DD 8V-71N Oil leak mystery, Cold smoking issues

[Garymci5]

Hi All,

I looked thru some of the archives but didn't find what I'm after.

The bus is a MCI Challenger and the oil loss appears to be coming from the front left (closest to rear bumper by thermostat housing on left) possibly where the block and cylinder head mate. It sprays (I assume) and drips onto the oil cooler, lower radiator hose and the frame rail. Really slobs it up. It does not appear to lose oil when idling and can't verify what happens going down the road. Cleand it up and it just comes back. Oil pressure gauge reads about 70-80 PSI at startup and about 40PSI when on the highway when hot. Engine starts right up even when it's near freezing and quickly clears out.

The car mechanic side of me says that the headgasket it failing or worse there is a minor crack that when hot expands and allows oil to spray out.  The total amount isn't too much but gunks up the house batteries and frame area. The oil is fresh but the contamination looks super black and is a bit thick, not somemuch unlike road tar. Coolant level is good and does not use any. Fluids are not cross contaminated. Lost about 2 gallons of oil in about 15 hours of driving. Take 11 gallons with a Luberfiner bypass filter.

While I'm at it, it also has prolonged white smoking when the engine is cold and warming up. It takes a few miles of driving to clear out. Under WOT and if not fully warmed it makes for a great mosquito fogger. Actually it's embarrassing and no doubt isn't good for the environoment (or engine). However, the engine runs "Good" the whole time, smooth and good power. It would run away from my old 40' Eagle, which had tall highway gears.

When I bought the bus it hadn't been driven for over 2 years and the fuel was also old.  The owner just ran the engine every month or so, but never worked it- something I would never do. Upon test drive it smoked like an army tank fogging itself for camoflauge. It was a sight to see! Once warmed up and on the freeway, ran it WOT for awhile. No smoke at any speed thereafter.

Maybe an injector going bad? Supercharger seals leaking? I couldn't see any blue smoke.

This is my third DD and aside from the $20K rebuild in another coach (from prior owner), this one runs and starts like it's nearly new (123K on hubometer, but records show the engine is likely at least 20+ years old). Exhaust manifolds seem to warm up okay, but due to mass variations cannot be absolutely sure. At least it runs smooth, so that is good.

Another thing is that there was a tank of old fuel and maybe the cetane droppped too much, causing white smoke? I then filled 1/2 tank with 99% Biodiesel (to make a 50% blend) and noticed an immediate increase in power/torque. Took a short 2.5hr one way trip to go camping in the mountains but same white smoke when cold. Bummer. I can barely throttle it, to prevent fogging out the highway, until it's warmed up. Ugh.

Changed the fuel filters, oil change and filters, cleaned the oil-bath filters, added various fuel improvers, still no improvement.

The only good news is that it's driveable, starts and runs great. Even had some truckers come over and say how nice it sounds.

Okay, so what ya'll think on this one? Should I just repower with a 6-92TA with a 6spd auto? (whish I could afford it)

Thanks for any input that might help or get me on course to solving this one.

Gary

[luvrbus]

On a 8v71 I would check were the rack control rod goes from the governor to the head the coupling is made of rubber and they are using plastic clamps now also check your valve cover gasket. 


good luck

[bevans6]

Here is an odd-ball suggestion - but it's happening on my 8v-71 so it could be happening on yours.  Mine had an "oil leaK" putting a mess on the left front of the engine (looking at it from the back of the bus, so kind of below the governor/fuel pump area)  It turned out to be fluid getting blown out from the band clamp that ties the exhaust pipe together.  It is probably oil blowby from the passenger side bank of cylinders.

White smoke to me (non-expert, learning as fast as I can) is incomplete combustion for some reason.  That could be low compression on one or more cylinders, or something like that.  It's possible that there is insufficient compression to support full combustion until the cylinder is a lot hotter, when it starts to come in.

Brian

[harpold700 3]

Check the clamp on your blower drive rubber, and also if it has a jake check to see that no one has left a wire caught in the valve cover gasket.  Old 71's usually have collapsed or broken oil rings, but as you have allready found, run clean after warm up. Plug it in if you are near power for a much quicker "clean up". 

[gus]

White smoke from a DD 2 stroke in cold weather is pretty much the norm.

My 671 smokes loads when it first starts cold but the smoke clears up pretty much by the time I fast idle it for 20-30 min - not too much in very cold weather.

It was 9* here this morning when I started it, very cold for the south.

[Fredward]

My 871 was leaking oil terribly until I removed and re-seated the valve covers. It was just crankcase pressure pushing oil out the top side of the valve cover and it ran down the front of the engine as you describe.

Mine used to make an embarassing cloud of smoke upon startup until I had the rack run. Sure enough, there was one injector that was not being allowed to close all the way to idle setting. That being said; I always plug it in for three or more hours before start up in a campground. Even when its 70 degrees. It clears right out in about 60 seconds under those conditions.

They're great old engines; I swore I'd never own one and now I don't think I'd want a 92 series. (A four stroke on the other hand.............ahem)
Fred

[Nellie Wilson]

Hi Gary -

I'd planned on introducing myself before replying to anything but couldn't resist this one. Mainly because I think you're needlessly worried.

To make sure we're on the same page: I assume "front left" means driver's side at 'pulley end' of the engine? If so, my 8-71 slobbers at the same place. And so does virtually every 8-71 I've seen. Mine also 'leaked' from an exhaust clamp (see Brian's reply)... but that turned out to be just unburned fuel (when engine cold) and not blow-by. Still, it looked bad and worried me a lot.

Mine also blew some white smoke but that disappeared once escaping the Frozen Tundra (see Fred and Gus's replies).

If your engine fires when cold you have good compression. And you say it "sounds good and runs smooth?" Heck, quit worrying - why ditch a perfectly good 8-71?

But your fuel and your oil pressure / level are question marks. Why not start with fresh fuel and see what happens?  (Any chance of algae?)

And are you sure you've got the original dipstick? Unless my math has gone bye-bye, 11 gallons is over 40 litres. By-pass filter or not, that's waaay overfull. And barfing 2 gallons in 15 hours suggests your engine is gagging on the stuff. Which seems to be confirmed by your oil pressure... which seems awfully high.

But that's just me. As I said, I'm a rank novice. Best of luck and keep us posted.

Nellie Wilson

PS. Happy New Year everybody!

[Van]

Welcome aboard Nellie, glad you made it. 

[Ed Hackenbruch]

As Nellie said, 11 gallons of oil is way too much unless that bypass oil filter you have holds 4? gallons.  An 8V71 holds 7 gallons/28 quarts.  Mine likes to run at about the 6-6 1/2 gallon level so even though i put 7 gallons in it at an oil change to make sure it is full, i know that within a short period of time it will get rid of the excess and stay at that level for the next 1200-1500 miles.

[Ed Hackenbruch]

Probably should have noted that my 5A is only one year newer than yours.

[bevans6]

Welcome to the board, Nellie!

Brian

[luvrbus]

I never saw a Lube Finer hold 4 gals but they will hold 2 and 3 gals and his oil pressure is about normal for a 8v71.
He proably needs a good tune up and for the smoke he may have blower seals going bad or if it turns too black smoke after running a new set of injectors are in his future.



good luck

[Garymci5]

Thanks for everyone's input, some of it was quite good and will give me a few things to check.

UPDATE:

I drove the bus yesterday and the smoking appears to be blueish and not white like I had thought.  Maybe the grey skies made it easier to see this time. That would probably explain some of the oil loss.

I left the oil level low to see if it would smoke less- no difference. However it did clear out faster than usual (about a mile and 120-140F coolant temp), and it was almost freezing last night, so the engine was pretty cold. It still started like a champ in about 3 seconds, barely smoked and ran clean right away, once I feathered the throttle to prevent engine roll (it could use a slight adjustment for cold weather).

The other clue, appears to be some oil loss at the exhaust cross-over connections. I thought it was the miter-box for the blower fans, since it seaps a little. However it couldn't spray upwards on the engine compartment.

'Suppose I should pull the inspection covers off to inspect the rings. Hoping that since it runs so nicely it'll be fine. Which will then point me towards the top end.  Someone said the valve seals might be worn out (they're old for sure), but since it's a 2 stroke and doesn't create engine vaccum (that would pull oil in), mostly rule that out.

The key symptom is she blows smoke under throttle. It's directly proportionate to engine load and RPM, but will also badly smoke on a snap-throttle (which simulates load for a moment): Load=Smoke, until she's fully warmed up.

Any add'l thoughts are welcome on this one!

[luvrbus]

Gary, it is not going to do any good checking the rings with the fast start up you have good compression and that is the only rings you can see in the air box the oil rings are not visible from there. 
Me I would remove the air horn on top of the blower use a light with the engine running if oil is running down on the end plates then you have bad blower seals 



good luck

[Hi yo silver]

I'm a rank amateur bus owner, too.  However, for what its worth, here's my experience thus far.  Mine is an MC9 with an 8V71N.  I can start it and let it idle 'til the cows come home, even on a summer day, and it won't warm up enough to stop smoking a little until I've driven the first four or 5 miles.  After that, the only time it smokes enough to see it from the driver's seat is when you're driving with your "foot in it" with the sun behind you, and you're new at driving it, and still a little nervous, but I'm saving that story for a rally, after a couple of glasses of wine! LOL  It's a DD two stroke; it's gonna smoke sometimes.

Mine has some dirty looking oil on the exhaust clamp too, that appears to have come from the front main seal (I guess that's the front).  I figured out that it was really noticeable after I topped off the oil level.  Then I remembered the advice on the board re. the oil "finding it's comfortable level".  It seems to do fine running about a half to one gal. below full.