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Author Topic: jake adjustment 6V92  (Read 1453 times)
skihor
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« on: January 24, 2013, 06:47:48 PM »

The Jake's pretty much quit working. They barely work when the motor is cold, and cold outside. After the motor is up to temp... nothing. Switch is good, buffer switch good and properly adjusted, power is good. I'm assuming it's a clearance/adjustment issue. Can the jakes be adjusted alone Huh Or do you have to do a complete overhead ? Secondly, if you do an overhead do you then have to "run the rack" also ? We are going back to Colorado next week and I would really like the Jakes to be functional.

Don & Sheila
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wg4t50
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« Reply #1 on: January 24, 2013, 06:51:21 PM »

Wondering if they stoped working all at once, or started getting weaker and weaker ?

Hope they quit all at once.

Dave M
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MCI7 20+ Yrs
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skihor
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« Reply #2 on: January 24, 2013, 07:08:35 PM »

I'm thinking weaker and weaker. but I'm not sure...
Of all the things I've lost I miss my mind the most...

Don & Sheila
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pvcces
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« Reply #3 on: January 24, 2013, 10:06:48 PM »

Don, I question the loss of adjustment at several places. An oil leak in the Jakes can cause them to fade away.

If that's the problem, the Jakes work when cold, but fade when hot. They get worse until you can't feel them come on.

Our case was that they caused surging when warm, but worked when cold. That turned out to be the front head wire had come loose, but it was hanging so close to the connection that slowing made an intermittent connection. It was hard to figure out, but easy to find when I got into the overhead.

Good luck!

Tom Caffrey
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Tom Caffrey PD4106-2576
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bevans6
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« Reply #4 on: January 25, 2013, 03:29:41 AM »

You can easily adjust the jakes without disturbing anything else, but at the same time you are barring the engine over and it's equally easy to check the other clearances (exhaust valve and injector timing height) while you are there.  You don't need to touch the rack at all.  You are setting a clearance between the exhaust valve bridge and the jake solenoid, the measurement is pretty precise so you need to determine the number and get an appropriate tool to measure with.  I would not use a stack-up of typical feeler gauges, and would get or make a tool to the exact measurement you decide you need.  Looser is safer than tighter.  As noted the jakes work from oil pressure.  The oil goes into the master unit via a hold-down bolt, and is transfered to the slave via a bridge tube.  You need to examine the bridge tubes to be sure they are adjusted correctly and the O-ring is in good shape.  I guess that a 6V-92 has two masters and one slave per head, but I don't know for sure.

FWIW mine, when I got the bus, were set at around an eighth of an inch (should have been .062") and the bridges were loose and had backed right off from the slave units.  Did not work at all.

Brian
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lostagain
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« Reply #5 on: January 25, 2013, 07:12:40 AM »

There are also O-rings on the solenoid valves that dry up. I would pull the Jakes out and overhaul them. Not really hard to do. See the manual on the Jakes site. Re install with 90 ft/lb torque on the rocker shaft bolts IIRC. The manual will tell you how much, and what to set the clearances to, IIRC I set mine at .059".

As Brian says, it won't disturb the fuel rack adjustment. And you can double check the valves and injector adjustments once done.

JC
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JC
Invermere, BC
1977 MC5C, 6V92/HT740
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« Reply #6 on: January 25, 2013, 07:16:20 AM »

Also on my 6V92, each head has a master in the middle and one slave on each side of it.

And I find that Jakes work better once the oil is at operating temperature, and at high rpm rather than low: more oil pressure.

JC
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JC
Invermere, BC
1977 MC5C, 6V92/HT740
hargreaves
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« Reply #7 on: January 25, 2013, 07:17:03 AM »

If you are going to go into the rocker covers to adjust things, replace the "O" rings that feed the Jake heads.  This is the most common problem . They need oil pressure to work and the "O" rings get hard and leak.   Cheers  Gerry
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azdieselman
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« Reply #8 on: January 26, 2013, 09:49:09 AM »

Where are you now?
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luvrbus
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« Reply #9 on: January 26, 2013, 03:53:20 PM »

The jumper pipe breaks between the master and slave very often because of over tightening of the nuts causing vibration where they are in contact with the slaves or master leave around 10 to 15 thous clearance between the nut and housing that was one of Tom's problem also fwiw
« Last Edit: January 26, 2013, 03:55:35 PM by luvrbus » Logged

Live each day like it was your last,one day it will be
skihor
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« Reply #10 on: January 26, 2013, 07:53:02 PM »

Where are you now?
We are in the Portland, Oregon area. Headed for Denver next week.

Don & Sheila
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sdc53
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« Reply #11 on: January 27, 2013, 11:04:43 PM »

Hillsboro diesel just west of Portland may be able to help you.  They are the local DD mechanics around here.
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Scott
Gladstone, OR
1969 PD4107
pvcces
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« Reply #12 on: January 27, 2013, 11:15:31 PM »

As Cliff pointed out, one of the screws that held the rubber seal was broken. This was in addition to the broken screw.

He straightened our Jakes out. They work nice!

Thanks, Cliff.

Tom Caffrey
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Tom Caffrey PD4106-2576
Suncatcher
Ketchikan, Alaska
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