Prevost 8v92 Jake Brake adjustment

[jok]

We just returned to Michigan after a week in Florida and while going down some of the hills (mountains to us in Michigan) it seemed that our Jake Brake was not functioning as good as it did years ago. You could tell it was working, just not very much.

What is involved in testing or adjusting them.

Thanks,
John

[Nick Badame Refrig/ACC]

Hi John,

Do you feel the jakes kick in at all?

If so, it sounds like you may have a bad solenoid or a broken wire leading to the solenoid.

The best way is to remove your valve covers and test each solenoid individually with voltage to see if they click.

If you find a bad one, you can either have it rebuilt or replaced at a DD dealer.

Good Luck
Nick-

[pvcces]

Hi, John.

If your Jakes are adjusted properly, and all the coils are powered up, then you might want to consider getting a tuneup kit. I believe that they run a little over $200.

We had the same complaint that you have, including very poor perfowmance with hot oil. We changed out the spools and the Jakes seem much improved. O-rings can cause poor performance, as well.

For what it's worth.

Tom Caffrey

[lostagain]

www.jakebrake.com has a manual that is very helpfull. I just used it to reinstall my Jakes, and adjust them, after I overhauled my 4-71.
By the way, I set them at .057". (The recommended standard by the book is .064"). It will open the valves that much more, to give you noticeably stronger braking.

JC

[jok]

Thanks for the responses. I believe that the Jake Brake is working slightly. On my bus the brake lights come on when the Jake is applied (the brake lights always come on when the bus is telling the Jake Brake to activate). On a small hill I can feel the Jake slightly working when I turn it on. It seems to slightly work in HIGH or LOW.

When testing the solenoid do I apply 12 volts or 24 volts?

Does anyone know off hand if I have a DDEC I, II, or III? It is a 1990 Prevost 8V92 with ATEC transmission control. Can I find out from a label on the body of the DDEC?

Thanks,
John

[JohnEd]

In another post a Knut said he was going to wire his Jake up with a separate switch to each head.  He inferred thAT IF HIS jAKE STARTED TO ACT UP HE COULD TRY USING EACH HEAD ALONE AND CHECK THAT EACH WAS ACTING THE SAME.  Sorry,,,caps lock.  I wasn't yelling.  That sure made sense to me and now here is a example.

John

[luvrbus]

John, the 1990 Prevosts are a DDEC11 and the Jake's are 12 V if it is working the same in high and low you have lost 1 side more than likely a wire going to one side check the leads on each head     good luck

[stevet903]

Here is a link to the DDEC II jake troubleshooting guide.

http://www.jakebrake.com/service/pdf2/021772.pdf

It covers the electronic parts well.   Many problems can be tracked to broken or shorted wires under the valve covers.  Mechanically, each solenoid has three o-rings that can leak and cause reduced braking, and an o-ring between the oil supply connectors between each jake housing that can leak as well.  The supply connectors can break and leak oil if they were installed incorrectly as well.  Here is a link to a tune up doc which may be helpful.

http://www.jakebrake.com/service/pdf2/003159.pdf

Finally, if the jake module failed at some time in the past, there was a Prevost doc on how to wire in a relay to replace it.  It is document number IS-99061 and is available on the Prevost web site.

Hope this helps  Steve