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Kylack9 · 06-13-2025, 10:55 PM

Hi Everyone,

Does anyone have access to a wiring diagram for a 2008 diplomat? It has the ISL 400. The engine braking is very weak on this motorhome compared to my previous DPs that I’ve had. My previous DPs had pac brakes but this one has the variable geometry turbo and engine brake combo. On my switch panel it has one switch that says “engine brake” that is a 2 position on/off. There is no hi/low switch or a space for one to go or a foot pedal switch. I pulled the valve cover off to ensure it has the engine brake solenoids which it does. My guess is Monaco only hooked it up as an on/off that’s only on the low setting? Anyway if anyone has info in regards to this I’d really appreciate it.

Thanks,

Kyle

Jim_HiTek · 06-14-2025, 10:51 AM

No one has responded to your post so since I'm a talkative person, I will ask if you've lubricated the mechanism?

I have an exhaust brake on my engine with the single Off/On switch on the dash and with mine, I'm supposed to lubricate the mechanism during every oil change with some special exhaust brake mechanism lube but I had a diesel tech tell me once that it was a waste of money and to just use silicon spray. I figured the lube was a hi-temp formulation so I bought it anyway.

Yours seems to have a few mechanical parts as shown in this

video

so I'd recommend checking your documentation for that system to see if it's supposed to be lubed occasionally.

YC1 · 06-15-2025, 08:17 PM

Op is probably correct in having a variable geometry turbo. There is no hi/lo, its on or off. The engine talks to the transmission and the combinations learns a bit.

However, the brake is not near as strong as a Jake brake in my opinion. I assume you have turned it on and off while testing and you should feel it kick off when you get to about 15 mph.