Just got an 1979 MCI MC-9. When I got it home I could hear air leak and believe is the air beam leaking on the passenger side. The bus is leaning to the right meaning the driver side is inflated and the passenger side is completely deflated and won't inflate anymore. It could be air hose. I can hear it between the rear diff and the air dry tank. I guess the only way to see it if from under the bus or taking off the wheel should give me enough clearance to see whats going on ? Also what is weird now is when I start the bus, the air pressure just keep raising , no purging, can't release the brakes, can't turn it off ( no air ) After I turn off the bus and let it sit for couple minutes the air just starts going to the air tank that supplies air to the park brake and engine shut off valve. Going crazy here. Any help would be appreciated.
So now the air pressure sits at 150, had to run in the back and shut it off manually. Things that don't work are wipers, fast idle, park brake release, fan belt tensioner, air horn, all the right side airbags are down, NO AIR, which air tank operates all these ? Can the leveling valve be stuck open ? Is there two leveling valves in the rear that control the front also ? The tank doesn't purge at 120 anymore.
Apparantly this bus has been sitting for a while? The air compressor governor is hanging up. Try removing it and clean. Or just buy a new or rebuilt,as they aren't expensive. Then you/we can work from there on some of the other issues. Since this is going to be a long term ownership?,you should obtain a factory service manual of some version.
wow thats a lot of things at once do the air compressor governor as chessie said then one thing at a time
The air compressor is pumping no problem, but the air is not dumping at 120 anymore. I drove it home ( 3 hour ride ) and no problem, it was dumping little passed 120 all the way. I parked it and was hearing this huge air leak in the back. I have to shut it off manually and couple times like 2 minutes after turning off the engine I would hear the air would just start going from one tank to another and then I can hear the air leak. Now nothing, it just pumps air without dumping.
Replace the governor first.
JC
Where is the governor located ? Is it possible to get the part number ? Can I take it apart and clean it ?
Governor is on the compressor. Yes, you can take it apart and clean it, but getting new seals will probably cost more than this...
http://www.ebay.com/itm/Bendix-D-2-Air-Governor-/171811693006?hash=item2800c661ce&vxp=mtr (http://www.ebay.com/itm/Bendix-D-2-Air-Governor-/171811693006?hash=item2800c661ce&vxp=mtr)
I did order it, thank you for the link, what is the exact function of the governor ? I know it governs air :) but to one air tank or 2 separate ones ?
The governor is usually located on the compressor, or close to it. It is the device that senses air pressure and tells the compressor to cut in at +-90psi, and cut out at +-120psi. Yours might not be telling your compressor to quit pumping, that is why you are getting 150psi. There is a good chance that most of your problem is caused by a faulty air pressure governor.
JC
Thank JC, will start with the governor, where it should be on a 8V71 ?
It is usually mounted on the compressor. If not, look for it using the picture in the link Timkar posted. Sounds like you need to get yourself a maintenance manual for your bus.
JC
compressor is rear mounted so its easy to access I suppose ?
Quote from: bcbusman on August 06, 2015, 11:39:22 AM
compressor is mounted so its easy to access I suppose ?
not usually. at least not on a coach.
I can officially say that selling my Setra was the biggest mistake. That bus is the best engineered bus with easy access to everything. :'( :'( :'(
Quote from: bcbusman on August 06, 2015, 12:58:07 PM
I can officially say that selling my Setra was the biggest mistake. That bus is the best engineered bus with easy access to everything. :'( :'( :'(
i have not read every word posted... but it is it possible that the governor is simply mis-adjusted ? by someone who was trying to solve a problem incorrectly ?
He indicated that it did cut out slightly above 120 psi on the way home, but not along with other issues, it pumps up to 150 now.
Tried to jack up the bus and take off the wheels but no luck even with my 5 foot ratchet, it just springs but won't loosen. If it says R on the nut you loosen counter clock wise right ?
Can someone please clarify where exactly is the air compressor governor?
Quote from: bcbusman on August 06, 2015, 06:00:01 PM
Can someone please clarify where exactly is the air compressor governor?
Most simply put. The governor is what gives instructions to the air compressor, and air dryer. That is what tells the air dryer to purge.
Make sense?
BC,
The governor is bolted to the side of the compressor. On your MC9, the compressor is gear driven off the back of the engine(towards the front of the bus). If your skinny and agile, you can access it through the curb side engine door. The rest of us get there by removing the access panels in the floor at the rear of the passenger compartment.
Bob
Was the access panel next to the toilet hole, same hight as the toilet hole but in the middle ?
Quote from: bcbusman on August 06, 2015, 06:34:38 PM
Was the access panel next to the toilet hole, same hight as the toilet hole but in the middle ?
the OEM toilet hole or the conversion hole ?
you might should call in an experienced observer.
Quote from: bcbusman on August 06, 2015, 05:54:17 PM
Tried to jack up the bus and take off the wheels but no luck even with my 5 foot ratchet, it just springs but won't loosen. If it says R on the nut you loosen counter clock wise right ?
Yup. RH thread on the RH side of the bus and LH thread on the left. Basically for removal always point the handle to the back of the bus and push down on the handle.
If the inner nut turns with the outer during removal the easiest tool to use is this https://www.acklandsgrainger.com/AGIPortalWeb/WebSource/ProductDisplay/globalProductDetailDisplay.do?gclid=CjwKEAjwi4yuBRDX_vq07YyF7l8SJAAhm0rpT-yLwbd-wO6dCN9Xj-xBdZ2Pa_w8542RJkksUYB2sRoCviLw_wcB&item_code=KTL30610&cm_mmc=PPC:%20Google%20PLA-_-PLA%20Campaign-_-PLA%20Ad%20Group-_-PLA&ef_id=U-mA6AAAAb34HEcv:20150807040045:s (https://www.acklandsgrainger.com/AGIPortalWeb/WebSource/ProductDisplay/globalProductDetailDisplay.do?gclid=CjwKEAjwi4yuBRDX_vq07YyF7l8SJAAhm0rpT-yLwbd-wO6dCN9Xj-xBdZ2Pa_w8542RJkksUYB2sRoCviLw_wcB&item_code=KTL30610&cm_mmc=PPC:%20Google%20PLA-_-PLA%20Campaign-_-PLA%20Ad%20Group-_-PLA&ef_id=U-mA6AAAAb34HEcv:20150807040045:s)
1-1/2" for the outer nut - 13/16" square for the inner nut
The factory toilet hole
I ordered the lugwrench.biz with the 1:78 ratio for the bolts, hopefully its gonna work. How do you use the wrench that you post it ?
After the outer wheel is off (with the inner and outer nuts still in one (or more) of the mounting holes put the wrench on the outer nut with the little "tail" over the lip in the center bore, then you put your impact (or ratchet) on the inner nut and separate the two. It's a bit tricky and easier to do with a pneumatic gun but with help you should be able to do it with a rachet.
Here is a fancy tool that shows how it's done. http://www.esco.net/tire-changing-equipment/product.php?productid=138&cat=5&page=3 (http://www.esco.net/tire-changing-equipment/product.php?productid=138&cat=5&page=3)
The engine access panel is in the floor.
Bob
Here is the Multiplier I use to take off the nuts 60 to 1. Just have to be careful putting them back on.
http://www.amazon.com/New-Torque-Multiplier-Set-Wrench/dp/B00N9S864C/ref=sr_1_7/177-7359387-1483414?ie=UTF8&qid=1438927521&sr=8-7&keywords=torque+wrench+multiplier (http://www.amazon.com/New-Torque-Multiplier-Set-Wrench/dp/B00N9S864C/ref=sr_1_7/177-7359387-1483414?ie=UTF8&qid=1438927521&sr=8-7&keywords=torque+wrench+multiplier)
Quote from: bcbusman on August 06, 2015, 06:00:01 PM
Can someone please clarify where exactly is the air compressor governor?
Here is pic of air compressor and governor on an 8V71...
Thank you for the pic :)
LOL that compressor is on a Eagle it's not going to be that easy on your MCI,like Bob said go through the side door you will find the compressor on a 75 degree tilt at the bottom of the bell housing remove the cap from the governor and try turn it down,they work backyards as to most regulators screw it in to lower the pressure
You probably have a pressure protection valve at the main tank preventing the other tanks from airing up
Got to it thru the floor opening service door, tapped the air governor with hammer and it started airing up. Still have to find the leak so now just waiting for the lug tool but will replace the air governor too
Quote from: bcbusman on August 07, 2015, 09:12:33 PM
Got to it thru the floor opening service door, tapped the air governor with hammer and it started airing up. Still have to find the leak so now just waiting for the lug tool but will replace the air governor too
The governors are not expensive and if they're showing any signs of acting up AT ALL, it's smart to replace it.
Found the leak, it was a hose, fixed, replaced the air governor, that didn't change anything, still have a problem with airing one of the tanks. So when I start the bus and lets say the air pressure is at 30PSI at start up and it starts raising, when it hits around 100PSI I can hear the air starts going to another air tank but only briefly and then it stops again so I don't have the throttle, wipers, high idle, belt tensioner, air horns, dump valve ( so the pressure just keeps raising and I have to shut off the bus manually) and right side air bags, none of these have any air. Can you please tell me which valve is it that opens to air all these and where is it located please.
Possibly a stuck pressure protection valve. should be somewhere between the wet tank and the aux tank I believe. Been a while since I messed with mine but I think it was at the aux tank.
The problem is that it just keeps airing up without dumping air because the air simply doesn't get to the dumping valve and to the rest
Anyone with some Wisdom please ?
If your governor is working it won't air past 135 or maybe 140 psi. Fix that first.
I did put brand new governor and it will go to 150 easy if I leave it
The D2 govenor has a 20 psi pressure differential. IE: cut in @ 95 - cut out @ 115 or in@90 out@110. It should therefore NOT go to 150. You are not getting signal pressure in your reservoir line from your supply (wet) tank to signal the govenor to put the compressor in unload.
Possible reasons are:
the small lines are connected wrong
the reservoir line is kinked or blocked
compressor sticking and not going into unload stage
Test: Connect an external charge port on your supply tank, disconnect the small lines at your governor (with system empty), then fill up your supply tank. You should get air leaking out your reservoir line. Make sure that line connects to the reservoir port on the governor.
ALWAYS WEAR EYE AND EAR PROTECTION - PLEASE!
(https://busconversionmagazine.com/forum/proxy.php?request=http%3A%2F%2Fwww.benzworld.org%2Fforums%2Fattachments%2Funimog%2F275554d1259375554-sbu-air-dryer-screen-capture-26.jpg&hash=f86c75d215552bbf1a07213bc2f65d77960efd0e)
EXCEPT...if it is not adjusted...some are not from the factory, I would check that for sure.
Did you adjust the new one...or just put it on ?
Secondly... there should be a pressure relief ( or two ) somewhere in that system that should pop off at 120psi....preventing it from ever seeing 150...
(https://busconversionmagazine.com/forum/proxy.php?request=http%3A%2F%2Fwww.pneumaticcontrol-valve.com%2Fphoto%2Fpneumaticcontrol-valve%2Feditor%2F20130927111902_51913.jpg&hash=a4496b9cfb3f810f63d5107f7c36a51a8f3e799d)
And there are times when you really need to put qualified eyes (and fingers) on the hardware.
It has to be the protection,check valve or the solenoid some MCI used,it is not going to unload the compressor till the governor receives a signal the tanks and the system are full.If has a air dryer that is where the signal will come from when the dryer purges the compressor is unloaded if the 1/4 inch tubing is bad or leaking it won't unload
It should start filling the other tanks around 65 lbs there should be a check valve before all the tanks except the wet tank and they go bad.
? have to tried to air the bus up from emergency air ports the one under the drivers window will air up the complete system the one at the rear is just for brakes
good luck
Thank you guys will try, I will also take the picture of the governor that was there . I deleted and connected the ports exactly as the old one but maybe the that was wrong was also wrong. Also would anyone have the part number for the pressure relief valve please ? The one between the last bay and rear axle under the tank, I tried to release it manually today and its stuck, won't move whatsoever.
You did be sure the new governor had the plugs in the same place as the old one ? sometimes you need to move the plugs
I did, same place 100%
Maybe this video can be of some help.
https://www.youtube.com/watch?v=PGFwVLEmhfI (https://www.youtube.com/watch?v=PGFwVLEmhfI)
You are going to need to find where the governor is receiving the signal from to unload the compressor,seems to me like it is picking it up from 1 of the tanks that is not airing up air it up with shop air and go from there jmo
No Air signal to the governor, The only air Tank that gets filled is the one for the brakes, no air after that, So I just went and let it go as far the air pressure can go and little over 150 PSI the right front tank protection valve is purging so I know that the air gets up to there and my guess is thats it. Is there a valve between the tanks to let the air go further ? Thank you in advance
Do you have a schematic of your air system?
Yes but its a crappy copy, that's why I'm trying to find help on the forum. Maybe someone has a good PDF ( even bought one on ebay in PDF file and still crappy )or anything of the air system on the 79 MC9 that would be great but knowledge is always good too.
Pressure protection valve
Pressure protection valve is releasing at 150PSI I know that
You are confusing the pressure protection valve with the pressure relief valve. the pressure protection valve is in line between the wet tank and auxiliary tank. It's purpose is to prevent air from entering the aux tank if the supply pressure is below 65. They do fail, and when they do it can cause the issue you describe.
I think I suggested that about a week and a half ago, be interested to hear if that turns out to be it. That's where I'd put my money.
Thank you, I will take floor apart and try to get to it tomorrow,
You shouldn't have to take the floor apart. you should be able to access it from underneath the bus.
I have no place to go under, Is it accessible under the floor ?
I seriously doubt it. You will need to get under the bus. I can't remember exactly where it's located but it will be between the dry tank and the auxiliary tank. Most likely next to either one, not in the middle. Someone should be able to chime in and tell you where to find it. If I was a betting man that's where I would put my money.
I gor out my service manual and took a look, I was incorrect. The pressure protection valve is located between the dry tank (located fore of the rear axle), and the tee inline supplying the park brake tank (passenger side above front axle) and the auxiliary tank (under driver). I believe the tee is located on the park brake tank, so the pressure protection valve could be located @ the tee, or less likely in the rear area next to the dry tank. I would start up front and go from there.
Quote from: thomasinnv on September 02, 2015, 04:05:14 PMI gor out my service manual and took a look, I was incorrect. The pressure protection valve is located between the dry tank (located fore of the rear axle), and the tee inline supplying the park brake tank (passenger side above front axle) and the auxiliary tank (under driver). I believe the tee is located on the park brake tank, so the pressure protection valve could be located @ the tee, or less likely in the rear area next to the dry tank. I would start up front and go from there.
This thread has dragged on so long that I can't find details but I think he said that he has air in the dry tank but nowhere else. This info on the location of the pressure protection valve pretty much nails it. Thanks, Thomas.
Just wanna double check where exactly is the protection pressure valve located on the 79 MC9, how it looks like and can I access it under the floor ?
Thank you in advance
Do mci's have a compartment under driver outside? That is where it is on GM.
MCI's do have a compartment under the driver which is where the auxiliary tank is located, but I'm pretty sure that the pressure protection valve and the tee feeding the tank is adjacent to the park brake tank above the front axle. There really is no access from above, the best way is to gain access from underneath, what ever you have to do to achieve that. I suppose you could possibly access it by going through the floor in the isle behind the driver, but that just doesn't seem like the logical way to go. if a fellas gonna own a bus he has to have the means to get under it, or a checkbook big enough to get it done.
I will build some ramps, I'm was use to getting access to everything on my Setra under the floor :) :) :) :)
I believe the pressure protection valve on an MC12 is in the front baggage compartment, passengers side right below the ceiling next to the front bulkhead. There is a cover held on with a screw. It it's connected tho the valve for the OTR heat valve. I'm not sure if a MC9 is the same, but a lot of things are similar between the two models.
Should be the same , thank you
Here are pictures of where mine is. first picture is for reference which compartment, second picture shows a view closer. My heat valve is removed, and there is electrical conduit I installed in the area. Third picture shows close up of my pressure protection valve. I installed a air line chuck where the heat valve was plumbed into the air system, ignore that.
2nd picture
3rd
Thank you for the pics, mine has only the coolant valve on the same spot
It would be in the front wheel well housing coming off the air dryer if you have one. If you don't it will be coming off the wet tank in same area...
Dave