8v92 (silver) heavy black smoke under accelleration

[RobSalsgiver]

Greetings all,

First off, admitting I'm a newbie to diesel engines. Have an Eagle '01 bus with a rebuilt 8v92T (previous owner) with 30k on it. Family and I are just finishing a 7000+ mile US trip with the bus / motorhome.

Before leaving had it in the shop to have various checkup items done. Also (myself) changed oil, oil filters, fuel filters, air filter, etc.

Since buying it the engine has run well, but has burned occasionally under heavy accelleration, but much less so once I read a little bit and learned how ot drive the engine properly (read: back off the throttle and downshift).

First 2/3rds of the trip went well, then noticed the engine started burning more and more, and the exhaust was thicker and thicker under accelleration. Checked oil religiously each day, and read before we started that it wouldn't hurt to run the engine a little over-full when running in hot climates, so kept it to the high side of full.

One maintenance item not done that was noticed just before leaving was the replacement of a flexible exhaust line that started wearing out. Initially just pinholes, but by the time we had been on the road a week, the holes kept getting larger and exhaust / soot was loading up the engine compartment. Replaced the flex-line on the road and kept on truckin'.

Finally the engine started loosing power on the top-end, requiring earlier down-shifts and increasing smoke. When running at-speed and level ground (no load), the exhaust is still clean.

Limped into Bozeman MT and did some surfing, and noticed a note indicating that the 8v92's took quite a while for the oil to drain back into the pan. As I had (the day before) notice the oil was down at the Add mark (unexpectedly), I popped another gallon into it. After reading the boards, I let the engine drain longer and checked, and it was 2+ gallons OVER full. Said a bunch of complementary words to myself and the next day drained 2 1/2 gallons off, and hit the road again.

Engine was definitely markedly better with respect to power, but still was burning black as coal under load.

Made it to a friends in Spokane for a couple of days and did an oil change. Oil was thick and black, but otherwise ok. Less than 8000 miles on it, and the only heavy work was in the hills of VA and West VA, other driving was Interstate and good state routes.

The last several days I've been dreading possible seized rings or some other such major work. Now in central Washington and hoping I'll get home, and had a brain cell come to life and thought to check the air filter.

Sure enough, it was so loaded it had collapsed in on itself. It looks like the leakage from the earlier exhaust pipe failure that was coating the engine compartment also got sucked into the intake, and that was the vast majority of the stuff that loaded up the filter. My expectation is that the engine was so starved for air it was sucking oil from the pan up past the rings on the intake cycle. Also fits with the jake not working like it should.

Have another air filter on order and should be able to replace in a couple days.

Question 1: Given the above description, are there other components I should be concerned about, or at least check on, or have the Gods smiled on me and let me get away with one to help cure my ignorance?

Question 2: How often is normal to check / replace the air filter when on the road? Obviously if you are in dusty environments it will be more often, but how about under "typical" driving conditions?

Any other thoughts / advice any of you might have in this situation? (be gentle )

Other than that, thought I would post my experience simply in case someone else hit a similar problem and could learn from my mistakes. Thanks all for the help I have gleaned from this board already.

Cheers,
Rob

[DeepRoots]

hours/milage is great, but get a vacuum gauge that shows when the filter is clogging. All engines will have a vacuum thats within specs.... 10inch or 15, look it up.
filter wraps are nice too to keep large particulates out.

[Gone Fishen]

Motor coach operqtors are a special breed. They object to being called 'bus' drivers, and in some cases 'motorhome' drivers. Note I said 'motorcoach'. Replace the air cleaner every year regardless of mileage. Paper gets old and can loose it's ability to filter the contaminates out. [also note I did not say 'dirt']. Same with the oil changes say every 10K or yearly. I know this is a shock but operation of the engine should be done weekly or at least monthly. This is to circulate the coolant in the cooling system and this also helps clean the engine. 2 times or more the radiator should be cleaned on the external fins. Make sure that all contaminates are washed out from the exterior. [we are not allowed to say dirt]. Oil level should be checked daily before starting engine and the coach should be on a level surface. Also check the transmission after 30 minutes of drive time to get the trans fluid up to operating temperature.
Fuel filters every 10K or thereabouts. They make a new filter setup and it takes 1 filter so you can view the condition of the filter to eliminate excessive filter changing. No not the 'Racor' you have installed. It is called Davco'. Any more questions just ask. Yes I am still pushing wrenches and trying to stay away from motorcoaces and busses.

[RobSalsgiver]

Thanks both of you for your input. I will be incorporating these changes into my routine. Thankfully not much is that different from what's already been done.

UPDATE
Once the air filter was changed, much of the problems went away. The engine returned to it's previous oil consumption and exhaust burn, and the power at the top-end is back at least 90%+ of what it was.

A secondary set of symptoms has not changed, and I would like your thoughts on it.

About the same time as the above problem started, the engine's exhaust >sound< changed. It now has what I would call a flat "bark" to it. Another description would be a noise similar to that of a small gasoline engine or go-kart engine's exhaust running in sync with the diesel.

About the only thing I can think of as a possible cause is that I may have an intake valve stuck or sticking. Another symptom that supports this is that my jake brake is not as effective, particularly at 60-65mph as it used to be. Previously it would hold and/or slow me on a 3-6% downgrade, now it accellerates on most any downgrade, but will slow me on a flat stretch.

I also thought possibly rings or a cracked piston, but if that were the case I would expect more oil burning, as before, and all I'm getting is the sound and the poor jake performance.

Lastly, I've done some looking and downloaded a couple of manuals, but don't see anything yet that tells me what the normal operating RPM and maximum RPMs are. I've seen many warnings not to over-run them, but nothing that tells me the recommended limits. This unit seems to run best at 65mph and 2000rpm. I did some brief experiments and found that 70mph at between 2100 2250 rpm gives the best performance with respect to climbing hills and not dropping out the turbo, but mileage of course takes a dive. Running at 65 and 2000rpm seems to be the best balance, but you do drop out and lose the turbo going below about 1700 a bit more often.

Hence the question about the rpm limits - I really need to know how I should be running this pup.

Thanks again for all the good info. My best to all. Rob

[DeepRoots]

two things to note:

firstly, you don't have intake valves. You only have exhaust valves. If the engine is smoking white often a valve will be burned or carboned up. You have a two stroke engine, so you have intake ports, the piston moves down uncovering them and the blower forces the fresh air in and exhaust air out (this is often referred to as scavanging).

Second you have inspection plates on the block. Generally there are upper and lower, the lower is for crank/connecting rod inspection, the upper (under the exhaust manifold) are for viewing the rings/top of pistons. With a boroscope you can also inspect the valves faces. Open one of the ports, rotate the crank until the rings are visible, rotate further and inspect the piston tops.... this will rule that out.

Dont' worry too much about the rpms, the governor should be set with a max rpm.... not telling you to run 3000+ but chances are you could run 24/7 at the governors rated speed.

I would also make sure the valves are set properly.
I set the valves to .016
you basically rotate the engine until the injector is fully depressed for that cylinder
than set the valves for that cylinder. On 71 series you adjust the valve at the pushrod, on 149 series you adjust the setscrew on the rocker.


I only work with 4-71 and 16v149, so my knowledge is limited.... Gone fishing has much more knowledge and experience....
I do have a set of v92 books (like 5 of them) at the house, but I won't be off my tugboat until september... if you need me to look up something specific I'd be happy to check at that point.

Drew

[Gone Fishen]

No intake valves like Bob said. Get into the coach and slam your finger in the door. Say a lot of cuss words and drive like you are pi**** at the engine. Do not lug it. Keep at 1650 or above. You might have a loose wire for the jake's. 01 engine????? 01 coach???????? What year? Is this engine electronic. Disconnect the belts at the rear and rev the engine up again. Does the barking sound go away? If you had a scored liner, or cracked piston you would not be able to keep any oil in the engine.

[Kaliburz]

Good luck w/ your engine....

[RobSalsgiver]

Thanks all once again for the info, and for being kind while I show my ignorance regarding intake valves .

The coach is an Eagle '01, 1967, vin 6776. Unfortunately that doesn't help, as the engine and tranny were replaced in 1990. I will look through the paperwork for the specs, but my suspicion is that I will have to get an engine vin to find out the true year, etc.

With respect to checking the pistons and the inspection ports - how should one do that (safely)... I have read to be extremely careful as to not accidently start them while working on them - how does one rotate the engine to inspect without risking that?

Fishen - I'll try it with the belts and let you know, but for the sake of my ignorance, what am I testing when I do that?

Lastly on the RPM, I'm glad to know I'm not running it to high. It likes to run around 2000-2200, and a couple times it's spiked up to 2400 or so. As this was a replaced engine, I am unsure of the governor status. Will have to do some research and check into it.

Cheers all,
Rob

[DeepRoots]

should be just a large nut on the crankshaft.
turn it. and turn it whatever direction the engine spins.... i know a bunch of buses spin backwards
I've not heard of engines starting, but as a precaution maybe just do it cold.... and if your really worried shut the air dams. Tho don't forget you shut them.

[Gone Fishen]

Removal of the belts is done to eliminate any interferance from those accessories driven by the belts. Baring the engine over is done with an 1 1/2 socket the left camshaft nut. The older engines had a 1 5/16 bolt on the crankshaft but hopefully the updated bolt is in use on the crankshaft and a 1 1/2 socket is used there as well. Inspection of the cylinder kits can be done by removal of the 2 small inspection covers and the 1 large cover on the side of the engine. You can actually look inside the engine while someone bars the engine over. You want things to look pretty, No burn'd looking parts. Piston rings can also be inspeced except the oil control rings. Engine normally is 2250 to 2300 rpm. Since you will have an electric tach the reading might be a little off. They are made to run at the upper rpm range. Since you might be laying around the starter, disconnect the battery power before the inspection. If this is an electronic engine, doubbtful on a startup since the computer has to have power to it's wiring from the dash before startup. If this is a mechanical there is usually an air solenoid on the top of the engine that keeps the engine from starting until dash power is applied to the solenoid. However the shutoff piston usually bneeds air to shut the engine down. Again disconnect battery power if there is any chance of accidental starting the engine.