What produces a high pitch squeal?

[CBari]

While pulling grades with a very light load I was hearing a High Pitched squeal. I would liken the sound to someone running fingernails down a chalk board but louder. It would start off barley noticeable and get progressively louder. If I let off the throttle it would quit until I apply enough throttle to over take the grade. The truck in question is my 04. 5 completely stock and always has been it has around 165k on it. The fuel mileage has been off a little lately.



My first though is that the sound is from the pressure relief valve on the rail. My theory is that I have one or more injectors that aren't flowing fuel as they should so the ECM is adding fuel and pressure for its needs in this higher use time the pressure is increasing above the relief valve limits. My problem with this theory is that I should be noticing some sort of sign that an injector is bad. The truck idles and starts fine no noticeable change in the exhaust either.



I know the easy thing to is just replace all the injectors as they are at the stage in their life when one goes they all start going or so I have been told, but I also see people with well over 250k without doing anything but changing the oil.



Thanks for all the advice.

 

[JR]

Are you sure you dont have a small boost leak somewhere? A minor leak that didnt present itself until higher boost could make a high pitched squeal

 

[AEdelheit]

Sounds like a boost leak to me

 

[JJPage]

I agree, boost leak. Go purchase a 4" pvc plug (threaded, it will hold better), drill and tap it for a schrader valve. Remove your intake tube from your air filter box but leave it connected to the turbo, hose clamp the 4" pvc plug into the end of the intake tube. Now apply air pressure through the schrader valve until you find the leak. Probably between 20# to 30# psi should do it.

 

[Bob4x4]

When the pressure relief valve opens you can get a big pop noise followed by huge drop in power. Start looking for a boost leak or a turbo on the way out

 

[AH64ID]

I agree with the boost leak.

The ECM won't add rail pressure like you are thinking.

 

[CBari]

Thanks guys I will start looking for boost leak. Question though if it is a boost leak should I not see black exhaust when it happens?

 

[JJPage]

Not unless it's very large. I had a grid heater/intake horn gasket let loose, it would make a high pitched squeal at around 45 psi.

 

[B.G. Smith]

If you use the 4" pvc plug setup to test be very careful and don't stand in line with the plug as it can come out with a lot of force. bg

 

[JJPage]

If you use the 4" pvc plug setup to test be very careful and don't stand in line with the plug as it can come out with a lot of force. bg

You are absolutely correct! This is why I suggested a threaded plug to clamp around, what I also should have said, using just a short piece of the intake hose/tube (my 3rd gen is 3 piece) may be easier.

I have a 4" long, 4" dia piece of silicon tubing I use for this, before going to a threaded plug, I blew the standard plug out of it's clamp, it promptly projected forward and destroyed my oil filter... always use care, wear eye protection too.

 

[CBari]

What pressure do you recommend I test it at. I don't remember what the max boost the 04. 5 makes stock.

 

[JJPage]

With a pressure regulator on your air compressor, you can start around 10 psi then increase in 5 psi increments until you discover the leak. You should hear it before you reach 40 psi, I believe max boost for a stock truck is around 38 psi. I didn't find my leak until reaching 45 psi.

 

[Bill Stockard]

Check this thread: https://www.turbodieselregister.com...-Finding-Boost-Leak&highlight=boost+leak+test

and this one: https://www.turbodieselregister.com...-test-intake-system&highlight=boost+leak+test

Bill

 

[JJPage]

Check this thread: https://www.turbodieselregister.com...-Finding-Boost-Leak&highlight=boost+leak+test



and this one: https://www.turbodieselregister.com...-test-intake-system&highlight=boost+leak+test



Bill

Good find Bill, this is what mine looks like except... I tapped the quick connect into the side of the square on the plug instead of into the end, for clearance issues.