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Author Topic: HELP HELP HELP 1970 mci7  (Read 3522 times)
moose
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« on: March 01, 2010, 07:56:29 AM »

Hello- we just picked up our bus in Palm Springs, CA. We live in Texas, but drove the bus to Canada-due to I am a Canadian and wanted to work on the bus where I live and work, before the travel season comes on. The bus has been sitting for 2 years, so any suggestions in regards to mechanical issues would be very helpful. But we did drive 1200 miles and only the issues below caused concern.
On the trip home, these are our experiences:the air system-would fill to 120psi and fluctuate down to 90psi and back again for the entire trip-is this cycling a normal situation or could there be something wrong?
Everytime we shut the bus off, it would drip oil to a very large pool. The trip was only 1200 miles and we used 1 gallon Von the whole trip, the pooling added to about 1 pint to 1 quart total. Is this normal for the Detroit diesel 8V71T? If not, where would the oil be coming from? Could there be a plugged line or vent, should I let the engine warm up longer?What is the normal practice to stop this from happening?
I roughly figure that I got between 6-8 mpg. running at 60-70 mph. How does this measure against normal usage?

Any assistance and guidance would be appreciated.
Trevor and Michelle
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wal1809
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« Reply #1 on: March 01, 2010, 08:06:06 AM »

I have a 6v92 and the oil usage is about the same.  I have noticed when I fill it to the line on the stick then it slobbers more oil.  As it loses the replaced oil the slobbering slows quite a bit.  I get around 7.8 as a lot of us do so your milage seems to be good.

Welcome to bus ownership.  I am new as well.  You got a set on you to get in and go 1200 on your first trip.  Congrats.
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bevans6
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« Reply #2 on: March 01, 2010, 08:27:38 AM »

the oil "slobbering" and usage sounds fairly normal.  the 8V71 has two drains on the engine that release fluid from the airbox, you can direct them to a can of some  sort to catch the fluid before it gets to the ground.  Google 8V-71 slobber tube, and you will get lots of information.

The air brakes also sound normal, but it tells me that you don't have even a rudimentary understanding of how air brakes work.  I went to the Alberta web site to see if air-brakes need a special endorsement on your license for RV driving and I couldn't tell.  Regardless of if you need an endorsement, you should give serious consideration to taking an air brake course at a local driving school.  In my opinion it's needlessly dangerous to operate an air-braked vehicle without knowing how they operate and what "normal" is.

Air brakes are fundamentally different from hydraulic brakes.  Air brakes have a quite complex system of compressors, tanks, valves and actuators that must all be actively operating and functioning correctly for the brakes to work.  Hydraulic brakes are basically nothing but a system of mechanical levers that need nothing to operate beyond the fluid in the system.  A vast difference, that makes daily inspections and constant diligence key to operating an air brake equipped vehicle.

Cheers, Brian

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1980 MCI MC-5C, 8V-71T from a M-110 self propelled howitzer
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RickB
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« Reply #3 on: March 01, 2010, 09:26:25 AM »

Trevor and Michelle,

First of all wlecome to our community of bus crazy people!

It is not abnormal to have your air system cycle from time to time on long trips because our buses tend to have a number of little leaks. Although an airtight system is preferred finding and solving all of your leaks is very time consuming and requires alot of knowledge and patience. So, when your system is reaching 90 lbs the air governor is engaging your air compressor and at around 115-120 lbs your compressor is reaching it's cutout pressure and it is shutting off the compressor. It would be acceptable to have your system engaging every half hour or so on long stretches of highway where your brakes are not engaged.

In minutes, how often is your air compressor cycling?

Regarding your oil usage I would also recommend that you do an oil change and use straight 40 wt Rotella oil or straight 40 wt Chevron Delo 400. These two strokes tend to leak multi weight oil alot more than the straight wt. oils and most, but not all, two stroke owners believe that the manufacturer intended these motors to only run straight 40 weight oil. It is quite possible the person you purchased the bus from may have run 15-40 multi weight in it, if possible maybe give them a call and ask them what the bus currently has in it.

Thanks Rick


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I will drive my Detroit hard... I will drive my Detroit hard.
buswarrior
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« Reply #4 on: March 01, 2010, 09:26:49 AM »

If that air pressure is going down while you are driving along, it isn't right.

If it goes down in measured amounts and hold steady each time you step on the brake pedal, that's ok.

Like Brian said, job one is an airbrake course. Getting it to stop is job one.

welcome to the madness!

happy coaching!
buswarrior
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RickB
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« Reply #5 on: March 01, 2010, 09:31:56 AM »

BW and Brian,

You guys must have alot more airtight systems than most of the busnuts I know. I have certainly been led to believe from most of my friends that an absolutely airtight bus is a rare bird.

Rick
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I will drive my Detroit hard... I will drive my Detroit hard.
bevans6
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« Reply #6 on: March 01, 2010, 10:00:29 AM »

My bus isn't air tight, and reasonable loss of air while driving is fairly normal, in my estimation.  I have some leaks from the accessories system, particularly when I have the air door turned on.  You will also lose air pressure while driving from operating things like wipers, the rad shutters if they are operable, the suspension levelling system, all the belt tensioning cylinders.  Standing still, with the bus aired up and engine off, I believe the spec for air loss without operating any air system is 10 lbs in 10 minutes.  More than that is OOS.  I wouldn't think that having the bus compressor cycle every half hour or so of highway driving is that far out of the ordinary.  I don't recall ever just driving for that long without doing something that needed air to try to time it, but I do see the pressure cycle up and down routinely.  Which is kind of what I said in my earlier post, actually, that I felt his air pressure operation sounded fairly normal, although the OP didn't say what the cycle time was.  It's driving the bus while not knowing that it may or may not be normal that raises my flags.  I just happen to be one of those who think that a prerequisite for driving a bus is knowing how the air systems work, is all.

Brian
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1980 MCI MC-5C, 8V-71T from a M-110 self propelled howitzer
Spicer 8844 4 speed Zen meditation device
Vintage race cars -
1978 Lola T440 Formula Ford
1972 NTM MK-4 B/SR
RickB
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« Reply #7 on: March 01, 2010, 10:06:23 AM »

I fully agree Brian... Smiley

Rick
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I will drive my Detroit hard... I will drive my Detroit hard.
Just Dallas
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« Reply #8 on: March 01, 2010, 10:20:42 AM »

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RickB
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« Reply #9 on: March 01, 2010, 10:59:46 AM »

Sorry Dallas is correct. My bad. It's Delo 100 40 wt that is recommended for our two strokes.

Rick

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« Reply #10 on: March 01, 2010, 12:37:58 PM »

You gave up to easy Rick 15/40 Delo is CJ-4 rated and 40W Delo is CF rated tells you on the jug good for all services in DDC/MTU   


good luck
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johns4104s
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« Reply #11 on: March 01, 2010, 12:48:16 PM »

I think you will find that when you have driven the bus for a while the oil use will get better. the dark oil leak could be coming from the air box drains. Which for the most part is unused fuel that has been discolored by engine heat and found its way though the air box to the two drains. Do not idle for long periods, yes you have to on start up. But don't idle unless you have to.
Watch your gauges, oil and water. don't lug the engine.

John
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moose
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« Reply #12 on: March 01, 2010, 02:03:14 PM »

Hello
Thank you for all your welcoming and advice and knowlege .
I am 50 now and i did have a ! air driving license for a couple of years wehen i was 19 to 20
My bus id 40 years old , just curious since just purchasing her ,and doing a long drive seeing how it operates learning all the characteristics of a 40 year old bus .some one ask the air pump cycle time it is about-120lbs then down to 90lbs  10 to 15mins
i know howe the air system works but i thinking about plating the air bag system .
1) also i am looking for all the history on this bus who would i contact for this
20 wind sheild wiper blades where do i get them
I am located in Calgary  i will have to find a good service shop as i need her gone thru
brakes ,drums(everything included in air system .) wheel bearings ,seals ,shocks
Thanks again to all
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moose
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« Reply #13 on: March 01, 2010, 02:41:19 PM »

Hello it is Trevor Again
the oil slobbering seems to be the worst when i jake braked on this trip i drove throught Glacier national park ,montana
Very steep ,long down grades ,so lots of jake braking
is this all right to do
will a lot of jake braking in the mountains harnm your engine
could this be threason for the large amount of slobbering
trevor
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Just Dallas
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« Reply #14 on: March 01, 2010, 03:13:34 PM »

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