Jake Brakes - Ongoing diagnosis...(SOLVED)

[GnarlyBus]

Ok luvrbus, that's helpful. Thank you!

I do have the 92 Series Engine Manual (even went crazy at the library one day printing most of it out!) and will reread the sections on valve adjustments. I just wasn't sure if I had to rotate the engine to adjust the jakes. Now it's clear that I do.

I'll wait for the solenoids to come and then see what happens when I install them. Oh and I just purchased a Jake Brake Feeler Gauge off eBay.

I'd like to run the engine for a bit with the valve covers off so I can see the operation of the valves and jakes. Would it be ok to run the engine with L shaped exhaust pipe that goes from the manifold on the left side up to the turbo off?

[GnarlyBus]

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    

Ok my solenoids and jake .059" feeler gauge came today.

I started on the Passenger side because it's a bit easier to see what I'm doing. I have no idea when the last time anyone adjusted the valves. I've owned the bus for 3.5 years but this is my first time on this bus. The exhaust valves all appear to be about .012-.014" cold. The manual says they should be .016", but I don't yet have the special wrenches to reach around and loosen/adjust the push rods. So I'm going to have to come back to this when my wrap around wrenches arrive. I heard somewhere that valves tighten over time as the valves kinda "seat" into the head. Is that correct?

It appears that when rotating the engine that two cylinders exhaust valves are closed (bridges wiggle) and ready to adjust at a time. Only one cylinder is in exhaust mode (per side) at a time, correct?

I checked my Jake slave piston clearances and they were loose. Two were ~.075" and one was way looser. That might explain why this side (whose solenoid was working) wasn't doing much that I could notice from the driver's area during the last test. I tightened all the slave piston clearances (which I will probably have to re-adjust once I do the valves. I double checked them a few times and made small adjustments.

Tomorrow I'll install the new solenoid on the driver's side and adjust the clearances.

Trying to learn this stuff without a teacher nearby is a little tough so I appreciate all the help! We're going to be leaving Yuma and heading to Laughlin for a few days and then Vegas for a few weeks before we run back up to Oregon. Trying to get the bus in order. Replacing fuel filters, oil change (Rotella 40W T1), Transmission Fluid Change (15w40 Delvac 1300), Coolant filter, etc all this week!

[GnarlyBus]

I wrote the long version because while trying to fix this problem I read every other jacobs brake thread on multiple forums and found little pieces that helped clarify and figure out what to do next. Hopefully this helps someone.

After my last post, I installed a new solenoid on the left side and finished adjusting all slave piston clearances. Having the .059 Jake Feeler Gauge was great and made it easy (thanks for the tip luvrbus). Sometimes I ran into a situation where one side or "foot" of the slave piston was tighter than the other side on the same valve. It confused me at first which side I should make sure was .059" but after re-reading the Jacobs manual it says that the tighter side should be .059" not the looser one. Good because that's what I did. So I had both side adjusted and solenoids clicking. I'm finally done, right?!

Then I hit the road and couldn't really tell for sure if even half the jakes were coming on or not, which means they probably weren't. I stopped in Laughlin and bypassed the buffer switch with a jumper wires so when I hit the dash switch, they would be forced to come on. Then I tested the switch when idling the bus. I read about this in another thread and it worked. As soon as I flipped the dash switch (well a second after) the engine started to Blap Blap Blap! I couldn't tell for sure but it seemed like only the left side with the new solenoid was engaging. It was a little hard to tell with how loud the engine is!

Time for a road test. I made sure only to switch them on when I let off the throttle and turn them off before idling. When I flipped that switch for the first time in between Laughlin and Vegas, man, words cannot explain how good it felt to hear that Jake and feel it slow me down! I was pretty sure that the right side was not working but was thrilled that the left side alone would slow me down like it did. A lot of folks on here seem to feel that jake brakes aren't the strongest on two stroke engines. Well, I have nothing to compare it to as I've never driven another vehicle with them, but I love how awesome it was even with half the engine braking.

I decided then that I'd add a Hi/Lo switch to my dash so I could choose. The left side jaking was perfect in town (which is what I really want them for).

I got to Vegas and tested the jakes again while idling. Yep, even though the solenoid clicks on the right side it didn't work. IDK why. I already purchased a second solenoid so I took the old one out and put the new one in. The O rings all seemed fine. If you replace a solenoid, don't miss the smallest one that usually gets stuck in the threads. Tested the jakes again while idling and BOTH SIDES WORK! Woohoo!

So I decided to add a Hi/Lo switch using a 12V relay which I mounted in the rear junction box. It was very easy and works great! I ended up sending the 12V from the dash switch to the rear using the "BL" terminal which is there for the Ether Spray Circuit I won't be using. I installed a Blue LED Hi/Lo toggle to match the Green LED On/Off switch I had already relocated from behind the drivers left elbow to just left of the steering wheel. eBay had a Peterbilt Jake name plate for cheap so I got that to make it all official!

Road tested them and they work! Hi and Lo! The microswitch on the governor works great too. I'm so glad I fixed them. This has been an ongoing saga for me and now its finished! For now...

[GnarlyBus]

Them Switches Tho.

[birdarchitect26]

I'm still following your progress for my future endeavors. I have the 8V92 Silver so I have 4 solenoids to worry about. I couldn't find a JB feeler gauge on eBay, do you have a link? (I only found a 7mm one)

I also have two switches on the left side of my steering wheel. I can't read the most left switch, so you give me hope that switch is in fact a HI-LOW toggle as I guessed. How does the microswitch on the governor work? I'm guessing while fast idle is active, valve pushed out, that switch gets activated, thus preventing the brake operation?

Jay

[GnarlyBus]

It's a project!

The micro switch is normally open (no current running through) when at idle, fast idle or foot on the throttle pedal. When you lift your foot off the pedal, the switch closes (power goes through to the Jake solenoids) until about idle.

Do you have the same micro switch as me? If so, you can stick a screwdriver in there carefully and pry the switch up  and test it at the right terminal to see if power is going through. This will test the operation of the microswitch. You can also by pass it giving you total power at the dash. Just be very careful to only turn the jakes on when your foot is off the pedal. You can flip them on at idle as a test but don't leave them on.

[bevans6]

More technically the micro switch closes when the governor goes to "no-fuel".  It does this whenever the engine is in "over-run", foot off the pedal so the speed control lever is in the idle position but the engine is not at actual idle speed, it's being pushed by the road wheels rolling along at speed.  It also goes to no-fuel when the engine is blipped, up to say 1500 - 2000 rpm and then back to idle.  If the jake switch is on and the jakes are working properly, you will hear them engage and rattle as the engine speed falls back down to idle.  When it reaches idle the governor comes out of no-fuel and goes to idle and with any luck the engine doesn't stall, but recovers from "jake-ness" to idle smoothly.

Brian