| Author | Message | ||
| Randy & Terri Kanai (Tmkrek)
Rating: |
I have a 88 MCI 96A2 that has been converted from a 6V92 to an 8V92. I went to the 8V because I will be towing a boat over the mountains of Colorado regularly. I have the larger radiators and smaller pulley on the blower but I am still over heating. In fact, I overheated driving without the boat into a headwind yesterday, is that an indication of other problems? What have others done to gain more cooling capacity with these older MCI's and what has worked sucessfully for others? | ||
| Randy & Terri Kanai (Tmkrek)
Rating: N/A |
A bit more info that is probably relevant, I have been told that I have the N90 injectors and I am rated at 475hp. I don't know what rear end I have. The bus runs great and I am pleased with the power, now I need to find the solution to keep things cool enough especially when pulling the grade to the Eisenhower tunnel and Vail pass. | ||
| RJ Long (Rjlong)
Rating: N/A |
#1 - Detroits pull best at 1700 - 1900 on a PARTIAL throttle. Keeping it floored at 2100 is inviting trouble. Watch your exhaust. If you're blowing black smoke, back out of the throttle until it clears up. If the bus maintains it's speed, you should be OK. #2 - If, when you back out of the throttle to clear the smoke, the bus starts losing speed, downshift manually to the next lower gear. (Read my comments about shifting in the "Articles of Interest" area of this site for some additional info.) #3 - Repeat steps 1 & 2 as necessary to get over the pass. Yes, even if that means going all the way down into 2nd. Better to take a few minutes longer getting over Rocky Top by keeping the beast cool than paying for an expensive tow and/or rebuild. Finally, don't forget that Ike Pass is what, 11,000 feet? Air's a lot thinner up there than at sea level, so you've got to concentrate more on what you're doing. I never had an MCI overheat on me when I was driving professionally, simply by paying attention to the above. So sit back and enjoy the ride, and especially the view!! HTH, RJ PD4106-2784 Fresno CA PS: 90% chance you've got the stock OEM axle at 3.70:1, btw. | ||
| Randy & Terri Kanai (Tmkrek)
Rating: N/A |
Thanks RJ for the info, let me elaborate a bit 1) I was NOT smoking at all, just cruising. This bus will cruise at 75-77mph on flat ground but I was down to 60mph with partial throttle on relatively flat lands of Eastern Colorado yesterday in a quartering headwind when I overtemped. I suspect part of my problem was starving the downwind radiator for air. That being said, I also overtemped in Ohio in a direct headwind earlier yesterday again going about 60-65mph feathering the throttle again and not trying to push things too hard. No smoke in Ohio either. 2) Never downshifted as I was pretty much in a flat area to very slight upgrade with no smoking. I drive a diesel pickup with a pyrometer and I can see when too much fuel is being sent to the motor and watch the temps rise. If it were not for the overheating, I think this bus would have pulled this very slight grade at least at 70mph with no smoke. I just talked to a local bus mechanic and he wants to check a lot of things. He suspects my overtemp shutdown may be shutting me off too early, radiators need to be cleaned, injectors too big for Colorado i.e. too much fuel, leaking seals around the radiator etc. All the normal stuff. RJ, he is like you, he is pretty confident that when things are working properly, I should not be over temping this bus. He did say though and this surprised me, as long as I am not smoking, the best cooling occurs when the bus is running as fast as possible. The most air through the motor, blowers running the fastest etc. This seems a little counter to what I expected, I always thought more fuel, more heat, hence the reason I backed out of the throttle when I started to get hot yesterday even though I was not smoking. Sounds like I need to take this in for a check up of the cooling systems. | ||
| Geoff (Geoff)
Rating: N/A |
I also have had overheating problems in a strong headwind. Sometimes the wind is coming at you in such a direction that the radiator becomes starved for air. The mechanic has some good areas to tackle to reduce you heat and increase air flow, but I don't think size 90 injectors are a problem if you are keeping your foot out of it when you hit a grade. Also, be careful on replacing the overheat shutdown temperature sender. You can cook one of these engines pretty easily-- stick with the factory setting. I think mine is 240 degrees and I have never let it get that hot before I pull over. I also installed a misting system for the few times I am towing up a mountain, which is (usually) the only time my engine starts getting hot. --Geoff '82 RTS CA | ||
| Sojourner (Jjimage)
Rating: N/A |
Amen of all what RJ said. Might add if you will to be sure core’s fins are in very good condition such as being tight & not-rotted. After all fins is what adsorb BTU from cord to cool air, Many have re-rodded core via tanks removed but over-look the fins condition to already limited rear engine's air-cooling supply. Result is better but not overly happy. So very important to have good radiator fins & core as well re-rodded & clean. Labor to R & R radiator is same for recore or re-rodded. Randy you said “a local bus mechanic” mention “injector too big” which means darker gray or black smoke. You can get same fuel rate injected as smaller injector by depressing less throttle pedal angle. Unless you want less HP & torque, I leave injector in unless it worn out. By going to smaller injector mean longer time to climb & lower gear shift point. So fuel economy is about same. Have it your way. FWIW Sojourn for Christ, Jerry | ||
| Rich International Bus & Parts
Rating: N/A |
Randy, Your Temperature Switch (alarmstat) $22.05. that automatically shuts down your coach are set to 212 degrees. Very important part on your coach. Make sure your temperature gauge & senders are in good working condition. We make "Ram Air Radiator Scoops" that attatch to the radiator screen area & pull in the cooler outside air & feed it into the blowers. Also make vented engine door panels. They let the heat out of the encapsilated engine cavity. Heat rises & the only way for engine heat to get out of the MCI engine compartments is under the bumper? The vented panels let a lot of heat out............My fleet owner operators tell me that the combination of the vented doors & ram air scoops drop the operating temperature 10-15 degrees. This will not repair a bad radiator or cooling system. But the results are immediate. Rich 800-468-5287 | ||
| TWODOGS (Twodogs)
Rating: N/A |
I saw a gold Eagle with 4" louvers instead of a back door...very well done & looked good | ||
| Don/TX
Rating: N/A |
I just KNEW you was going to tell him to go with electric fans to solve his problem Two Dogs, but you didn't! | ||
| Jim Shepherd (Rv_safetyman)
Rating: N/A |
One other thought is whether you have installed some sort of “mud flap” below the rear bumper to protect your trailer. I have always wondered if they would restrict the air flow out of the engine compartment. Jim Shepherd Evergreen, CO ’85 Eagle 10 Bus Project details: http://www.rvsafetysystems.com/busproject.htm (updated 2/17/05) | ||
| bruce king
Rating: N/A |
I just had to buy a set of radiators for my mci 9 in preparation for a switch from an 8v71 to an 8v92. I can't tell you how to verify that you have the larger radiator without emptying your coolant, disconnecting the lower hose on (probably the drivers side radiator) a radiator, and then using a flashlight to look up into it. The standard mci radiator will have either 4 or 6 tubes thick; the larger radiator (the one that mci puts into an 8v92 coach) has 8 tubes. In addition, the larger radiator tubes are dimpled, making the flow of water through the tube more turbulent, increasing the efficiency of the heat transfer. So if you don't see an 8 rod version with dimpled tubes, you're running a smaller radiator than factory. An 8 rod radiator is $892.00 each side, has a leadtime of 2 weeks to build, and a week for ground shipping. They weigh something like 55lbs each. This compares favorably with the ~550 recore price, plus ~250 to reassemble, plus 8.x% sales tax in seattle. the two prices turn out to be within 50 bucks for me, so i chose to wait for the larger ones from a company in illinois. The fins aren't important just for cooling. they are a structural element that keeps the coolant tubes from expanding and splitting. If the fins are rotted or damaged, the tubes stand a greater chance of splitting. The fins rot is caused mostly by road salt. Look for rotting on the inside of your radiator closest to the back of the coach -- you can't check there without pulling the radiator itself, which takes about 45 minutes and is a hassle, but you can do it with a small socket set and some patience. I just went through this 3 days ago, and just ordered the new radiators yesterday. Called MCI to get the specs on the OEM radiators they installed, and then sourced the company that made them for mci to save a few bucks. The smaller pulley is one way to increase the RPM of the squirrel cages, but the 8v92 coaches used a larger blower -- different part number. You can find these larger blower sets on the used parts market from time to time. I got mine from Sam Caylor out of an 8v92 equipped coach. Finally, if you are running into overheat situations occasionally, you may consider installing a valve to spray water on the radiators with a switch up in the drivers area, allowing you to increase the cooling a little on demand. and if your coach is configured with the louvres to decrease air flow over the radiator during cold spells, you've got to verify that they are in the full open position when you're aired up and running. I am really looking foward to my engine swap. Bruce | ||
| TWODOGS (Twodogs)
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DON....it was in a rest area...& I did a walkaround on his bus...(BUT)....not looking like a choirboy...guess they were afraid to come out...it might have been the Eagle that already has electric fans...supposed to belong to an 80 year old gentleman | ||
| gusc Rating: N/A |
An old truck driver told me that 318 Detroits were supposed to be kept wound up or you would kill them. I think he said to keep it around 2500 rpms but that sounds high to me. He said the worst drivers were the ones used to Cummins low rpm and when they drove Detroits the same way they wrecked the bearings. Evidently Detroits don't take kindly to being lugged. | ||
| Jack Conrad (Jackconrad)
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Bruce King, Where did you purchase the radiators? Did this include new tanks or just the cores? Inquiring minds want to know, Jack | ||
| Don/TX
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Gusc I used to hear that story too, but I suppose it could be so for the 318hp DD, but not for the 265hp or so bus version. GMC governed them down around 1700-1900 rpm, and in fact when they put the VS2 Allison on them, it was IMPOSSIBLE to get over 1700 rpm, EVER! They also did not want it to shift down until you got it to 1150 rpm, so lugging up a hill at 1200 rpm was "natural" for them. Maximum torque is 1200 rpm, it drops off pretty sharp from there as the rpms increase. I had the opportunity to gear mine on road trips three different ways, and can assure you that the more the rpms, the poorer the fuel mileage and the less torque developed. | ||
| Bill K Rating: N/A |
Iam running a 8v92 in a mc8 I installed new larger radiators and the larger fans, Then for a little extra cooling I went up in the coach heating comp. where the fiberglass shoots direct the heat through the bus, on each side I made a device that you can shut off the heat to the coach and direct it out side. If the temp begins to climb just turn on the heater. the heater core is a big radiator, when you stand buy the bus and the fans are on it will blow you hat off. | ||
| Tom Caffrey (Pvcces)
Rating: N/A |
Gusc, I imagine that advanced timing in the truck engine played a role in lugging, too. As Don pointed out, with standard timing and C60 injectors, peak torque is around 1200 rpm. The truck engine has a peak torque at 1600 rpm, IIRC. The way I see it, the bus engines are just about perfectly matched to four speed standard shift engines, and truck engines are much better matched to ten or more speeds. 1200 to 1900 versus 1600 to 1900. Our high gear seems to be good from 46 mph to 83mph. That's really not too hard to live with even in city driving. I can even stay in high gear through Idaho on US 12! For what it's worth. Tom Caffrey PD4106-2576 Suncatcher | ||
| Al Newell (The_peregrine)
Rating: N/A |
Here is a article I put on the board in 2003 about solving my heating problem. Todate it is still running fine and we are taking off in 48 hrs for a six month trip with the bus. Apparently my last post of cooling my DD 8V71 has open the floodgates to my e-mail box. Rather than answering everyone on a individual basis let me post it for all on this board. First off I am not nor ever have been a diesel mechanic, just a retired high voltage electrician, power dispatcher and other jobs in the electrical power utility. OK, my GM 4502 bus is a 1967 suburban 35 foot transit. I run N65 injectors, “A” timing, 170 degree thermostats, Allison V-730 tranny plus a Jake Brake. The fan is moved by hydrostatic (oil) coupling. The rear end ratio is 4:12 and all tires are 11R24.5 XZE’s steering type. The rig was just converted when we bought it in 1991 due to the sudden death of the builder owner. The conversion is total, the front door was replaced, the sides are re-skinned, the floor area lowered and rear exit removed. Yep, heating problems right away in the mountains or on the deserts. I had the radiator removed and a new one built as follows: 5 ½ thick X 30 wide X 36 high. Yes some modifications had to be made to fit it in. That did not solve the heat problem, but did help. Darn near burnt up the engine climbing the grade, 7,000 ft, from Phoenix to Flagstaff in 115 degree heat. Had to pull over three times. Next was a special custom shroud built and a 8 bladed by 28 inch diameter fan was installed. Now the air really flowed threw the thick, 5 ½ inch radiator. Engine was fine but the tranny was getting hot on long 6 % grades and the heat exchanger was affecting engine heat of course. Had a very large tranny cooler installed under the bus in front of the rear axle with a large 12 volt fan. Only place left to install anything. Did have it on outside of the radiator for a time. Correct distance away and all that but it just caused more heat than it cured. Any way from the tranny cooler oil goes to the heat exchanger. Yep, that helped, but I was still having excessive engine heat plus at 3,000 feet I had some black smoke and more so on throttle increase. This smoking problem had been with me from the start and was worse when I went to N65 injectors and the “A” timing. Along the way I had the muffler removed as it was between the block and the radiator, damn stupid design. I had the 4 inch exhaust pipes routed into 2 mufflers that are 32 long X 6 ½ diameter. These mufflers are mounted under the rear bumper and just a bit forward. If nothing else they really talk when the Jake Brake is switched on. So far I had been listening to all the pro’s who spoke from mountains on high. This included Detroit Diesel Engineers. The one thing I had that always bothered me was the air intake to the engine. The original had been removed on conversion and a Donaldson system was installed. A 6 inch in diameter fitting came out and then immediately had two 90 degree bends so that the filter canister was cradled between the two banks on the 8V71. The huge radiator fan was pushing hot air at the canister; which had the intake cut into the canister. All of the pro’s (?) said it should not make a difference at all. I got to thinking after all the money through 8 years of full timing and started my own research. I found that my engine need 874 cubic feet of air per minute at no load and full throttle. Well if there is a vacuum at the rear of the bus, most of the air that is available comes through the radiator. That is very warm air. I also found there is a 3% power loss for every 8 degrees rise in intake air temperature above ambient. The hell with the pro’s. I bought all the fittings to go out the left side of the bus just above the radiator, make a 90 degree turn skyward and added enough tubing to place a new air filter canister at the roof level. I did not want to go into the inside of the bus and mess with bedroom cabinets and leakage. I used the Donaldson Catalogue to make all the selections, fittings, elbows, different bends, tubing and canister and filter. All tubing and such is now 7 inch inside diameter. The cost was $800, well worth it. Now I have a air system that is designed for well over 1700 cubic feet of air per minute. NO MORE heat, smoke or worries. The Siskiyou Mtns at the CA-OR border area on I-5 has always been the challenge. Before where it was 1st gear it was now 2nd, before when 2nd it was now 3rd gear. Sometimes when it was not a higher gear it was at lock up and right at 2250 RPM. Where I had run the course at 205 degrees and occasionally had to pulled over it was now 175-190 and get out of my way as I’m coming through. The mileage has gotten better by a good amount but I can’t say for now as My speed has increased so the comparison isn’t fair. Sorry no pictures or drawings. A few pictures but I’m without a scanner at the present. Good Cooling, Al Newell | ||
| bruce king
Rating: N/A |
The "big" radiators are the 102 style, part number 6k-1-5. You need two of these. I ordered them from Diesel Radiator Co. 1985 Janice Ave Melrose Park, IL 60160-1077 Ph: 800-221-0240 708-345-9244 They wouldn't quote me a shipping cost until they've been built, two week leadtime to build. Apparently they weigh more than i thought; two of them and a pallet are over 300lbs. | ||
| Randy Kanai (Randyk)
Rating: N/A |
Well, I had the mechanic take a look at things and I am calling Diesel Radiator in the morning to order a pair of 6K-1-5's. I had one alarmastat that was a little over active and shutting me down early, replaced both alarmastats just to be safe when we dropped all the coolant rather then replace the obvious bad one only to find out later that the other one was bad too. Went for a drive and still overheated. Back to the shop and pressure washed the radiators and on one, the water flowed through the fins just fine, on the other, very little water flow through the fins. If pressurized water can't make it through the fins, I imagine air would have even a tougher time getting through, one radiator definately has an an air flow issue and could be the last problem left to solve. Radiators looked a little long on the tooth too so who knows what the core looks like in each and how much water is actually flowing through, so I made the decision to order 2 new radiators, hopefully this will take care of my overheating problem. Thanks to all for your suggestions! |
