Trouble with Jake on My 99 Mack e7-460

[allfritz123]

My jake brake was working fine and then stopped working.  Trying to figure out why.   The Jake brake will come on at about 1200 or 1300 rpm - therefore assume still must have the wiring attached.  Does this mean it needs to be adjusted?  It always worked good until now and really had no signs of dying and all of sudden went to 1200 or 1300 rpm operation only.   One thing I noticed for a long time is that the switch needed to be in on position for a bit before it ever starts to work.   I assume that was a normal function.  I am quite  illiterate as to how  the system works and what has happened and what is wrong.    Hopefully someone can enlighten me as I love using my jake and it is hard on the brakes and don't know if I have a major issue....... 

[allfritz123]

I have also noticed that the oil pressure is no longer 50 or 60 psi which is likely related to the electronics and jake brake.   The oil doesn't look diluted nor above full.  I have ordered a oil pressure sending unit.   I now have to try locate it as it is NOT on the oil filter housing.   I can unplug that sensor and nothing happens and the oil pressure is still reading 35 psi.     Should be here Wednesday -had to come out of Chicago. Hope that fixes the problem!

[Mack Technician]

Loss of oil pressure will make your Jakes dysfunctional at the lower RPM range. Mack had multiple updates for that engine to get brakes to work. Low oil pressure to top of engine (brakes) is often a sign of worn engine bearings. If you see a sudden drop in oil pressure it’s a bad sign.