Repairing eng brake

[mpreiss321]

2011 Int'l prostar Cummins cm871 engine w/685936 miles. I'm about to replace an injector because 1 possibly more have gone bad. I also want to fix an eng. brake issue at the same time. Ok here's the issue- most of the time it works at 1/2 braking power when used in 9th or 10th gear (dash switch on eng 3 setting) While only getting 1/2 braking power I'm hearing a loud squel ( think AC belt pulley seizing up squeal ). That sound will disappear if I change the engine brake switch to eng.2 or eng.1 ( but I would still have 1/2 effective power ). Again truck is traveling in 9 or 10th gear. Engine brake seams to operate fine in lower gears ( all 3 settings). What can be the problem? And how do I fix it?

[Waterloo]

Well, I can't help with the squeal, but under the lid of your motor, valve cover, is your engine brake harness. The harness gets old and brittle after a time and need to be replaced. It should enter on the Turbo side center. Inspect that, I bet that is your issue. It is plug and play and most dealers stock it. Also, there are clips that hold it all in place, sometimes they fail and work there way into the motor. Be careful when inspecting. I believe the new harness will come with new clips.

[Rawze]

The squeal might be a manifold gasket leak or turbo mounting gasket. That is the most common issue with squealing.

[trucklogger2]

Take the belt off your a/c if it is separate from your main srpentine belt,eliminating that factor and try it again. Also you can spin the a/c pulley with engine off,you can see or feel if it's worn out.
Thanks Rawze for that, good to know.