| Author | Message | ||
| joe shelton (Littlewind) (67.241.230.74)
Rating: N/A |
after an 30 minute run @ 65 mph the temp of the top (head) of the air compressor was 425 F. i replaced the top compressor coolant line about 200 miles ago but wouldn't an obstruction have shown up right away? checked coming home last night after running 50 mph for an hour; 390 F. I figure it should be about same temp as engine (190 F). I'm surprised it didn't come apart. should I figure a replacement cause it got so hot? and could it over heat cause of something other than lack of coolant (old and worn out)? thanks, Joe 4106-2119 | ||
| Peter (Sdibaja) (209.242.148.130)
Rating: N/A |
Could it be that you have a low oil flow (pressure is not real important, volume is)? The oil cools too. How about disconnection both of the return lines (one at a time), fire it up and see if you get a reasonable flow. If so, blow on the retun line (towards the motor) and see if that in clogged. FWIW Peter | ||
| joe shelton (Littlewind) (67.241.228.36)
Rating: N/A |
I have found a number of factors that may be contributing to my compressor hi temp. first, my air gov is set too hi @ 130 psi. I will adjust (I never done noth'n like this before). second, I have an air leak. the compressor should cycle on every ten min or so to keep the pressure up. if it has to run non-stop or close to it, it will get hot (so I'm told). The eng stop air cycle is leaking air from around the plunger shaft, but I didn't think it was enough to keep the compressor running. will repair and see. Third, coolant supply restriction. will check. Joe | ||
| Peter (Sdibaja) (209.242.148.130)
Rating: N/A |
Joe: you may want to just replace the governor, I replaced mine for less than $20... truck stop price at Santa Nella, Ca TA Peter PS: mine was not bad but I now have a spare... Where you at? I am In San Diego... you could have my old one for the price of a cold one... | ||
| Jim Ashworth (Jimnh) (172.136.84.65)
Rating: N/A |
Joe- if your compressor is cycling every ten minutes, the bus probably should not be on the road. I can't find my manual, but I belive DOT standards call for leakage under 2psi per minute for a bus. With a 30psi differential, you are in the 3psi per minute range. Without using wipers or brakes on an interstate run, your compressor should only come on every 45 minutes or so. Fix the air leaks and then recheck the compressor temperature. 130psi is higher than normal but not in the danger zone. If you want to drop it to 120, then remove the plastic cap on the governer, loosen the nut and unscrew the slotted bolt a bit until the cutout pressure is back to 120 or so. Then lock it back in place and put the plastic cap on. If the governor is doing it's job, it should cycle between 90-95 and 120. If it doesn't replace it. Jim | ||
| joe shelton (Littlewind) (67.241.230.9)
Rating: N/A |
The air gov is about 30 days old. second in the past 12 months. Jim, good advice. Thanks, will find/fix all leaks! I said: "The eng stop air cylinder is leaking air from around the plunger shaft " I was told that if there was air supplied to the eng stop air cylinder, the engine would stop. Gee wiz, I never thuck of that before. So it must be the fast idle air cylinder or related plumbing. I checked it with the eng running on fast idle and only by putting my glove over the stop air cylinder (sound of air leak changed). I'll get out the soap/water bottle. Figure 8, section 8 of the governor cover & related throttle and stop levers looks quite different than what's on my 06 so I'm not sure what I'm looking at. I have an air throttle so that's one thing but it appears the throttle and stop shafts are in diff places. Any advice would be appreciated. Joe | ||
| Jim Ashworth (Jimnh) (172.150.110.217)
Rating: N/A |
If the air leak is loud enough to be heard while the engine is running, soapy water won't do any good. It will be blown away as fast as you can squirt and will never bubble. Try airing the bus with shop air so it is quiet enough to hear the smaller leaks and then verify with soapy water. Most air leaks are cheap and easy to fix. It's finding them that is the difficult part. Good luck with it. Jim | ||
| Ian Giffin (Admin) (64.228.43.148)
Rating: N/A |
Hi Jim, Joe and others, Jim, here's some additional information and the standard you were looking for. Your bus compressor is "on" all the time. It is connected directly to the engine or on a separate bracket connected to the engine by a belt. Of course, the compressor feeds the air tanks. Regulating how much air the compressor delivers, is the air compressor governor. It's function is to control when the air compressor will pump air into the air tanks. While the air tanks are at their maximum pressure, the governor stops the compressor from pumping air. While the system is this condition, air drawn in through the compressor is exhausted through its intake. When the air tank pressure reaches its minimum pressure, the govenor causes the compressor to start pumping air into the air tanks again. Cut-in and cut-out pressures vary. Most operate at approximately 100 to 125 psi. The cut-in pressure must not be below 80 psi and the cut-out pressure must not be greater than 135 psi. In Ontario, Canada, these numbers are written in law. Check with your local regulations. Too much air delivery to an air tank will cause it to rupture, so a safety valve protects the system and is set to 150 psi. Too little air delivery to an air tank will cause the spring brakes to deploy suddenly, so a low-air pressure warning signal in the form of a dashboard light and either a bell, buzzer or alarm will come on before pressure in your air tanks falls below 55 psi. The standard for air leakage is 3 psi in one minute of applied brake. Again, this is Ontario law so check with your local laws. As a handy reference for you, here are some functional checks for your air brake system: Air pressure build-up time: Reduce air pressure in the system to below 80 psi. Idle your engine at 600 to 900 rpm. Measure the time it takes to build air pressure from 85 psi to 100 psi. If air pessure build up time is greater than 2 minutes, your bus is defective. Compressor governor settings: With engine running, look at the air pressure gauge and note the cut-out pressure. If it is over 135 psi, your bus is defective; With the engine running, slowly pump the brake pedal to reduce the air pressure and note the cut-in pressure. If it is under 80 psi, your bus is defective. Low air pressure warning: Pump the brake pedal to reduce air pressure and note the pressure at which the low air pressure warning activates. If it activates below 55 psi or not at all, your bus is defective. Air loss rate: Chock the wheels of your bus. Release the parking brakes. Build up system pressure to cut-out limit. Shut off engine. Make and hold a full brake application for one minute while observing the air pressure gauges. If your bus loses more than 3 psi in one minute (after the actual application of the brakes), your bus is defective. If your bus is defective in any one of the checks listed above, stop your vehicle as soon as possible if it is running. Do not drive it to your local repair shop - it can kill you or other users of the road. Have it towed to the nearest shop or have a mobile service come to you. Hope this information firms up some of your questions. Regards, Ian www.busnut.com | ||
| joe shelton (Littlewind) (67.241.230.98)
Rating: N/A |
Thanks Ian, I will perform the test you described. I adjusted my air gov from 130 psi to 120 psi (less than 1/4 turn on adjusting screw). I turn the adjusting screw IN on mine to lower the pressure. As I have read some of your responses, I understand that the air gov turns the compressor on and off (so to speek); on my 4106 should turn ON @ 90 psi and OFF @ 120 psi. Should I see the gage cycle between these pressures? I don't, my gage stays on 120 psi and never comes off of it. That tells me my compressor was working all the time, right? I don't think it is because of an air leak so it must be the new gov. | ||
| Charley DeWalt (64.255.86.139) Rating: N/A |
Joe, I'm just thinking out loud here,but if the compressor were running all the time,you should hear the relief blow every few minutes?? Could your air gage line be comming from a brake tank so that you don't see a fluctuation on the gage,or maybe your cut in pressure is set to high,to close to 120p.s.i. that the gage doesn't see the fluctuation?? Just some thoughts. Charley | ||
| Ian Giffin (Admin) (64.228.43.145)
Rating: N/A |
Hi Joe, There was probably no need to make an adjustment to your air compressor governor because it complied with the 135 psi benchmark, shutting down at 130 psi. More correctly, the air compressor governor allows the compressor to move air into the air tanks, rather than to say that the compressor turns on and off. This diagram shows how the compressor reacts to input from the governor...  To say that your 4106 should turn on and turn off at 90 and 120 psi is misinformation. We define compliance as what it shouldn't be, not what it should be. For example, your compressor cut-in pressure is 90 psi, therefore, it is compliant. If the cut-in pressure falls below 80 psi, it is not compliant and you should not drive your vehicle. This diagram shows the governor's placement in the system. The system is shown in its unloaded state, which is when the compressor is not pumping air into the tank, or, as explained in my earlier message, when the air which the compressor is drawing in is being exhausted through the intake.  In a perfect world, once the air system is fully charged - in your case, at 120 psi - it can stay there for extended periods of time, especially if underway and not using any of the air-using systems such as wipers or brakes. This may also be the case if your vehicle is shut down. But I would suspect that your 4106, by virtue of its 'experience', should likely be trickling out a little bit of air, signalling the governor to load the compressor occasionally. As I mentioned before, your compressor is 'working' all the time. Do the "Compressor governor settings" test, above. As you pump down the air system, listen for the compressor to start pumping. If it continues to operate and you hear the telltale 'pshhhht' at the end of the cycle, note the air pressure which, in your case, should be 120 psi. You mentioned in an earlier conversation with Jim that the leak you were looking for seemed to be coming from an item that looked nothing like the one in your manual. Could it be the air dryer? In the test above, if the compressor continues to run and your air dryer is leaking air, you have neither a problem with your compressor nor your air dryer, but rather, your governor is still defective. Hope this helps. Ian www.busnut.com | ||
| joe shelton (Littlewind) (67.241.228.111)
Rating: N/A |
Ian, Thanks for all the great info! I never here or notice when the compressor starts pumping, nor the telltale 'pshhhht' at the end of the cycle. Because this is a new gov I am beginning to suspect the compressor uploader. I thought I would disconnect the compressor intake hose from the air filter and check what the air movement is at the differant system pressures (i.e. 90 psi & 120 psi). Should be sucking from 90 to 120 psi and sucking & blowing @ 120 psi, right? I'm also going to install an air press gage in the engine compartment , taking the pressure from the supply line from the dry tank to the gov. comments? | ||
| Ian Giffin (Admin) (64.228.43.102)
Rating: N/A |
Hi Joe, The way to tell if your compressor starts pumping is to watch your air gauges when performing the 'Compressor governor settings' test. As you slowly pump down your system with the brake pedal, note the pressure at which the needles of your air pressure gauge start to go back up. If you are having trouble hearing the 'pshhht' at the end of the cycle, try shutting off your bus, blow the air off to below 55 psi, start up your bus again. Your compressor should be pumping right away, therefore you will see the needles climb. When they reach about 120 psi, watch closely for them to stop moving. At the same time as you see the needles stop moving, you should hear the 'pshhhht'. That noise, by the way, comes from your air dryer. Joe, you must pay close attention to this: Your compressor, to use your language, should be sucking between 80 psi and 135 psi and it should take no longer than two minutes to get from 85 psi to 100 psi with the engine idling from 600 to 900 rpm. Although the numbers you are using are within the correct range, they are meaningless. Use only the numbers noted above. If your bus fails the test from 85 psi to 100 psi, your air system is non-compliant and must be serviced. If your air compressor continues to fill your air tank to beyond 135 psi, again, it is non-compliant. By the way, don't worry if it does rise beyond that, the air tank is protected by a safety valve which opens at 150 psi. I don't see a reason to connect an air gauge in the engine compartment, but that is your choice. By the way, we are likely talking about the same thing but the dry tank you mention is actually the wet tank if it is connected to the governor. The service tanks, formerly called the primary and secondary tanks, are hooked up after the wet tank. You should drain all your tanks at least once a day. Hope this clarifies the subject of governors. Ian www.busnut.com | ||
| Buswarrior (Buswarrior) (64.229.208.77)
Rating: N/A |
Hello Joe. One thing to ask, do you have an air dryer? If my history is properly remembered, were air dryers even invented when 4106 was built? There won't be any loud air noise when the governor cuts out if you don't have one. Governors out of the box are generally considered to have a 20 to 25 lb spread between cut-out and cut-in. When you are dropping the air pressure from maximum with the brake pedal, as Ian has detailed, just pump it down a bit past 25 lbs and then wait for 5 or 6 seconds, the responce on the air gauge may be a bit slow to show that the governor has indeed cut the compressor back in. As an airbrake instructor for a transit fleet, I'll vouch for the air brake checks that Ian has detailed. He's pretty good, for a firefighter! It would be a good thing to do these checks on your coach periodically to be sure the air system is in good shape. happy coaching! buswarrior |