8V71 New Engine Issues

zimmysurprise · August 14, 2018, 02:42:10 AM

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

bevans6 · August 14, 2018, 04:13:05 AM

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.

luvrbus · August 14, 2018, 06:05:05 AM

Sounds more like a valve problem no compression on a cylinder,somebody probably got the valve bridge adjustment wrong and caused valve damage JAWAG

TomC · August 14, 2018, 07:55:41 AM

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

Jim Eh. · August 14, 2018, 08:02:32 PM

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

zimmysurprise · August 15, 2018, 04:00:46 AM

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?

luvrbus · August 15, 2018, 05:55:46 AM

The heads will work but the blower I doubt is the same ,there are 16 different blowers and 4 different gear ratios

bevans6 · August 15, 2018, 06:16:43 AM

Most factory turbo engines would have 17:1 compression pistons, would they not? Mine does.

Geoff · August 15, 2018, 01:24:23 PM

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.

zimmysurprise · August 15, 2018, 02:55:50 PM

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

zimmysurprise · August 15, 2018, 02:57:53 PM

Quote from: luvrbus on August 15, 2018, 05:55:46 AM
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.

Geoff · August 15, 2018, 03:02:34 PM

Quote from: zimmysurprise on August 15, 2018, 02:55:50 PM
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.

luvrbus · August 15, 2018, 03:08:26 PM

Oh there is bunch and they will all have numbers stamped on the housing

Geoff · August 15, 2018, 03:43:43 PM

Quote from: luvrbus on August 15, 2018, 03:08:26 PM
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.

luvrbus · August 15, 2018, 04:01:45 PM

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