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Author Topic: Jake Brakes the potenial source of all the worlds problems???  (Read 2034 times)
viento1
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« on: February 26, 2010, 05:42:43 PM »

Hey Guys,

Just to recap...

mc5 with 8v71 65 injectors with 50k miles on rebuild.
No smoke of any color or flavor no matter how hard I drive it.
644 Automatic and Jake brakes
3.71 rear end (I am pretty sure)

Problem:
Low power, poor starting, white cloud of smoke at start up. Black goo pouring out of every part of exhaust manifold.
horrible mileage

I spent 3k for a local high end shop to tell me that the motor was dusted. (particals in intake that scored the cylinder walls) but that still does not make sense as it does not burn any oil (unless it is disguised as the black goo?)

I local mechanic told me that the problem is simply the jakes are not adjusted and that explains all the symptoms. Does that sound correct? Do I trust my baby to a backyard mechanic who drinks a wee bit too much home made whiskey?
« Last Edit: February 26, 2010, 05:46:15 PM by viento1 » Logged

Ok, it's time to go on another road trip.
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redbus
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« Reply #1 on: February 26, 2010, 06:32:26 PM »

I think I would worry more about a Detroit mechanic that did not drink Grin Grin Grin
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« Reply #2 on: February 26, 2010, 06:37:00 PM »

  I'm sure opinions will run amok here. But why not get the jakes adjusted to find out for sure? If that fixes it great. If not at least they are adjusted correctly...Cable
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Sofar Sogood
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luvrbus
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« Reply #3 on: February 26, 2010, 06:55:10 PM »

You guys have at it I would not touch this one with a pair of rubber gloves

good luck
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bevans6
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« Reply #4 on: February 27, 2010, 05:11:27 AM »

You guys have at it I would not touch this one with a pair of rubber gloves

good luck

I hate it when he does that   Grin   Makes me wonder what I am about to step in to...

Random thoughts... 

white smoke on starting, hard to start, low power, black goo - all signs of low compression and/or too much fuel.

dusted engine = bad compression rings = low compression, see above.

good oil consumption = good oil rings, which have nothing to do with the dusted and bad compression rings since they don't really see the part of the cylinder that sees the dusty air.

Checking the adjustment of the jake brakes doesn't seem all that hard to do

Maybe the injectors are bad, or the engine isn't advance timed and should be for the n65 injectors.  Injectors that are bad or mis-timed might result in unburnt fuel creating black goo.

A good 2 stroke mechanic could afford store-bought whisky, I would think.

Brian

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1980 MCI MC-5C, 8V-71T from a M-110 self propelled howitzer
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TomC
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« Reply #5 on: February 27, 2010, 09:05:37 AM »

Sounds like your engine was rebuilt by a mechanic that doesn't know how to install the cylinder kits correctly-since 50,000 miles is about the time the rings will be toast if not installed right.  Find yourself a certified Detroit mechanic and have you engine overhauled the proper way. You'll pay more for this overhaul, but quite possibly will never have to have the engine overhauled again in your lifetime.  Or you can be cheap and do it over and over and over......Good Luck, TomC
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Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.
viento1
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« Reply #6 on: February 27, 2010, 04:45:51 PM »

Hmmm,

well, another detail I left out was that I was driving along in Montana and all of the sudden I got a surge of power and the bus ramped up to 75 mph and rocketed up the hill in 4th... I thought it was my imagination but my co driver made the same comment when it was his turn to drive.

Again the local guy says when the the jakes are not adjusted that it will feel like there is a restricted exhaust and he thought something was not adjusted properly.

I had not heard that diagnosis before...
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Ok, it's time to go on another road trip.
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ilyafish
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« Reply #7 on: March 01, 2010, 11:27:25 PM »


well, another detail I left out was that I was driving along in Montana and all of the sudden I got a surge of power and the bus ramped up to 75 mph and rocketed up the hill in 4th

is it a toyota by any chance??  Grin Grin
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bevans6
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« Reply #8 on: March 02, 2010, 04:39:45 AM »

Why not check them instead of wondering about it?  I haven't done it yet, but will be this spring.  It seems to me like a thorough check would be to measure the valve clearances and the clearance between the jake and the bridge.  Fiddly but straight forward, unless you have to take the jakes off to measure the valve clearance.  Any thoughts on the procedure to do this check?

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
luvrbus
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« Reply #9 on: March 02, 2010, 05:09:34 AM »

Brian, no need to remove the Jakes to make life easier for you buy a go no go feeler gauge and the Jake gauge and you need the offset push rod adjustment wrenchs or it will be a bitch


good luck
« Last Edit: March 02, 2010, 05:15:24 AM by luvrbus » Logged

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johns4104s
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« Reply #10 on: March 02, 2010, 05:22:42 AM »

white smoke on starting, hard to start, low power, black goo - all signs of low compression and/or too much fuel.

dusted engine = bad compression rings = low compression, see above.

Brian,
I understand the White/grey smoke on start up is caused by

1) The oil pressure switch not allowing the engine to start until the 2,3 or 5Ib (there are diffrent pressure switches) pressure is reached.

2) In turning the engine over to get the pressure the rack is in the wide open position.

3) With the rack in this position it is pouring fuel in, it is unburnt this mixes with a little oil as expansion has not yet occurred on the cylinder walls.

On start up Hey presto you get a puff/cloud or whatever of white/grey smoke, that being the cold unburnt/half burnt fuel and oil mixture.

John
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bevans6
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« Reply #11 on: March 02, 2010, 05:32:08 AM »

John, all true I think, but it's a question of degree.  My bus doesn't have a "don't start until oil pressure is up" switch, so I don't know about that.  I was more thinking  of "hard starting"  as a lot of cranking needed when it's warm out and a "normal" engine would start in a revolution or two like mine does at 60 degrees or warmer.

But I agree the white smoke is a result of the hard starting, and suggest that the hard starting may be a result of low compression, basically.  One could try the trick I just learned of cranking with the stop lever applied for five seconds, then slowly releasing.  When I tried that it jumped to life at 40 degrees, with no white smoke at all.  Quite amazed me, it did!

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
luvrbus
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« Reply #12 on: March 02, 2010, 05:43:36 AM »

Have you guys ever had the starting aid on the governor checked or adjusted ? 




good luck
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johns4104s
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« Reply #13 on: March 02, 2010, 07:17:53 AM »

Brian,

If both the oil, temperature and air shut downs are in place and corrected properly then one the engine has had air and is not overtemperature the following is what I understand to be the procedure.

The engine has been stopped, the skinner valve has pushed the rack to full/shut down. When you turn the key the engine turns over but waits for the oil pressure to be up and no temperature condition, then it sends a signal to the skinner valve to dump air, which in turn releases the plunger which aloes the rack to go into start mode.

Then the governor spins allowing the weighs to spin out and bring the rack back to idle.

I do not know very much about engines, and have only found this out by asking so it could all be wrong.

John
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TomC
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« Reply #14 on: March 02, 2010, 07:26:30 AM »

Sudden surge of power rocketing up the hill- tells me your engine is burning enough oil to be running on the oil (like having bigger injectors).  Be aware that sometime you might have a run away engine with it running on the oil.  Make sure your emergency shut down flap is working correctly.  Sounds like you'll be needing it soon.

Unless your valves or Jakes are severely out of adjustment, it is time to have a certified 2 stroke Detroit shop pull the engine and overhaul it.  Good Luck, TomC
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Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.
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« Reply #15 on: March 02, 2010, 08:16:48 AM »

Quote
Sudden surge of power rocketing up the hill- tells me your engine is burning enough oil to be running on the oil (like having bigger injectors).  Be aware that sometime you might have a run away engine with it running on the oil.  Make sure your emergency shut down flap is working correctly.  Sounds like you'll be needing it soon.

I agree, you are surging on crankcase oil. Are your blower seals ok?
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