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Bus Discussion => Bus Topics ( click here for quick start! ) => Topic started by: Ryker on March 28, 2019, 09:56:47 PM
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I was driving down Hwy 37 today with the windshield wipers on. I noticed the wipers slowing down, then noticed that I was losing power. I checked the air gauge and it was at 30 lbs but the low air alarm was not going off. I immediately pulled over and coasted to a stop on the side of the freeway. I checked the engine bay and a high-pressure, steel bradded, 3/4" line came apart at the compressor.
A couple strange things happened:
During my ownership, on occasion, I press the parking brake button and the brakes are not on. The normal procedure is to pump the brakes and then they release. I noticed today that the brakes were off before I touched the pedal. I am wondering why my brakes did not engage all the way down to 30 lbs. I feel I may have avoided a disaster by losing my air on a flat freeway.
I started it when the tow truck got here to make sure the transmission was in neutral because I am having problems with my transmission toggle switch. When I tried to turn the engine off, it kept running. I used the emergency shut-off for the first time. Does this have something to do no air?
I am a bit nervous to drive anywhere if there is a chance of losing air with no warning. I am pretty good at watching my gauges but this air loss was very quick.
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I can't answer all your questions, but a couple I can...
The engine shut-down cylinder is air operated. You need to have some air in the system or you cannot shut down the system using the switch on the dash. Important to remember this, as once your air bleeds down you cannot shut down the engine for a few minutes from the dash.
If there is reason for concern about having to shut down before air builds, or if you know that air won't build, then it's probably best to start the engine from the rear of the bus. The only way to shut down (other than the emergency stop) is to manually work the lever that the shut-down cylinder normally operates.
Your e-brakes should have popped at 60 psi. When is the last time you tested that system? Sounds like at the least you need a low-air sensor and/or a new parking brake valve. Others know more about the air brakes and hopefully someone will provide more definite answers on this one.
Transmission toggle? Have you checked for loose wires/connectors behind the toggle?
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I understand the engine shut down now. That makes sense to me, and is what I suspected. I did not think of working the lever but I am familiar with the lever, so that is great advice.
Good to know that when it is working correctly, I will still have control over the brakes in the event of air loss. I feel I still had some brake power left but I mostly coasted to a stop. I was trying to make an offramp but I was also concerned that the brakes would simply engage at any moment, which is about as bad as no brakes at all. The brake button did pop but the brakes still are not engaged. My low air light always works, so I wonder why it failed this time. When working properly, what is supposed to happen? I would think alarm at 80 lbs, brakes on at 65 lbs. It all worked out but I feel I got very lucky. Had trouble sleeping last night thinking of different possible scenarios both losing brakes or suddenly engaging brakes without warning.
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You can jumper the low pressure switch to check it. Could be the low pressure switch or the buzzer in panel to left of driver. Have you ever had your brakes inspected and adjusted. You shouldn't pump brakes to get them to release. A full air pressure brake application should release them after previously setting by pulling up on brake button. This is if the system is in good and properly adjusted condition.
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Glad you are here to ask questions.
First, this is a 1974 coach? FMVSS 121 did not take effect until 1975, so everyone's "airbrake knowledge" doesn't apply to this coach.
Yes, it might be configured to just keep on rolling with no air pressure, by the manufacturer, or by someone doing "repairs" over the last 45 years...
Transmission toggle? Do you have an air shifter?
Brakes not "on"? With the button in the "parked" position? When we're the brakes adjusted last, and by who? Tightened up, or loosened off?
Low air warning. Where in the system is it plumbed, how many are there, and have they all been tested individually by emptying that particular part of the system? (HUGE failing for this for those with dual system, which low air sensor was tested when you fan the brakes down, which wasn't?)
Which kind of brake system is, or was, in in this 1974 GM coach? DD3, spring brake, hand brake?
This compressor pipe failure may have uncovered something more important.
You want this whole system gone through, to be sure it is "safe" according to its design, and working properly.
And you want to know how to do the periodic tests to be sure.
Happy coaching!
Buswarrior
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I'm not sure that your braking system is working the way it's supposed to based on your description. Here's a bit of text from the Operator's Manual:
EMERGENCY OPERATION - If normal application fails to stop the vehicle, emergency brake application should be made by pulling the control valve knob all the way up. This system is designed for emergency use only, producing a severe, sudden stop, and should be used ONLY under emergency conditions.
LOSS OF AIR PRESSURE - A warning tell-tale, "LOW AIR" will light and a buzzer will sound when the air pressure in the system drops below 60 pounds. The vehicle should be stopped and the cause of pressure loss determined and corrected before proceeding. However, if warning devices are ignored and parking brake pressure drops below 40 pounds, making operation of the vehicle unsafe, the emergency brake will apply automatically.
If your pressure dropped to 30 pounds and the e-brake did not engage then something in your system is not functioning properly. Since you said that your buzzer did not sound either, then my suspicion is that your low-air sensor is not working or not connected. If your button did pop but the brakes did not engage, then perhaps the pressure dropped so suddenly that there was inadequate reserve left in the parking brake tank.
There is a thread on one of the bus forums about what happens when the e-brake applies while the bus is in motion. If I remember correctly, it applies the brakes forcefully, but not enough so to lock the wheels or make the bus uncontrollable. Regardless, in most situations I'd assume that stopping suddenly is better than not being able to stop at all. I've had that experience and it sucks (we survived due to a well-placed berm next to a driveway which caught under the nose of the bus.)
My advice? Get the entire air system checked out by someone knowledgeable/qualified to diagnosis things properly once you get the air compressor line repaired.
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Richard, that bit of operator's manual quote only applies to one brake system type.
Until we know what brake system is involved, all we're doing is driving Gary's Google points up without helping.
GM built 'em whichever way the customer ordered 'em.
Ryker?
Happy coaching!
Buswarrior
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Richard, that bit of operator's manual quote only applies to one brake system type.
Until we know what brake system is involved, all we're doing is driving Gary's Google points up without helping.
GM built 'em whichever way the customer ordered 'em.
Ryker?
Happy coaching!
Buswarrior
I thought that DD3 brakes were standard on these - did GM offer other options in 1974 in a 4905?
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45 years is a long time for foolishness to happen.
Ryker, what parts are really under your coach?
On the rear brake chambers, is there one, two or three airlines attached?
Happy coaching!
Buswarrior
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They are dd3's. No room for anything else, btw.Only change with later models was short lived antilock and then dual brake system
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Same with MCI 5's and 7's
I saw it in change orders that came with my manual years ago. I thought interesting in 1979 and older that they would have anti-lock. a mechanic told me at greyhound that they took them out because they didn't work well on wet and icy road.
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Man, this has gone from bad to worse. Got the air hose made and back on yesterday morning and drove about 20 miles with no issues, air at 120 lbs. Stopped for a couple hours then drove just 3 miles and started losing air again. Dropped to 60 lbs and would not come up so I pulled over and air went back up to 120 lbs while parked and idling. Shut it down for a couple hours, started it up and drove 80 miles with no issues. This morning was driving home and made it 25 miles and white smoke started billowing out the back, started losing power and engine died. A couple people honked at me because smoke was so bad. I coasted to the side of the road, and I still had air and brakes. Jumped out to make sure there was not a fire in the engine compartment.
One point to make is that about a month ago I heard a very loud whistle coming from around the rear axle. Air was leaking out of something. I haven't heard the whistle since but my 15 year old niece and 30 year old daughter heard it a couple times this week. They said it was very loud but my 52 year old ears could not hear it. It was not the pressure release valve high up in the engine compartment because I checked that when I was hearing it, and I also replaced the valve because it used to bleed out all of the air.
Not sure these issues are related but maybe the air line popping off pointed to bigger issues.
Now getting it towed home.
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Where is Home? About city or area? :)
did the engine even turn over after that? You might want to just try Baring it over to see if it turns but make sure your rack is turned to no fuel, fuel shut off is turn to off if you have one before the fuel filters or just pull your fuel filters or it could start. If you just hit the key trying to start it and it does start and you have a mechanical issue. It will only make it worse.
Those clear white air lines if there were any still there go bad over time and crack or snap off. It needs to be DOT vinyl hose or flexible copper on any lines.
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I'm in Sacramento, CA.
I got it to my shop and before I saw your response, I tried to start it. The starter just makes a big clunk but will not turn the engine at all. Am I jumping to conclusions that the engine is seized? Tomorrow I will pull the muffler and put a socket on the accessory drive nut to see if I can turn it.
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Just a wild thought, but could the compressor have failed and caused the engine to seize?
Possibly the governor failed first, resulting in a high-pressure situation - possibly explaining how that 3/4" line blew.
When it fully failed, the failure went further into the engine, which explains the white smoke seen from the rear of the bus?
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It would be prudent to deal with each of these symptoms/failures alone.
If they prove to be related later on, that's fine. Compressor drives don't partially fail and start working again...
A busnut goes flapping their gums to a mechanic about their theories... the mechanic quickly learns a) there is a gold mine of ignorance to be exploited, b) you distract from the traditional trouble shooting strategy
Either way, time that is being paid for gets wasted.
Was the brake adjustment ever confirmed? Block the wheels, both sides, and put a tag on the steering wheel that brake adjustment AND parking brake function has not been confirmed. Nobody works on it without being informed.
Don't be driving that coach anymore until the proper functioning of the air system and parking brake has been proven correct.
Engine first, then the rest.
Happy coaching!
Buswarrior
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Thank you, Buswarrior! Ted does not think that high pressure would seize the engine but he is not certain. One more tidbit, when I brought my old hose into the hydraulic shop, the tech said there was a lot of carbon build up in the old air line. I did not mention this to Ted but he said, "The "ping" tank or line or main check valve to the main air tank could be carboned up (restricted)." Not sure how you go about removing carbon from inside the airlines.
I feel I am still jumping around a bit, and maybe these 2 things are not related. Today I am going to try to turn the engine to see if it is truly seized and go from there.
Don't worry, I do not think I will be driving it for awhile! I actually have an appointment to bring it to Terminal Truck & Frame tomorrow morning to have the braking system gone through but I doubt that is happening. They are the ones who did all of my suspension work.
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Just let the engine guy do his diagnosis, don't confuse that issue with air system chatter.
Did the Hydraulic shop sell you a correct metal hose, suitable for use right up against the hot compressor?
To sort out the air system, and be sure that it is safe to move the coach any further on its own, you need someone who knows exactly what an old pre-FMVSS 121, DD3 brake system is supposed to do, and knows EXACTLY how to completely test its functionality.
This person must be able to identify if this brake system has been modified or otherwise been meddled with by someone who DIDN'T know what they were doing, and rendered it unsafe, under failure conditions.
This knowledge of DD3 was thin to begin with, and is mostly died out now.
Brian Evans, are you any more motivated than I am?
Ryker, where are you? Within roadtrip distance?
happy coaching!
buswarrior
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The air hose guy said that the liner in my hose was burned out a couple inches in, and that is why it failed at the hot compressor, like it melted the inside liner. I am assuming he knows what he is doing since he mentioned that. He is a very reputable shop in the Bay Area but I will call him tomorrow to ask about it.
I pulled my muffler and put a breaker bar on the nut at the accessory pulley just now. I can not budge that engine. For comparison, I turned the nut on my spare engine and I had no problem turning that one.
The owner of Terminal Truck & Frame (Cowboy is his name) is very knowledgeable and he said that he knows this brake system but I do not know how to be sure of that.
I am in Sacramento. Road trip to where? I understand there is a mobile mechanic who goes around the country and works on Detroits. He did the Opti Force One engine recently.
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You broke a liner or drop some valves you have bigger things to worry about now more than a air system or hoses
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Your air hose melted be because it was the wrong hose. You are supposed to use a copper line for 3-4 ft or so before it connects to a steel braided DOT air line. The air coming out of the compressor is HOT.
On your engine, white smoke is raw fuel from lack of compression. Like Clifford said, something broke. Try barring your engine the opposite direction you have been trying, and if it moves, it is a dropped valve.
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I tried both directions and couldn't budge it. I pulled the easy valve cover (the one in front) and everything looks normal there.
I have maybe 10" of steel pipe before the braided line.
Yes, it was white smoke.
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Pull the inspection covers and have a look in the cylinders to see if you can see the broken sleeve or maybe the top of a blown piston top or broken rings etc.
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I am in Sacramento. Road trip to where?
The road trip would be mine, not yours...
happy coaching!
buswarrior
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My vote is with everyone else - engine first, then air system issues. You may be using that spare engine sooner than you had hoped...
As far as air issues are concerned, the first thing you need to understand is where the pressure gauge is reading from. On my bus it reads the dry tank pressure, on other buses I know it can read the accessory system pressure. This could be a pre/post FMVSS deal. There is a pressure protection valve usually present between the dry tank and the rest of the air system, so if you are reading 30 psi on a gauge connected to the accessory system you could have a big leak there, pressure drops, but you still have 60 psi in the dry tank. On my bus (1980 MCI, post FMVSS) the Push/pull valve for the emergency parking brake is fed from the emergency brake tank, which is separated from the rest of the air system with a check valve. It's perfectly possible for the emergency brake tank to retain 120 psi pressure when the rest of the system is at zero psi, showing nothing on the gauge. Yet the parking brake would still work if needed, and the PP valve would not pop automatically until pressure in the emergency tank dropped below 40 psi. Knowing tidbits like the presence of that check valve and the E-brake tank being separate, knowing that the PP valve won't pop until 40 psi in the E-brake tank, and knowing where the gauge reads air pressure are the little details that a Busnut needs to know about THEIR particular bus and air system.
Regardless, engine first, maybe a new air compressor while it's out and easy to change, and then go through the 50 year old air brake system. My theory on old air brakes and systems is that if I didn't change it, it's old enough to need changing anyway...
Oh! When my bus whistled loud and high enough to annoy dogs for miles around, it was the 80 PSI pressure limiter located on the forward wall of the rear axle bay. That limiter, which you may or may not have, limits air pressure to the inversion have and hence to the parking brake chambers of the DD3, so that the maximum application the emergency/parking brake system can make is limited to 80 psi
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The road trip would be mine, not yours...
happy coaching!
buswarrior
Ha! Well, that makes more sense. My brain is fried trying to figure all of this out. Come to Cali, the weather could not be better than in the Spring.
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Dropped the oil pan today and it is full of metal shavings. Looked up into the engine and do not see anything obviously broken but...metal shavings.
Spare engine is starting to make me nervous. The exhaust was not covered so people are telling me I could have rust in the exhaust valves and sleeves.
What about purchasing a bus with engine history but otherwise a mess, and swapping engines? Or easier to rebuild what I got maybe, with further investigation?
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Any curved that look like silver and copper? Might be main or rod bearings. Sound like you need to go further. Have you pulled even the inspection hole covers on each side or the close side to look in the cylinders? Any pieces that might look like a part of something like a piston or injector tip pieces, or rod pieces etc.
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If it were my engine, I'd wait until there was a diagnosis before condemning it.
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Any curved that look like silver and copper? Might be main or rod bearings. Sound like you need to go further. Have you pulled even the inspection hole covers on each side or the close side to look in the cylinders? Any pieces that might look like a part of something like a piston or injector tip pieces, or rod pieces etc.
Here is the largest piece. Very thin and sort of a silver/copper color.
I have not yet pulled the inspection ports. They all seem to be in the most inconvenient spots.
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Part of a bearing shell probably from the rear main they go first because they are last in line for oil.Rust is not good but really not that bad if you change the oil after a few hours of running. Mikey engine set in a drump truck bed for 10 years and was rusted he has been running that engine in his 4106 for 5 years now with no hiccups.LOL I would condemn that engine for sure if it spun a main the machine shop cost to line bore one now is out of sight cost wise.FWIW that heavy @$# flywheel used with the V730 will take a toll on the mains
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I have been following this thread, and the picture raised a question.
Why does the shaving look burnt? That's not from sitting in the oil pan is it?
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Don't bother. That engine is going to need serious repair or replacement. And don't waste the time trying to do an inframe.
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not just from sitting in the oil. Sometimes when no lub to bearing they get hot swell or stick to the crank and spin with it after breaking the small holding tabs on the bearing ends. Oil journals might be block etc. When all this happens and it can be over time or very fast the metal will get scrapped and sometimes burnt then thrown out and generally they don't come all the way out and the crank gets seized. The crank at that point is probably done with scratches and grooves that even if machined may not be good.
Just how it can happen didn't say it did but very possible.
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Heat is why it's discolored that could be a thrust bearing
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not just from sitting in the oil. Sometimes when no lub to bearing they get hot swell or stick to the crank and spin with it after breaking the small holding tabs on the bearing ends. ...
Yes, I think you hit the nail on the head, Dave. This particular one looks to me like the bearing material got peeled off the steel backing and pushed out in the oil -- and that's going to be a very hot, high pressure situation whether it's a main or con rod or thrust bearing (as Clifford says). And, agree on the probable damage to the crank.
Just how it can happen didn't say it did but very possible.
And it makes me wonder if this was the original failure or if it was a subsequent problem caused by something else. Whatever, I'm in agreement that there's probably a lot of damage in other places in this engine and -- if it can be "saved" in a practical sense - it's almost certain to need an oil pan-to-valve cover total rebuild. But only way to know is to open it up.
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Looks like what's left of a rod bearing. The one furthest from the oil supply channels in the crank. Running almost completely out of oil will do it.
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Looks like what's left of a rod bearing. The one furthest from the oil supply channels in the crank. Running almost completely out of oil will do it.
Definitely not out of oil. I checked the oil all of the time. It did not go through much oil either.
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Coolant real low or overheat, or severely lugging engine on grade, or worn out bearings till one left go? Did you figure where all the white smoke came from? Coolant level normal?
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Is there any coolant or fuel in your oil? you really need to take it somewhere or if your doing it yourself pull the Valve cover off to see if any valves have dropped and are really loose.
Other option is start getting it ready to pull out and check it that way. the only way your going to get to the back easily.
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Time to rename this thread. Because I thought California actually lost an Airline (as in Southwest or Delta) lol. Turns out it was an air line and beyond that, this thread got real dark real fast now that we know your engine is toast...major bummer and makes me nervous about my own every time I see someone blow theirs up I wonder if it's my turn. Keep us updated.
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Yes, I think you hit the nail on the head, Dave. This particular one looks to me like the bearing material got peeled off the steel backing and pushed out in the oil -- and that's going to be a very hot, high pressure situation whether it's a main or con rod or thrust bearing (as Clifford says). And, agree on the probable damage to the crank.
Alright...that makes sense to me. Thanks for the explanation.
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Yes, I think you hit the nail on the head, Dave. This particular one looks to me like the bearing material got peeled off the steel backing and pushed out in the oil -- and that's going to be a very hot, high pressure situation whether it's a main or con rod or thrust bearing (as Clifford says). And, agree on the probable damage to the crank.
And it makes me wonder if this was the original failure or if it was a subsequent problem caused by something else. Whatever, I'm in agreement that there's probably a lot of damage in other places in this engine and -- if it can be "saved" in a practical sense - it's almost certain to need an oil pan-to-valve cover total rebuild. But only way to know is to open it up.
Alright...that makes sense to me. Thanks for the explanation.
Clifford mentioned the thrust bearing. I went back and looked at the original photo and noticed some curved edges on what a basically flat piece of metal. That metal is pretty beat up but I think those curved edges would be much more damaged if they were from a basically cylindrical bearing shell that got pounded flat; I think it's maybe likely a thrust bearing that was flat with curved edges to start with. But it is so damaged, it's hard to make much out about it.
It doesn't really matter, the outcome is the same -- severely damaged engine.
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Yep makes sense. Clifford wins the ticket, lol :)
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Scott,
I fly commercial often, and that was my first thought! How do you lose a whole fleet of airplanes(big ones)?!
I would have felt really bad commenting on that earlier.
Fortunately (or not, depending on your perspective), I had my engine rebuilt in my first coach(city bus) and then had it transferred to my current coach, so I feel confident I know its history. BUT--I didn't rebuild the whole bus, so bad things can still happen.
Hopefully Ryker can get his spare engine in without too much trouble.
PAbusnut
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Time to rename this thread. Because I thought California actually lost an Airline (as in Southwest or Delta) lol. Turns out it was an air line and beyond that, this thread got real dark real fast now that we know your engine is toast...major bummer and makes me nervous about my own every time I see someone blow theirs up I wonder if it's my turn. Keep us updated.
That's what I get for posting on my iPhone while broken down on the side of the freeway with my family in the coach. I did laugh when you pointed this out, and I wonder why I did not catch my mistake. No, we didn't lose an Airline, and sorry for the thread drift. Was such a shock to fix the discharge hose, only to seize the engine the next day 2 miles from home. Felt that they were related but I don't know how that can be. I feel that the engine in my bus is done, and since I already have an engine in my warehouse, I will try to make that work. From what I can determine by pulling the valve covers and headers, and looking through the inspection ports, that engine looks pretty clean.