BCM Community
Bus Discussion => Bus Topics ( click here for quick start! ) => Topic started by: zimmysurprise on August 14, 2018, 02:42:10 AM
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Hello all- put 4200 miles on the bus to celebrate its 40th birthday this year. Overall a great year, but noticed the Detroit started having issues at idle at stoplights. Sounds like it wants to stall, although it never does. It's an automatic transmission, so I sometimes put it in neutral just to prevent a stall at busy intersections. No issues when I accelerate.
About 6 hours from home, I noticed blue smoke from the exhaust at anything more than half throttle. When I got home and parked it in the barn, noticed a new, and fairly significant leak under the engine. Turns out it's diesel fuel leaking from the exhaust pipe on the firewall side of the engine. Running the bus on high idle creates a pretty good leak, which probably explains the blue smoke.
I'm not a diesel mechanic, but from what I'm reading in the forums it might be injectors? What's your take?
Thanks
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Blue smoke is usually oil, black is usually over-fueling, white is usually no air (when starting). First thing I would do is check the air intake, air filter for soundness, look for any signs of dust in the intake above the blower. When my engine acted like that, it was dusted from a dry oil-bath filter. The fuel signs you see may be combustion byproducts from not fully burnt fuel and oil. Mine dripped black fluid copiously from the exhaust joints. I think it's kind of soot, oil, fuel, mixed with water from the exhaust.
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Sounds more like a valve problem no compression on a cylinder,somebody probably got the valve bridge adjustment wrong and caused valve damage JAWAG
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Sounds like it is time to pull the engine to do an overhaul (replace only what is needed to be replaced). A rebuild is when everything in the engine is replaced with new ($$$$$). Good Luck, TomC
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Could it be a blower issue? This may be interesting if that is a possibility ...
https://www.gcsurplus.ca/mn-eng.cfm?snc=wfsav&sc=enc-bid&scn=307149&lcn=454550&lct=L&srchtype=&lci=&str=1&ltnf=1&frmsr=1&sf=ferm-clos
Item:Detroit Diesel-Allison 8V-71 Series Blower Engine
Minimum bid:125.00
Closing date:17-August-2018 @ 11:18 a.m. EASTERN TIME
Remaining:2 days 12 hours 38 minutes
Quantity:1 (each)
Description :
Blower Engine
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Thanks for the input guys- It doesn't seem to be an air issue, and its definitely diesel from the exhaust and only on one side of the engine. I had my wife follow me to the mechanic and she describes it as a white "charcoal" so a little more reading and a bad valve might explain all the issues. The engine has had nothing done inside the valve covers in the past 15 years, but it looks like it will now. Jim- thanks for the lead on the blower, good news is a have a donor engine in the barn on a pallet with a good blower if that ends up being the issue.
The donor engine is out of a White Road Boss of the same year, and has a turbo. I'm assuming the heads and blower would be interchangeable (if needed) even on a left rotation engine?
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The heads will work but the blower I doubt is the same ,there are 16 different blowers and 4 different gear ratios
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Most factory turbo engines would have 17:1 compression pistons, would they not? Mine does.
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I'm waiting to hear what the "shop" has to say. Many horror stories come from non-Detroit 2-stroke shops, like they don't know what they are doing but overcharge anyway. And the work is done wrong. Or they oversell the repair, like saying the blower needs to be rebuilt when it is only the mounting gasket leaking.
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Thanks for the reassurance Geoff!!! :-[ Actually I've known the guy for a long time and he lets me work alongside him. Not something you find very often. I'll keep you posted.
Don
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The heads will work but the blower I doubt is the same ,there are 16 different blowers and 4 different gear ratios
Yeesh didn't realize there were so many. My donor has a turbo so I wasn't sure.
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Thanks for the reassurance Geoff!!! :-[ Actually I've known the guy for a long time and he lets me work alongside him. Not something you find very often. I'll keep you posted.
Don
Yes, pleaseease do keep us informed.
This group is great at double checking other's work. Of course, most are wrong, but you'll figure that out.
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Oh there is bunch and they will all have numbers stamped on the housing
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Oh there is bunch and they will all have numbers stamped on the housing
Those numbers are to keep track of the f-ups who did the work.
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LOL those are large stamped numbers Geoff ,people can screw one up I have one the rebuilder left the plugs out of the roots and used a soft hollow roll pins to pin it with it swelled up so much I can not get the roots out of the case
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LOL those are large stamped numbers Geoff ,people can screw one up I have one the rebuilder left the plugs out of the roots and used a soft hollow roll pins to pin it with it swelled up so much I can not get the roots out of the case
I have to see that one!! I have rebuilt blowers that lost a bearing and the lobes were beat to (almost) death.
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An update on the 8V71. After researching other threads about how to pull the monster, I went to my local industrial supply store and picked up a cart I thought would be heavy duty enough to hold the cradle and contents for 99 bucks. I did a little welding on it to change the wheel direction, then added (4) 7/8" bolts and U-channels to lift the engine close to it's engine mounts.
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I threaded up my bolts to take some weight off the mounts and unbolted it. The exhaust clamps gave me the worst trouble, as well as the grounding strap. (I have no idea how anyone could get to it). I ended up cutting it and will relocate it when it goes back in. I was by myself so I put a ratchet strap from my truck bumper to the cart to keep some pressure on it while I watched all the lines, wires and hoses. Came out like a champ. My wife showed up just in time to snap a picture. Total time from hood up to on the trailer (including building the cart)- 16 hours.
I used chain binders to strap it to the cart, then used my lift to set it on the car trailer. The original plan was to take the whole bus to the mechanic but I was afraid it might be buried in there forever. The cradle rode the 5 miles on the trailer.
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5 hours at the mechanic's and the problem done showed itself...
ding ding ding-
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Looks like Clifford called it😎
Bob
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I see you have the buried muffler.... Make darn sure it is in good condition. There have been occasional issues of fires from a rotted out muffler.
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Clifford did hit in on the head. :-\ (and a couple valves)
Yes but the buried muffler is no more. I ordered the Donaldson that several of you went with inside the rear bumper vertically by the fan. Just like Chris and Cherie from Technomadia did.
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It looks like the valve stem broke, so it wasn't wrong valve bridge adjustment. That happens right away. Are you going to put the turbo engine in?
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LOL maybe the Jake got it, we had a rash of valve stems breaking not long ago with the after market valves machine shops were using
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Double LOL, my tight Jakes haven't got me yet! That engine just looks tired.
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I have saw the spring and snap ring break on the Jake head that holds the slave piston in place and will drop a valve before the fat lady can start to sing not just on Detroit's
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Thank you Santa. 8)
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It's amazing what those 3d machines can make these days! LOL
Good luck in whatever you have in mind!
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It's been a busy winter but spring is around the corner!
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Last post and we'll let this thread die. Broken in locally for 500 miles and 18.2 hours, changed the fluids, heading south this weekend.