2006 ISL 400 Engine

[Bob (WA0MQE)]

I've been setting at a campground for about a month. Engine had not been started during that time. Yesterday I started the coach, took it to a dealer and had it serviced. Oil change, oil filter, chassis lube.

I drove it home and when I shut the engine off I hear a loud SQUEAK like noise, or maybe loud CHIRP is a better description. You can even hear it from the drivers seat, although it's not too loud, but when standing back at the engine, and have wife turn off ignition, it's real loud.

It happens within a couple of seconds once the engine physically stops. I'm thinking it's related to the air system, but not sure. I started it back up, let it run a few minutes, shut it off and the same thing. Meaning it does it each time I shut down.

Any help is appreciated.

[Kuppajoe]

I had a somewhat similar sound on mine and it was the bearing going out on the alternator. Please post back what your issue turns out to be.

[Lault]

I had it also on a 06 ISL but never knew what caused it.

[Bob (WA0MQE)]

Thanks for the responses, at first I suspected a belt or alternator bearing. But standing back at the engine (mines a side radiator so with the rear engine cover open I'm looking right at the pulley/s and belts. The belts, alternator and ac compressor are completely stopped when the noise happens. It sounds more like a "pfft" except it's a high pitched squeal type of "pfft." As though something is relieving itself, like passing air. It also seems like the sound is coming further back near the right side as I'm facing the engine (curb side).

I do have a call into Cummins to ask them about it. I'll try to remember to post my findings once I know.

[Ann n Gene]

It could be a weak valve in the top of the air dryer that is releasing pressure when the engine shuts down. just my opinion

[Mr_D]

Yep, sounds like the air dryer or auto purge valve on the air system.

[Bob (WA0MQE)]

Well, Cummins was no help at all. Which is probably understandable given my description. Their suggestion was to take it to a Cummins Service Facility, which if I can't chase it down myself will be the next step.

[Happycarz]

Bob,
Try eliminating a chirping belt noise by taking off the serpentine belt, and, the A/C belt if it has one. But before doing so start it and turn it off to verify that the noise is there. If it is, repeat with the belt off. If it is too difficult to remove belt(s), spray them down with a squirt bottle filled with water. Be sure wet both side of the serpentine belt. Then start and stop it to see if the noise has gone away. I've seen failing belt tensioners cause this chirping noise.

[andy4393]

Check for exhaust leak by the block,,,look for small marks

[Gary RVRoamer]

I'm not surprised that Cummins can't help - they have nothing to do with any of the components that have been suggested so far. Your chassis manufacturer (Roadmaster) is more likely to be able to help.

[Bob (WA0MQE)]

Okay, I've made a little headway on my squeaky air release problem. I removed the cover in the bedroom which allows access to the top rear portion of the engine.

After having my wife start and stop the engine so I could hear and hopefully pin-point where the noise was coming from I finally found the culprit. I'm attaching a picture so hopefully one of you guys could help identify what the purpose of this item is and what does it mean when it spits air out after engine shutdown.

Here is the photo:

The letter "A" identify's the device I'm referring to it's mounted on the opposite side of the engine the actual Turbo is on, just above the injectors and almost to the rear of the engine. The letter "B" is pointing to a small air tube or a breather tube that attaches to the side of the device and crosses over the top of the engine then is attached to the top of the turbo charger impeller housing.

On the lower side of this device (opposite from where the letter "A" is pointing) is a small disc, with a screw in the middle, that's fitted into a dwell in the side of the device. When the engine shut's down, then in approximately 1.5 to 2 seconds the squeaky air sound (referenced in my original post) discharges from around this small disc. I sprayed water around this area and that's when I saw it.

Again, hoping somebody knows enough about these late model diesel engines to explain what this is. Oh, and there's a plate on the side that says:
Holset Turbo Chargers, it has a ID # 4088070690000300, then another number, called Cust # 4040341-00

Thanks in advance.

[Ann n Gene]

I would say that small disk with the screw that the air is coming out is likely the air governor but it should be small about 2-3 inches long and 1-1.5 inches around and should be detachable from the other piece (likely the air compressor but my eyes are not good enough to identify it for sure. IF it is the air governor and you an get it off, they are inexpensive, easy to find and easy to replace, they also go bad fairly regular. all just my opinion based on my bad eyes trying to see. lol

[Happycarz]

That box is the controller for the Holset VGT (turbo.) It controls the amount of air sent to the actuator, which moves the sliding nozzle ring, changing turbo boost.

Take a peek here.

It is under pressure from the air tank even with the engine off. Maybe it is just a gasket, but a call to Cummins would probably be in order.