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Topic: 92 u-300 jake brake? (Read 1271 times) previous topic - next topic

92 u-300 jake brake?

Well I have dug through the archives all this week. My 1992 u-300, 6v-92 jake brake does not work. I have taken it to a local truck mechanic to repair. He has all the fancy old school diagnostics stuff to check everything. He is thinking that it is the jake (retarder control module) is bad. He cant find a part number or any numbers on the controller at all. Its a little control board right behind the "retarder switch" Have any of you guys replaced that little control board? I'm getting ready to leave this place for a week, and a part # or anything would be great right now. I pull a trailer with my big ol critter, itd sure be a nice option.

Re: 92 u-300 jake brake?

Reply #2 –
Ted,  Did it ever  work?  As to my knowledge almost all Detroit  6V92's had "Jake Brakes".  I would look for a Detroit Diesel  Shop in Your area,  I found this one;  Montana Truck & Trailer Repair | Power Generators | Industrial Bearings,...
Looks like they should have the ability to diagnose your problem.  Sometimes it is only a set-up problem that needs to be addressed in the "engine computer".

Re: 92 u-300 jake brake?

Reply #3 –
If you have a rear radiator U300, it will come with 50hp less, an Allison 6xx transmission and a retarder unless a Jake was special ordered. The models with the side radiator came with a 746 Allison with a higher torque input rating and the Jake. This is the famed "garbage truck" transmission.

Weather or not it has a Jake, the switch on the dash has "retarder" written on it.

Pierce

Re: 92 u-300 jake brake?

Reply #4 –
It did work when I brought it home a year ago. When I first got it when I pulled off the interstate it was working. Sounded just like a jake. The guy I have working on is close with interstate Detroit diesel (in the link above). In the past they have done tons of work to my coach. Including an in frame rebuild 70k miles ago. The mechanic I have working on mine is leaning more toward an under the valve cover problem.  The control module, runs about $400.00 Interstate got back to him today with those part numbers. I guess theyre just a little slow, or maybe that busy. It is a rear radiator with an Allison ht 746 transmission. I was hoping to do some leg work for the guy, it sounds like there are many combinations how the jake works. Ill just stand back and watch!

Re: 92 u-300 jake brake?

Reply #5 –
Quote from: MT Ted –
It is a rear radiator with an Allison ht 746 transmission.
So, your radiator is just inside the engine door and driven directly off the engine with no hydraulic pump/motors? The HT746 does not have a retarder.

The dash Jake (labeled retarder) has two positions. The first position operates a solenoid on the exhaust valves on the right side of the engine with the second position operating on both sides of the engine. Below is a video of testing a 8V-92TA on each side.

The Jake operates as the piston nears the top of the stroke, opening the exhaust valves. Since the compressed air can't push the piston down, it turns the engine into a big compressor. If both sides don't work, I would suspect either a wiring problem or Jake module. Another member had a coach with only one side operating.

You can always tell if your Detroit has a Jake by the valve covers. The engines w/o the Jake have lower valve covers with a really nice raised "Detroit Diesel" as part of the casting. The Jake versions are taller and don't have the prominent letters in the casting.

Pierce

Re: 92 u-300 jake brake?

Reply #7 –
Attached photo of a non Jake Detroit valve cover: (I mislabeled the photo)

Re: 92 u-300 jake brake?

Reply #8 –
Ted, you did check the fuse, didn't you?

Re: 92 u-300 jake brake?

Reply #9 –
Ted,

I looked at my diagram for the Jake in my user manual and it shows a transmission prom part no. 29504213  for jake brake alert if you need that one. The 800 number for service on the diagram is not correct.

Jerry

Re: 92 u-300 jake brake?

Reply #10 –
Ted,

Here is the wiring diagram and how to troubleshoot instructions for the two or three mode Jakes. This should be put in the Foretravel library.

https://www.jacobsvehiclesystems.com/files/support/docs-pdfs/021772.pdf

It looks really easy to check with a digital VOM and you can quickly see if it's the module or wiring. I'm putting my money on a wiring, switch or connection problem. The sequence used here is exactly what a shop will do and probably better as most places today learn at your expense.

Pierce

Re: 92 u-300 jake brake?

Reply #11 –
Quote from: kb0zke –
Ted, you did check the fuse, didn't you?
That was the first thing I checked. It was blown, changed it blew it again. Now it has a new fuse and it wont blow. Its just weird!

Re: 92 u-300 jake brake?

Reply #12 –
Quote from: MT Ted –
That was the first thing I checked. It was blown, changed it blew it again. Now it has a new fuse and it wont blow. Its just weird!
That might indicate a wiring fault, possibly grounding against something.

Pierce
 

Re: 92 u-300 jake brake?

Reply #13 –
The reason I asked about the fuse is that mine worked for a while on low, but would blow the fuse almost immediately on high, so I just left it off. I guess it got tired of being ignored, because one day I tried it just to see what would happen. It has worked perfectly ever since. Obviously, when the engine was rebuilt last year they had to mess with it, but whatever was causing the problem was fixed by then, and when they put the engine back together it still worked fine.