Jake Brakes - Ongoing diagnosis...(SOLVED)

GnarlyBus · February 18, 2018, 09:42:17 PM

I've had an MC9 with a 6V92 for a few years now and was told it had Jake Brakes when I purchased it. They've never worked for me. After finding the dash switch and testing it, nothing happened. Ended up working from to back. New switch up front and tested the micro buffer switch for proper operation by hooking it to a horn instead and it honked when i let off the throttle pedal. The horn went off at the correct times so I believe the buffer switch is working properly.

When I power up the jakes with the engine off and use a screwdriver to press on the buffer switch closed there seems to be a click on the right side, but nothing on the left. I've checked both wires to make sure power is getting to the solenoids.

Now heres a twist. I just learned today that the solenoids on my 6v92 are 12v? Mine is wired 24V. Not hard for me to rewire, but the solenoids are probably damaged now.

1. I'd like to remove the solenoids to test them and inspect the seals. How do I get them out? A special tool?

2. To test the solenoids I can test them with an ohm meter? Also, if I power them up, they should activate obviously, right?

GnarlyBus · February 18, 2018, 11:05:22 PM

I decided to go get the solenoid off so I could test it inside. I don't have the special tool so I used channel lock plyers. There's a plastic piece near where the wire connects to the solenoid that broke off, but I did get it off. Looking at it now I am pretty sure it didn't work even before I mangled it getting it off, it seems seized. If it was working and I didn't just break it, what would it do with 12v? Plunge something I assume? Also ohm meter reads open.

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chessie4905 · February 19, 2018, 04:26:39 AM

I believe they use to use12 volt solenoids before they later came out with specific 24 volt ones.
If you apply Voltage to the disconnected terminal of the solenoid, you will see the top depress about 1/16 to 1/8 inch and hear it click. You really don't even have to disconnect wire. Just watch one at a time.
Also, there is a threaded hollow tube aout halfway down casting between each unit. There is to be a specific gap there, set by loosening locknut, turning tube, and setting to specs. There is a small cupped shaped end on this tube that holds an o-ring. If you go to the Jacobs brake site, they have all the info on these, and adjustment specs.
There are different solenoid versions. Or requires a spanner wrench to remove. Others use a hex. I bought a spanner wrench on eBay to replace one solenoid on mine. Also, there was about 1/4 inch gapetween one of the tubes on mine.

luvrbus · February 19, 2018, 04:51:06 AM

They did use the same solenoid for years 12 or 24v ,you would see condensers (capacitors) mounted on ea master to give it a little more voltage,just remember they will not work below 15# PSI oil pressure

chessie4905 · February 19, 2018, 06:36:07 AM

In your picture, if you apply voltage to that terminal where the wire connects, you will see that disc on end of solenoid move a little if it is ok.

busfan · February 19, 2018, 07:42:31 AM

Saw a solenoid or two posted in the parts section, 1 is under title 71/92 and 1 from a guy with a prevost who is getting rid of everything..Good luck!

GnarlyBus · February 19, 2018, 09:47:27 AM

Quote from: luvrbus on February 19, 2018, 04:51:06 AM
They did use the same solenoid for years 12 or 24v ,you would see condensers (capacitors) mounted on ea master to give it a little more voltage,just remember they will not work below 15# PSI oil pressure

It's toast. It never did anything when I applied voltage.

The 24v solenoid are much more common and cheaper. Can I use one of those? Like a 1013472?

chessie4905 · February 19, 2018, 10:07:31 AM

Can't say for sure if it would make a difference in operation, but should work.

GnarlyBus · February 19, 2018, 10:27:30 AM

Ok after much searching I found a few pictures online with people who have 71/92 Series engine using the 1013472 24V Solenoids (attached one). I ordered 2 just in case.

I've read up on adjusting the slave piston clearance so we'll see if that needs done when the solenoids get here.

luvrbus · February 19, 2018, 11:42:51 AM

You probably should pull those and install a rebuild kit and be done with it. I get my kits from PacBrake for $129.00 ,all new seals,harness and flow valves with the springs and not complicated to install

GnarlyBus · February 19, 2018, 07:54:11 PM

Not a bad idea to rebuild, but I'm not sure when I'll be somewhere where I can do that for a while.

Using several Jake Brake Manuals, I inspected the slave piston clearances on the left engine head and it appears that the cylinder closes to the bumper is WAY off by about 1/2" (the threaded adjustment rod is backed way off too), but the other two seem very close to proper setting (see photo). When the engine is off, all that needs to be done is to remove the valve cover and set the clearance, correct? There isn't any Top Dead Center or other aligning engine rotations that are needed, right? So, I can adjust the adjustment rod down using the feeler gauges without doing anything else if that makes sense...

Man, going in and trying to figure out someone else's reasoning and work is not very fun. I really appreciate all the help.

luvrbus · February 20, 2018, 04:20:27 AM

Doesn't look like the valves are closed on the one,you have to rotate the engine to each cylinder check the valve clearance .015 then adjust the Jake with the adjustment screw on top of the Jake housing.
Don't mess with bridge adjustment the adjustment screw you see in the front or you will be removing those to make a bridge adjustment? do you have a engine manual you are in a land there that can cost you some big bucks if not careful.Anyways the valves need to be fully closed with clearance and that should be on the injection cycle on each cylinder and I would buy me a Jake gauge

birdarchitect26 · February 20, 2018, 05:40:05 AM

I want to chime in here, I plan to diagnose my Jakes next and will hopefully help / gain knowledge about the details. I would think to adjust anything relating to exhaust valves you would have to have that specific cylinder at BDC (full closed) or somewhere in the compression stroke to release some power? The jake lets out some compression to retard the engine if I'm not mistaken.

Gnarly,
Do you have a link / copy of the 92 jakes?

I recently printed this out, I printed about 4 different sections relating only to DD / Manual (non-DDEC) for my application.
https://www.jacobsvehiclesystems.com/files/file/Troubleshooting-Guide.pdf

J

luvrbus · February 20, 2018, 05:53:03 AM

Just roll the engine till you can wiggle the bridges and the valves are closed ,Jakes are add on everything under the Jake has to be according to Hoyle,the bridge adjustment and the valves adjustment or they will cause you major problems you need a engine manual to go with the Jake manual.
The old timers like me and others could adjust those with engine running with no gauge but I don't recommend doing that on a Detroit but I still do it on Cat engines and sometimes on a Detroit just to check myself

GnarlyBus · February 20, 2018, 11:35:22 AM

Quote from: birdarchitect26 on February 20, 2018, 05:40:05 AM
Gnarly,
Do you have a link / copy of the 92 jakes?

I recently printed this out, I printed about 4 different sections relating only to DD / Manual (non-DDEC) for my application.
https://www.jacobsvehiclesystems.com/files/file/Troubleshooting-Guide.pdf

That one is good, and this one is helpful, too.

https://www.jacobsvehiclesystems.com/files/support/docs-pdfs/003879.pdf