| Author | Message | ||
| Karl VanShellenbeck (Kvan)
Registered Member Username: Kvan Post Number: 12 Registered: 7-2005 Posted From: 66.68.82.97  Rating: N/A |
Lurking for a while, you guys have so much valuable info for us new guys. My first coach was a 78 bb 33fc wanderlodge, had it for almost 10 years but decided I wanted something with a little more power to deal with the mountains out west. I live in central Texas and try to go to the mountains during the summer time to avoid our heat. I currently have a 84 mc9, it is a very early marathon conversion #103, I believe the third one. It is a great coach but Marathon is lacking in some info on it. It was a new mc9 send to marathon with a 8v92ta and an allison 743? 5 speed auto if I remember the number correctly. I am experiencing two issues. The first is the coachair does not cool the rear of the bus well at all. I am assuming this is a Marathon problem rather than an MCI problem but would love to hear from the experts. Are all of the floor vents in the rear return airs? Can they be turned off? Mine do not seem to have any suction on them and are definately not flowing any positive air flow. I have three knobs to the left of the drivers station, the most forward rotary knob controls the instrument lights, what do the other two do? Are they a/c related? Is there a manual available that can enlighten me on the coach air system. I had mine converted to r134 by mci a few years ago, but I have to run my cruise-airs in order to stay comfortable on the road, especially in the back. I am about to replace my cruise air a/c systems. I have read many posting on split systems vs roof units vs basement. Is the general consensus that the roof airs just make more sense due to the cost of the split sytems? I do like how quiet the split systems are but are they worth the cost of replacement? Two of my condensing units are in the front area behind the front bumper and one is in a side compartment just behind my generator. They seem to work fairly well but they are old systems and close to their end of life. All comments welcome. For those of you running 8v92ta with auto's, what kind of fuel mileage is expected running say 60 mph approx on level ground? Thanks in advance for your help. | ||
| RJ Long (Rjlong)
Registered Member Username: Rjlong Post Number: 1550 Registered: 12-2000 Posted From: 98.192.173.82  Rating: N/A |
Karl - To answer your last question first, 5.5 - 6.5 is an overall average for MC-9s, regardless of engine. Base your fuel stops on 5 mpg and you'll never run it dry. If you have just the main tank (144 gal), figure 120 useable. If you have the main & aux tanks (179 gal) figure 150 useable. This translates to 600 or 750 miles between fill-ups, depending on your tank configuration. Safer yet - fuel every morning after the previous day's run, or do what many bus companies do - plan fuel stops at 500 mile intervals. Repriming a Detroit after it's run out of fuel is NOT fun! As for the transmission, what's the shift pattern indicated on the gear selector tower? Post it here, and we'll give you a better idea of what you've got. Remember, the four-speed feels like a five-speed as it shifts, but that extra "shift" is actually the torque converter locking up. Nick will probably chime in with more info for you regarding your a/c. BTW, where did you find your Marathon? FWIW & HTH. . .  | ||
| Buswarrior (Buswarrior)
Registered Member Username: Buswarrior Post Number: 1607 Registered: 12-2000 Posted From: 76.66.18.100  Rating: N/A |
First thing I'd do is put a set of gauges on the coach air to see what the situation is with the R134. You have to start with good pressures. Mine worked great with just the conversion, no adjustments needed from the old R12. Next, confirm all air filters are clean/in place/inspected/ etc. Next is to figure out what the vents are supposed to do, and what dampers might be out of control, or what blockage to proper air flow there might be. Did it ever cool well back there? happy coaching! buswarrior (Message edited by buswarrior on May 18, 2009) | ||
| JR Lynch (Njt5047)
Registered Member Username: Njt5047 Post Number: 272 Registered: 7-2006 Posted From: 71.75.10.27 Rating: N/A |
The rearmost knob is probably a non-functional temp control. It controls the water valve located in the upper RH front bay. You are correct that all but two of the floor openings are return ducts. They could be covered, but there's no cut-offs on them. The AC and heat outlets are ducted from two large outlets beneath about the 3rd front windows. OEM AC ducts ran down the side of the bus above the floor. They are often removed so as to have a flat floor to work. I would have assumed Marathon would have considered the OTR ducting, but a good many factory conversions require that the genset operate to cool the bus. If the front of the MH stays cold, while the rear is not, there's no OTR ducting to the rear of the bus. The OTR AC should easily frost up the front of the bus. If not, it may be time to service the OTR AC. The heat of the engine combined with no outlets in the rear of the bus, and the floor returns sucking out the cool air would make the bus warm in the rear. An 8V92TA will get 5-6 MPG typically. The HVAC guys will have more to offer regarding your Cruise-Aires and specific HVAC needs. Rooftops would be too much trouble to install in a converted coach. JR | ||
| Karl VanShellenbeck (Kvan)
Registered Member Username: Kvan Post Number: 15 Registered: 7-2005 Posted From: 66.68.82.97 Rating: N/A |
I have a little a/c flow to the rear of the coach on the drivers side by the windows, but its not much. Certainly not enough to overcome the additional heat of the engine. Is there any place that vents could be closed off? I really think that when we first got the coach the coachair worked better in the rear. On the last trip I took in the coach I had to run the cruise-airs off of the gen all of the time. My coach is an all electric unlike my prior wanderlodge so I am virtually always running the genset. Very possible the tranny is a four speed w/lockup. It has one more gear than my old wanderlodge. I am running out to its storage location tomorrow so I will post info on its shift layout. Do the two strokes always wet your tow vehicles? My tow vehicle is always covered in oil. Is this from slobber or exhaust? Normal? The bus has about 100k on it total. Has anyone done a conversion to run exhaust to the top of the bus on an mc9, possibly including the diesel genset? | ||
| Karl VanShellenbeck (Kvan)
Registered Member Username: Kvan Post Number: 17 Registered: 7-2005 Posted From: 66.68.82.97 Rating: N/A |
As far as the 5.5-6.5mpg. Do any of the new 4 strokes offer a significant increase in fuel mileage? ISM with a world tranny or auto/manual 10 sp. We have considered taking advantage of some of the grant money programs available to get the older "dirty diesels" off of the road and upgrade to a 4 stroke. Anyone have any experience with the ism. I like the series 60 but they seem to be a major conversion to make them fit an mc9. | ||
| Karl VanShellenbeck (Kvan)
Registered Member Username: Kvan Post Number: 18 Registered: 7-2005 Posted From: 66.68.82.97 Rating: N/A |
I found the Marathon in San Antonio Texas. We had decided to upgrade our bb 33fc to a pusher and had driven from Austin, Tx to Texarcana to look at an 85 bb 35' pusher that needed only a couple of things. After driving a long way to look at it it needed a lot more than a few things. On the way back to Austin we decided to stop off in Fort Worth to look at a custom-coach mc9 with an 8v71 and a manual tranny. It was a very nice coach custom built with lots of storage, drop down bunks, and very well thought out. Since it was getting late we decided to look at one more coach in San Antonio before we decided on what to buy. The following day we looked at the one we bought. It was a vehicle with around 80k original miles. It had been shipped to Marathon new from MCI with an 8v92ta. It was very nice and very low mileage. Set up for a couple, nice large bathroom, full kitchen, large refer, ice maker, etc. Although it did not fit as well for our kids as the wanderlodge, we knew we would not have kids forever. The only thing we miss with the new coach is 8+ mpg the wanderlodge gave us. | ||
| Roger Baughman (Roger)
Registered Member Username: Roger Post Number: 104 Registered: 11-2006 Posted From: 69.232.76.217  Rating: N/A |
Karl, I have a Marthon MCI-9 1984 also. I was told that it was the 7th one they did. I have a 8-71. When we tow our jeep, I didn't have any noticable oil on it after a trip to Reno and back to San Diego. Although I had all of the oil leaks repaired by Freightliner repair. I have a lot of trouble with my oem air too. The compressor went out and the cost of a rebuilt was $1.500 plus 30 pounds of refridgerent was just too much for a system that did't work that well. I have decided to install a 24 volt 4000 watt inverter and run the two roof airs off of the engine alternator. | ||
| Karl VanShellenbeck (Kvan)
Registered Member Username: Kvan Post Number: 19 Registered: 7-2005 Posted From: 66.68.82.97 Rating: N/A |
Roger, what kind of fuel mileage do you get @ 60mph? Do you have an auto tranny? Do you have multiple rotary knobs to the left of the drivers station? Know what they do? Do you have cruise air split units in yours also? Thanks Karl | ||
| Tim (Timkar)
Registered Member Username: Timkar Post Number: 127 Registered: 10-2004 Posted From: 24.64.223.203 Rating: N/A |
Hi Karl...re: your oil covered car..What type and viscosity of oil are you running in the 8V92? | ||
| Karl VanShellenbeck (Kvan)
Registered Member Username: Kvan Post Number: 20 Registered: 7-2005 Posted From: 66.68.82.97 Rating: N/A |
I just went out and looked at the bus. Its been to long and my memory isn't what it used to be. I think my old bb was a 643 allison. That must be where the 43 came from, well thats my story and I am sticking to it. The pattern on my shifter is 1,2,3,4,D,N,R. I think after looking in my books its a 754 Allison. Does that sound right? As far as oil I believe we are using a multiweight rotella 15/40. Should I switch to a straight weight? I do see some oil leaks under the bus when parked, two areas about lining up with the edges of the engine on both sides. I really have not investigated too much because, it's not excessive, and all of the conversations I have had with other dd 2cycle users talk about oil usage and slobbering. I also guessed since it has an oil tank for refilling the engine that holds 2 gallons that might suggest that it is normal to use some oil on a regular basis. I would love to find out that all these things don't leak oil. | ||
| JR Lynch (Njt5047)
Registered Member Username: Njt5047 Post Number: 273 Registered: 7-2006 Posted From: 71.75.10.27 Rating: N/A |
Clean up the engine compartment and see where the oil is coming from. You may find that the airbox drains are oiling the toad. If so, you could install a catch-can on the drains. Anything that's below the the oil pan flange will work. Could be oil leaks. Even though the chassis mileage is low, the age of the engine coupled with long periods of inactivity may cause oil leaks. Shouldn't be enough oil in the exhaust to oil the toad. That would be bad. If the engine is clean, but the lower bumper area is oiled, an airbox catch may solve your problem. Resist the urge to add oil until the engine has been shut down long enough to get an accurate dipstick reading. Coooled down. If you overfill the engine, the extra oil will get out. Regarding your AC, if you still have the beneath the window outlets, sounds as though you have the OEM MC9 ducting in place. Should cool the back of the bus. Could be time to service the OTR AC. While your coach may gain a few MPG with a 4 stroke, it isn't worth the effort...not for fuel mileage only. Your HP is already good. Any 4 stroke that approximates your 8V92 in performance isn't going to add much in mileage. Repowering is a major chore. The only 'bolt-in' 4 stroke is an S50. Bolt-in is a relative term. You can find some factory mod S50s. S60 requires extensive body modification, but will offer similar performance to your 8V92. Various 6 cyl Cummins and Cats will work, but you'll have a full-time job fabricating components. Another issue is the operating RPM of large 4 strokes. Typiclly around 12-1400 RPM. Your 2 stroke cruises at 1800 and maxes at 2100. You'll either have to find an overdrive auto, or a change the final drive ratios. May I suggest buying a 4 stroke powered coach? | ||
| JR Lynch (Njt5047)
Registered Member Username: Njt5047 Post Number: 274 Registered: 7-2006 Posted From: 71.75.10.27 Rating: N/A |
Those knobs you are asking about are the dash and switch panel illumination controls. My 9 has two knobs that are identical. The knobs have no AC function. Some 9s had intercom volume control mounted just below the 2 dash light knobs. The front knob controls the gauge backlighting. The rear knob controls the switch panel and legend lights. There's also a knob on the switch panel next to the pax AC that controls the HVAC temp. Most of the temp control rotary switches have failed, or don't work. I suppose you may have a failed (always 'on') water heat valve. You might want to turn off one of the gate valves that controls the heating system. The easiest to reach is beside the RH engine cradle mount. You may be mixing heated air with your AC. Post a pix of the 'third' knob. Someone will ID the thing. The pax AC only has a "HI/LO" switch. Same for the driver's AC. So two switches control the OTR AC. The drivers heat valve, below the 2 rotary knobs, should be oriented up. However, it the heater gates are closed, it won't make any difference. (Message edited by njt5047 on May 19, 2009) | ||
| Karl VanShellenbeck (Kvan)
Registered Member Username: Kvan Post Number: 21 Registered: 7-2005 Posted From: 71.145.187.168 Rating: N/A |
Buswarrior, These dampers you speak of, how do I determine where they are? I have been unable to find any info that came with the coach referring to the factory a/c operation. Anyone have a diagram that would assist me in trouble shooting. I tried to buy a manual advertised online but it has been sold. | ||
| Karl VanShellenbeck (Kvan)
Registered Member Username: Kvan Post Number: 22 Registered: 7-2005 Posted From: 71.145.187.168 Rating: N/A |
Njt5047 I do not have any oil coming out of the exhaust. As a matter of fact it does not smoke on startup either. I believe my engine is already equipped with catch cans (tanks). Are these engine likely to leak from certain areas most often? I don't mind getting my hands dirty but dd's are not my forte, so I don't know their ideosyncricies. I read a thread earlier concerning a possible oil leak at the alternator, is that a common one? As far as the power train goes if I can get the engine so it does not leak I will be happy camper. I normally average about 5.5-6 so I guess I can't complain, and it does climb mountains well. Do you know if the 754 allison is infact a 5 speed or a 4 speed w/lockup? | ||
| Jack Conrad (Jackconrad)
Registered Member Username: Jackconrad Post Number: 1075 Registered: 12-2000 Posted From: 71.3.157.139  Rating: N/A |
The 754 is a 5 speed transmission. The 740 is a 4 speed and the 730 (angle drive used in GMs) is a 3 speed. all have a lock-up torque converter. Jack | ||
| JR Lynch (Njt5047)
Registered Member Username: Njt5047 Post Number: 275 Registered: 7-2006 Posted From: 71.75.10.27 Rating: N/A |
If oil is getting on your toad, either your catch cans are full and puking, or you got a leak. The catch can(s) may be full. There is some method to drain them. Should be. If factory catch, there's a big drain bolt on the bottom. Be ready to catch the stuff...it's nasty. Otherwise, the engine is leaking somewhere. They'll definitely leak. The main seals will leak, heads, blower connections, power steering..ad infinitum. Alternators are not known for leaking, but they could. They are both oil cooled, and mounted to an adaptor that, if loose or misaligned, could leak. Anything mounted on the bell housing could leak. Clean the engine and see what gets wet. Look under the coach for oil dripping from the bottom of the bell housing. Often, drops of oil will drip off the engine below the leak. Check the catch cans before you do any other work... Be careful to not overfill the engine oil. Motorhome use really doesn't need the capacity of the extra oil tank. Just adds to the clutter in the engine room. If the engine is serviceable, it won't use much oil. Shouldn't use much oil. Let the oil run on down almost to the 'add' mark before adding oil. If it's using excessive oil, you might find that the oil consumption drops as the oil level moves toward the add mark. Check the engine oil cold on level ground. Is the back of the bus oiled up? Jack has an idea for 'deflecting' engine grime off the toad...maybe he'll share a pic!? | ||
| RJ Long (Rjlong)
Registered Member Username: Rjlong Post Number: 1554 Registered: 12-2000 Posted From: 98.192.173.82 Rating: N/A |
Karl - First, get that multi-weight oil out of your engine asap. Detroit specifically says to use straight 40wt, CF-2, 1% or less sulfated ash content oil in the two-stroke engines. Read Section 2.2, straight from the horse's mouth: http://www.detroitdiesel.com/support/on-highway/manuals/Lubricants_Fuels_Coolants/7se270.p df You won't find it on the shelf at your local WallyWorld. You'll have to order it from NAPA or a fuel/oil distributor in your area. Comes six gallons to a case, takes two cases for an oil change with some left over. Change the filter, too, of course. Shell Rotella & Chevron Delo 100 are the two most popular, but there are others that meet the specs, too. Best time to check the oil is in the morning, before you start it up for the day. Should be part of your pre-trip anyway. (What's a pre-trip? Here's a pre-trip: http://www.busnut.com/bbs/messages/12262/16203.html?1167072614 ) As for your transmission, based on the shifter data you quoted, you've got an HT-754. Good gearbox, gives you one extra gear that the 740 guys don't have to play with. Great for those gradual grades that are too steep for "D", but perfect in 4th. Now you need to take the coach out with somebody and determine the maximum road speed in 2nd, 3rd & 4th. Armed with that data, it will make it much easier for you to keep the engine in the correct operating range for conditions, as well as helping you with your downshift points for climbing RockyTop. Which reminds me - ALWAYS downshift manually when pulling grades - don't wait for the Allison to do it on it's own. These engines pull best (and stay a lot cooler) at 1700 - 1900 on a partial throttle. Shift it manually to keep it in this range. More shifting tips here, near the bottom of the article: http://www.busnut.com/bbs/messages/12262/16204.html?1167073154 FWIW & HTH. . . | ||
| Karl VanShellenbeck (Kvan)
Registered Member Username: Kvan Post Number: 26 Registered: 7-2005 Posted From: 66.68.82.97 Rating: N/A |
Rjlong Thanks for the post. My mistake on the oil. I was thinking of our ford powerstroke. We are running straight 40wt. We have been running Delo 100 40wt. As for the tranny and running in the mountains I do downshift manually. When we first started looking at detroits a local mechanic warned us about driving a 2cycle, lugging is a no no. Although our prior coach was a 4 cycle 3208 cat non-turbo, I had to manually shift the gearbox in that one a lot. Quite a few trips over I70 west out of Denver so I got accustomed to climbing hills in 1st gear. Fortunately I don't have to slow down that much with the detroit, just keep it revved up some and off of the floor. | ||
| R.C.Bishop (Chuckllb)
Registered Member Username: Chuckllb Post Number: 735 Registered: 7-2006 Posted From: 70.217.222.205 Rating: N/A |
Good post RJL...! RCB | ||
| Buswarrior (Buswarrior)
Registered Member Username: Buswarrior Post Number: 1608 Registered: 12-2000 Posted From: 76.68.133.147 Rating: N/A |
Hello Karl. The big question is whether Marathon made any modifications to the coach HVAC system, or not. Without some pics of the right stuff, or someone to have a quick look, it is very hard to trouble shoot. Take some pics of where the AC goes, take some pics of the controls, take some pics of the AC equipment in the engine room, take some pics of everything you think might be a vent or intake and where it goes. Figure out how to post them, or e-mail the whoppers to the bossnut, or me, Ian will stuff them into a post for you. My first diagnostic step continues to be to put a set of gauges on it and see if there is the proper amount of refrigerant in it. No good trouble shooting an engine with half the spark plugs missing.... Nothing else matters, you are wasting your time thinking about anything else, until you confirm it can actually have the potential to make some proper cold. We have to confirm you are getting cold, feel the two pipes off the AC compressor, one too hot to touch, the other nice and cold, dripping condensation? We'll move to closing the manual heater valves in a later post, after we check the other stuff. If it is a stock style MC9 HVAC, there are two "fresh air" controls in the first baggage bay against the front wall which must be closed for proper operation. You have to make sure someone didn't open them. These are cable affairs with a handle on the end. By the way, they are useless in their advertised function. Close them and keep them that way. If you are lucky, they are already seized closed. While in there, that large piece of plywood against the front wall in the middle seals the air circulation system. If that board does not seal tightly all the way around, there will be little air through the evaporator or heat exchanger, the air will be sucked in through the edges around the board from the front bay. Confirm the fans are clean and running. The air filter for the HVAC lives inside that cute little door on the angle at the back of the battery compartment. Yank it out and see what you have, make sure the door is properly closed. It should be a permanent metal screen, you clean it and put it back. Next, what does the "heat on" green light in the dashboard do? On, off, a little of both? Do you have the small temperature dial adjuster in the middle of the side instrument panel? And the 3 position, switch, up for coach AC, middle off, down for coach heat? The Condenser fan outside runs in the AC position? Turn the temp dial all the way to cold. Do you have the manual 90 degree turn valve mounted down low to the driver's left in the side wall below the side switches? up and down is closed, fore and aft is open, for the heat to the dashboard/defroster? You'll want that closed. Did I mention to CHECK THE REFRIGERANT LEVEL WITH A SET OF GAUGES??? ok, let us know! happy coaching! buswarrior | ||
| Karl VanShellenbeck (Kvan)
Registered Member Username: Kvan Post Number: 27 Registered: 7-2005 Posted From: 66.68.82.97 Rating: N/A |
Buswarrior, you are correct there are many more questions than answers right now. I can hook a set of gauges up to the system probably by this weekend. I have looked at the site glass in the dryer before when I was concerned about the freon level and according to the site glass the level was fine. Is the site glass method inaccurate in this case? I am currently blowing lots of cold air out of the floor vent on the passenger side approx 6-8 feet from the door. I could store meat above that vent. Unfortunately that is one of only two areas that get lots of cold air. The other area is in the same area of the bus on the drivers side and it is coming out of a vent from the side not the floor. Not nearly as much flow as the passenger side but still quite a bit. I am still looking for those darn sparkplugs, I still can't find them in the engine or the diesel generator. lol I have closed the manual valves by hand before just to make sure that was not a problem, since I do not have a hvac manual. I wanted to eliminate the flow to the heater cores. I am going to have to look for the fresh air controls in the front baggage compartment. I can't say I have ever seen them but they could be covered up with something like carpeting. Where exactly are they? The large piece of plywood you are referring to is in the front luggage compartment also? I have inspected and cleaned the evap filters many times before but it's always a good idea to eliminate the easy stuff. What heat on green light on the dash? I have never seen any such light on our coach. That does not mean its not there but I don't know what marathon did with it. As far as a 3 position switch on the side instrument panel, that is another one I have no idea where it is. The only thing I have to the left of the drives station is three rotary knobs and the heater valve that we uncovered when we removed the carpeting from that side wall. The condensor fan definitely runs when the ac is on, it sounds like the coach will lift off at any moment, and if you do not turn it off before entering dusty campgrounds everyone close to you gives you a "shut that da$% thing off look". The manual valve is pointed straight up. What was that about checking the freon level? lol I will get pressures and outside temps this weekend if not sooner. Thanks for your help. Are there some dampeners that could close off or reduce the flow to the back of the coach? You would not happen to have a schematic of the air flow through the original mc9 hvac system would you? Karl | ||
| RJ Long (Rjlong)
Registered Member Username: Rjlong Post Number: 1555 Registered: 12-2000 Posted From: 98.192.173.82 Rating: N/A |
Karl - Will these help? They're from the MC-9 sales brochure. I sent copies to your private email.   FWIW & HTH. . . | ||
| George M. Todd (George_mc6)
Registered Member Username: George_mc6 Post Number: 836 Registered: 8-2006 Posted From: 76.171.79.185 Rating: N/A |
Karl, If you can see clear liquid Freon in one of the sight glasses on the drier after the system has run at high idle for at least a couple of minutes, the refrigeration portion of the system is operating properly. It sounds to me like a damper is closed, or a piece of insulation has come off of the inside of the rear ducting, and is blocking AIR flow from the front. G | ||
| don goldsmith (Bottomacher)
Registered Member Username: Bottomacher Post Number: 253 Registered: 12-2000 Posted From: 72.15.86.59 Rating: N/A |
I agree with George. Clearly, you have cold air. The duct system is the culprit. Do you still have the factory stainless ducts on each side of the coach at the floor line? If so, is either of them dented? Is air flow noticeably stronger on one side of the bus than the other? Do you know if you have two blowers or one? |