EcoDiesel Engine Chirping Noise

[nsa250x]

I have a 21 JLURD with 6,200 miles on it. It has the automatic transmission.

I've noticed a chirping noise related to the speed of the engine. It's becomes noticeable just above idle. The sound has become louder and louder over the past several months.

The chirping noise reminds me of the sound my 1976 CJ7 made when the clutch throwout bearing was going bad.

Anybody else have this problem?

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[StuartR]

No but I have a repeating sound of a siren that happens all the time. Drives me a little crazy to be honest but not enough to take it in.....

 

[KrawlSpace]

I too have the "siren" type noise. I thought I was going crazy.

 

[imjester77]

my dealer told me it was the internal dumping of the blowoff valve. since our system is self contained with no atmospheric dumping, it pushes exhaust pressure back into the system. but it still will make a sound, some are louder than others. So Ive Been Told. personally I call BS, but that is what the service tech told me when I asked a few months back.

 

[Gorilla57]

my dealer told me it was the internal dumping of the blowoff valve. since our system is self contained with no atmospheric dumping, it pushes exhaust pressure back into the system. but it still will make a sound, some are louder than others. So Ive Been Told. personally I call BS, but that is what the service tech told me when I asked a few months back.

That service tech doesn't know anything about a diesel......as a diesel doesn't have a blowoff valve. A blowoff valve is needed on a gas setup, as those have a throttle valve. The blowoff valve releases the boost pressure when the throttle valve slams shut, which causes a rebound pressure wave to hit the compressor side of a turbo.

 

[imjester77]

That service tech doesn't know anything about a diesel......as a diesel doesn't have a blowoff valve. A blowoff valve is needed on a gas setup, as those have a throttle valve. The blowoff valve releases the boost pressure when the throttle valve slams shut, which causes a rebound pressure wave to hit the compressor side of a turbo.

But will that cause the chirping? Cause I have the same issue too.

 

[Compression-Ignition]

Only chirping I've ever been familiar with in association with diesels has to do with the fan belt. My understanding was that upon shutdown, the engine stops so abruptly, that the belt skips/slides over one of the pulleys.

So to me when I read the thread topic it reminded me of that and I wondered if it might be something similar. All that torque being pumped out and then one of the engine components connected by pulley gets to far out of sync RPM wise.

Just a theory....perhaps a bad one....

 

[Gorilla57]

But will that cause the chirping? Cause I have the same issue too.

As I said before, you don’t have a throttle valve/plate. Compressor surge can be heard in a diesel, that’s the pressure wave hitting the turbo. But it’s rare and only happens when boost pressure spikes hard and fast. At the same moment, you have to lift off the throttle causing the RPM to drop. The boost pressure has no where to go. This is usually seen with big turbos/high boost diesels.

So, are you hearing this chirping sound when you go WOT and let off the throttle a moment later?

Are you hearing this at shut-down? As state above, that’s the belt slipping, which was very common on older Cummins motors.

 

[nsa250x]

I hear it when lightly accelerating and cruising up to 30 mph. Above 30-35 mph I don't hear as much due to wind / road / tire noise.

 

[imjester77]

If I blip my throttle off idle i can here it. or if i roll heavily on the throttle under load. its minimal, but noticeable. Sorry for my ignorance on the subject, never owned a Turbo diesel before. Turbo cars, Plenty, but never a diesel or a Turbo diesel at that.

 

[Willys53]

No but I have a repeating sound of a siren that happens all the time. Drives me a little crazy to be honest but not enough to take it in.....

I have the same ... distant siren

 

[calemasters]

I have a 21 JLURD with 6,200 miles on it. It has the automatic transmission.

I've noticed a chirping noise related to the speed of the engine. It's becomes noticeable just above idle. The sound has become louder and louder over the past several months.

The chirping noise reminds me of the sound my 1976 CJ7 made when the clutch throwout bearing was going bad.

Anybody else have this problem?

Just guessing:

1.) Serpentine drive belt slipping
2.) Drive belt tensioner or pulley bearing
3.) Water pump

 

[hazards280]

I have the same ... distant siren

Spot on with the distant siren. I can't tell you how many times I've checked in my rear view while sitting at a stop light. I'm getting to the point where I know to tell myself it's the Jeep, but I still glance just to make sure.

 

[calemasters]

No but I have a repeating sound of a siren that happens all the time. Drives me a little crazy to be honest but not enough to take it in.....

Is not that the turbo spooling down?

 

[Plongson]

Sitting stopped and at an idle, mine has a sound like a cat meow-ing under the hood...LOL. My wife says "there's that cat again"...

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