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Author Topic: update on oil leaks - finding and fixing  (Read 1860 times)
thomasinnv
Derrick Thomas
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« on: October 02, 2010, 06:27:41 PM »

I replaced both valve cover gaskets, both of them had about 1 1/2" or so that was curled under along the top side.  I also replaced a badly leaking low oil pressure switch.  Evidently the one i took out was so bad it wasn't only leaking but it wasn't doing it's job either.  Now I find i have to hold the start button for a second or two after it starts for the oil pressure to build or the engine just shuts off when I let off the button, never did that before.  good to know it's doing it's job now.  So anyway, I drove about 350 miles to my next destination.  The front of the towed has some spots on it but not nearly as bad as before.  The dipstick was only down about 1 - 1.5 quarts.  Previously it would be down about a gallon every 400-500 miles, so there is a definite improvement.  there are still some pretty good sized circles under the back of the bus, but I have searched high and low and I have exhausted my capabilities.  I am busy with revivals until the beginning of November, but after that I plan on heading south toward Arizona.  On my way I plan to accept the offers made by two kind gentlemen on this board to help me locate and fix the leaks.

On another matter, I have found one of the front airbags to be leaking.  One side has old bags and the other side not very old.  One of the old ones is leaking right through the rubber material.  It has become porous.  I would like to replace the 2 old ones while we are fixing oil leaks if possible.  (hint hint)  But I will be happy and satisfied with what ever I can get done.
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There are three kinds of people in this world....those that make things happen, those that watch things happen, and those that just wonder what the heck is happening. Which one are you?

1977 MCI Crusader MC-8
8V71N/740
95% converted (they're never really done, are they?)
Van
Billy Van Hagen
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« Reply #1 on: October 02, 2010, 08:31:35 PM »

Good to see you moving forward, and seeing results as well. Good luck.  V
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bevans6
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« Reply #2 on: October 03, 2010, 03:43:04 AM »

I changed out my front air bags this summer, it's not an easy job but more persistence required than anything else.  Check with Luke for the bags and fasteners.

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
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thomasinnv
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« Reply #3 on: October 03, 2010, 09:19:56 AM »

I changed out my front air bags this summer, it's not an easy job but more persistence required than anything else.  Check with Luke for the bags and fasteners.

Brian

block off plates have been installed long ago.  I had already planned on 2 new bags and all the nuts/bolts to go with them.  They are the double bellows type.  (for lack of knowledge thats what I'll call them until someone educates me) 

I want to install a vanner sometime soon too.  I will check with Luke to see if he has one also.
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There are three kinds of people in this world....those that make things happen, those that watch things happen, and those that just wonder what the heck is happening. Which one are you?

1977 MCI Crusader MC-8
8V71N/740
95% converted (they're never really done, are they?)
thomasinnv
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« Reply #4 on: October 12, 2010, 01:10:28 PM »

I finally got around to installing some hoses and catch jugs on the air box drains.  the right bank (passenger side) is clear and no oil at all.  the left bank is blowing oil steadily.  not large amounts, but steady none the less.  that is definitely a source of some oil loss.  I don't believe I have check valves, as the air box drains blow air at any and all rpm's.  what is the most likely cause of the oil blowing out?  what should I look for?
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There are three kinds of people in this world....those that make things happen, those that watch things happen, and those that just wonder what the heck is happening. Which one are you?

1977 MCI Crusader MC-8
8V71N/740
95% converted (they're never really done, are they?)
bevans6
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« Reply #5 on: October 13, 2010, 05:40:07 AM »

Those drains (slobber tubes) are directly venting the main airbox of the engine, which feeds the cylinders with air compressed by the blower.  The  airbox is full of air at around 2 psi greater pressure than the atmosphere so if you have no check valve the drain will indeed continually vent.  There are two main sources of excess oil inside the airbox, which is continuous from side to side - the blower seals and the oil rings on the pistons.  Presuming that the drain that is NOT leaking isn't simply blocked off with crud, if you had both putting out oil you might think of blower seals, putting excess oil everywhere.  If you had just one putting out oil you might think of bad oil rings on a cylinder in that bank.  You can install check valves - they block off the slobber tubes when the pressure inside the airbox reaches a certain level, and I think you can get them set for two different RPM's.  As with everything else I get for the bus, I just called up Luke and told him to send me what he thought I needed....

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 #6 on: October 13, 2010, 07:05:59 AM »

I was told once that about one out of three two strokes have cracked or poorly seated oil rings that were improperly installed during an overhaul. Apparently it is either not an easy procedure or it is easily misunderstood in the manuals. I believe that is the case with my motor as I cannot get it to quit going through oil and it is not my blower seals and I have great compression. I cleaned and pressure checked my airdox drain tubes and they are working fine. My advice would be to limit your idle time and find a way to get okay with an imperfect but super dependable motor. My motor doesn't leak a drop out of the block but I still go through a galon or two every 1000 miles. All in my home made pvc catch cans.

RB
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luvrbus
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« Reply #7 on: October 13, 2010, 07:50:24 AM »

Most of the time on a 2 stroke pepole will not buy the correct tool for the piston pin seals they drive those in with a hammer and socket and never pull the vacuum for testing then they use the wrong ring compressor braking the oil rings when that happens you never get one to stop using oil.
When a 71 or 92 series are rebuilt right you get very little oil from the air box drains
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bevans6
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« Reply #8 on: October 13, 2010, 08:20:14 AM »

There are other tests for determining what is putting the oil into the air box.  Two things that have been suggested in the past is running the engine with an air box cover plate removed - you can then see the oil coming past the piston with the bad oil rings.  You remove one ring at a time.  Also suggested is running the engine with the exhaust manifold removed, see which one is throwing oil out the port.  Also taking the top off the blower and looking to see if the seals are leaking.

All sorts of ways to amuse yourself!  Me, I stopped when the jugs to catch the overflow and the check valves were in place.  My oil leaks aren't there anymore, so I need to go deeper.

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
thomasinnv
Derrick Thomas
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« Reply #9 on: October 13, 2010, 06:12:04 PM »

just to clarify, the side that is NOT blowing oil is not clogged.  there is a steady stream of air blowing out both sides, but only one side has oil coming out.  I still have a few small external oil leaks, but the big ones are stopped.  I have considerably less "pavement marking" then before.

Clifford, I will be heading your direction in about a week and a half so I may drop in for a visit and a little "schooling" if the offer still stands.
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There are three kinds of people in this world....those that make things happen, those that watch things happen, and those that just wonder what the heck is happening. Which one are you?

1977 MCI Crusader MC-8
8V71N/740
95% converted (they're never really done, are they?)
thomasinnv
Derrick Thomas
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« Reply #10 on: October 22, 2010, 10:49:52 PM »

I replaced 2 front airbags today.  One was seeping through the rubber so I replaced both on that side since I had it tore down.  The job went fairly well with just a few hitches.  For those that have not done airbags before, I STRONGLY suggest just replacing the nuts and bolts and not trying to reuse them.  For those that HAVE done airbags before, you know why!  I did go to the hardware store and buy new nuts for the second bag, it went in a lot better than the first one.  Hopefully when I step out of the bus in the morning, it will still be up in the air.

And FYI, the date on the leaking airbag was 1987.  I guess it served pretty well.
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There are three kinds of people in this world....those that make things happen, those that watch things happen, and those that just wonder what the heck is happening. Which one are you?

1977 MCI Crusader MC-8
8V71N/740
95% converted (they're never really done, are they?)
bevans6
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« Reply #11 on: October 23, 2010, 05:41:32 AM »

That's a good job to be finishing and not starting, yes?   Cheesy  Now you have to do the other side and the rears, unless you get lucky...  I bought all new bolts and nuts when I did mine.  Where did you end up buying the springs and how much were they?  What brand?

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
thomasinnv
Derrick Thomas
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I may be nuts, but only for buses


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« Reply #12 on: October 23, 2010, 08:24:32 PM »

Well, unfortunately the front bags were bled off again this morning.  I am going to see if I can get a new check valve for the leveling valve I took out and put that valve back in.  The "new" leveling valve has leaked a few times so I am just going to take it out.  I have checked all the bags and fittings and hoses over and over and over with soapy water (that's how I found the bag that was leaking) but I can't find any leaks.  Feel like i'm chasing my tail in circles.  I need to find another fresh set of eyes.


That's a good job to be finishing and not starting, yes?   Cheesy  Now you have to do the other side and the rears, unless you get lucky...  I bought all new bolts and nuts when I did mine.  Where did you end up buying the springs and how much were they?  What brand?

Brian

the other side and the rears have been done within the last couple years, these were the last to be done for a while.  I got the bags from MCI for $92, which was about the same as US Coach, but MCI does not charge for shipping.  They are Goodyears.
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There are three kinds of people in this world....those that make things happen, those that watch things happen, and those that just wonder what the heck is happening. Which one are you?

1977 MCI Crusader MC-8
8V71N/740
95% converted (they're never really done, are they?)
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