Boost leak CM870......check engine light?

[tlzimmerman]

Got back to work on the truck today. 06 International 9900i with a CM870 ISX. In my last thread I had questions about the turbo leaking oil at the actuator, and I mentioned that I thought I could hear a boost leak from in the cab, but nothing outside next to or around the turbo or any of the intake.

Well...I found the boost leak. The tube that carries the EGR gasses out of the cooler around the back of the engine was BARELY hooked up at the first hose clamp and I could see a gap on the hose with a mirror, one small tug and it came completely off. The engine just had the EGR valve replaced before I bought it, not sure if this was the problem then or if he checked the EGR cooler then and didn't get things hooked back up well. I should have caught it when I cleaned the tubes for the delta P sensor but I didn't. All or most of my boost had to be traveling out of the intake down the egr tube and out at the back of the engine.

I am fixing this first thing in the morning, but it spawned a question in my head tonight. Shouldn't the truck struggling to build any boost have triggered a check engine light or something? Worried that I need to have the truck hooked up and make sure I have a stock tune before I hook it up and start hauling.

[Rawze]

Unfortunately ISX engine will not usually throw CEL for low boost unless it is so severe it will not make any.

[tlzimmerman]

Thanks Rawze.....appreciate it.

[snailexpress]

(08-08-2017 )Rawze Wrote:  Unfortunately ISX engine will not usually throw CEL for low boost unless it is so severe it will not make any.

In this case it highly possible. The ECM commanded EGR valve to open to mix more exhaust in the intake to keep temperature down. But exhaust (EGR part) escapes out before intake manifold.

[Nilao]

I believe the egr on this engine has been disabled. My friend had his inframed and the shop forgot to move the threaded plug from one head to the other. Needless to say he had a major boost leak and no CEL. So it's safe to say a isx won't code for low boost.

[tlzimmerman]

Hopefully will get some time to work on it today. I am pretty sure the engine isn't de-mandated. At least it doesn't make sense that they just put a brand new EGR valve in just to disable it...but I suppose weirder things have happened. I'll make sure I get exhaust gasses at the back side of the EGR cooler today before I hook everything back up. Be a good time to check to make sure the EGR cooler isn't leaking while I have everything apart checking all the connections.

[tlzimmerman]

Another question, would this have effected my engine brake as well? I have heard the engine brakes on the ISX's were great, and I was disappointed. Granted I haven't pulled more than an empty trailer at this point from yard to yard, but still.

I'll be interested to see if the engine brake comes alive.

[Nilao]

Yessir it definitely will affect the engine brake as the egr circuit is before the turbo and any leak in the system will cause the backpressure driving the turbo to drop off resulting in reduced engine brake as well as reduced mpg and power.

[tlzimmerman]

Well now I'm stumped. There was a rubber plug in the egr cooler. I removed it and was able to hook the egr tubing back up tight to it and clamp them down. Fired up the truck and took her for a spin with an empty trailer. Same noise....and I dont think it's building boost. I've got to work on all the other trucks today. I suppose the next step is taking the entire tubing off and check the integrity?