have air bag suspension? My bus will air up real quick if the bags didn't deflate, but "stall" just like you described at 60-90 PSI if the bags deflated from being parked non level or for a long time.
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Old 06-08-2021, 01:11 PM   #14
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Quote:
Originally Posted by Simplicity View Post
Maybe you can find something in here?


Advanced Troubleshooting Guide for Air Brake Compressors*

https://www.bendix.com/media/documen...otingguide.pdf
Very helpful. Thank you. A minor adjustment of the air governor did the trick. I also dumped the air tanks, somthing I should have been doing g on a scheduled basis. Got a little oil but less than a teaspoon. Not bad considering I never did it before,(laziness is not my friend.) I've had the bus going on 2 years and 15k miles.

Again thank you for the very helpful troubleshooting guide.
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Old 06-08-2021, 01:15 PM   #15
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Quote:
Originally Posted by Jsneeb View Post
Do you have air bag suspension? My bus will air up real quick if the bags didn't deflate, but "stall" just like you described at 60-90 PSI if the bags deflated from being parked non level or for a long time.
This is also the case with my rig. An adjustment to the governor bumped my static pressure up to 130psi. Now the bags dont leak down flat. They hold 40 to 60 psi for days. The system recovers fast at 550 rpm to about 100 psi. If I bump the rpm to 1000 it will build to 130 psi quickly.
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