Air tank breake pressure question

[musigenesis]

I drove my bus today for the first time in about two weeks (I normally drive it 4 to 5 times a week) and it seemed at first like I was having the same problem as you. It built up to a little over 60 PSI and then seemed to stall there for a good while longer than it usually does (usually it keeps going right on up to 125 from this point). I decided to move the bus out of the parking spot anyway so I could put my car in the spot, and when I revved up the engine for this, that seemed to get the supply pressure gauges moving and they went right on up to 125.

Can the compressor or governor get sort of "stuck" such that revving the engine well above idle will clear things up?

[Peterjk]

Interesting, Id test that theory, but cant take mine out for a spin, legal or not, mainly cause the brakes wont work at 50 psi. I'm wondering if that's whats happening here too, tomorrow ill be testing for leaks.

[flattracker]

The "new Crown" has had a similar problem, but quit building pressure at 90 psi until I revved up the engine some, then it would go to 120 psi. In the next day or so the now rebuilt compressor will be installed, so I can troubleshoot to see if the problem has been fixed.

[Booyah45828]

Originally Posted by musigenesis

Can the compressor or governor get sort of "stuck" such that revving the engine well above idle will clear things up?

If they get gummy with water/corrosion/grease they can.

Which if it's mounted remotely somewhere down low on the frame it's pretty common for them to do, low point in a line always collects water, but I was under the impression his governor was mounted to the compressor.

It still could get gummy there, but not as likely.

[Peterjk]

I havent done anything yet other then start it today, its been raining, so just waiting for it to stop.
Heres a pic of the compressor.
I have no clue where the governor is yet.
The air pressure at the bus when I got here was 25, siting for 2 days.
I started it up, and it only got to 65 after 10 minutes, no higher.

Just waiting on the rain to stop before I crawl under the bus.

Hour later, pressure is still holding at about 65

[Tejon7]

Originally Posted by Peterjk

Just waiting on the rain to stop before I crawl under the bus.

Too bad you can't drive it. You could squirt a whole bottle of Dawn into a big puddle, then splash through at 35 MPH. You'd find your air leak in a jiffy!

[Booyah45828]

If the governor is attached to the compressor, it will be attached to the compressor head. It doesn't look to be attached at the front of the compressor, maybe it's on the back. It's the gray item on the right in the picture here.

If not, follow the unloader line to where-ever the governor is, as the unloader line will lead will be connected to the governor, compressor, and dryer.

[Peterjk]

Ok, I completed the bus crawl. Found this guy, see pic, underneath.

Saw a tiny bit oil on the pan bolts, so might be a start of a oil pan leak.

Sprayed the heck of every air fitting I saw, and no bubbles.

I DO NOT have any air bags in the suspension.

I still have not been able to locate the governor, so ill save that for crawl number 2 after lunch.

[Oscar1]

Here’s a pic of my C7 mine is a 2005 Cat see the aluminum body on the back of the compressor? That’s the governor there. Engine running you can spray around all those hard lines there just be careful of spinning things trying to grab you. Also do not spray up near the top of compressor as that is where the intake is and you definitely don’t want to be trying to compress water, hint! It doesn’t
And don’t forget those chocks.

[Peterjk]

I mentioned I had some oil seepage which collected around the oil pan bolts.

I found that to be only on the compressor side of the engine.

Then I think I found where it was coming from, that bottom line coming out of the compressor.

Would that be the Oil Supply line ?

The whole side of the engine is covered like that, o my guess is its slowly seeping out of that line. I checked the eng oil and it full, so must be a tiny leak. But enough to cover the engine and show some drops on the oil pan bolts.

[Peterjk]

WOOO!!!! Got pressure! Ok, too many names to thank here, but I think the issue is resolved. Oscar, Booya, rossvtaylor, o1mark, Musigenesis, Flattracker, Tejon, THANK YOU all.

There was no problem, remember, I was just idling it once in a while. Flattracker and Tejon got me thinking, if you could only drive it. But you'all sure help me here. It does take a village.

We'll I cant drive it yet, but I can rev the piss out of it, so I took it up to 2k and held it there, about 5 times, then eased off in between to idle, then repeated.

I got it up to 120+ till I heard the whoosh of air from the governor, releasing the excess pressure.

I also found the governor@ Right there under my nose by the back door.

So in the process, I discovered, what looks like a leaking Compressor line, I believe, as the one side of the bottom of the engine is sooted up. I prob will need someone to fix it in a shop, as there isnt the room to remove it, without pulling the radiator first in the pusher set up.

Thank you all, turns out there wasn't a problem w the compressor after all, but I did find the leak in the process!

PS, when I store it now, I'll leave the tank release valves fully open.

Peter : )

[Booyah45828]

Originally Posted by Oscar1

Here’s a pic of my C7 mine is a 2005 Cat see the aluminum body on the back of the compressor? That’s the governor there. Engine running you can spray around all those hard lines there just be careful of spinning things trying to grab you. Also do not spray up near the top of compressor as that is where the intake is and you definitely don’t want to be trying to compress water, hint! It doesn’tAttachment 61421
And don’t forget those chocks.

I don't see a governor in your picture. That aluminum thing bolted to the back of the compressor with a bar code label on it is a power steering pump.

[Booyah45828]

Originally Posted by Peterjk

Ok, I completed the bus crawl. Found this guy, see pic, underneath.

Saw a tiny bit oil on the pan bolts, so might be a start of a oil pan leak.

Sprayed the heck of every air fitting I saw, and no bubbles.

I DO NOT have any air bags in the suspension.

I still have not been able to locate the governor, so ill save that for crawl number 2 after lunch.

That's the dryer. Follow where the yellow hose on that leads to, and you should find the governor.

[Booyah45828]

You have an adip dryer for future reference.

[Booyah45828]

Originally Posted by Peterjk

WOOO!!!! Got pressure! Ok, too many names to thank here, but I think the issue is resolved. Oscar, Booya, rossvtaylor, o1mark, Musigenesis, Flattracker, Tejon, THANK YOU all.

There was no problem, remember, I was just idling it once in a while. Flattracker and Tejon got me thinking, if you could only drive it. But you'all sure help me here. It does take a village.

We'll I cant drive it yet, but I can rev the piss out of it, so I took it up to 2k and held it there, about 5 times, then eased off in between to idle, then repeated.

I got it up to 120+ till I heard the whoosh of air from the governor, releasing the excess pressure.

I also found the governor@ Right there under my nose by the back door.

So in the process, I discovered, what looks like a leaking Compressor line, I believe, as the one side of the bottom of the engine is sooted up. I prob will need someone to fix it in a shop, as there isnt the room to remove it, without pulling the radiator first in the pusher set up.

Thank you all, turns out there wasn't a problem w the compressor after all, but I did find the leak in the process!

PS, when I store it now, I'll leave the tank release valves fully open.

Peter : )

You found it! Good to hear. Compressor rpm is related to engine rpm, so revving the engine speeds up the compressor and increases the cfm it's pumping.

I guess if you didn't find any large leaks, that's a good thing, but this being broken and fixed without really doing anything is kind of suspicious. I know I criticized you for suggesting throwing parts at this thing to fix it. But I'm going to contradict myself here and suggest you throw a governor at this. I've got my doubts on it being the problem, but a governor is cheap enough that you can try one and see.

[Peterjk]

Originally Posted by Booyah45828

That's the dryer. Follow where the yellow hose on that leads to, and you should find the governor.

Another close up of the same pc, is that not the governor ?

When I follow the hoses it leads to the compresor.

I will happily buy/replace the governor.

This looks to be the same one:
https://www.ebay.com/itm/29158333629...YAAOSw0HVWFKqE

Once I have this thing finished, I'll need to take it to a shop to replace, what I believe is a leaking compressor line.

[Oscar1]

Originally Posted by Booyah45828

I don't see a governor in your picture. That aluminum thing bolted to the back of the compressor with a bar code label on it is a power steering pump.

Thanks for the correction, in my haste to get a pic for Peter I didn’t crawl under and just stuck my arm up in there. Sorry for the misdirection.
Cheers

[Booyah45828]

Originally Posted by Peterjk

Another close up of the same pc, is that not the governor ?

When I follow the hoses it leads to the compresor.

I will happily buy/replace the governor.

This looks to be the same one:
https://www.ebay.com/itm/29158333629...YAAOSw0HVWFKqE

Once I have this thing finished, I'll need to take it to a shop to replace, what I believe is a leaking compressor line.

That is the governor. The governor sends a hose to the compressor and to the dryer to cut out the compressor and turn on the purge cycle in the dryer. That hose might lead to a tee on the compressor, but it should still lead back to the dryer in some fashion. Often times, if the governor is bolted to the dryer, they'll be direct connected without a hose.

It's a d2 governor from bendix. They're commonly available. Genuine bendix units are about 4x that cost. Not sure where exactly you're located, but my local napa has one on the shelf for $17.87.

[magnakansas]

I have been working on a 1991 blue bird all american front engine. Air pressure would only hit about 75 psi. I did not hear any leaks. I finally go under the bus and went over the system again. We even adjusted the governor settings. Improved, but still low. So low never got the purge valve to open. Funny thing is the purge valve area was very clean like it had worked until very recently.

Pressures were sitting at 75 psi. From 0psi to 75 psi happens quickly which led me to believe that the compressor was in good health and would be able to get the job done. I just had to find why we were limited to 75 psi.

I had my head up under the bus right under where the driver sits yesterday.

I found the cause of the low pressure.

The air line to the air ride drivers seat was open and venting air. We reconnected the air seat and the problem was almost solved.
We adjusted the governor to bring maximum pressure from about 105-110 up to 120.

Now I am happy with the air brake system.

I could not hear that open line venting pressure very well at all. I had to have quiet all around me to hear it. Engine start, run up pressure to maximum - 75psi then engine off and quiet. It was really faint to hear, but the hose was only about 24 inches away from my head, and right in front of my face. When I did hear it, I had to swivel my head around trying to locate the direction of the leak so I knew kind of where to look.

william

[Peterjk]

Originally Posted by Booyah45828

That is the governor. The governor sends a hose to the compressor and to the dryer to cut out the compressor and turn on the purge cycle in the dryer. That hose might lead to a tee on the compressor, but it should still lead back to the dryer in some fashion. Often times, if the governor is bolted to the dryer, they'll be direct connected without a hose.

It's a d2 governor from bendix. They're commonly available. Genuine bendix units are about 4x that cost. Not sure where exactly you're located, but my local napa has one on the shelf for $17.87.

Thanks Booyah, I have this one on order just to have in a emergency: https://www.bigmachineparts.com/prod...x-d-2-bmps6106